Adding upstream version 115.7.0esr.upstream/115.7.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

7 files changed, 2519 insertions, 0 deletions

diff --git a/browser/components/urlbar/private/AddonSuggestions.sys.mjs b/browser/components/urlbar/private/AddonSuggestions.sys.mjs
new file mode 100644
index 0000000000..7232ad99f8
--- /dev/null
+++ b/browser/components/urlbar/private/AddonSuggestions.sys.mjs
@@ -0,0 +1,424 @@
+/* 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/. */
+
+import { BaseFeature } from "resource:///modules/urlbar/private/BaseFeature.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  AddonManager: "resource://gre/modules/AddonManager.sys.mjs",
+  QuickSuggest: "resource:///modules/QuickSuggest.sys.mjs",
+  QuickSuggestRemoteSettings:
+    "resource:///modules/urlbar/private/QuickSuggestRemoteSettings.sys.mjs",
+  SuggestionsMap:
+    "resource:///modules/urlbar/private/QuickSuggestRemoteSettings.sys.mjs",
+  UrlbarPrefs: "resource:///modules/UrlbarPrefs.sys.mjs",
+  UrlbarResult: "resource:///modules/UrlbarResult.sys.mjs",
+  UrlbarUtils: "resource:///modules/UrlbarUtils.sys.mjs",
+  UrlbarView: "resource:///modules/UrlbarView.sys.mjs",
+});
+
+const VIEW_TEMPLATE = {
+  attributes: {
+    selectable: true,
+  },
+  children: [
+    {
+      name: "content",
+      tag: "span",
+      overflowable: true,
+      children: [
+        {
+          name: "icon",
+          tag: "img",
+        },
+        {
+          name: "header",
+          tag: "span",
+          children: [
+            {
+              name: "title",
+              tag: "span",
+              classList: ["urlbarView-title"],
+            },
+            {
+              name: "separator",
+              tag: "span",
+              classList: ["urlbarView-title-separator"],
+            },
+            {
+              name: "url",
+              tag: "span",
+              classList: ["urlbarView-url"],
+            },
+          ],
+        },
+        {
+          name: "description",
+          tag: "span",
+        },
+        {
+          name: "footer",
+          tag: "span",
+          children: [
+            {
+              name: "ratingContainer",
+              tag: "span",
+              children: [
+                {
+                  classList: ["urlbarView-dynamic-addons-rating"],
+                  name: "rating0",
+                  tag: "span",
+                },
+                {
+                  classList: ["urlbarView-dynamic-addons-rating"],
+                  name: "rating1",
+                  tag: "span",
+                },
+                {
+                  classList: ["urlbarView-dynamic-addons-rating"],
+                  name: "rating2",
+                  tag: "span",
+                },
+                {
+                  classList: ["urlbarView-dynamic-addons-rating"],
+                  name: "rating3",
+                  tag: "span",
+                },
+                {
+                  classList: ["urlbarView-dynamic-addons-rating"],
+                  name: "rating4",
+                  tag: "span",
+                },
+              ],
+            },
+            {
+              name: "reviews",
+              tag: "span",
+            },
+          ],
+        },
+      ],
+    },
+  ],
+};
+
+const RESULT_MENU_COMMAND = {
+  HELP: "help",
+  NOT_INTERESTED: "not_interested",
+  NOT_RELEVANT: "not_relevant",
+  SHOW_LESS_FREQUENTLY: "show_less_frequently",
+};
+
+/**
+ * A feature that supports Addon suggestions.
+ */
+export class AddonSuggestions extends BaseFeature {
+  constructor() {
+    super();
+    lazy.UrlbarResult.addDynamicResultType("addons");
+    lazy.UrlbarView.addDynamicViewTemplate("addons", VIEW_TEMPLATE);
+  }
+
+  get shouldEnable() {
+    return (
+      lazy.UrlbarPrefs.get("addonsFeatureGate") &&
+      lazy.UrlbarPrefs.get("suggest.addons") &&
+      lazy.UrlbarPrefs.get("suggest.quicksuggest.nonsponsored")
+    );
+  }
+
+  get enablingPreferences() {
+    return ["suggest.addons", "suggest.quicksuggest.nonsponsored"];
+  }
+
+  enable(enabled) {
+    if (enabled) {
+      lazy.QuickSuggestRemoteSettings.register(this);
+    } else {
+      lazy.QuickSuggestRemoteSettings.unregister(this);
+    }
+  }
+
+  queryRemoteSettings(searchString) {
+    const suggestions = this.#suggestionsMap?.get(searchString);
+    if (!suggestions) {
+      return [];
+    }
+
+    return suggestions.map(suggestion => ({
+      icon: suggestion.icon,
+      url: suggestion.url,
+      title: suggestion.title,
+      description: suggestion.description,
+      rating: suggestion.rating,
+      number_of_ratings: suggestion.number_of_ratings,
+      guid: suggestion.guid,
+      score: suggestion.score,
+      is_top_pick: suggestion.is_top_pick,
+    }));
+  }
+
+  async onRemoteSettingsSync(rs) {
+    const records = await rs.get({ filters: { type: "amo-suggestions" } });
+    if (rs != lazy.QuickSuggestRemoteSettings.rs) {
+      return;
+    }
+
+    const suggestionsMap = new lazy.SuggestionsMap();
+
+    for (const record of records) {
+      const { buffer } = await rs.attachments.download(record);
+      if (rs != lazy.QuickSuggestRemoteSettings.rs) {
+        return;
+      }
+
+      const results = JSON.parse(new TextDecoder("utf-8").decode(buffer));
+
+      // The keywords in remote settings are full keywords. Map each one to an
+      // array containing the full keyword's first word plus every subsequent
+      // prefix of the full keyword.
+      await suggestionsMap.add(results, fullKeyword => {
+        let keywords = [fullKeyword];
+        let spaceIndex = fullKeyword.search(/\s/);
+        if (spaceIndex >= 0) {
+          for (let i = spaceIndex; i < fullKeyword.length; i++) {
+            keywords.push(fullKeyword.substring(0, i));
+          }
+        }
+        return keywords;
+      });
+      if (rs != lazy.QuickSuggestRemoteSettings.rs) {
+        return;
+      }
+    }
+
+    this.#suggestionsMap = suggestionsMap;
+  }
+
+  async makeResult(queryContext, suggestion, searchString) {
+    if (!this.isEnabled) {
+      // The feature is disabled on the client, but Merino may still return
+      // addon suggestions anyway, and we filter them out here.
+      return null;
+    }
+
+    // If the user hasn't clicked the "Show less frequently" command, the
+    // suggestion can be shown. Otherwise, the suggestion can be shown if the
+    // user typed more than one word with at least `showLessFrequentlyCount`
+    // characters after the first word, including spaces.
+    if (this.showLessFrequentlyCount) {
+      let spaceIndex = searchString.search(/\s/);
+      if (
+        spaceIndex < 0 ||
+        searchString.length - spaceIndex < this.showLessFrequentlyCount
+      ) {
+        return null;
+      }
+    }
+
+    // If is_top_pick is not specified, handle it as top pick suggestion.
+    suggestion.is_top_pick = suggestion.is_top_pick ?? true;
+
+    const { guid, rating, number_of_ratings } =
+      suggestion.source === "remote-settings"
+        ? suggestion
+        : suggestion.custom_details.amo;
+
+    const addon = await lazy.AddonManager.getAddonByID(guid);
+    if (addon) {
+      // Addon suggested is already installed.
