summaryrefslogtreecommitdiffstats
path: root/toolkit/components/places/SyncedBookmarksMirror.sys.mjs
blob: 2e197d2964e1a907adeb4ce6e75dc92620b1511d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/**
 * This file implements a mirror and two-way merger for synced bookmarks. The
 * mirror matches the complete tree stored on the Sync server, and stages new
 * bookmarks changed on the server since the last sync. The merger walks the
 * local tree in Places and the mirrored remote tree, produces a new merged
 * tree, then updates the local tree to reflect the merged tree.
 *
 * Let's start with an overview of the different classes, and how they fit
 * together.
 *
 * - `SyncedBookmarksMirror` sets up the database, validates and upserts new
 *   incoming records, attaches to Places, and applies the changed records.
 *   During application, we fetch the local and remote bookmark trees, merge
 *   them, and update Places to match. Merging and application happen in a
 *   single transaction, so applying the merged tree won't collide with local
 *   changes. A failure at this point aborts the merge and leaves Places
 *   unchanged.
 *
 * - A `BookmarkTree` is a fully rooted tree that also notes deletions. A
 *   `BookmarkNode` represents a local item in Places, or a remote item in the
 *   mirror.
 *
 * - A `MergedBookmarkNode` holds a local node, a remote node, and a
 *   `MergeState` that indicates which node to prefer when updating Places and
 *   the server to match the merged tree.
 *
 * - `BookmarkObserverRecorder` records all changes made to Places during the
 *   merge, then dispatches `PlacesObservers` notifications. Places uses
 *   these notifications to update the UI and internal caches. We can't dispatch
 *   during the merge because observers won't see the changes until the merge
 *   transaction commits and the database is consistent again.
 *
 * - After application, we flag all applied incoming items as merged, create
 *   Sync records for the locally new and updated items in Places, and upload
 *   the records to the server. At this point, all outgoing items are flagged as
 *   changed in Places, so the next sync can resume cleanly if the upload is
 *   interrupted or fails.
 *
 * - Once upload succeeds, we update the mirror with the uploaded records, so
 *   that the mirror matches the server again. An interruption or error here
 *   will leave the uploaded items flagged as changed in Places, so we'll merge
 *   them again on the next sync. This is redundant work, but shouldn't cause
 *   issues.
 */

import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";

const lazy = {};

ChromeUtils.defineESModuleGetters(lazy, {
  Async: "resource://services-common/async.sys.mjs",
  Log: "resource://gre/modules/Log.sys.mjs",
  PlacesSyncUtils: "resource://gre/modules/PlacesSyncUtils.sys.mjs",
  PlacesUtils: "resource://gre/modules/PlacesUtils.sys.mjs",
});

XPCOMUtils.defineLazyGetter(lazy, "MirrorLog", () =>
  lazy.Log.repository.getLogger("Sync.Engine.Bookmarks.Mirror")
);

const SyncedBookmarksMerger = Components.Constructor(
  "@mozilla.org/browser/synced-bookmarks-merger;1",
  "mozISyncedBookmarksMerger"
);

// These can be removed once they're exposed in a central location (bug
// 1375896).
const DB_URL_LENGTH_MAX = 65536;
const DB_TITLE_LENGTH_MAX = 4096;

// The current mirror database schema version. Bump for migrations, then add
// migration code to `migrateMirrorSchema`.
const MIRROR_SCHEMA_VERSION = 8;

// Use a shared jankYielder in these functions
XPCOMUtils.defineLazyGetter(lazy, "yieldState", () => lazy.Async.yieldState());

/** Adapts a `Log.sys.mjs` logger to a `mozIServicesLogSink`. */
class LogAdapter {
  constructor(log) {
    this.log = log;
  }

  get maxLevel() {
    let level = this.log.level;
    if (level <= lazy.Log.Level.All) {
      return Ci.mozIServicesLogSink.LEVEL_TRACE;
    }
    if (level <= lazy.Log.Level.Info) {
      return Ci.mozIServicesLogSink.LEVEL_DEBUG;
    }
    if (level <= lazy.Log.Level.Warn) {
      return Ci.mozIServicesLogSink.LEVEL_WARN;
    }
    if (level <= lazy.Log.Level.Error) {
      return Ci.mozIServicesLogSink.LEVEL_ERROR;
    }
    return Ci.mozIServicesLogSink.LEVEL_OFF;
  }

  trace(message) {
    this.log.trace(message);
  }

  debug(message) {
    this.log.debug(message);
  }

  warn(message) {
    this.log.warn(message);
  }

  error(message) {
    this.log.error(message);
  }
}

/**
 * A helper to track the progress of a merge for telemetry and shutdown hang
 * reporting.
 */
class ProgressTracker {
  constructor(recordStepTelemetry) {
    this.recordStepTelemetry = recordStepTelemetry;
    this.steps = [];
  }

  /**
   * Records a merge step, updating the shutdown blocker state.
   *
   * @param {String} name A step name from `ProgressTracker.STEPS`. This is
   *        included in shutdown hang crash reports, along with the timestamp
   *        the step was recorded.
   * @param {Number} [took] The time taken, in milliseconds.
   * @param {Array} [counts] An array of additional counts to report in the
   *        shutdown blocker state.
   */
  step(name, took = -1, counts = null) {
    let info = { step: name, at: Date.now() };
    if (took > -1) {
      info.took = took;
    }
    if (counts) {
      info.counts = counts;
    }
    this.steps.push(info);
  }

  /**
   * Records a merge step with timings and counts for telemetry.
   *
   * @param {String} name The step name.
   * @param {Number} took The time taken, in milliseconds.
   * @param {Array} [counts] An array of additional `{ name, count }` tuples to
   *        record in telemetry for this step.
   */
  stepWithTelemetry(name, took, counts = null) {
    this.step(name, took, counts);
    this.recordStepTelemetry(name, took, counts);
  }

  /**
   * Records a merge step with the time taken and item count.
   *
   * @param {String} name The step name.
   * @param {Number} took The time taken, in milliseconds.
   * @param {Number} count The number of items handled in this step.
   */
  stepWithItemCount(name, took, count) {
    this.stepWithTelemetry(name, took, [{ name: "items", count }]);
  }

  /**
   * Clears all recorded merge steps.
   */
  reset() {
    this.steps = [];
  }

  /**
   * Returns the shutdown blocker state. This is included in shutdown hang
   * crash reports, in the `AsyncShutdownTimeout` annotation.
   *
   * @see    `fetchState` in `AsyncShutdown` for more details.
   * @return {Object} A stringifiable object with the recorded steps.
   */
  fetchState() {
    return { steps: this.steps };
  }
}

/** Merge steps for which we record progress. */
ProgressTracker.STEPS = {
  FETCH_LOCAL_TREE: "fetchLocalTree",
  FETCH_REMOTE_TREE: "fetchRemoteTree",
  MERGE: "merge",
  APPLY: "apply",
  NOTIFY_OBSERVERS: "notifyObservers",
  FETCH_LOCAL_CHANGE_RECORDS: "fetchLocalChangeRecords",
  FINALIZE: "finalize",
};

/**
 * A mirror maintains a copy of the complete tree as stored on the Sync server.
 * It is persistent.
 *
 * The mirror schema is a hybrid of how Sync and Places represent bookmarks.
 * The `items` table contains item attributes (title, kind, URL, etc.), while
 * the `structure` table stores parent-child relationships and position.
 * This is similar to how iOS encodes "value" and "structure" state,
 * though we handle these differently when merging. See `BookmarkMerger` for
 * details.
 *
 * There's no guarantee that the remote state is consistent. We might be missing
 * parents or children, or a bookmark and its parent might disagree about where
 * it belongs. This means we need a strategy to handle missing parents and
 * children.
 *
 * We treat the `children` of the last parent we see as canonical, and ignore
 * the child's `parentid` entirely. We also ignore missing children, and
 * temporarily reparent bookmarks with missing parents to "unfiled". When we
 * eventually see the missing items, either during a later sync or as part of
 * repair, we'll fill in the mirror's gaps and fix up the local tree.
 *
 * During merging, we won't intentionally try to fix inconsistencies on the
 * server, and opt to build as complete a tree as we can from the remote state,
 * even if we diverge from what's in the mirror. See bug 1433512 for context.
 *
 * If a sync is interrupted, we resume downloading from the server collection
 * last modified time, or the server last modified time of the most recent
 * record if newer. New incoming records always replace existing records in the
 * mirror.
 *
 * We delete the mirror database on client reset, including when the sync ID
 * changes on the server, and when the user is node reassigned, disables the
 * bookmarks engine, or signs out.
 */
export class SyncedBookmarksMirror {
  constructor(
    db,
    wasCorrupt = false,
    {
      recordStepTelemetry,
      recordValidationTelemetry,
      finalizeAt = lazy.PlacesUtils.history.shutdownClient.jsclient,
    } = {}
  ) {
    this.db = db;
    this.wasCorrupt = wasCorrupt;
    this.recordValidationTelemetry = recordValidationTelemetry;

    this.merger = new SyncedBookmarksMerger();
    this.merger.db = db.unsafeRawConnection.QueryInterface(
      Ci.mozIStorageConnection
    );
    this.merger.logger = new LogAdapter(lazy.MirrorLog);

    // Automatically close the database connection on shutdown. `progress`
    // tracks state for shutdown hang reporting.
    this.progress = new ProgressTracker(recordStepTelemetry);
    this.finalizeController = new AbortController();
    this.finalizeAt = finalizeAt;
    this.finalizeBound = () => this.finalize({ alsoCleanup: false });
    this.finalizeAt.addBlocker(
      "SyncedBookmarksMirror: finalize",
      this.finalizeBound,
      { fetchState: () => this.progress }
    );
  }

  /**
   * Sets up the mirror database connection and upgrades the mirror to the
   * newest schema version. Automatically recreates the mirror if it's corrupt;
   * throws on failure.
   *
   * @param  {String} options.path
   *         The path to the mirror database file, either absolute or relative
   *         to the profile path.
   * @param  {Function} options.recordStepTelemetry
   *         A function with the signature `(name: String, took: Number,
   *         counts: Array?)`, where `name` is the name of the merge step,
   *         `took` is the time taken in milliseconds, and `counts` is an
   *         array of named counts (`{ name, count }` tuples) with additional
   *         counts for the step to record in the telemetry ping.
   * @param  {Function} options.recordValidationTelemetry
   *         A function with the signature `(took: Number, checked: Number,
   *         problems: Array)`, where `took` is the time taken to run
   *         validation in milliseconds, `checked` is the number of items
   *         checked, and `problems` is an array of named problem counts.
   * @param  {AsyncShutdown.Barrier} [options.finalizeAt]
   *         A shutdown phase, barrier, or barrier client that should
   *         automatically finalize the mirror when triggered. Exposed for
   *         testing.
   * @return {SyncedBookmarksMirror}
   *         A mirror ready for use.
   */
  static async open(options) {
    let db = await lazy.PlacesUtils.promiseUnsafeWritableDBConnection();
    if (!db) {
      throw new TypeError("Can't open mirror without Places connection");
    }
    let path;
    if (PathUtils.isAbsolute(options.path)) {
      path = options.path;
    } else {
      path = PathUtils.join(PathUtils.profileDir, options.path);
    }
    let wasCorrupt = false;
    try {
      await attachAndInitMirrorDatabase(db, path);
    } catch (ex) {
      if (isDatabaseCorrupt(ex)) {
        lazy.MirrorLog.warn(
          "Error attaching mirror to Places; removing and " +
            "recreating mirror",
          ex
        );
        wasCorrupt = true;
        await IOUtils.remove(path);
        await attachAndInitMirrorDatabase(db, path);
      } else {
        lazy.MirrorLog.error(
          "Unrecoverable error attaching mirror to Places",
          ex
        );
        throw ex;
      }
    }
    return new SyncedBookmarksMirror(db, wasCorrupt, options);
  }

