/* 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/. */

/* eslint-env mozilla/chrome-worker */

// This is a worker which reads offline heap snapshots into memory and performs
// heavyweight analyses on them without blocking the main thread. A
// HeapAnalysesWorker is owned and communicated with by a HeapAnalysesClient
// instance. See HeapAnalysesClient.js.

"use strict";

/* import-globals-from /toolkit/components/workerloader/require.js */
importScripts("resource://gre/modules/workers/require.js");
/* import-globals-from ../worker/helper.js */
importScripts("resource://devtools/shared/worker/helper.js");
const {
  censusReportToCensusTreeNode,
} = require("resource://devtools/shared/heapsnapshot/census-tree-node.js");
const DominatorTreeNode = require("resource://devtools/shared/heapsnapshot/DominatorTreeNode.js");
const CensusUtils = require("resource://devtools/shared/heapsnapshot/CensusUtils.js");

const DEFAULT_START_INDEX = 0;
const DEFAULT_MAX_COUNT = 50;

/**
 * The set of HeapSnapshot instances this worker has read into memory. Keyed by
 * snapshot file path.
 */
const snapshots = Object.create(null);

/**
 * The set of `DominatorTree`s that have been computed, mapped by their id (aka
 * the index into this array).
 *
 * @see /dom/webidl/DominatorTree.webidl
 */
const dominatorTrees = [];

/**
 * The i^th HeapSnapshot in this array is the snapshot used to generate the i^th
 * dominator tree in `dominatorTrees` above. This lets us map from a dominator
 * tree id to the snapshot it came from.
 */
const dominatorTreeSnapshots = [];

/**
 * @see HeapAnalysesClient.prototype.readHeapSnapshot
 */
workerHelper.createTask(self, "readHeapSnapshot", ({ snapshotFilePath }) => {
  snapshots[snapshotFilePath] = ChromeUtils.readHeapSnapshot(snapshotFilePath);
  return true;
});

/**
 * @see HeapAnalysesClient.prototype.deleteHeapSnapshot
 */
workerHelper.createTask(self, "deleteHeapSnapshot", ({ snapshotFilePath }) => {
  const snapshot = snapshots[snapshotFilePath];
  if (!snapshot) {
    throw new Error(`No known heap snapshot for '${snapshotFilePath}'`);
  }

  snapshots[snapshotFilePath] = undefined;

  const dominatorTreeId = dominatorTreeSnapshots.indexOf(snapshot);
  if (dominatorTreeId != -1) {
    dominatorTreeSnapshots[dominatorTreeId] = undefined;
    dominatorTrees[dominatorTreeId] = undefined;
  }
});

/**
 * @see HeapAnalysesClient.prototype.takeCensus
 */
workerHelper.createTask(
  self,
  "takeCensus",
  ({ snapshotFilePath, censusOptions, requestOptions }) => {
    if (!snapshots[snapshotFilePath]) {
      throw new Error(`No known heap snapshot for '${snapshotFilePath}'`);
    }

    let report = snapshots[snapshotFilePath].takeCensus(censusOptions);
    let parentMap;

    if (requestOptions.asTreeNode || requestOptions.asInvertedTreeNode) {
      const opts = { filter: requestOptions.filter || null };
      if (requestOptions.asInvertedTreeNode) {
        opts.invert = true;
      }
      report = censusReportToCensusTreeNode(
        censusOptions.breakdown,
        report,
        opts
      );
      parentMap = CensusUtils.createParentMap(report);
    }

    return { report, parentMap };
  }
);

/**
 * @see HeapAnalysesClient.prototype.getCensusIndividuals
 */
workerHelper.createTask(self, "getCensusIndividuals", request => {
  const {
    dominatorTreeId,
    indices,
    censusBreakdown,
    labelBreakdown,
    maxRetainingPaths,
    maxIndividuals,
  } = request;

  const dominatorTree = dominatorTrees[dominatorTreeId];
  if (!dominatorTree) {
    throw new Error(
      `There does not exist a DominatorTree with the id ${dominatorTreeId}`
    );
  }

  const snapshot = dominatorTreeSnapshots[dominatorTreeId];
  const nodeIds = CensusUtils.getCensusIndividuals(
    indices,
    censusBreakdown,
    snapshot
  );

  const nodes = nodeIds
    .sort(
      (a, b) =>
        dominatorTree.getRetainedSize(b) - dominatorTree.getRetainedSize(a)
    )
    .slice(0, maxIndividuals)
    .map(id => {
      const { label, shallowSize } = DominatorTreeNode.getLabelAndShallowSize(
        id,
        snapshot,
        labelBreakdown
      );
      const retainedSize = dominatorTree.getRetainedSize(id);
      const node = new DominatorTreeNode(id, label, shallowSize, retainedSize);
      node.moreChildrenAvailable = false;
      return node;
    });

  DominatorTreeNode.attachShortestPaths(
    snapshot,
    labelBreakdown,
    dominatorTree.root,
    nodes,
    maxRetainingPaths
  );

  return { nodes };
});