+      return null;
+    }
+
+    const payload = {
+      source: suggestion.source,
+      icon: suggestion.icon,
+      url: suggestion.url,
+      title: suggestion.title,
+      description: suggestion.description,
+      rating: Number(rating),
+      reviews: Number(number_of_ratings),
+      helpUrl: lazy.QuickSuggest.HELP_URL,
+      shouldNavigate: true,
+      dynamicType: "addons",
+      telemetryType: "amo",
+    };
+
+    return Object.assign(
+      new lazy.UrlbarResult(
+        lazy.UrlbarUtils.RESULT_TYPE.DYNAMIC,
+        lazy.UrlbarUtils.RESULT_SOURCE.SEARCH,
+        ...lazy.UrlbarResult.payloadAndSimpleHighlights(
+          queryContext.tokens,
+          payload
+        )
+      ),
+      { showFeedbackMenu: true }
+    );
+  }
+
+  getViewUpdate(result) {
+    const treatment = lazy.UrlbarPrefs.get("addonsUITreatment");
+    const rating = result.payload.rating;
+
+    return {
+      content: {
+        attributes: { treatment },
+      },
+      icon: {
+        attributes: {
+          src: result.payload.icon,
+        },
+      },
+      url: {
+        textContent: result.payload.url,
+      },
+      title: {
+        textContent: result.payload.title,
+      },
+      description: {
+        textContent: result.payload.description,
+      },
+      rating0: {
+        attributes: {
+          fill: this.#getRatingStar(0, rating),
+        },
+      },
+      rating1: {
+        attributes: {
+          fill: this.#getRatingStar(1, rating),
+        },
+      },
+      rating2: {
+        attributes: {
+          fill: this.#getRatingStar(2, rating),
+        },
+      },
+      rating3: {
+        attributes: {
+          fill: this.#getRatingStar(3, rating),
+        },
+      },
+      rating4: {
+        attributes: {
+          fill: this.#getRatingStar(4, rating),
+        },
+      },
+      reviews: {
+        l10n:
+          treatment === "b"
+            ? { id: "firefox-suggest-addons-recommended" }
+            : {
+                id: "firefox-suggest-addons-reviews",
+                args: {
+                  quantity: result.payload.reviews,
+                },
+              },
+      },
+    };
+  }
+
+  getResultCommands(result) {
+    const commands = [];
+
+    if (this.canShowLessFrequently) {
+      commands.push({
+        name: RESULT_MENU_COMMAND.SHOW_LESS_FREQUENTLY,
+        l10n: {
+          id: "firefox-suggest-command-show-less-frequently",
+        },
+      });
+    }
+
+    commands.push(
+      {
+        l10n: {
+          id: "firefox-suggest-command-dont-show-this",
+        },
+        children: [
+          {
+            name: RESULT_MENU_COMMAND.NOT_RELEVANT,
+            l10n: {
+              id: "firefox-suggest-command-not-relevant",
+            },
+          },
+          {
+            name: RESULT_MENU_COMMAND.NOT_INTERESTED,
+            l10n: {
+              id: "firefox-suggest-command-not-interested",
+            },
+          },
+        ],
+      },
+      { name: "separator" },
+      {
+        name: RESULT_MENU_COMMAND.HELP,
+        l10n: {
+          id: "urlbar-result-menu-learn-more-about-firefox-suggest",
+        },
+      }
+    );
+
+    return commands;
+  }
+
+  handlePossibleCommand(queryContext, result, selType) {
+    switch (selType) {
+      case RESULT_MENU_COMMAND.HELP:
+        // "help" is handled by UrlbarInput, no need to do anything here.
+        break;
+      // selType == "dismiss" when the user presses the dismiss key shortcut.
+      case "dismiss":
+      case RESULT_MENU_COMMAND.NOT_INTERESTED:
+      case RESULT_MENU_COMMAND.NOT_RELEVANT:
+        lazy.UrlbarPrefs.set("suggest.addons", false);
+        queryContext.view.acknowledgeDismissal(result);
+        break;
+      case RESULT_MENU_COMMAND.SHOW_LESS_FREQUENTLY:
+        queryContext.view.acknowledgeFeedback(result);
+        this.incrementShowLessFrequentlyCount();
+        break;
+    }
+  }
+
+  #getRatingStar(nth, rating) {
+    // 0    <= x <  0.25 = empty
+    // 0.25 <= x <  0.75 = half
+    // 0.75 <= x <= 1    = full
+    // ... et cetera, until x <= 5.
+    const distanceToFull = rating - nth;
+    if (distanceToFull < 0.25) {
+      return "empty";
+    }
+    if (distanceToFull < 0.75) {
+      return "half";
+    }
+    return "full";
+  }
+
+  incrementShowLessFrequentlyCount() {
+    if (this.canShowLessFrequently) {
+      lazy.UrlbarPrefs.set(
+        "addons.showLessFrequentlyCount",
+        this.showLessFrequentlyCount + 1
+      );
+    }
+  }
+
+  get showLessFrequentlyCount() {
+    const count = lazy.UrlbarPrefs.get("addons.showLessFrequentlyCount") || 0;
+    return Math.max(count, 0);
+  }
+
+  get canShowLessFrequently() {
+    const cap =
+      lazy.UrlbarPrefs.get("addonsShowLessFrequentlyCap") ||
+      lazy.QuickSuggestRemoteSettings.config.show_less_frequently_cap ||
+      0;
+    return !cap || this.showLessFrequentlyCount < cap;
+  }
+
+  #suggestionsMap = null;
+}
diff --git a/browser/components/urlbar/private/AdmWikipedia.sys.mjs b/browser/components/urlbar/private/AdmWikipedia.sys.mjs
new file mode 100644
index 0000000000..4393ae317f
--- /dev/null
+++ b/browser/components/urlbar/private/AdmWikipedia.sys.mjs
@@ -0,0 +1,280 @@
+/* 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/. */
+
+import { BaseFeature } from "resource:///modules/urlbar/private/BaseFeature.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  QuickSuggest: "resource:///modules/QuickSuggest.sys.mjs",
+  QuickSuggestRemoteSettings:
+    "resource:///modules/urlbar/private/QuickSuggestRemoteSettings.sys.mjs",
+  SuggestionsMap:
+    "resource:///modules/urlbar/private/QuickSuggestRemoteSettings.sys.mjs",
+  UrlbarPrefs: "resource:///modules/UrlbarPrefs.sys.mjs",
+  UrlbarResult: "resource:///modules/UrlbarResult.sys.mjs",
+  UrlbarUtils: "resource:///modules/UrlbarUtils.sys.mjs",
+});
+
+const NONSPONSORED_IAB_CATEGORIES = new Set(["5 - Education"]);
+
+/**
+ * A feature that manages sponsored adM and non-sponsored Wikpedia (sometimes
+ * called "expanded Wikipedia") suggestions in remote settings.