  /**
   * Returns the newer of the bookmarks collection last modified time, or the
   * server modified time of the newest record. The bookmarks engine uses this
   * timestamp as the "high water mark" for all downloaded records. Each sync
   * downloads and stores records that are strictly newer than this time.
   *
   * @return {Number}
   *         The high water mark time, in seconds.
   */
  async getCollectionHighWaterMark() {
    // The first case, where we have records with server modified times newer
    // than the collection last modified time, occurs when a sync is interrupted
    // before we call `setCollectionLastModified`. We subtract one second, the
    // maximum time precision guaranteed by the server, so that we don't miss
    // other records with the same time as the newest one we downloaded.
    let rows = await this.db.executeCached(
      `
      SELECT MAX(
        IFNULL((SELECT MAX(serverModified) - 1000 FROM items), 0),
        IFNULL((SELECT CAST(value AS INTEGER) FROM meta
                WHERE key = :modifiedKey), 0)
      ) AS highWaterMark`,
      { modifiedKey: SyncedBookmarksMirror.META_KEY.LAST_MODIFIED }
    );
    let highWaterMark = rows[0].getResultByName("highWaterMark");
    return highWaterMark / 1000;
  }

  /**
   * Updates the bookmarks collection last modified time. Note that this may
   * be newer than the modified time of the most recent record.
   *
   * @param {Number|String} lastModifiedSeconds
   *        The collection last modified time, in seconds.
   */
  async setCollectionLastModified(lastModifiedSeconds) {
    let lastModified = Math.floor(lastModifiedSeconds * 1000);
    if (!Number.isInteger(lastModified)) {
      throw new TypeError("Invalid collection last modified time");
    }
    await this.db.executeBeforeShutdown(
      "SyncedBookmarksMirror: setCollectionLastModified",
      db =>
        db.executeCached(
          `
        REPLACE INTO meta(key, value)
        VALUES(:modifiedKey, :lastModified)`,
          {
            modifiedKey: SyncedBookmarksMirror.META_KEY.LAST_MODIFIED,
            lastModified,
          }
        )
    );
  }

  /**
   * Returns the bookmarks collection sync ID. This corresponds to
   * `PlacesSyncUtils.bookmarks.getSyncId`.
   *
   * @return {String}
   *         The sync ID, or `""` if one isn't set.
   */
  async getSyncId() {
    let rows = await this.db.executeCached(
      `
      SELECT value FROM meta WHERE key = :syncIdKey`,
      { syncIdKey: SyncedBookmarksMirror.META_KEY.SYNC_ID }
    );
    return rows.length ? rows[0].getResultByName("value") : "";
  }

  /**
   * Ensures that the sync ID in the mirror is up-to-date with the server and
   * Places, and discards the mirror on mismatch.
   *
   * The bookmarks engine store the same sync ID in Places and the mirror to
   * "tie" the two together. This allows Sync to do the right thing if the
   * database files are copied between profiles connected to different accounts.
   *
   * See `PlacesSyncUtils.bookmarks.ensureCurrentSyncId` for an explanation of
   * how Places handles sync ID mismatches.
   *
   * @param {String} newSyncId
   *        The server's sync ID.
   */
  async ensureCurrentSyncId(newSyncId) {
    if (!newSyncId || typeof newSyncId != "string") {
      throw new TypeError("Invalid new bookmarks sync ID");
    }
    let existingSyncId = await this.getSyncId();
    if (existingSyncId == newSyncId) {
      lazy.MirrorLog.trace("Sync ID up-to-date in mirror", { existingSyncId });
      return;
    }
    lazy.MirrorLog.info(
      "Sync ID changed from ${existingSyncId} to " +
        "${newSyncId}; resetting mirror",
      { existingSyncId, newSyncId }
    );
    await this.db.executeBeforeShutdown(
      "SyncedBookmarksMirror: ensureCurrentSyncId",
      db =>
        db.executeTransaction(async function () {
          await resetMirror(db);
          await db.execute(
            `
          REPLACE INTO meta(key, value)
          VALUES(:syncIdKey, :newSyncId)`,
            { syncIdKey: SyncedBookmarksMirror.META_KEY.SYNC_ID, newSyncId }
          );
        })
    );
  }

  /**
   * Stores incoming or uploaded Sync records in the mirror. Rejects if any
   * records are invalid.
   *
   * @param {PlacesItem[]} records
   *        Sync records to store in the mirror.
   * @param {Boolean} [options.needsMerge]
   *        Indicates if the records were changed remotely since the last sync,
   *        and should be merged into the local tree. This option is set to
   *        `true` for incoming records, and `false` for successfully uploaded
   *        records. Tests can also pass `false` to set up an existing mirror.
   * @param {AbortSignal} [options.signal]
   *        An abort signal that can be used to interrupt the operation. If
   *        omitted, storing incoming items can still be interrupted when the
   *        mirror is finalized.
   */
  async store(records, { needsMerge = true, signal = null } = {}) {
    let options = {
      needsMerge,
      signal: anyAborted(this.finalizeController.signal, signal),
    };
    await this.db.executeBeforeShutdown("SyncedBookmarksMirror: store", db =>
      db.executeTransaction(async () => {
        for (let record of records) {
          if (options.signal.aborted) {
            throw new SyncedBookmarksMirror.InterruptedError(
              "Interrupted while storing incoming items"
            );
          }
          let guid = lazy.PlacesSyncUtils.bookmarks.recordIdToGuid(record.id);
          if (guid == lazy.PlacesUtils.bookmarks.rootGuid) {
            // The engine should hard DELETE Places roots from the server.
            throw new TypeError("Can't store Places root");
          }
          if (lazy.MirrorLog.level <= lazy.Log.Level.Trace) {
            lazy.MirrorLog.trace(
              `Storing in mirror: ${record.cleartextToString()}`
            );
          }
          switch (record.type) {
            case "bookmark":
              await this.storeRemoteBookmark(record, options);
              continue;

            case "query":
              await this.storeRemoteQuery(record, options);
              continue;

            case "folder":
              await this.storeRemoteFolder(record, options);
              continue;

            case "livemark":
              await this.storeRemoteLivemark(record, options);
              continue;

            case "separator":
              await this.storeRemoteSeparator(record, options);
              continue;

            default:
              if (record.deleted) {
                await this.storeRemoteTombstone(record, options);
                continue;
              }
          }
          lazy.MirrorLog.warn("Ignoring record with unknown type", record.type);
        }
      })
    );
  }

  /**
   * Builds a complete merged tree from the local and remote trees, resolves
   * value and structure conflicts, dedupes local items, applies the merged
   * tree back to Places, and notifies observers about the changes.
   *
   * Merging and application happen in a transaction, meaning code that uses the
   * main Places connection, including the UI, will fail to write to the
   * database until the transaction commits. Asynchronous consumers will retry
   * on `SQLITE_BUSY`; synchronous consumers will fail after waiting for 100ms.
   * See bug 1305563, comment 122 for details.
   *
   * @param  {Number} [options.localTimeSeconds]
   *         The current local time, in seconds.
   * @param  {Number} [options.remoteTimeSeconds]
   *         The current server time, in seconds.
   * @param  {Boolean} [options.notifyInStableOrder]
   *         If `true`, fire observer notifications for items in the same folder
   *         in a stable order. This is disabled by default, to avoid the cost
   *         of sorting the notifications, but enabled in some tests to simplify
   *         their checks.
   * @param  {AbortSignal} [options.signal]
   *         An abort signal that can be used to interrupt a merge when its
   *         associated `AbortController` is aborted. If omitted, the merge can
   *         still be interrupted when the mirror is finalized.
   * @return {Object.<String, BookmarkChangeRecord>}
   *         A changeset containing locally changed and reconciled records to
   *         upload to the server, and to store in the mirror once upload
   *         succeeds.
   */
  async apply({
    localTimeSeconds,
    remoteTimeSeconds,
    notifyInStableOrder,
    signal = null,
  } = {}) {
    // We intentionally don't use `executeBeforeShutdown` in this function,
    // since merging can take a while for large trees, and we don't want to
    // block shutdown. Since all new items are in the mirror, we'll just try
    // to merge again on the next sync.

    let finalizeOrInterruptSignal = anyAborted(
      this.finalizeController.signal,
      signal
    );

    let changeRecords;
    try {
      changeRecords = await this.tryApply(
        finalizeOrInterruptSignal,
        localTimeSeconds,
        remoteTimeSeconds,
        notifyInStableOrder
      );
    } finally {
      this.progress.reset();
    }

    return changeRecords;
  }

  async tryApply(
    signal,
    localTimeSeconds,
    remoteTimeSeconds,
    notifyInStableOrder = false
  ) {
    let wasMerged = await withTiming("Merging bookmarks in Rust", () =>
      this.merge(signal, localTimeSeconds, remoteTimeSeconds)
    );

    if (!wasMerged) {
      lazy.MirrorLog.debug("No changes detected in both mirror and Places");
      return {};
    }

    // At this point, the database is consistent, so we can notify observers and
    // inflate records for outgoing items.