/**
 * @see HeapAnalysesClient.prototype.takeCensusDiff
 */
workerHelper.createTask(self, "takeCensusDiff", request => {
  const {
    firstSnapshotFilePath,
    secondSnapshotFilePath,
    censusOptions,
    requestOptions,
  } = request;

  if (!snapshots[firstSnapshotFilePath]) {
    throw new Error(`No known heap snapshot for '${firstSnapshotFilePath}'`);
  }

  if (!snapshots[secondSnapshotFilePath]) {
    throw new Error(`No known heap snapshot for '${secondSnapshotFilePath}'`);
  }

  const first = snapshots[firstSnapshotFilePath].takeCensus(censusOptions);
  const second = snapshots[secondSnapshotFilePath].takeCensus(censusOptions);
  let delta = CensusUtils.diff(censusOptions.breakdown, first, second);
  let parentMap;

  if (requestOptions.asTreeNode || requestOptions.asInvertedTreeNode) {
    const opts = { filter: requestOptions.filter || null };
    if (requestOptions.asInvertedTreeNode) {
      opts.invert = true;
    }
    delta = censusReportToCensusTreeNode(censusOptions.breakdown, delta, opts);
    parentMap = CensusUtils.createParentMap(delta);
  }

  return { delta, parentMap };
});

/**
 * @see HeapAnalysesClient.prototype.getCreationTime
 */
workerHelper.createTask(self, "getCreationTime", snapshotFilePath => {
  if (!snapshots[snapshotFilePath]) {
    throw new Error(`No known heap snapshot for '${snapshotFilePath}'`);
  }
  return snapshots[snapshotFilePath].creationTime;
});

/**
 * @see HeapAnalysesClient.prototype.computeDominatorTree
 */
workerHelper.createTask(self, "computeDominatorTree", snapshotFilePath => {
  const snapshot = snapshots[snapshotFilePath];
  if (!snapshot) {
    throw new Error(`No known heap snapshot for '${snapshotFilePath}'`);
  }

  const id = dominatorTrees.length;
  dominatorTrees.push(snapshot.computeDominatorTree());
  dominatorTreeSnapshots.push(snapshot);
  return id;
});

/**
 * @see HeapAnalysesClient.prototype.getDominatorTree
 */
workerHelper.createTask(self, "getDominatorTree", request => {
  const {
    dominatorTreeId,
    breakdown,
    maxDepth,
    maxSiblings,
    maxRetainingPaths,
  } = request;

  if (!(dominatorTreeId >= 0 && dominatorTreeId < dominatorTrees.length)) {
    throw new Error(
      `There does not exist a DominatorTree with the id ${dominatorTreeId}`
    );
  }

  const dominatorTree = dominatorTrees[dominatorTreeId];
  const snapshot = dominatorTreeSnapshots[dominatorTreeId];

  const tree = DominatorTreeNode.partialTraversal(
    dominatorTree,
    snapshot,
    breakdown,
    maxDepth,
    maxSiblings
  );

  const nodes = [];
  (function getNodes(node) {
    nodes.push(node);
    if (node.children) {
      for (let i = 0, length = node.children.length; i < length; i++) {
        getNodes(node.children[i]);
      }
    }
  })(tree);

  DominatorTreeNode.attachShortestPaths(
    snapshot,
    breakdown,
    dominatorTree.root,
    nodes,
    maxRetainingPaths
  );

  return tree;
});

/**
 * @see HeapAnalysesClient.prototype.getImmediatelyDominated
 */
workerHelper.createTask(self, "getImmediatelyDominated", request => {
  const {
    dominatorTreeId,
    nodeId,
    breakdown,
    startIndex,
    maxCount,
    maxRetainingPaths,
  } = request;

  if (!(dominatorTreeId >= 0 && dominatorTreeId < dominatorTrees.length)) {
    throw new Error(
      `There does not exist a DominatorTree with the id ${dominatorTreeId}`
    );
  }

  const dominatorTree = dominatorTrees[dominatorTreeId];
  const snapshot = dominatorTreeSnapshots[dominatorTreeId];

  const childIds = dominatorTree.getImmediatelyDominated(nodeId);
  if (!childIds) {
    throw new Error(`${nodeId} is not a node id in the dominator tree`);
  }

  const start = startIndex || DEFAULT_START_INDEX;
  const count = maxCount || DEFAULT_MAX_COUNT;
  const end = start + count;

  const nodes = childIds.slice(start, end).map(id => {
    const { label, shallowSize } = DominatorTreeNode.getLabelAndShallowSize(
      id,
      snapshot,
      breakdown
    );
    const retainedSize = dominatorTree.getRetainedSize(id);
    const node = new DominatorTreeNode(id, label, shallowSize, retainedSize);
    node.parentId = nodeId;
    // DominatorTree.getImmediatelyDominated will always return non-null here
    // because we got the id directly from the dominator tree.
    node.moreChildrenAvailable = !!dominatorTree.getImmediatelyDominated(id)
      .length;
    return node;
  });

  const path = [];
  let id = nodeId;
  do {
    path.push(id);
    id = dominatorTree.getImmediateDominator(id);
  } while (id !== null);
  path.reverse();

  const moreChildrenAvailable = childIds.length > end;

  DominatorTreeNode.attachShortestPaths(
    snapshot,
    breakdown,
    dominatorTree.root,
    nodes,
    maxRetainingPaths
  );

  return { nodes, moreChildrenAvailable, path };
});