+ */
+export class AdmWikipedia extends BaseFeature {
+  constructor() {
+    super();
+    this.#suggestionsMap = new lazy.SuggestionsMap();
+  }
+
+  get shouldEnable() {
+    return (
+      lazy.UrlbarPrefs.get("quickSuggestRemoteSettingsEnabled") &&
+      (lazy.UrlbarPrefs.get("suggest.quicksuggest.nonsponsored") ||
+        lazy.UrlbarPrefs.get("suggest.quicksuggest.sponsored"))
+    );
+  }
+
+  get enablingPreferences() {
+    return [
+      "suggest.quicksuggest.nonsponsored",
+      "suggest.quicksuggest.sponsored",
+    ];
+  }
+
+  enable(enabled) {
+    if (enabled) {
+      lazy.QuickSuggestRemoteSettings.register(this);
+    } else {
+      lazy.QuickSuggestRemoteSettings.unregister(this);
+    }
+  }
+
+  async queryRemoteSettings(searchString) {
+    let suggestions = this.#suggestionsMap.get(searchString);
+    if (!suggestions) {
+      return [];
+    }
+
+    // Start each icon fetch at the same time and wait for them all to finish.
+    let icons = await Promise.all(
+      suggestions.map(({ icon }) => this.#fetchIcon(icon))
+    );
+
+    return suggestions.map(suggestion => ({
+      full_keyword: this.#getFullKeyword(searchString, suggestion.keywords),
+      title: suggestion.title,
+      url: suggestion.url,
+      click_url: suggestion.click_url,
+      impression_url: suggestion.impression_url,
+      block_id: suggestion.id,
+      advertiser: suggestion.advertiser,
+      iab_category: suggestion.iab_category,
+      is_sponsored: !NONSPONSORED_IAB_CATEGORIES.has(suggestion.iab_category),
+      score: suggestion.score,
+      position: suggestion.position,
+      icon: icons.shift(),
+    }));
+  }
+
+  async onRemoteSettingsSync(rs) {
+    let dataType = lazy.UrlbarPrefs.get("quickSuggestRemoteSettingsDataType");
+    this.logger.debug("Loading remote settings with type: " + dataType);
+
+    let [data] = await Promise.all([
+      rs.get({ filters: { type: dataType } }),
+      rs
+        .get({ filters: { type: "icon" } })
+        .then(icons =>
+          Promise.all(icons.map(i => rs.attachments.downloadToDisk(i)))
+        ),
+    ]);
+    if (rs != lazy.QuickSuggestRemoteSettings.rs) {
+      return;
+    }
+
+    let suggestionsMap = new lazy.SuggestionsMap();
+
+    this.logger.debug(`Got data with ${data.length} records`);
+    for (let record of data) {
+      let { buffer } = await rs.attachments.download(record);
+      if (rs != lazy.QuickSuggestRemoteSettings.rs) {
+        return;
+      }
+
+      let results = JSON.parse(new TextDecoder("utf-8").decode(buffer));
+      this.logger.debug(`Adding ${results.length} results`);
+      await suggestionsMap.add(results);
+      if (rs != lazy.QuickSuggestRemoteSettings.rs) {
+        return;
+      }
+    }
+
+    this.#suggestionsMap = suggestionsMap;
+  }
+
+  makeResult(queryContext, suggestion, searchString) {
+    // Replace the suggestion's template substrings, but first save the original
+    // URL before its timestamp template is replaced.
+    let originalUrl = suggestion.url;
+    lazy.QuickSuggest.replaceSuggestionTemplates(suggestion);
+
+    let payload = {
+      originalUrl,
+      url: suggestion.url,
+      icon: suggestion.icon,
+      isSponsored: suggestion.is_sponsored,
+      source: suggestion.source,
+      telemetryType: suggestion.is_sponsored
+        ? "adm_sponsored"
+        : "adm_nonsponsored",
+      requestId: suggestion.request_id,
+      urlTimestampIndex: suggestion.urlTimestampIndex,
+      sponsoredImpressionUrl: suggestion.impression_url,
+      sponsoredClickUrl: suggestion.click_url,
+      sponsoredBlockId: suggestion.block_id,
+      sponsoredAdvertiser: suggestion.advertiser,
+      sponsoredIabCategory: suggestion.iab_category,
+      helpUrl: lazy.QuickSuggest.HELP_URL,
+      helpL10n: {
+        id: "urlbar-result-menu-learn-more-about-firefox-suggest",
+      },
+      blockL10n: {
+        id: "urlbar-result-menu-dismiss-firefox-suggest",
+      },
+    };
+
+    // Determine if the suggestion itself is a best match.
+    let isSuggestionBestMatch = false;
+    if (lazy.QuickSuggestRemoteSettings.config.best_match) {
+      let { best_match } = lazy.QuickSuggestRemoteSettings.config;
+      isSuggestionBestMatch =
+        best_match.min_search_string_length <= searchString.length &&
+        !best_match.blocked_suggestion_ids.includes(suggestion.block_id);
+    }
+
+    // Determine if the urlbar result should be a best match.
+    let isResultBestMatch =
+      isSuggestionBestMatch &&
+      lazy.UrlbarPrefs.get("bestMatchEnabled") &&
+      lazy.UrlbarPrefs.get("suggest.bestmatch");
+    if (isResultBestMatch) {
+      // Show the result as a best match. Best match titles don't include the
+      // `full_keyword`, and the user's search string is highlighted.
+      payload.title = [suggestion.title, lazy.UrlbarUtils.HIGHLIGHT.TYPED];
+    } else {
+      // Show the result as a usual quick suggest. Include the `full_keyword`
+      // and highlight the parts that aren't in the search string.
+      payload.title = suggestion.title;
+      payload.qsSuggestion = [
+        suggestion.full_keyword,
+        lazy.UrlbarUtils.HIGHLIGHT.SUGGESTED,
+      ];
+    }
+    payload.isBlockable = lazy.UrlbarPrefs.get(
+      isResultBestMatch
+        ? "bestMatchBlockingEnabled"
+        : "quickSuggestBlockingEnabled"
+    );
+
+    let result = new lazy.UrlbarResult(
+      lazy.UrlbarUtils.RESULT_TYPE.URL,
+      lazy.UrlbarUtils.RESULT_SOURCE.SEARCH,
+      ...lazy.UrlbarResult.payloadAndSimpleHighlights(
+        queryContext.tokens,
+        payload
+      )
+    );
+
+    if (isResultBestMatch) {
+      result.isBestMatch = true;
+      result.suggestedIndex = 1;
+    }
+
+    return result;
+  }
+
+  /**
+   * Gets the "full keyword" (i.e., suggestion) for a query from a list of
+   * keywords. The suggestions data doesn't include full keywords, so we make
+   * our own based on the result's keyword phrases and a particular query. We
+   * use two heuristics:
+   *
+   * (1) Find the first keyword phrase that has more words than the query. Use
+   *     its first `queryWords.length` words as the full keyword. e.g., if the
+   *     query is "moz" and `keywords` is ["moz", "mozi", "mozil", "mozill",
+   *     "mozilla", "mozilla firefox"], pick "mozilla firefox", pop off the
+   *     "firefox" and use "mozilla" as the full keyword.
+   * (2) If there isn't any keyword phrase with more words, then pick the
+   *     longest phrase. e.g., pick "mozilla" in the previous example (assuming
+   *     the "mozilla firefox" phrase isn't there). That might be the query
+   *     itself.
+   *
+   * @param {string} query
+   *   The query string.
+   * @param {Array} keywords
+   *   An array of suggestion keywords.
+   * @returns {string}
+   *   The full keyword.
+   */
+  #getFullKeyword(query, keywords) {
+    let longerPhrase;
+    let trimmedQuery = query.toLocaleLowerCase().trim();
+    let queryWords = trimmedQuery.split(" ");
+
+    for (let phrase of keywords) {
+      if (phrase.startsWith(query)) {
+        let trimmedPhrase = phrase.trim();
+        let phraseWords = trimmedPhrase.split(" ");
+        // As an exception to (1), if the query ends with a space, then look for
+        // phrases with one more word so that the suggestion includes a word
+        // following the space.