    let observersToNotify = new BookmarkObserverRecorder(this.db, {
      signal,
      notifyInStableOrder,
    });

    await withTiming(
      "Notifying Places observers",
      async () => {
        try {
          // Note that we don't use a transaction when fetching info for
          // observers, so it's possible we might notify with stale info if the
          // main connection changes Places between the time we finish merging,
          // and the time we notify observers.
          await observersToNotify.notifyAll();
        } catch (ex) {
          // Places relies on observer notifications to update internal caches.
          // If notifying observers failed, these caches may be inconsistent,
          // so we invalidate them just in case.
          lazy.PlacesUtils.invalidateCachedGuids();
          await lazy.PlacesUtils.keywords.invalidateCachedKeywords();
          lazy.MirrorLog.warn("Error notifying Places observers", ex);
        } finally {
          await this.db.executeTransaction(async () => {
            await this.db.execute(`DELETE FROM itemsAdded`);
            await this.db.execute(`DELETE FROM guidsChanged`);
            await this.db.execute(`DELETE FROM itemsChanged`);
            await this.db.execute(`DELETE FROM itemsRemoved`);
            await this.db.execute(`DELETE FROM itemsMoved`);
          });
        }
      },
      time =>
        this.progress.stepWithTelemetry(
          ProgressTracker.STEPS.NOTIFY_OBSERVERS,
          time
        )
    );

    let { changeRecords } = await withTiming(
      "Fetching records for local items to upload",
      async () => {
        try {
          let result = await this.fetchLocalChangeRecords(signal);
          return result;
        } finally {
          await this.db.execute(`DELETE FROM itemsToUpload`);
        }
      },
      (time, result) =>
        this.progress.stepWithItemCount(
          ProgressTracker.STEPS.FETCH_LOCAL_CHANGE_RECORDS,
          time,
          result.count
        )
    );

    return changeRecords;
  }

  merge(signal, localTimeSeconds = Date.now() / 1000, remoteTimeSeconds = 0) {
    return new Promise((resolve, reject) => {
      let op = null;
      function onAbort() {
        signal.removeEventListener("abort", onAbort);
        op.cancel();
      }
      let callback = {
        QueryInterface: ChromeUtils.generateQI([
          "mozISyncedBookmarksMirrorProgressListener",
          "mozISyncedBookmarksMirrorCallback",
        ]),
        // `mozISyncedBookmarksMirrorProgressListener` methods.
        onFetchLocalTree: (took, itemCount, deleteCount, problemsBag) => {
          let counts = [
            {
              name: "items",
              count: itemCount,
            },
            {
              name: "deletions",
              count: deleteCount,
            },
          ];
          this.progress.stepWithTelemetry(
            ProgressTracker.STEPS.FETCH_LOCAL_TREE,
            took,
            counts
          );
          // We don't record local tree problems in validation telemetry.
        },
        onFetchRemoteTree: (took, itemCount, deleteCount, problemsBag) => {
          let counts = [
            {
              name: "items",
              count: itemCount,
            },
            {
              name: "deletions",
              count: deleteCount,
            },
          ];
          this.progress.stepWithTelemetry(
            ProgressTracker.STEPS.FETCH_REMOTE_TREE,
            took,
            counts
          );
          // Record validation telemetry for problems in the remote tree.
          let problems = bagToNamedCounts(problemsBag, [
            "orphans",
            "misparentedRoots",
            "multipleParents",
            "nonFolderParents",
            "parentChildDisagreements",
            "missingChildren",
          ]);
          let checked = itemCount + deleteCount;
          this.recordValidationTelemetry(took, checked, problems);
        },
        onMerge: (took, countsBag) => {
          let counts = bagToNamedCounts(countsBag, [
            "items",
            "dupes",
            "remoteRevives",
            "localDeletes",
            "localRevives",
            "remoteDeletes",
          ]);
          this.progress.stepWithTelemetry(
            ProgressTracker.STEPS.MERGE,
            took,
            counts
          );
        },
        onApply: took => {
          this.progress.stepWithTelemetry(ProgressTracker.STEPS.APPLY, took);
        },
        // `mozISyncedBookmarksMirrorCallback` methods.
        handleSuccess(result) {
          signal.removeEventListener("abort", onAbort);
          resolve(result);
        },
        handleError(code, message) {
          signal.removeEventListener("abort", onAbort);
          switch (code) {
            case Cr.NS_ERROR_STORAGE_BUSY:
              reject(new SyncedBookmarksMirror.MergeConflictError(message));
              break;

            case Cr.NS_ERROR_ABORT:
              reject(new SyncedBookmarksMirror.InterruptedError(message));
              break;

            default:
              reject(new SyncedBookmarksMirror.MergeError(message));
          }
        },
      };
      op = this.merger.merge(localTimeSeconds, remoteTimeSeconds, callback);
      if (signal.aborted) {
        op.cancel();
      } else {
        signal.addEventListener("abort", onAbort);
      }
    });
  }

  /**
   * Discards the mirror contents. This is called when the user is node
   * reassigned, disables the bookmarks engine, or signs out.
   */
  async reset() {
    await this.db.executeBeforeShutdown("SyncedBookmarksMirror: reset", db =>
      db.executeTransaction(() => resetMirror(db))
    );
  }

  /**
   * Fetches the GUIDs of all items in the remote tree that need to be merged
   * into the local tree.
   *
   * @return {String[]}
   *         Remotely changed GUIDs that need to be merged into Places.
   */
  async fetchUnmergedGuids() {
    let rows = await this.db.execute(`
      SELECT guid FROM items
      WHERE needsMerge
      ORDER BY guid`);
    return rows.map(row => row.getResultByName("guid"));
  }

  async storeRemoteBookmark(record, { needsMerge, signal }) {
    let guid = lazy.PlacesSyncUtils.bookmarks.recordIdToGuid(record.id);

    let url = validateURL(record.bmkUri);
    if (url) {
      await this.maybeStoreRemoteURL(url);
    }

    let parentGuid = lazy.PlacesSyncUtils.bookmarks.recordIdToGuid(
      record.parentid
    );
    let serverModified = determineServerModified(record);
    let dateAdded = determineDateAdded(record);
    let title = validateTitle(record.title);
    let keyword = validateKeyword(record.keyword);
    let validity = url
      ? Ci.mozISyncedBookmarksMerger.VALIDITY_VALID
      : Ci.mozISyncedBookmarksMerger.VALIDITY_REPLACE;

    await this.db.executeCached(
      `
      REPLACE INTO items(guid, parentGuid, serverModified, needsMerge, kind,
                         dateAdded, title, keyword, validity,
                         urlId)
      VALUES(:guid, :parentGuid, :serverModified, :needsMerge, :kind,
             :dateAdded, NULLIF(:title, ''), :keyword, :validity,
             (SELECT id FROM urls
              WHERE hash = hash(:url) AND
                    url = :url))`,
      {
        guid,
        parentGuid,
        serverModified,
        needsMerge,
        kind: Ci.mozISyncedBookmarksMerger.KIND_BOOKMARK,
        dateAdded,
        title,
        keyword,
        url: url ? url.href : null,
        validity,
      }
    );

    let tags = record.tags;
    if (tags && Array.isArray(tags)) {
      for (let rawTag of tags) {
        if (signal.aborted) {
          throw new SyncedBookmarksMirror.InterruptedError(
            "Interrupted while storing tags for incoming bookmark"
          );
        }
        let tag = validateTag(rawTag);
        if (!tag) {
          continue;
        }
        await this.db.executeCached(
          `
          INSERT INTO tags(itemId, tag)
          SELECT id, :tag FROM items
          WHERE guid = :guid`,
          { tag, guid }
        );
      }
    }
  }

  async storeRemoteQuery(record, { needsMerge }) {
    let guid = lazy.PlacesSyncUtils.bookmarks.recordIdToGuid(record.id);

    let validity = Ci.mozISyncedBookmarksMerger.VALIDITY_VALID;

    let url = validateURL(record.bmkUri);
    if (url) {
      // The query has a valid URL. Determine if we need to rewrite and reupload
      // it.
      let params = new URLSearchParams(url.href.slice(url.protocol.length));
      let type = +params.get("type");
      if (type == Ci.nsINavHistoryQueryOptions.RESULTS_AS_TAG_CONTENTS) {
        // Legacy tag queries with this type use a `place:` URL with a `folder`
        // param that points to the tag folder ID. Rewrite the query to directly
        // reference the tag stored in its `folderName`, then flag the rewritten
        // query for reupload.
        let tagFolderName = validateTag(record.folderName);
        if (tagFolderName) {
          try {
            url.href = `place:tag=${tagFolderName}`;
            validity = Ci.mozISyncedBookmarksMerger.VALIDITY_REUPLOAD;
          } catch (ex) {
            // The tag folder name isn't URL-encoded (bug 1449939), so we might
            // produce an invalid URL. However, invalid URLs are already likely
            // to cause other issues, and it's better to replace or delete the
            // query than break syncing or the Firefox UI.
            url = null;
          }
        } else {
          // The tag folder name is invalid, so replace or delete the remote
          // copy.
          url = null;
        }
      } else {
        let folder = params.get("folder");
        if (folder && !params.has("excludeItems")) {
          // We don't sync enough information to rewrite other queries with a
          // `folder` param (bug 1377175). Referencing a nonexistent folder ID
          // causes the query to return all items in the database, so we add
          // `excludeItems=1` to stop it from doing so. We also flag the
          // rewritten query for reupload.
          try {
            url.href = `${url.href}&excludeItems=1`;
            validity = Ci.mozISyncedBookmarksMerger.VALIDITY_REUPLOAD;
          } catch (ex) {
            url = null;
          }
        }
      }

      // Other queries are implicitly valid, and don't need to be reuploaded
      // or replaced.
    }

    if (url) {
      await this.maybeStoreRemoteURL(url);
    } else {
      // If the query doesn't have a valid URL, we must replace the remote copy
      // with either a valid local copy, or a tombstone if the query doesn't
      // exist locally.
      validity = Ci.mozISyncedBookmarksMerger.VALIDITY_REPLACE;
    }

    let parentGuid = lazy.PlacesSyncUtils.bookmarks.recordIdToGuid(
      record.parentid
    );
    let serverModified = determineServerModified(record);
    let dateAdded = determineDateAdded(record);
    let title = validateTitle(record.title);

    await this.db.executeCached(
      `
      REPLACE INTO items(guid, parentGuid, serverModified, needsMerge, kind,
                         dateAdded, title,
                         urlId,
                         validity)
      VALUES(:guid, :parentGuid, :serverModified, :needsMerge, :kind,
             :dateAdded, NULLIF(:title, ''),
             (SELECT id FROM urls
              WHERE hash = hash(:url) AND
                    url = :url),
             :validity)`,
      {
        guid,
        parentGuid,
        serverModified,
        needsMerge,
        kind: Ci.mozISyncedBookmarksMerger.KIND_QUERY,
        dateAdded,
        title,
        url: url ? url.href : null,
        validity,
      }
    );
  }

  async storeRemoteFolder(record, { needsMerge, signal }) {
    let guid = lazy.PlacesSyncUtils.bookmarks.recordIdToGuid(record.id);
    let parentGuid = lazy.PlacesSyncUtils.bookmarks.recordIdToGuid(
      record.parentid
    );
    let serverModified = determineServerModified(record);
    let dateAdded = determineDateAdded(record);
    let title = validateTitle(record.title);