+        let extra = query.endsWith(" ") ? 1 : 0;
+        let len = queryWords.length + extra;
+        if (len < phraseWords.length) {
+          // We found a phrase with more words.
+          return phraseWords.slice(0, len).join(" ");
+        }
+        if (
+          query.length < phrase.length &&
+          (!longerPhrase || longerPhrase.length < trimmedPhrase.length)
+        ) {
+          // We found a longer phrase with the same number of words.
+          longerPhrase = trimmedPhrase;
+        }
+      }
+    }
+    return longerPhrase || trimmedQuery;
+  }
+
+  /**
+   * Fetch the icon from RemoteSettings attachments.
+   *
+   * @param {string} path
+   *   The icon's remote settings path.
+   */
+  async #fetchIcon(path) {
+    if (!path) {
+      return null;
+    }
+
+    let { rs } = lazy.QuickSuggestRemoteSettings;
+    if (!rs) {
+      return null;
+    }
+
+    let record = (
+      await rs.get({
+        filters: { id: `icon-${path}` },
+      })
+    ).pop();
+    if (!record) {
+      return null;
+    }
+    return rs.attachments.downloadToDisk(record);
+  }
+
+  #suggestionsMap;
+}
diff --git a/browser/components/urlbar/private/BaseFeature.sys.mjs b/browser/components/urlbar/private/BaseFeature.sys.mjs
new file mode 100644
index 0000000000..4893ffdf1c
--- /dev/null
+++ b/browser/components/urlbar/private/BaseFeature.sys.mjs
@@ -0,0 +1,168 @@
+/* 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/. */
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  UrlbarPrefs: "resource:///modules/UrlbarPrefs.sys.mjs",
+  UrlbarUtils: "resource:///modules/UrlbarUtils.sys.mjs",
+});
+
+/**
+ * Base class for quick suggest features. It can be extended to implement a
+ * feature that is part of the larger quick suggest feature and that should be
+ * enabled only when quick suggest is enabled.
+ *
+ * You can extend this class as an alternative to implementing your feature
+ * directly in `QuickSuggest`. Doing so has the following advantages:
+ *
+ * - If your feature is gated on a Nimbus variable or preference, `QuickSuggest`
+ *   will manage its lifetime automatically. This is really only useful if the
+ *   feature has state that must be initialized when the feature is enabled and
+ *   uninitialized when it's disabled.
+ *
+ * - Encapsulation. You can keep all the code related to your feature in one
+ *   place, without mixing it with unrelated code and cluttering up
+ *   `QuickSuggest`. You can also test it in isolation from `QuickSuggest`.
+ *
+ * - Remote settings management. You can register your feature with
+ *   `QuickSuggestRemoteSettings` and it will be called at appropriate times to
+ *   sync from remote settings.
+ *
+ * - If your feature also serves suggestions from remote settings, you can
+ *   implement one method, `queryRemoteSettings()`, to hook into
+ *   `UrlbarProviderQuickSuggest`.
+ *
+ * - Your feature will automatically get its own logger.
+ *
+ * To register your subclass with `QuickSuggest`, add it to the `FEATURES` const
+ * in QuickSuggest.sys.mjs.
+ */
+export class BaseFeature {
+  /**
+   * {boolean}
+   *   Whether the feature should be enabled. Typically the subclass will check
+   *   the values of one or more Nimbus variables or preferences. `QuickSuggest`
+   *   will access this getter only when the quick suggest feature as a whole is
+   *   enabled. Otherwise the subclass feature will be disabled automatically.
+   */
+  get shouldEnable() {
+    throw new Error("`shouldEnable` must be overridden");
+  }
+
+  /**
+   * @returns {Array}
+   *   If the subclass's `shouldEnable` implementation depends on preferences
+   *   instead of Nimbus variables, the subclass should override this getter and
+   *   return their names in this array so that `enable()` can be called when
+   *   they change. Names should be in the same format that `UrlbarPrefs.get()`
+   *   expects.
+   */
+  get enablingPreferences() {
+    return null;
+  }
+
+  /**
+   * This method should initialize or uninitialize any state related to the
+   * feature.
+   *
+   * @param {boolean} enabled
+   *   Whether the feature should be enabled or not.
+   */
+  enable(enabled) {}
+
+  /**
+   * If the feature manages suggestions from remote settings that should be
+   * returned by UrlbarProviderQuickSuggest, the subclass should override this
+   * method. It should return remote settings suggestions matching the given
+   * search string.
+   *
+   * @param {string} searchString
+   *   The search string.
+   * @returns {Array}
+   *   An array of matching suggestions, or null if not implemented.
+   */
+  async queryRemoteSettings(searchString) {
+    return null;
+  }
+
+  /**
+   * If the feature manages data in remote settings, the subclass should
+   * override this method. It should fetch the data and build whatever data
+   * structures are necessary to support the feature.
+   *
+   * @param {RemoteSettings} rs
+   *   The `RemoteSettings` client object.
+   */
+  async onRemoteSettingsSync(rs) {}
+
+  /**
+   * If the feature corresponds to a type of suggestion, the subclass should
+   * override this method. It should return a new `UrlbarResult` for a given
+   * suggestion, which can come from either remote settings or Merino.
+   *
+   * @param {UrlbarQueryContext} queryContext
+   *   The query context.
+   * @param {object} suggestion
+   *   The suggestion from either remote settings or Merino.
+   * @param {string} searchString
+   *   The search string that was used to fetch the suggestion. It may be
+   *   different from `queryContext.searchString` due to trimming, lower-casing,
+   *   etc. This is included as a param in case it's useful.
+   * @returns {UrlbarResult}
+   *   A new result for the suggestion.
+   */
+  async makeResult(queryContext, suggestion, searchString) {
+    return null;
+  }
+
+  // Methods not designed for overriding below
+
+  /**
+   * @returns {Logger}
+   *   The feature's logger.
+   */
+  get logger() {
+    if (!this._logger) {
+      this._logger = lazy.UrlbarUtils.getLogger({
+        prefix: `QuickSuggest.${this.name}`,
+      });
+    }
+    return this._logger;
+  }
+
+  /**
+   * @returns {boolean}
+   *   Whether the feature is enabled. The enabled status is automatically
+   *   managed by `QuickSuggest` and subclasses should not override this.
+   */
+  get isEnabled() {
+    return this.#isEnabled;
+  }
+
+  /**
+   * @returns {string}
+   *   The feature's name.
+   */
+  get name() {
+    return this.constructor.name;
+  }
+
+  /**
+   * Enables or disables the feature according to `shouldEnable` and whether
+   * quick suggest is enabled. If the feature is already enabled appropriately,
+   * does nothing.
+   */
+  update() {
+    let enable =
+      lazy.UrlbarPrefs.get("quickSuggestEnabled") && this.shouldEnable;
+    if (enable != this.isEnabled) {
+      this.logger.info(`Setting enabled = ${enable}`);
+      this.enable(enable);
+      this.#isEnabled = enable;
+    }
+  }
+
+  #isEnabled = false;
+}
diff --git a/browser/components/urlbar/private/BlockedSuggestions.sys.mjs b/browser/components/urlbar/private/BlockedSuggestions.sys.mjs
new file mode 100644
index 0000000000..d74a0979d1
--- /dev/null
+++ b/browser/components/urlbar/private/BlockedSuggestions.sys.mjs
@@ -0,0 +1,187 @@
+/* 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/. */
+
+import { BaseFeature } from "resource:///modules/urlbar/private/BaseFeature.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  TaskQueue: "resource:///modules/UrlbarUtils.sys.mjs",
+  UrlbarPrefs: "resource:///modules/UrlbarPrefs.sys.mjs",
+});
+
+/**
+ * A set of blocked suggestions for quick suggest.
+ */
+export class BlockedSuggestions extends BaseFeature {
+  constructor() {
+    super();
+    this.#taskQueue = new lazy.TaskQueue();
+    lazy.UrlbarPrefs.addObserver(this);
+  }
+
+  get shouldEnable() {
+    // Return true so that we'll always load blocked digests when quick suggest
+    // is enabled, even if blocking new suggestions is currently disabled.
+    // Blocking may have been enabled previously, and blocked suggestions should
+    // remain blocked as long as quick suggest as a whole remains enabled.
+    return true;
+  }
+
+  enable(enabled) {
+    if (enabled) {
+      this.#loadDigests();
+    }
+  }
+
+  /**
+   * Blocks a suggestion.
+   *
+   * @param {string} originalUrl
+   *   The suggestion's original URL with its unreplaced timestamp template.
+   */
+  async add(originalUrl) {
+    this.logger.debug(`Queueing add: ${originalUrl}`);
+    await this.#taskQueue.queue(async () => {
+      this.logger.info(`Blocking suggestion: ${originalUrl}`);
+      let digest = await this.#getDigest(originalUrl);
+      this.logger.debug(`Got digest for '${originalUrl}': ${digest}`);
+      this.#digests.add(digest);
+      let json = JSON.stringify([...this.#digests]);
+      this.#updatingDigests = true;
+      try {
+        lazy.UrlbarPrefs.set("quicksuggest.blockedDigests", json);
+      } finally {
+        this.#updatingDigests = false;
+      }
+      this.logger.debug(`All blocked suggestions: ${json}`);
+    });
+  }
+
+  /**
+   * Gets whether a suggestion is blocked.
+   *
+   * @param {string} originalUrl
+   *   The suggestion's original URL with its unreplaced timestamp template.
+   * @returns {boolean}
+   *   Whether the suggestion is blocked.
+   */
+  async has(originalUrl) {
+    this.logger.debug(`Queueing has: ${originalUrl}`);
+    return this.#taskQueue.queue(async () => {
+      this.logger.info(`Getting blocked status: ${originalUrl}`);
+      let digest = await this.#getDigest(originalUrl);
+      this.logger.debug(`Got digest for '${originalUrl}': ${digest}`);
+      let isBlocked = this.#digests.has(digest);
+      this.logger.info(`Blocked status for '${originalUrl}': ${isBlocked}`);
+      return isBlocked;
+    });
+  }
+
+  /**
+   * Unblocks all suggestions.
+   */
+  async clear() {
+    this.logger.debug(`Queueing clearBlockedSuggestions`);
+    await this.#taskQueue.queue(() => {
+      this.logger.info(`Clearing all blocked suggestions`);
+      this.#digests.clear();
+      lazy.UrlbarPrefs.clear("quicksuggest.blockedDigests");
+    });
+  }
+
+  /**
+   * Called when a urlbar pref changes.
+   *
+   * @param {string} pref
+   *   The name of the pref relative to `browser.urlbar`.
+   */
+  onPrefChanged(pref) {
+    switch (pref) {
+      case "quicksuggest.blockedDigests":
+        if (!this.#updatingDigests) {
+          this.logger.info(
+            "browser.urlbar.quicksuggest.blockedDigests changed"
+          );
+          this.#loadDigests();
+        }
+        break;
+    }
+  }
+
+  /**
+   * Loads blocked suggestion digests from the pref into `#digests`.
+   */
+  async #loadDigests() {
+    this.logger.debug(`Queueing #loadDigests`);
+    await this.#taskQueue.queue(() => {
+      this.logger.info(`Loading blocked suggestion digests`);
+      let json = lazy.UrlbarPrefs.get("quicksuggest.blockedDigests");
+      this.logger.debug(
+        `browser.urlbar.quicksuggest.blockedDigests value: ${json}`
+      );
+      if (!json) {
+        this.logger.info(`There are no blocked suggestion digests`);
+        this.#digests.clear();
+      } else {
+        try {
+          this.#digests = new Set(JSON.parse(json));
+          this.logger.info(`Successfully loaded blocked suggestion digests`);
+        } catch (error) {
+          this.logger.error(
+            `Error loading blocked suggestion digests: ${error}`
+          );
+        }
+      }
+    });
+  }
+
+  /**
+   * Returns the SHA-1 digest of a string as a 40-character hex-encoded string.
+   *
+   * @param {string} string
+   *   The string to convert to SHA-1
+   * @returns {string}
+   *   The hex-encoded digest of the given string.
+   */
+  async #getDigest(string) {
+    let stringArray = new TextEncoder().encode(string);
+    let hashBuffer = await crypto.subtle.digest("SHA-1", stringArray);
+    let hashArray = new Uint8Array(hashBuffer);
+    return Array.from(hashArray, b => b.toString(16).padStart(2, "0")).join("");
+  }
+
+  get _test_readyPromise() {
+    return this.#taskQueue.emptyPromise;
+  }
+
+  get _test_digests() {
+    return this.#digests;
+  }
+
+  _test_getDigest(string) {
+    return this.#getDigest(string);
+  }
+
+  // Set of digests of the original URLs of blocked suggestions. A suggestion's
+  // "original URL" is its URL straight from the source with an unreplaced
+  // timestamp template. For details on the digests, see `#getDigest()`.
+  //
+  // The only reason we use URL digests is that suggestions currently do not
+  // have persistent IDs. We could use the URLs themselves but SHA-1 digests are
+  // only 40 chars long, so they save a little space. This is also consistent
+  // with how blocked tiles on the newtab page are stored, but they use MD5. We
+  // do *not* store digests for any security or obfuscation reason.
+  //
+  // This value is serialized as a JSON'ed array to the
+  // `browser.urlbar.quicksuggest.blockedDigests` pref.
+  #digests = new Set();
+
+  // Used to serialize access to blocked suggestions. This is only necessary
+  // because getting a suggestion's URL digest is async.
+  #taskQueue = null;
+
+  // Whether blocked digests are currently being updated.
+  #updatingDigests = false;
+}
diff --git a/browser/components/urlbar/private/ImpressionCaps.sys.mjs b/browser/components/urlbar/private/ImpressionCaps.sys.mjs
new file mode 100644
index 0000000000..b50d87bf9e
--- /dev/null
+++ b/browser/components/urlbar/private/ImpressionCaps.sys.mjs
@@ -0,0 +1,566 @@
+/* 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/. */
+
+import { BaseFeature } from "resource:///modules/urlbar/private/BaseFeature.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  AsyncShutdown: "resource://gre/modules/AsyncShutdown.sys.mjs",
+  QuickSuggest: "resource:///modules/QuickSuggest.sys.mjs",
+  QuickSuggestRemoteSettings:
+    "resource:///modules/urlbar/private/QuickSuggestRemoteSettings.sys.mjs",
+  UrlbarPrefs: "resource:///modules/UrlbarPrefs.sys.mjs",
+  clearInterval: "resource://gre/modules/Timer.sys.mjs",
+  setInterval: "resource://gre/modules/Timer.sys.mjs",
+});
+
+const IMPRESSION_COUNTERS_RESET_INTERVAL_MS = 60 * 60 * 1000; // 1 hour
+
+// This object maps impression stats object keys to their corresponding keys in
+// the `extra` object of impression cap telemetry events. The main reason this
+// is necessary is because the keys of the `extra` object are limited to 15
+// characters in length, which some stats object keys exceed. It also forces us
+// to be deliberate about keys we add to the `extra` object, since the `extra`
+// object is limited to 10 keys.