    await this.db.executeCached(
      `
      REPLACE INTO items(guid, parentGuid, serverModified, needsMerge, kind,
                         dateAdded, title)
      VALUES(:guid, :parentGuid, :serverModified, :needsMerge, :kind,
             :dateAdded, NULLIF(:title, ''))`,
      {
        guid,
        parentGuid,
        serverModified,
        needsMerge,
        kind: Ci.mozISyncedBookmarksMerger.KIND_FOLDER,
        dateAdded,
        title,
      }
    );

    let children = record.children;
    if (children && Array.isArray(children)) {
      let offset = 0;
      for (let chunk of lazy.PlacesUtils.chunkArray(
        children,
        this.db.variableLimit - 1
      )) {
        if (signal.aborted) {
          throw new SyncedBookmarksMirror.InterruptedError(
            "Interrupted while storing children for incoming folder"
          );
        }
        // Builds a fragment like `(?2, ?1, 0), (?3, ?1, 1), ...`, where ?1 is
        // the folder's GUID, [?2, ?3] are the first and second child GUIDs
        // (SQLite binding parameters index from 1), and [0, 1] are the
        // positions. This lets us store the folder's children using as few
        // statements as possible.
        let valuesFragment = Array.from(
          { length: chunk.length },
          (_, index) => `(?${index + 2}, ?1, ${offset + index})`
        ).join(",");
        await this.db.execute(
          `
          INSERT INTO structure(guid, parentGuid, position)
          VALUES ${valuesFragment}`,
          [guid, ...chunk.map(lazy.PlacesSyncUtils.bookmarks.recordIdToGuid)]
        );
        offset += chunk.length;
      }
    }
  }

  async storeRemoteLivemark(record, { needsMerge }) {
    let guid = lazy.PlacesSyncUtils.bookmarks.recordIdToGuid(record.id);
    let parentGuid = lazy.PlacesSyncUtils.bookmarks.recordIdToGuid(
      record.parentid
    );
    let serverModified = determineServerModified(record);
    let feedURL = validateURL(record.feedUri);
    let dateAdded = determineDateAdded(record);
    let title = validateTitle(record.title);
    let siteURL = validateURL(record.siteUri);

    let validity = feedURL
      ? Ci.mozISyncedBookmarksMerger.VALIDITY_VALID
      : Ci.mozISyncedBookmarksMerger.VALIDITY_REPLACE;

    await this.db.executeCached(
      `
      REPLACE INTO items(guid, parentGuid, serverModified, needsMerge, kind,
                         dateAdded, title, feedURL, siteURL, validity)
      VALUES(:guid, :parentGuid, :serverModified, :needsMerge, :kind,
             :dateAdded, NULLIF(:title, ''), :feedURL, :siteURL, :validity)`,
      {
        guid,
        parentGuid,
        serverModified,
        needsMerge,
        kind: Ci.mozISyncedBookmarksMerger.KIND_LIVEMARK,
        dateAdded,
        title,
        feedURL: feedURL ? feedURL.href : null,
        siteURL: siteURL ? siteURL.href : null,
        validity,
      }
    );
  }

  async storeRemoteSeparator(record, { needsMerge }) {
    let guid = lazy.PlacesSyncUtils.bookmarks.recordIdToGuid(record.id);
    let parentGuid = lazy.PlacesSyncUtils.bookmarks.recordIdToGuid(
      record.parentid
    );
    let serverModified = determineServerModified(record);
    let dateAdded = determineDateAdded(record);

    await this.db.executeCached(
      `
      REPLACE INTO items(guid, parentGuid, serverModified, needsMerge, kind,
                         dateAdded)
      VALUES(:guid, :parentGuid, :serverModified, :needsMerge, :kind,
             :dateAdded)`,
      {
        guid,
        parentGuid,
        serverModified,
        needsMerge,
        kind: Ci.mozISyncedBookmarksMerger.KIND_SEPARATOR,
        dateAdded,
      }
    );
  }

  async storeRemoteTombstone(record, { needsMerge }) {
    let guid = lazy.PlacesSyncUtils.bookmarks.recordIdToGuid(record.id);
    let serverModified = determineServerModified(record);

    await this.db.executeCached(
      `
      REPLACE INTO items(guid, serverModified, needsMerge, isDeleted)
      VALUES(:guid, :serverModified, :needsMerge, 1)`,
      { guid, serverModified, needsMerge }
    );
  }

  async maybeStoreRemoteURL(url) {
    await this.db.executeCached(
      `
      INSERT OR IGNORE INTO urls(guid, url, hash, revHost)
      VALUES(IFNULL((SELECT guid FROM urls
                     WHERE hash = hash(:url) AND
                                  url = :url),
                    GENERATE_GUID()), :url, hash(:url), :revHost)`,
      { url: url.href, revHost: lazy.PlacesUtils.getReversedHost(url) }
    );
  }

  /**
   * Inflates Sync records for all staged outgoing items.
   *
   * @param  {AbortSignal} signal
   *         Stops fetching records when the associated `AbortController`
   *         is aborted.
   * @return {Object}
   *         A `{ changeRecords, count }` tuple, where `changeRecords` is a
   *         changeset containing Sync record cleartexts for outgoing items and
   *         tombstones, keyed by their Sync record IDs, and `count` is the
   *         number of records.
   */
  async fetchLocalChangeRecords(signal) {
    let changeRecords = {};
    let childRecordIdsByLocalParentId = new Map();
    let tagsByLocalId = new Map();

    let childGuidRows = [];
    await this.db.execute(
      `SELECT parentId, guid FROM structureToUpload
       ORDER BY parentId, position`,
      null,
      (row, cancel) => {
        if (signal.aborted) {
          cancel();
        } else {
          // `Sqlite.sys.mjs` callbacks swallow exceptions (bug 1387775), so we
          // accumulate all rows in an array, and process them after.
          childGuidRows.push(row);
        }
      }
    );

    await lazy.Async.yieldingForEach(
      childGuidRows,
      row => {
        if (signal.aborted) {
          throw new SyncedBookmarksMirror.InterruptedError(
            "Interrupted while fetching structure to upload"
          );
        }
        let localParentId = row.getResultByName("parentId");
        let childRecordId = lazy.PlacesSyncUtils.bookmarks.guidToRecordId(
          row.getResultByName("guid")
        );
        let childRecordIds = childRecordIdsByLocalParentId.get(localParentId);
        if (childRecordIds) {
          childRecordIds.push(childRecordId);
        } else {
          childRecordIdsByLocalParentId.set(localParentId, [childRecordId]);
        }
      },
      lazy.yieldState
    );

    let tagRows = [];
    await this.db.execute(
      `SELECT id, tag FROM tagsToUpload`,
      null,
      (row, cancel) => {
        if (signal.aborted) {
          cancel();
        } else {
          tagRows.push(row);
        }
      }
    );

    await lazy.Async.yieldingForEach(
      tagRows,
      row => {
        if (signal.aborted) {
          throw new SyncedBookmarksMirror.InterruptedError(
            "Interrupted while fetching tags to upload"
          );
        }
        let localId = row.getResultByName("id");
        let tag = row.getResultByName("tag");
        let tags = tagsByLocalId.get(localId);
        if (tags) {
          tags.push(tag);
        } else {
          tagsByLocalId.set(localId, [tag]);
        }
      },
      lazy.yieldState
    );

    let itemRows = [];
    await this.db.execute(
      `SELECT id, syncChangeCounter, guid, isDeleted, type, isQuery,
              tagFolderName, keyword, url, IFNULL(title, '') AS title,
              position, parentGuid,
              IFNULL(parentTitle, '') AS parentTitle, dateAdded
       FROM itemsToUpload`,
      null,
      (row, cancel) => {
        if (signal.interrupted) {
          cancel();
        } else {
          itemRows.push(row);
        }
      }
    );

    await lazy.Async.yieldingForEach(
      itemRows,
      row => {
        if (signal.aborted) {
          throw new SyncedBookmarksMirror.InterruptedError(
            "Interrupted while fetching items to upload"
          );
        }
        let syncChangeCounter = row.getResultByName("syncChangeCounter");

        let guid = row.getResultByName("guid");
        let recordId = lazy.PlacesSyncUtils.bookmarks.guidToRecordId(guid);

        // Tombstones don't carry additional properties.
        let isDeleted = row.getResultByName("isDeleted");
        if (isDeleted) {
          changeRecords[recordId] = new BookmarkChangeRecord(
            syncChangeCounter,
            {
              id: recordId,
              deleted: true,
            }
          );
          return;
        }

        let parentGuid = row.getResultByName("parentGuid");
        let parentRecordId =
          lazy.PlacesSyncUtils.bookmarks.guidToRecordId(parentGuid);

        let type = row.getResultByName("type");
        switch (type) {
          case lazy.PlacesUtils.bookmarks.TYPE_BOOKMARK: {
            let isQuery = row.getResultByName("isQuery");
            if (isQuery) {
              let queryCleartext = {
                id: recordId,
                type: "query",
                // We ignore `parentid` and use the parent's `children`, but older
                // Desktops and Android use `parentid` as the canonical parent.
                // iOS is stricter and requires both `children` and `parentid` to
                // match.
                parentid: parentRecordId,
                // Older Desktops use `hasDupe` (along with `parentName` for
                // deduping), if hasDupe is true, then they won't attempt deduping
                // (since they believe that a duplicate for this record should
                // exist). We set it to true to prevent them from applying their
                // deduping logic.
                hasDupe: true,
                parentName: row.getResultByName("parentTitle"),
                // Omit `dateAdded` from the record if it's not set locally.
                dateAdded: row.getResultByName("dateAdded") || undefined,
                bmkUri: row.getResultByName("url"),
                title: row.getResultByName("title"),
                // folderName should never be an empty string or null
                folderName: row.getResultByName("tagFolderName") || undefined,
              };
              changeRecords[recordId] = new BookmarkChangeRecord(
                syncChangeCounter,
                queryCleartext
              );
              return;
            }

            let bookmarkCleartext = {
              id: recordId,
              type: "bookmark",
              parentid: parentRecordId,
              hasDupe: true,
              parentName: row.getResultByName("parentTitle"),
              dateAdded: row.getResultByName("dateAdded") || undefined,
              bmkUri: row.getResultByName("url"),
              title: row.getResultByName("title"),
            };
            let keyword = row.getResultByName("keyword");
            if (keyword) {
              bookmarkCleartext.keyword = keyword;
            }
            let localId = row.getResultByName("id");
            let tags = tagsByLocalId.get(localId);
            if (tags) {
              bookmarkCleartext.tags = tags;
            }
            changeRecords[recordId] = new BookmarkChangeRecord(
              syncChangeCounter,
              bookmarkCleartext
            );
            return;
          }