+const TELEMETRY_IMPRESSION_CAP_EXTRA_KEYS = {
+  // stats object key -> `extra` telemetry event object key
+  intervalSeconds: "intervalSeconds",
+  startDateMs: "startDate",
+  count: "count",
+  maxCount: "maxCount",
+  impressionDateMs: "impressionDate",
+};
+
+/**
+ * Impression caps and stats for quick suggest suggestions.
+ */
+export class ImpressionCaps extends BaseFeature {
+  constructor() {
+    super();
+    lazy.UrlbarPrefs.addObserver(this);
+  }
+
+  get shouldEnable() {
+    return (
+      lazy.UrlbarPrefs.get("quickSuggestImpressionCapsSponsoredEnabled") ||
+      lazy.UrlbarPrefs.get("quickSuggestImpressionCapsNonSponsoredEnabled")
+    );
+  }
+
+  enable(enabled) {
+    if (enabled) {
+      this.#init();
+    } else {
+      this.#uninit();
+    }
+  }
+
+  /**
+   * Increments the user's impression stats counters for the given type of
+   * suggestion. This should be called only when a suggestion impression is
+   * recorded.
+   *
+   * @param {string} type
+   *   The suggestion type, one of: "sponsored", "nonsponsored"
+   */
+  updateStats(type) {
+    this.logger.info("Starting impression stats update");
+    this.logger.debug(
+      JSON.stringify({
+        type,
+        currentStats: this.#stats,
+        impression_caps: lazy.QuickSuggestRemoteSettings.config.impression_caps,
+      })
+    );
+
+    // Don't bother recording anything if caps are disabled.
+    let isSponsored = type == "sponsored";
+    if (
+      (isSponsored &&
+        !lazy.UrlbarPrefs.get("quickSuggestImpressionCapsSponsoredEnabled")) ||
+      (!isSponsored &&
+        !lazy.UrlbarPrefs.get("quickSuggestImpressionCapsNonSponsoredEnabled"))
+    ) {
+      this.logger.info("Impression caps disabled, skipping update");
+      return;
+    }
+
+    // Get the user's impression stats. Since stats are synced from caps, if the
+    // stats don't exist then the caps don't exist, and don't bother recording
+    // anything in that case.
+    let stats = this.#stats[type];
+    if (!stats) {
+      this.logger.info("Impression caps undefined, skipping update");
+      return;
+    }
+
+    // Increment counters.
+    for (let stat of stats) {
+      stat.count++;
+      stat.impressionDateMs = Date.now();
+
+      // Record a telemetry event for each newly hit cap.
+      if (stat.count == stat.maxCount) {
+        this.logger.info(`'${type}' impression cap hit`);
+        this.logger.debug(JSON.stringify({ type, hitStat: stat }));
+        this.#recordCapEvent({
+          stat,
+          eventType: "hit",
+          suggestionType: type,
+        });
+      }
+    }
+
+    // Save the stats.
+    this.#updatingStats = true;
+    try {
+      lazy.UrlbarPrefs.set(
+        "quicksuggest.impressionCaps.stats",
+        JSON.stringify(this.#stats)
+      );
+    } finally {
+      this.#updatingStats = false;
+    }
+
+    this.logger.info("Finished impression stats update");
+    this.logger.debug(JSON.stringify({ newStats: this.#stats }));
+  }
+
+  /**
+   * Returns a non-null value if an impression cap has been reached for the
+   * given suggestion type and null otherwise. This method can therefore be used
+   * to tell whether a cap has been reached for a given type. The actual return
+   * value an object describing the impression stats that caused the cap to be
+   * reached.
+   *
+   * @param {string} type
+   *   The suggestion type, one of: "sponsored", "nonsponsored"
+   * @returns {object}
+   *   An impression stats object or null.
+   */
+  getHitStats(type) {
+    this.#resetElapsedCounters();
+    let stats = this.#stats[type];
+    if (stats) {
+      let hitStats = stats.filter(s => s.maxCount <= s.count);
+      if (hitStats.length) {
+        return hitStats;
+      }
+    }
+    return null;
+  }
+
+  /**
+   * Called when a urlbar pref changes.
+   *
+   * @param {string} pref
+   *   The name of the pref relative to `browser.urlbar`.
+   */
+  onPrefChanged(pref) {
+    switch (pref) {
+      case "quicksuggest.impressionCaps.stats":
+        if (!this.#updatingStats) {
+          this.logger.info(
+            "browser.urlbar.quicksuggest.impressionCaps.stats changed"
+          );
+          this.#loadStats();
+        }
+        break;
+    }
+  }
+
+  #init() {
+    this.#loadStats();
+
+    // Validate stats against any changes to the impression caps in the config.
+    this._onConfigSet = () => this.#validateStats();
+    lazy.QuickSuggestRemoteSettings.emitter.on("config-set", this._onConfigSet);
+
+    // Periodically record impression counters reset telemetry.
+    this.#setCountersResetInterval();
+
+    // On shutdown, record any final impression counters reset telemetry.
+    this._shutdownBlocker = () => this.#resetElapsedCounters();
+    lazy.AsyncShutdown.profileChangeTeardown.addBlocker(
+      "QuickSuggest: Record impression counters reset telemetry",
+      this._shutdownBlocker
+    );
+  }
+
+  #uninit() {
+    lazy.QuickSuggestRemoteSettings.emitter.off(
+      "config-set",
+      this._onConfigSet
+    );
+    this._onConfigSet = null;
+
+    lazy.clearInterval(this._impressionCountersResetInterval);
+    this._impressionCountersResetInterval = 0;
+
+    lazy.AsyncShutdown.profileChangeTeardown.removeBlocker(
+      this._shutdownBlocker
+    );
+    this._shutdownBlocker = null;
+  }
+
+  /**
+   * Loads and validates impression stats.
+   */
+  #loadStats() {
+    let json = lazy.UrlbarPrefs.get("quicksuggest.impressionCaps.stats");
+    if (!json) {
+      this.#stats = {};
+    } else {
+      try {
+        this.#stats = JSON.parse(
+          json,
+          // Infinity, which is the `intervalSeconds` for the lifetime cap, is
+          // stringified as `null` in the JSON, so convert it back to Infinity.
+          (key, value) =>
+            key == "intervalSeconds" && value === null ? Infinity : value
+        );
+      } catch (error) {}
+    }
+    this.#validateStats();
+  }
+
+  /**
+   * Validates impression stats, which includes two things:
+   *
+   * - Type checks stats and discards any that are invalid. We do this because
+   *   stats are stored in prefs where anyone can modify them.
+   * - Syncs stats with impression caps so that there is one stats object
+   *   corresponding to each impression cap. See the `#stats` comment for info.
+   */
+  #validateStats() {
+    let { impression_caps } = lazy.QuickSuggestRemoteSettings.config;
+
+    this.logger.info("Validating impression stats");
+    this.logger.debug(
+      JSON.stringify({
+        impression_caps,
+        currentStats: this.#stats,
+      })
+    );
+
+    if (!this.#stats || typeof this.#stats != "object") {
+      this.#stats = {};
+    }
+
+    for (let [type, cap] of Object.entries(impression_caps || {})) {
+      // Build a map from interval seconds to max counts in the caps.
+      let maxCapCounts = (cap.custom || []).reduce(
+        (map, { interval_s, max_count }) => {
+          map.set(interval_s, max_count);
+          return map;
+        },
+        new Map()
+      );
+      if (typeof cap.lifetime == "number") {
+        maxCapCounts.set(Infinity, cap.lifetime);
+      }
+
+      let stats = this.#stats[type];
+      if (!Array.isArray(stats)) {
+        stats = [];
+        this.#stats[type] = stats;
+      }
+
+      // Validate existing stats:
+      //
+      // * Discard stats with invalid properties.
+      // * Collect and remove stats with intervals that aren't in the caps. This
+      //   should only happen when caps are changed or removed.
+      // * For stats with intervals that are in the caps:
+      //   * Keep track of the max `stat.count` across all stats so we can
+      //     update the lifetime stat below.
+      //   * Set `stat.maxCount` to the max count in the corresponding cap.
+      let orphanStats = [];
+      let maxCountInStats = 0;
+      for (let i = 0; i < stats.length; ) {
+        let stat = stats[i];
+        if (
+          typeof stat.intervalSeconds != "number" ||
+          typeof stat.startDateMs != "number" ||
+          typeof stat.count != "number" ||
+          typeof stat.maxCount != "number" ||
+          typeof stat.impressionDateMs != "number"
+        ) {
+          stats.splice(i, 1);
+        } else {
+          maxCountInStats = Math.max(maxCountInStats, stat.count);
+          let maxCount = maxCapCounts.get(stat.intervalSeconds);
+          if (maxCount === undefined) {
+            stats.splice(i, 1);
+            orphanStats.push(stat);
+          } else {
+            stat.maxCount = maxCount;
+            i++;
+          }
+        }
+      }
+
+      // Create stats for caps that don't already have corresponding stats.
+      for (let [intervalSeconds, maxCount] of maxCapCounts.entries()) {
+        if (!stats.some(s => s.intervalSeconds == intervalSeconds)) {
+          stats.push({
+            maxCount,
+            intervalSeconds,
+            startDateMs: Date.now(),
+            count: 0,
+            impressionDateMs: 0,
+          });
+        }
+      }
+
+      // Merge orphaned stats into other ones if possible. For each orphan, if
+      // its interval is no bigger than an existing stat's interval, then the
+      // orphan's count can contribute to the existing stat's count, so merge
+      // the two.
+      for (let orphan of orphanStats) {
+        for (let stat of stats) {
+          if (orphan.intervalSeconds <= stat.intervalSeconds) {
+            stat.count = Math.max(stat.count, orphan.count);
+            stat.startDateMs = Math.min(stat.startDateMs, orphan.startDateMs);
+            stat.impressionDateMs = Math.max(
+              stat.impressionDateMs,
+              orphan.impressionDateMs
+            );
+          }
+        }
+      }
+
+      // If the lifetime stat exists, make its count the max count found above.
+      // This is only necessary when the lifetime cap wasn't present before, but
+      // it doesn't hurt to always do it.
+      let lifetimeStat = stats.find(s => s.intervalSeconds == Infinity);
+      if (lifetimeStat) {
+        lifetimeStat.count = maxCountInStats;
+      }
+
+      // Sort the stats by interval ascending. This isn't necessary except that
+      // it guarantees an ordering for tests.
+      stats.sort((a, b) => a.intervalSeconds - b.intervalSeconds);
+    }
+
+    this.logger.debug(JSON.stringify({ newStats: this.#stats }));
+  }
+
+  /**
+   * Resets the counters of impression stats whose intervals have elapased.
+   */
+  #resetElapsedCounters() {
+    this.logger.info("Checking for elapsed impression cap intervals");
+    this.logger.debug(
+      JSON.stringify({
+        currentStats: this.#stats,
+        impression_caps: lazy.QuickSuggestRemoteSettings.config.impression_caps,
+      })
+    );
+
+    let now = Date.now();
+    for (let [type, stats] of Object.entries(this.#stats)) {
+      for (let stat of stats) {
+        let elapsedMs = now - stat.startDateMs;
+        let intervalMs = 1000 * stat.intervalSeconds;
+        let elapsedIntervalCount = Math.floor(elapsedMs / intervalMs);
+        if (elapsedIntervalCount) {
+          // At least one interval period elapsed for the stat, so reset it. We
+          // may also need to record a telemetry event for the reset.
+          this.logger.info(
+            `Resetting impression counter for interval ${stat.intervalSeconds}s`
+          );
+          this.logger.debug(
+            JSON.stringify({ type, stat, elapsedMs, elapsedIntervalCount })
+          );
+
+          let newStartDateMs =
+            stat.startDateMs + elapsedIntervalCount * intervalMs;
+
+          // Compute the portion of `elapsedIntervalCount` that happened after
+          // startup. This will be the interval count we report in the telemetry
+          // event. By design we don't report intervals that elapsed while the
+          // app wasn't running. For example, if the user stopped using Firefox
+          // for a year, we don't want to report a year's worth of intervals.
+          //
+          // First, compute the count of intervals that elapsed before startup.
+          // This is the same arithmetic used above except here it's based on
+          // the startup date instead of `now`. Keep in mind that startup may be
+          // before the stat's start date. Then subtract that count from
+          // `elapsedIntervalCount` to get the portion after startup.
+          let startupDateMs = this._getStartupDateMs();
+          let elapsedIntervalCountBeforeStartup = Math.floor(
+            Math.max(0, startupDateMs - stat.startDateMs) / intervalMs
+          );
+          let elapsedIntervalCountAfterStartup =
+            elapsedIntervalCount - elapsedIntervalCountBeforeStartup;
+
+          if (elapsedIntervalCountAfterStartup) {
+            this.#recordCapEvent({
+              eventType: "reset",
+              suggestionType: type,
+              eventDateMs: newStartDateMs,
+              eventCount: elapsedIntervalCountAfterStartup,
+              stat: {
+                ...stat,
+                startDateMs:
+                  stat.startDateMs +
+                  elapsedIntervalCountBeforeStartup * intervalMs,
+              },
+            });
+          }
+
+          // Reset the stat.
+          stat.startDateMs = newStartDateMs;
+          stat.count = 0;
+        }
+      }
+    }
+
+    this.logger.debug(JSON.stringify({ newStats: this.#stats }));
+  }
+
+  /**
+   * Records an impression cap telemetry event.
+   *
+   * @param {object} options
+   *   Options object
+   * @param {"hit" | "reset"} options.eventType
+   *   One of: "hit", "reset"
+   * @param {string} options.suggestionType
+   *   One of: "sponsored", "nonsponsored"
+   * @param {object} options.stat
+   *   The stats object whose max count was hit or whose counter was reset.
+   * @param {number} options.eventCount
+   *   The number of intervals that elapsed since the last event.
+   * @param {number} options.eventDateMs
+   *   The `eventDate` that should be recorded in the event's `extra` object.
+   *   We include this in `extra` even though events are timestamped because
+   *   "reset" events are batched during periods where the user doesn't perform
+   *   any searches and therefore impression counters are not reset.