          case lazy.PlacesUtils.bookmarks.TYPE_FOLDER: {
            let folderCleartext = {
              id: recordId,
              type: "folder",
              parentid: parentRecordId,
              hasDupe: true,
              parentName: row.getResultByName("parentTitle"),
              dateAdded: row.getResultByName("dateAdded") || undefined,
              title: row.getResultByName("title"),
            };
            let localId = row.getResultByName("id");
            let childRecordIds = childRecordIdsByLocalParentId.get(localId);
            folderCleartext.children = childRecordIds || [];
            changeRecords[recordId] = new BookmarkChangeRecord(
              syncChangeCounter,
              folderCleartext
            );
            return;
          }

          case lazy.PlacesUtils.bookmarks.TYPE_SEPARATOR: {
            let separatorCleartext = {
              id: recordId,
              type: "separator",
              parentid: parentRecordId,
              hasDupe: true,
              parentName: row.getResultByName("parentTitle"),
              dateAdded: row.getResultByName("dateAdded") || undefined,
              // Older Desktops use `pos` for deduping.
              pos: row.getResultByName("position"),
            };
            changeRecords[recordId] = new BookmarkChangeRecord(
              syncChangeCounter,
              separatorCleartext
            );
            return;
          }

          default:
            throw new TypeError("Can't create record for unknown Places item");
        }
      },
      lazy.yieldState
    );

    return { changeRecords, count: itemRows.length };
  }

  /**
   * Closes the mirror database connection. This is called automatically on
   * shutdown, but may also be called explicitly when the mirror is no longer
   * needed.
   *
   * @param {Boolean} [options.alsoCleanup]
   *                  If specified, drop all temp tables, views, and triggers,
   *                  and detach from the mirror database before closing the
   *                  connection. Defaults to `true`.
   */
  finalize({ alsoCleanup = true } = {}) {
    if (!this.finalizePromise) {
      this.finalizePromise = (async () => {
        this.progress.step(ProgressTracker.STEPS.FINALIZE);
        this.finalizeController.abort();
        this.merger.reset();
        if (alsoCleanup) {
          // If the mirror is finalized explicitly, clean up temp entities and
          // detach from the mirror database. We can skip this for automatic
          // finalization, since the Places connection is already shutting
          // down.
          await cleanupMirrorDatabase(this.db);
        }
        await this.db.execute(`PRAGMA mirror.optimize(0x02)`);
        await this.db.execute(`DETACH mirror`);
        this.finalizeAt.removeBlocker(this.finalizeBound);
      })();
    }
    return this.finalizePromise;
  }
}

/** Key names for the key-value `meta` table. */
SyncedBookmarksMirror.META_KEY = {
  LAST_MODIFIED: "collection/lastModified",
  SYNC_ID: "collection/syncId",
};

/**
 * An error thrown when the merge was interrupted.
 */
class InterruptedError extends Error {
  constructor(message) {
    super(message);
    this.name = "InterruptedError";
  }
}
SyncedBookmarksMirror.InterruptedError = InterruptedError;

/**
 * An error thrown when the merge failed for an unexpected reason.
 */
class MergeError extends Error {
  constructor(message) {
    super(message);
    this.name = "MergeError";
  }
}
SyncedBookmarksMirror.MergeError = MergeError;

/**
 * An error thrown when the merge can't proceed because the local tree
 * changed during the merge.
 */
class MergeConflictError extends Error {
  constructor(message) {
    super(message);
    this.name = "MergeConflictError";
  }
}
SyncedBookmarksMirror.MergeConflictError = MergeConflictError;

/**
 * An error thrown when the mirror database is corrupt, or can't be migrated to
 * the latest schema version, and must be replaced.
 */
class DatabaseCorruptError extends Error {
  constructor(message) {
    super(message);
    this.name = "DatabaseCorruptError";
  }
}

// Indicates if the mirror should be replaced because the database file is
// corrupt.
function isDatabaseCorrupt(error) {
  if (error instanceof DatabaseCorruptError) {
    return true;
  }
  if (error.errors) {
    return error.errors.some(
      error =>
        error instanceof Ci.mozIStorageError &&
        (error.result == Ci.mozIStorageError.CORRUPT ||
          error.result == Ci.mozIStorageError.NOTADB)
    );
  }
  return false;
}

/**
 * Attaches a cloned Places database connection to the mirror database,
 * migrates the mirror schema to the latest version, and creates temporary
 * tables, views, and triggers.
 *
 * @param {Sqlite.OpenedConnection} db
 *        The Places database connection.
 * @param {String} path
 *        The full path to the mirror database file.
 */
async function attachAndInitMirrorDatabase(db, path) {
  await db.execute(`ATTACH :path AS mirror`, { path });
  try {
    await db.executeTransaction(async function () {
      let currentSchemaVersion = await db.getSchemaVersion("mirror");
      if (currentSchemaVersion > 0) {
        if (currentSchemaVersion < MIRROR_SCHEMA_VERSION) {
          await migrateMirrorSchema(db, currentSchemaVersion);
        }
      } else {
        await initializeMirrorDatabase(db);
      }
      // Downgrading from a newer profile to an older profile rolls back the
      // schema version, but leaves all new columns in place. We'll run the
      // migration logic again on the next upgrade.
      await db.setSchemaVersion(MIRROR_SCHEMA_VERSION, "mirror");
      await initializeTempMirrorEntities(db);
    });
  } catch (ex) {
    await db.execute(`DETACH mirror`);
    throw ex;
  }
}

/**
 * Migrates the mirror database schema to the latest version.
 *
 * @param {Sqlite.OpenedConnection} db
 *        The mirror database connection.
 * @param {Number} currentSchemaVersion
 *        The current mirror database schema version.
 */
async function migrateMirrorSchema(db, currentSchemaVersion) {
  if (currentSchemaVersion < 5) {
    // The mirror was pref'd off by default for schema versions 1-4.
    throw new DatabaseCorruptError(
      `Can't migrate from schema version ${currentSchemaVersion}; too old`
    );
  }
  if (currentSchemaVersion < 6) {
    await db.execute(`CREATE INDEX IF NOT EXISTS mirror.itemURLs ON
                      items(urlId)`);
    await db.execute(`CREATE INDEX IF NOT EXISTS mirror.itemKeywords ON
                      items(keyword) WHERE keyword NOT NULL`);
  }
  if (currentSchemaVersion < 7) {
    await db.execute(`CREATE INDEX IF NOT EXISTS mirror.structurePositions ON
                      structure(parentGuid, position)`);
  }
  if (currentSchemaVersion < 8) {
    // Not really a "schema" update, but addresses the defect from bug 1635859.
    // In short, every bookmark with a corresponding entry in the mirror should
    // have syncStatus = NORMAL.
    await db.execute(`UPDATE moz_bookmarks AS b
                      SET syncStatus = ${lazy.PlacesUtils.bookmarks.SYNC_STATUS.NORMAL}
                      WHERE EXISTS (SELECT 1 FROM mirror.items
                                    WHERE guid = b.guid)`);
  }
}

/**
 * Initializes a new mirror database, creating persistent tables, indexes, and
 * roots.
 *
 * @param {Sqlite.OpenedConnection} db
 *        The mirror database connection.
 */
async function initializeMirrorDatabase(db) {
  // Key-value metadata table. Stores the server collection last modified time
  // and sync ID.
  await db.execute(`CREATE TABLE mirror.meta(
    key TEXT PRIMARY KEY,
    value NOT NULL
  ) WITHOUT ROWID`);

  // Note: description and loadInSidebar are not used as of Firefox 63, but
  // remain to avoid rebuilding the database if the user happens to downgrade.
  await db.execute(`CREATE TABLE mirror.items(
    id INTEGER PRIMARY KEY,
    guid TEXT UNIQUE NOT NULL,
    /* The "parentid" from the record. */
    parentGuid TEXT,
    /* The server modified time, in milliseconds. */
    serverModified INTEGER NOT NULL DEFAULT 0,
    needsMerge BOOLEAN NOT NULL DEFAULT 0,
    validity INTEGER NOT NULL DEFAULT ${Ci.mozISyncedBookmarksMerger.VALIDITY_VALID},
    isDeleted BOOLEAN NOT NULL DEFAULT 0,
    kind INTEGER NOT NULL DEFAULT -1,
    /* The creation date, in milliseconds. */
    dateAdded INTEGER NOT NULL DEFAULT 0,
    title TEXT,
    urlId INTEGER REFERENCES urls(id)
                  ON DELETE SET NULL,
    keyword TEXT,
    description TEXT,
    loadInSidebar BOOLEAN,
    smartBookmarkName TEXT,
    feedURL TEXT,
    siteURL TEXT
  )`);

  await db.execute(`CREATE TABLE mirror.structure(
    guid TEXT,
    parentGuid TEXT REFERENCES items(guid)
                    ON DELETE CASCADE,
    position INTEGER NOT NULL,
    PRIMARY KEY(parentGuid, guid)
  ) WITHOUT ROWID`);

  await db.execute(`CREATE TABLE mirror.urls(
    id INTEGER PRIMARY KEY,
    guid TEXT NOT NULL,
    url TEXT NOT NULL,
    hash INTEGER NOT NULL,
    revHost TEXT NOT NULL
  )`);

  await db.execute(`CREATE TABLE mirror.tags(
    itemId INTEGER NOT NULL REFERENCES items(id)
                            ON DELETE CASCADE,
    tag TEXT NOT NULL
  )`);

  await db.execute(
    `CREATE INDEX mirror.structurePositions ON structure(parentGuid, position)`
  );

  await db.execute(`CREATE INDEX mirror.urlHashes ON urls(hash)`);

  await db.execute(`CREATE INDEX mirror.itemURLs ON items(urlId)`);

  await db.execute(`CREATE INDEX mirror.itemKeywords ON items(keyword)
                    WHERE keyword NOT NULL`);

  await createMirrorRoots(db);
}

/**
 * Drops all temp tables, views, and triggers used for merging, and detaches
 * from the mirror database.
 *
 * @param {Sqlite.OpenedConnection} db
 *        The mirror database connection.
 */
async function cleanupMirrorDatabase(db) {
  await db.executeTransaction(async function () {
    await db.execute(`DROP TABLE changeGuidOps`);
    await db.execute(`DROP TABLE itemsToApply`);
    await db.execute(`DROP TABLE applyNewLocalStructureOps`);
    await db.execute(`DROP VIEW localTags`);
    await db.execute(`DROP TABLE itemsAdded`);
    await db.execute(`DROP TABLE guidsChanged`);
    await db.execute(`DROP TABLE itemsChanged`);
    await db.execute(`DROP TABLE itemsMoved`);
    await db.execute(`DROP TABLE itemsRemoved`);
    await db.execute(`DROP TABLE itemsToUpload`);
    await db.execute(`DROP TABLE structureToUpload`);
    await db.execute(`DROP TABLE tagsToUpload`);
  });
}

/**
 * Sets up the syncable roots. All items in the mirror we apply will descend
 * from these roots - however, malformed records from the server which create
 * a different root *will* be created in the mirror - just not applied.
 *
 *
 * @param {Sqlite.OpenedConnection} db
 *        The mirror database connection.
 */
async function createMirrorRoots(db) {
  const syncableRoots = [
    {
      guid: lazy.PlacesUtils.bookmarks.rootGuid,
      // The Places root is its own parent, to satisfy the foreign key and
      // `NOT NULL` constraints on `structure`.
      parentGuid: lazy.PlacesUtils.bookmarks.rootGuid,
      position: -1,
      needsMerge: false,
    },
    ...lazy.PlacesUtils.bookmarks.userContentRoots.map((guid, position) => {
      return {
        guid,
        parentGuid: lazy.PlacesUtils.bookmarks.rootGuid,
        position,
        needsMerge: true,
      };
    }),
  ];

  for (let { guid, parentGuid, position, needsMerge } of syncableRoots) {
    await db.executeCached(
      `
      INSERT INTO items(guid, parentGuid, kind, needsMerge)
      VALUES(:guid, :parentGuid, :kind, :needsMerge)`,
      {
        guid,
        parentGuid,
        kind: Ci.mozISyncedBookmarksMerger.KIND_FOLDER,
        needsMerge,
      }
    );

    await db.executeCached(
      `
      INSERT INTO structure(guid, parentGuid, position)
      VALUES(:guid, :parentGuid, :position)`,
      { guid, parentGuid, position }
    );
  }
}

/**
 * Creates temporary tables, views, and triggers to apply the mirror to Places.
 *
 * @param {Sqlite.OpenedConnection} db
 *        The mirror database connection.
 */
async function initializeTempMirrorEntities(db) {
  await db.execute(`CREATE TEMP TABLE changeGuidOps(
    localGuid TEXT PRIMARY KEY,
    mergedGuid TEXT UNIQUE NOT NULL,
    syncStatus INTEGER,
    level INTEGER NOT NULL,
    lastModifiedMicroseconds INTEGER NOT NULL
  ) WITHOUT ROWID`);

  await db.execute(`
    CREATE TEMP TRIGGER changeGuids
    AFTER DELETE ON changeGuidOps
    BEGIN
      /* Record item changed notifications for the updated GUIDs. */
      INSERT INTO guidsChanged(itemId, oldGuid, level)
      SELECT b.id, OLD.localGuid, OLD.level
      FROM moz_bookmarks b
      WHERE b.guid = OLD.localGuid;

      UPDATE moz_bookmarks SET
        guid = OLD.mergedGuid,
        lastModified = OLD.lastModifiedMicroseconds,
        syncStatus = IFNULL(OLD.syncStatus, syncStatus)
      WHERE guid = OLD.localGuid;
    END`);

  await db.execute(`CREATE TEMP TABLE itemsToApply(
    mergedGuid TEXT PRIMARY KEY,
    localId INTEGER UNIQUE,
    remoteId INTEGER UNIQUE NOT NULL,
    remoteGuid TEXT UNIQUE NOT NULL,
    newLevel INTEGER NOT NULL,
    newType INTEGER NOT NULL,
    localDateAddedMicroseconds INTEGER,
    remoteDateAddedMicroseconds INTEGER NOT NULL,
    lastModifiedMicroseconds INTEGER NOT NULL,
    oldTitle TEXT,
    newTitle TEXT,
    oldPlaceId INTEGER,
    newPlaceId INTEGER,
    newKeyword TEXT
  )`);

  await db.execute(`CREATE INDEX existingItems ON itemsToApply(localId)
                    WHERE localId NOT NULL`);

  await db.execute(`CREATE INDEX oldPlaceIds ON itemsToApply(oldPlaceId)
                    WHERE oldPlaceId NOT NULL`);

  await db.execute(`CREATE INDEX newPlaceIds ON itemsToApply(newPlaceId)
                    WHERE newPlaceId NOT NULL`);

  await db.execute(`CREATE INDEX newKeywords ON itemsToApply(newKeyword)
                    WHERE newKeyword NOT NULL`);

  await db.execute(`CREATE TEMP TABLE applyNewLocalStructureOps(
    mergedGuid TEXT PRIMARY KEY,
    mergedParentGuid TEXT NOT NULL,
    position INTEGER NOT NULL,
    level INTEGER NOT NULL,
    lastModifiedMicroseconds INTEGER NOT NULL
  ) WITHOUT ROWID`);

  await db.execute(`
    CREATE TEMP TRIGGER applyNewLocalStructure
    AFTER DELETE ON applyNewLocalStructureOps
    BEGIN
      INSERT INTO itemsMoved(itemId, oldParentId, oldParentGuid, oldPosition,
                             level)
      SELECT b.id, p.id, p.guid, b.position, OLD.level
      FROM moz_bookmarks b
      JOIN moz_bookmarks p ON p.id = b.parent
      WHERE b.guid = OLD.mergedGuid;

      UPDATE moz_bookmarks SET
        parent = (SELECT id FROM moz_bookmarks
                  WHERE guid = OLD.mergedParentGuid),
        position = OLD.position,
        lastModified = OLD.lastModifiedMicroseconds
      WHERE guid = OLD.mergedGuid;
    END`);

  // A view of local bookmark tags. Tags, like keywords, are associated with
  // URLs, so two bookmarks with the same URL should have the same tags. Unlike
  // keywords, one tag may be associated with many different URLs. Tags are also
  // different because they're implemented as bookmarks under the hood. Each tag
  // is stored as a folder under the tags root, and tagged URLs are stored as
  // untitled bookmarks under these folders. This complexity can be removed once
  // bug 424160 lands.
  await db.execute(`
    CREATE TEMP VIEW localTags(tagEntryId, tagEntryGuid, tagFolderId,
                               tagFolderGuid, tagEntryPosition, tagEntryType,
                               tag, placeId, lastModifiedMicroseconds) AS
    SELECT b.id, b.guid, p.id, p.guid, b.position, b.type,
           p.title, b.fk, b.lastModified
    FROM moz_bookmarks b
    JOIN moz_bookmarks p ON p.id = b.parent
    WHERE b.type = ${lazy.PlacesUtils.bookmarks.TYPE_BOOKMARK} AND
          p.parent = (SELECT id FROM moz_bookmarks
                      WHERE guid = '${lazy.PlacesUtils.bookmarks.tagsGuid}')`);

  // Untags a URL by removing its tag entry.
  await db.execute(`
    CREATE TEMP TRIGGER untagLocalPlace
    INSTEAD OF DELETE ON localTags
    BEGIN
      /* Record an item removed notification for the tag entry. */
      INSERT INTO itemsRemoved(itemId, parentId, position, type, placeId, guid,
                               parentGuid, title, isUntagging)
      VALUES(OLD.tagEntryId, OLD.tagFolderId, OLD.tagEntryPosition,
             OLD.tagEntryType, OLD.placeId, OLD.tagEntryGuid,
             OLD.tagFolderGuid, OLD.tag, 1);

      DELETE FROM moz_bookmarks WHERE id = OLD.tagEntryId;

      /* Fix the positions of the sibling tag entries. */
      UPDATE moz_bookmarks SET
        position = position - 1
      WHERE parent = OLD.tagFolderId AND
            position > OLD.tagEntryPosition;
    END`);

  // Tags a URL by creating a tag folder if it doesn't exist, then inserting a
  // tag entry for the URL into the tag folder. `NEW.placeId` can be NULL, in
  // which case we'll just create the tag folder.
  await db.execute(`
    CREATE TEMP TRIGGER tagLocalPlace
    INSTEAD OF INSERT ON localTags
    BEGIN
      /* Ensure the tag folder exists. */
      INSERT OR IGNORE INTO moz_bookmarks(guid, parent, position, type, title,
                                          dateAdded, lastModified)
      VALUES(IFNULL((SELECT b.guid FROM moz_bookmarks b
                     JOIN moz_bookmarks p ON p.id = b.parent
                     WHERE b.title = NEW.tag AND
                           p.guid = '${lazy.PlacesUtils.bookmarks.tagsGuid}'),
                    GENERATE_GUID()),
             (SELECT id FROM moz_bookmarks
              WHERE guid = '${lazy.PlacesUtils.bookmarks.tagsGuid}'),
             (SELECT COUNT(*) FROM moz_bookmarks b
              JOIN moz_bookmarks p ON p.id = b.parent
              WHERE p.guid = '${lazy.PlacesUtils.bookmarks.tagsGuid}'),
             ${lazy.PlacesUtils.bookmarks.TYPE_FOLDER}, NEW.tag,
             NEW.lastModifiedMicroseconds,
             NEW.lastModifiedMicroseconds);

      /* Record an item added notification if we created a tag folder.
         "CHANGES()" returns the number of rows affected by the INSERT above:
         1 if we created the folder, or 0 if the folder already existed. */
      INSERT INTO itemsAdded(guid, isTagging)
      SELECT b.guid, 1
      FROM moz_bookmarks b
      JOIN moz_bookmarks p ON p.id = b.parent
      WHERE CHANGES() > 0 AND
            b.title = NEW.tag AND
            p.guid = '${lazy.PlacesUtils.bookmarks.tagsGuid}';

      /* Add a tag entry for the URL under the tag folder. Omitting the place
         ID creates a tag folder without tagging the URL. */
      INSERT OR IGNORE INTO moz_bookmarks(guid, parent, position, type, fk,
                                          dateAdded, lastModified)
      SELECT IFNULL((SELECT b.guid FROM moz_bookmarks b
                     JOIN moz_bookmarks p ON p.id = b.parent
                     WHERE b.fk = NEW.placeId AND
                           p.title = NEW.tag AND
                           p.parent = (SELECT id FROM moz_bookmarks
                                       WHERE guid = '${lazy.PlacesUtils.bookmarks.tagsGuid}')),
                    GENERATE_GUID()),
             (SELECT b.id FROM moz_bookmarks b
              JOIN moz_bookmarks p ON p.id = b.parent
              WHERE p.guid = '${lazy.PlacesUtils.bookmarks.tagsGuid}' AND
                    b.title = NEW.tag),
             (SELECT COUNT(*) FROM moz_bookmarks b
              JOIN moz_bookmarks p ON p.id = b.parent
              WHERE p.title = NEW.tag AND
                    p.parent = (SELECT id FROM moz_bookmarks
                                WHERE guid = '${lazy.PlacesUtils.bookmarks.tagsGuid}')),
             ${lazy.PlacesUtils.bookmarks.TYPE_BOOKMARK}, NEW.placeId,
             NEW.lastModifiedMicroseconds,
             NEW.lastModifiedMicroseconds
      WHERE NEW.placeId NOT NULL;

      /* Record an item added notification for the tag entry. */
      INSERT INTO itemsAdded(guid, isTagging)
      SELECT b.guid, 1
      FROM moz_bookmarks b
      JOIN moz_bookmarks p ON p.id = b.parent
      WHERE CHANGES() > 0 AND
            b.fk = NEW.placeId AND
            p.title = NEW.tag AND
            p.parent = (SELECT id FROM moz_bookmarks
                        WHERE guid = '${lazy.PlacesUtils.bookmarks.tagsGuid}');
    END`);

  // Stores properties to pass to `onItem{Added, Changed, Moved, Removed}`
  // bookmark observers for new, updated, moved, and deleted items.
  await db.execute(`CREATE TEMP TABLE itemsAdded(
    guid TEXT PRIMARY KEY,
    isTagging BOOLEAN NOT NULL DEFAULT 0,
    keywordChanged BOOLEAN NOT NULL DEFAULT 0,
    level INTEGER NOT NULL DEFAULT -1
  ) WITHOUT ROWID`);

  await db.execute(`CREATE INDEX addedItemLevels ON itemsAdded(level)`);

  await db.execute(`CREATE TEMP TABLE guidsChanged(
    itemId INTEGER PRIMARY KEY,
    oldGuid TEXT NOT NULL,
    level INTEGER NOT NULL DEFAULT -1
  )`);

  await db.execute(`CREATE INDEX changedGuidLevels ON guidsChanged(level)`);

  await db.execute(`CREATE TEMP TABLE itemsChanged(
    itemId INTEGER PRIMARY KEY,
    oldTitle TEXT,
    oldPlaceId INTEGER,
    keywordChanged BOOLEAN NOT NULL DEFAULT 0,
    level INTEGER NOT NULL DEFAULT -1
  )`);

  await db.execute(`CREATE INDEX changedItemLevels ON itemsChanged(level)`);

  await db.execute(`CREATE TEMP TABLE itemsMoved(
    itemId INTEGER PRIMARY KEY,
    oldParentId INTEGER NOT NULL,
    oldParentGuid TEXT NOT NULL,
    oldPosition INTEGER NOT NULL,
    level INTEGER NOT NULL DEFAULT -1
  )`);

  await db.execute(`CREATE INDEX movedItemLevels ON itemsMoved(level)`);

  await db.execute(`CREATE TEMP TABLE itemsRemoved(
    itemId INTEGER PRIMARY KEY,
    guid TEXT NOT NULL,
    parentId INTEGER NOT NULL,
    position INTEGER NOT NULL,
    type INTEGER NOT NULL,
    title TEXT NOT NULL,
    placeId INTEGER,
    parentGuid TEXT NOT NULL,
    /* We record the original level of the removed item in the tree so that we
       can notify children before parents. */
    level INTEGER NOT NULL DEFAULT -1,
    isUntagging BOOLEAN NOT NULL DEFAULT 0,
    keywordRemoved BOOLEAN NOT NULL DEFAULT 0
  )`);

  await db.execute(
    `CREATE INDEX removedItemLevels ON itemsRemoved(level DESC)`
  );

  // Stores locally changed items staged for upload.
  await db.execute(`CREATE TEMP TABLE itemsToUpload(
    id INTEGER PRIMARY KEY,
    guid TEXT UNIQUE NOT NULL,
    syncChangeCounter INTEGER NOT NULL,
    isDeleted BOOLEAN NOT NULL DEFAULT 0,
    parentGuid TEXT,
    parentTitle TEXT,
    dateAdded INTEGER, /* In milliseconds. */
    type INTEGER,
    title TEXT,
    placeId INTEGER,
    isQuery BOOLEAN NOT NULL DEFAULT 0,
    url TEXT,
    tagFolderName TEXT,
    keyword TEXT,
    position INTEGER
  )`);

  await db.execute(`CREATE TEMP TABLE structureToUpload(
    guid TEXT PRIMARY KEY,
    parentId INTEGER NOT NULL REFERENCES itemsToUpload(id)
                              ON DELETE CASCADE,
    position INTEGER NOT NULL
  ) WITHOUT ROWID`);

  await db.execute(
    `CREATE INDEX parentsToUpload ON structureToUpload(parentId, position)`
  );

  await db.execute(`CREATE TEMP TABLE tagsToUpload(
    id INTEGER REFERENCES itemsToUpload(id)
               ON DELETE CASCADE,
    tag TEXT,
    PRIMARY KEY(id, tag)
  ) WITHOUT ROWID`);
}

async function resetMirror(db) {
  await db.execute(`DELETE FROM meta`);
  await db.execute(`DELETE FROM structure`);
  await db.execute(`DELETE FROM items`);
  await db.execute(`DELETE FROM urls`);

  // Since we need to reset the modified times and merge flags for the syncable
  // roots, we simply delete and recreate them.
  await createMirrorRoots(db);
}

// Converts a Sync record's last modified time to milliseconds.
function determineServerModified(record) {
  return Math.max(record.modified * 1000, 0) || 0;
}

// Determines a Sync record's creation date.
function determineDateAdded(record) {
  let serverModified = determineServerModified(record);
  return lazy.PlacesSyncUtils.bookmarks.ratchetTimestampBackwards(
    record.dateAdded,
    serverModified
  );
}

function validateTitle(rawTitle) {
  if (typeof rawTitle != "string" || !rawTitle) {
    return null;
  }
  return rawTitle.slice(0, DB_TITLE_LENGTH_MAX);
}

function validateURL(rawURL) {
  if (typeof rawURL != "string" || rawURL.length > DB_URL_LENGTH_MAX) {
    return null;
  }
  let url = null;
  try {
    url = new URL(rawURL);
  } catch (ex) {}
  return url;
}

function validateKeyword(rawKeyword) {
  if (typeof rawKeyword != "string") {
    return null;
  }
  let keyword = rawKeyword.trim();
  // Drop empty keywords.
  return keyword ? keyword.toLowerCase() : null;
}

function validateTag(rawTag) {
  if (typeof rawTag != "string") {
    return null;
  }
  let tag = rawTag.trim();
  if (!tag || tag.length > lazy.PlacesUtils.bookmarks.MAX_TAG_LENGTH) {
    // Drop empty and oversized tags.
    return null;
  }
  return tag;
}

/**
 * Measures and logs the time taken to execute a function, using a monotonic
 * clock.
 *
 * @param  {String} name
 *         The name of the operation, used for logging.
 * @param  {Function} func
 *         The function to time.
 * @param  {Function} [recordTiming]
 *         An optional function with the signature `(time: Number)`, where
 *         `time` is the measured time.
 * @return The return value of the timed function.
 */
async function withTiming(name, func, recordTiming) {
  lazy.MirrorLog.debug(name);

  let startTime = Cu.now();
  let result = await func();
  let elapsedTime = Cu.now() - startTime;

  lazy.MirrorLog.debug(`${name} took ${elapsedTime.toFixed(3)}ms`);
  if (typeof recordTiming == "function") {
    recordTiming(elapsedTime, result);
  }

  return result;
}

/**
 * Fires bookmark and keyword observer notifications for all changes made during
 * the merge.
 */
class BookmarkObserverRecorder {
  constructor(db, { notifyInStableOrder, signal }) {
    this.db = db;
    this.notifyInStableOrder = notifyInStableOrder;
    this.signal = signal;
    this.placesEvents = [];
    this.shouldInvalidateKeywords = false;
  }

  /**
   * Fires observer notifications for all changed items, invalidates the
   * livemark cache if necessary, and recalculates frecencies for changed
   * URLs. This is called outside the merge transaction.
   */
  async notifyAll() {
    await this.noteAllChanges();
    if (this.shouldInvalidateKeywords) {
      await lazy.PlacesUtils.keywords.invalidateCachedKeywords();
    }
    this.notifyBookmarkObservers();
    if (this.signal.aborted) {
      throw new SyncedBookmarksMirror.InterruptedError(
        "Interrupted before recalculating frecencies for new URLs"
      );
    }
  }

  orderBy(level, parent, position) {
    return `ORDER BY ${
      this.notifyInStableOrder ? `${level}, ${parent}, ${position}` : level
    }`;
  }

  /**
   * Records Places observer notifications for removed, added, moved, and
   * changed items.
   */
  async noteAllChanges() {
    lazy.MirrorLog.trace("Recording observer notifications for removed items");
    // `ORDER BY v.level DESC` sorts deleted children before parents, to ensure
    // that we update caches in the correct order (bug 1297941).
    await this.db.execute(
      `SELECT v.itemId AS id, v.parentId, v.parentGuid, v.position, v.type,
              (SELECT h.url FROM moz_places h WHERE h.id = v.placeId) AS url,
              v.title, v.guid, v.isUntagging, v.keywordRemoved
       FROM itemsRemoved v
       ${this.orderBy("v.level", "v.parentId", "v.position")}`,
      null,
      (row, cancel) => {
        if (this.signal.aborted) {
          cancel();
          return;
        }
        let info = {
          id: row.getResultByName("id"),
          parentId: row.getResultByName("parentId"),
          position: row.getResultByName("position"),
          type: row.getResultByName("type"),
          urlHref: row.getResultByName("url"),
          title: row.getResultByName("title"),
          guid: row.getResultByName("guid"),
          parentGuid: row.getResultByName("parentGuid"),
          isUntagging: row.getResultByName("isUntagging"),
        };
        this.noteItemRemoved(info);
        if (row.getResultByName("keywordRemoved")) {
          this.shouldInvalidateKeywords = true;
        }
      }
    );
    if (this.signal.aborted) {
      throw new SyncedBookmarksMirror.InterruptedError(
        "Interrupted while recording observer notifications for removed items"
      );
    }

    lazy.MirrorLog.trace("Recording observer notifications for changed GUIDs");
    await this.db.execute(
      `SELECT b.id, b.lastModified, b.type, b.guid AS newGuid,
              p.guid AS parentGuid, gp.guid AS grandParentGuid
       FROM guidsChanged c
       JOIN moz_bookmarks b ON b.id = c.itemId
       JOIN moz_bookmarks p ON p.id = b.parent
       LEFT JOIN moz_bookmarks gp ON gp.id = p.parent
       ${this.orderBy("c.level", "b.parent", "b.position")}`,
      null,
      (row, cancel) => {
        if (this.signal.aborted) {
          cancel();
          return;
        }
        let info = {
          id: row.getResultByName("id"),
          lastModified: row.getResultByName("lastModified"),
          type: row.getResultByName("type"),
          newGuid: row.getResultByName("newGuid"),
          parentGuid: row.getResultByName("parentGuid"),
          grandParentGuid: row.getResultByName("grandParentGuid"),
        };
        this.noteGuidChanged(info);
      }
    );
    if (this.signal.aborted) {
      throw new SyncedBookmarksMirror.InterruptedError(
        "Interrupted while recording observer notifications for changed GUIDs"
      );
    }

    lazy.MirrorLog.trace("Recording observer notifications for new items");
    await this.db.execute(
      `SELECT b.id, p.id AS parentId, b.position, b.type,
              (SELECT h.url FROM moz_places h WHERE h.id = b.fk) AS url,
              IFNULL(b.title, '') AS title, b.dateAdded, b.guid,
              p.guid AS parentGuid, n.isTagging, n.keywordChanged
       FROM itemsAdded n
       JOIN moz_bookmarks b ON b.guid = n.guid
       JOIN moz_bookmarks p ON p.id = b.parent
       ${this.orderBy("n.level", "b.parent", "b.position")}`,
      null,
      (row, cancel) => {
        if (this.signal.aborted) {
          cancel();
          return;
        }
        let info = {
          id: row.getResultByName("id"),
          parentId: row.getResultByName("parentId"),
          position: row.getResultByName("position"),
          type: row.getResultByName("type"),
          urlHref: row.getResultByName("url"),
          title: row.getResultByName("title"),
          dateAdded: row.getResultByName("dateAdded"),
          guid: row.getResultByName("guid"),
          parentGuid: row.getResultByName("parentGuid"),
          isTagging: row.getResultByName("isTagging"),
        };
        this.noteItemAdded(info);
        if (row.getResultByName("keywordChanged")) {
          this.shouldInvalidateKeywords = true;
        }
      }
    );
    if (this.signal.aborted) {
      throw new SyncedBookmarksMirror.InterruptedError(
        "Interrupted while recording observer notifications for new items"
      );
    }

    lazy.MirrorLog.trace("Recording observer notifications for moved items");
    await this.db.execute(
      `SELECT b.id, b.guid, b.type, p.guid AS newParentGuid, c.oldParentGuid,
              b.position AS newPosition, c.oldPosition,
              gp.guid AS grandParentGuid,
              (SELECT h.url FROM moz_places h WHERE h.id = b.fk) AS url
       FROM itemsMoved c
       JOIN moz_bookmarks b ON b.id = c.itemId
       JOIN moz_bookmarks p ON p.id = b.parent
       LEFT JOIN moz_bookmarks gp ON gp.id = p.parent
       ${this.orderBy("c.level", "b.parent", "b.position")}`,
      null,
      (row, cancel) => {
        if (this.signal.aborted) {
          cancel();
          return;
        }
        let info = {
          id: row.getResultByName("id"),
          guid: row.getResultByName("guid"),
          type: row.getResultByName("type"),
          newParentGuid: row.getResultByName("newParentGuid"),
          oldParentGuid: row.getResultByName("oldParentGuid"),
          newPosition: row.getResultByName("newPosition"),
          oldPosition: row.getResultByName("oldPosition"),
          urlHref: row.getResultByName("url"),
          grandParentGuid: row.getResultByName("grandParentGuid"),
        };
        this.noteItemMoved(info);
      }
    );
    if (this.signal.aborted) {
      throw new SyncedBookmarksMirror.InterruptedError(
        "Interrupted while recording observer notifications for moved items"
      );
    }

    lazy.MirrorLog.trace("Recording observer notifications for changed items");
    await this.db.execute(
      `SELECT b.id, b.guid, b.lastModified, b.type,
              IFNULL(b.title, '') AS newTitle,
              IFNULL(c.oldTitle, '') AS oldTitle,
              (SELECT h.url FROM moz_places h
               WHERE h.id = b.fk) AS newURL,
              (SELECT h.url FROM moz_places h
               WHERE h.id = c.oldPlaceId) AS oldURL,
              p.id AS parentId, p.guid AS parentGuid,
              c.keywordChanged,
              gp.guid AS grandParentGuid,
              (SELECT h.url FROM moz_places h WHERE h.id = b.fk) AS url
       FROM itemsChanged c
       JOIN moz_bookmarks b ON b.id = c.itemId
       JOIN moz_bookmarks p ON p.id = b.parent
       LEFT JOIN moz_bookmarks gp ON gp.id = p.parent
       ${this.orderBy("c.level", "b.parent", "b.position")}`,
      null,
      (row, cancel) => {
        if (this.signal.aborted) {
          cancel();
          return;
        }
        let info = {
          id: row.getResultByName("id"),
          guid: row.getResultByName("guid"),
          lastModified: row.getResultByName("lastModified"),
          type: row.getResultByName("type"),
          newTitle: row.getResultByName("newTitle"),
          oldTitle: row.getResultByName("oldTitle"),
          newURLHref: row.getResultByName("newURL"),
          oldURLHref: row.getResultByName("oldURL"),
          parentId: row.getResultByName("parentId"),
          parentGuid: row.getResultByName("parentGuid"),
          grandParentGuid: row.getResultByName("grandParentGuid"),
        };
        this.noteItemChanged(info);
        if (row.getResultByName("keywordChanged")) {
          this.shouldInvalidateKeywords = true;
        }
      }
    );
    if (this.signal.aborted) {
      throw new SyncedBookmarksMirror.InterruptedError(
        "Interrupted while recording observer notifications for changed items"
      );
    }
  }

  noteItemAdded(info) {
    this.placesEvents.push(
      new PlacesBookmarkAddition({
        id: info.id,
        parentId: info.parentId,
        index: info.position,
        url: info.urlHref || "",
        title: info.title,
        // Note that both the database and the legacy `onItem{Moved, Removed,
        // Changed}` notifications use microsecond timestamps, but
        // `PlacesBookmarkAddition` uses milliseconds.
        dateAdded: info.dateAdded / 1000,
        guid: info.guid,
        parentGuid: info.parentGuid,
        source: lazy.PlacesUtils.bookmarks.SOURCES.SYNC,
        itemType: info.type,
        isTagging: info.isTagging,
      })
    );
  }

  noteGuidChanged(info) {
    lazy.PlacesUtils.invalidateCachedGuidFor(info.id);
    this.placesEvents.push(
      new PlacesBookmarkGuid({
        id: info.id,
        itemType: info.type,
        url: info.urlHref,
        guid: info.newGuid,
        parentGuid: info.parentGuid,
        lastModified: info.lastModified,
        source: lazy.PlacesUtils.bookmarks.SOURCES.SYNC,
        isTagging:
          info.parentGuid === lazy.PlacesUtils.bookmarks.tagsGuid ||
          info.grandParentGuid === lazy.PlacesUtils.bookmarks.tagsGuid,
      })
    );
  }

  noteItemMoved(info) {
    this.placesEvents.push(
      new PlacesBookmarkMoved({
        id: info.id,
        itemType: info.type,
        url: info.urlHref,
        guid: info.guid,
        parentGuid: info.newParentGuid,
        source: lazy.PlacesUtils.bookmarks.SOURCES.SYNC,
        index: info.newPosition,
        oldParentGuid: info.oldParentGuid,
        oldIndex: info.oldPosition,
        isTagging:
          info.newParentGuid === lazy.PlacesUtils.bookmarks.tagsGuid ||
          info.grandParentGuid === lazy.PlacesUtils.bookmarks.tagsGuid,
      })
    );
  }

  noteItemChanged(info) {
    if (info.oldTitle != info.newTitle) {
      this.placesEvents.push(
        new PlacesBookmarkTitle({
          id: info.id,
          itemType: info.type,
          url: info.urlHref,
          guid: info.guid,
          parentGuid: info.parentGuid,
          title: info.newTitle,
          lastModified: info.lastModified,
          source: lazy.PlacesUtils.bookmarks.SOURCES.SYNC,
          isTagging:
            info.parentGuid === lazy.PlacesUtils.bookmarks.tagsGuid ||
            info.grandParentGuid === lazy.PlacesUtils.bookmarks.tagsGuid,
        })
      );
    }
    if (info.oldURLHref != info.newURLHref) {
      this.placesEvents.push(
        new PlacesBookmarkUrl({
          id: info.id,
          itemType: info.type,
          url: info.newURLHref,
          guid: info.guid,
          parentGuid: info.parentGuid,
          lastModified: info.lastModified,
          source: lazy.PlacesUtils.bookmarks.SOURCES.SYNC,
          isTagging:
            info.parentGuid === lazy.PlacesUtils.bookmarks.tagsGuid ||
            info.grandParentGuid === lazy.PlacesUtils.bookmarks.tagsGuid,
        })
      );
    }
  }

  noteItemRemoved(info) {
    this.placesEvents.push(
      new PlacesBookmarkRemoved({
        id: info.id,
        parentId: info.parentId,
        index: info.position,
        url: info.urlHref || "",
        title: info.title,
        guid: info.guid,
        parentGuid: info.parentGuid,
        source: lazy.PlacesUtils.bookmarks.SOURCES.SYNC,
        itemType: info.type,
        isTagging: info.isUntagging,
        isDescendantRemoval: false,
      })
    );
  }

  notifyBookmarkObservers() {
    lazy.MirrorLog.trace("Notifying bookmark observers");

    if (this.placesEvents.length) {
      PlacesObservers.notifyListeners(this.placesEvents);
    }

    lazy.MirrorLog.trace("Notified bookmark observers");
  }
}

/**
 * Holds Sync metadata and the cleartext for a locally changed record. The
 * bookmarks engine inflates a Sync record from the cleartext, and updates the
 * `synced` property for successfully uploaded items.
 *
 * At the end of the sync, the engine writes the uploaded cleartext back to the
 * mirror, and passes the updated change record as part of the changeset to
 * `PlacesSyncUtils.bookmarks.pushChanges`.
 */
class BookmarkChangeRecord {
  constructor(syncChangeCounter, cleartext) {
    this.tombstone = cleartext.deleted === true;
    this.counter = syncChangeCounter;
    this.cleartext = cleartext;
    this.synced = false;
  }
}

function bagToNamedCounts(bag, names) {
  let counts = [];
  for (let name of names) {
    let count = bag.getProperty(name);
    if (count > 0) {
      counts.push({ name, count });
    }
  }
  return counts;
}

/**
 * Returns an `AbortSignal` that aborts if either `finalizeSignal` or
 * `interruptSignal` aborts. This is like `Promise.race`, but for
 * cancellations.
 *
 * @param  {AbortSignal} finalizeSignal
 * @param  {AbortSignal?} signal
 * @return {AbortSignal}
 */
function anyAborted(finalizeSignal, interruptSignal = null) {
  if (finalizeSignal.aborted || !interruptSignal) {
    // If the mirror was already finalized, or we don't have an interrupt
    // signal for this merge, just use the finalize signal.
    return finalizeSignal;
  }
  if (interruptSignal.aborted) {
    // If the merge was interrupted, return its already-aborted signal.
    return interruptSignal;
  }
  // Otherwise, we return a new signal that aborts if either the mirror is
  // finalized, or the merge is interrupted, whichever happens first.
  let controller = new AbortController();
  function onAbort() {
    finalizeSignal.removeEventListener("abort", onAbort);
    interruptSignal.removeEventListener("abort", onAbort);
    controller.abort();
  }
  finalizeSignal.addEventListener("abort", onAbort);
  interruptSignal.addEventListener("abort", onAbort);
  return controller.signal;
}

// In conclusion, this is why bookmark syncing is hard.