+   */
+  #recordCapEvent({
+    eventType,
+    suggestionType,
+    stat,
+    eventCount = 1,
+    eventDateMs = Date.now(),
+  }) {
+    // All `extra` object values must be strings.
+    let extra = {
+      type: suggestionType,
+      eventDate: String(eventDateMs),
+      eventCount: String(eventCount),
+    };
+    for (let [statKey, value] of Object.entries(stat)) {
+      let extraKey = TELEMETRY_IMPRESSION_CAP_EXTRA_KEYS[statKey];
+      if (!extraKey) {
+        throw new Error("Unrecognized stats object key: " + statKey);
+      }
+      extra[extraKey] = String(value);
+    }
+    Services.telemetry.recordEvent(
+      lazy.QuickSuggest.TELEMETRY_EVENT_CATEGORY,
+      "impression_cap",
+      eventType,
+      "",
+      extra
+    );
+  }
+
+  /**
+   * Creates a repeating timer that resets impression counters and records
+   * related telemetry. Since counters are also reset when suggestions are
+   * triggered, the only point of this is to make sure we record reset telemetry
+   * events in a timely manner during periods when suggestions aren't triggered.
+   *
+   * @param {number} ms
+   *   The number of milliseconds in the interval.
+   */
+  #setCountersResetInterval(ms = IMPRESSION_COUNTERS_RESET_INTERVAL_MS) {
+    if (this._impressionCountersResetInterval) {
+      lazy.clearInterval(this._impressionCountersResetInterval);
+    }
+    this._impressionCountersResetInterval = lazy.setInterval(
+      () => this.#resetElapsedCounters(),
+      ms
+    );
+  }
+
+  /**
+   * Gets the timestamp of app startup in ms since Unix epoch. This is only
+   * defined as its own method so tests can override it to simulate arbitrary
+   * startups.
+   *
+   * @returns {number}
+   *   Startup timestamp in ms since Unix epoch.
+   */
+  _getStartupDateMs() {
+    return Services.startup.getStartupInfo().process.getTime();
+  }
+
+  get _test_stats() {
+    return this.#stats;
+  }
+
+  _test_reloadStats() {
+    this.#stats = null;
+    this.#loadStats();
+  }
+
+  _test_resetElapsedCounters() {
+    this.#resetElapsedCounters();
+  }
+
+  _test_setCountersResetInterval(ms) {
+    this.#setCountersResetInterval(ms);
+  }
+
+  // An object that keeps track of impression stats per sponsored and
+  // non-sponsored suggestion types. It looks like this:
+  //
+  //   { sponsored: statsArray, nonsponsored: statsArray }
+  //
+  // The `statsArray` values are arrays of stats objects, one per impression
+  // cap, which look like this:
+  //
+  //   { intervalSeconds, startDateMs, count, maxCount, impressionDateMs }
+  //
+  //   {number} intervalSeconds
+  //     The number of seconds in the corresponding cap's time interval.
+  //   {number} startDateMs
+  //     The timestamp at which the current interval period started and the
+  //     object's `count` was reset to zero. This is a value returned from
+  //     `Date.now()`.  When the current date/time advances past `startDateMs +
+  //     1000 * intervalSeconds`, a new interval period will start and `count`
+  //     will be reset to zero.
+  //   {number} count
+  //     The number of impressions during the current interval period.
+  //   {number} maxCount
+  //     The maximum number of impressions allowed during an interval period.
+  //     This value is the same as the `max_count` value in the corresponding
+  //     cap. It's stored in the stats object for convenience.
+  //   {number} impressionDateMs
+  //     The timestamp of the most recent impression, i.e., when `count` was
+  //     last incremented.
+  //
+  // There are two types of impression caps: interval and lifetime. Interval
+  // caps are periodically reset, and lifetime caps are never reset. For stats
+  // objects corresponding to interval caps, `intervalSeconds` will be the
+  // `interval_s` value of the cap. For stats objects corresponding to lifetime
+  // caps, `intervalSeconds` will be `Infinity`.
+  //
+  // `#stats` is kept in sync with impression caps, and there is a one-to-one
+  // relationship between stats objects and caps. A stats object's corresponding
+  // cap is the one with the same suggestion type (sponsored or non-sponsored)
+  // and interval. See `#validateStats()` for more.
+  //
+  // Impression caps are stored in the remote settings config. See
+  // `QuickSuggestRemoteSettingsClient.confg.impression_caps`.
+  #stats = {};
+
+  // Whether impression stats are currently being updated.
+  #updatingStats = false;
+}
diff --git a/browser/components/urlbar/private/QuickSuggestRemoteSettings.sys.mjs b/browser/components/urlbar/private/QuickSuggestRemoteSettings.sys.mjs
new file mode 100644
index 0000000000..326b649780
--- /dev/null
+++ b/browser/components/urlbar/private/QuickSuggestRemoteSettings.sys.mjs
@@ -0,0 +1,395 @@
+/* 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/. */
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  EventEmitter: "resource://gre/modules/EventEmitter.sys.mjs",
+  RemoteSettings: "resource://services-settings/remote-settings.sys.mjs",
+  UrlbarUtils: "resource:///modules/UrlbarUtils.sys.mjs",
+});
+
+const RS_COLLECTION = "quicksuggest";
+
+// Default score for remote settings suggestions.
+const DEFAULT_SUGGESTION_SCORE = 0.2;
+
+// Entries are added to `SuggestionsMap` map in chunks, and each chunk will add
+// at most this many entries.
+const SUGGESTIONS_MAP_CHUNK_SIZE = 1000;
+
+const TELEMETRY_LATENCY = "FX_URLBAR_QUICK_SUGGEST_REMOTE_SETTINGS_LATENCY_MS";
+
+/**
+ * Manages quick suggest remote settings data.
+ */
+class _QuickSuggestRemoteSettings {
+  /**
+   * @returns {number}
+   *   The default score for remote settings suggestions, a value in the range
+   *   [0, 1]. All suggestions require a score that can be used for comparison,
+   *   so if a remote settings suggestion does not have one, it's assigned this
+   *   value.
+   */
+  get DEFAULT_SUGGESTION_SCORE() {
+    return DEFAULT_SUGGESTION_SCORE;
+  }
+
+  constructor() {
+    this.#emitter = new lazy.EventEmitter();
+  }
+
+  /**
+   * @returns {RemoteSettings}
+   *   The underlying `RemoteSettings` client object.
+   */
+  get rs() {
+    return this.#rs;
+  }
+
+  /**
+   * @returns {EventEmitter}
+   *   The client will emit events on this object.
+   */
+  get emitter() {
+    return this.#emitter;
+  }
+
+  /**
+   * @returns {object}
+   *   Global quick suggest configuration stored in remote settings. When the
+   *   config changes the `emitter` property will emit a "config-set" event. The
+   *   config is an object that looks like this:
+   *
+   *   {
+   *     best_match: {
+   *       min_search_string_length,
+   *       blocked_suggestion_ids,
+   *     },
+   *     impression_caps: {
+   *       nonsponsored: {
+   *         lifetime,
+   *         custom: [
+   *           { interval_s, max_count },
+   *         ],
+   *       },
+   *       sponsored: {
+   *         lifetime,
+   *         custom: [
+   *           { interval_s, max_count },
+   *         ],
+   *       },
+   *     },
+   *     show_less_frequently_cap,
+   *   }
+   */
+  get config() {
+    return this.#config;
+  }
+
+  /**
+   * @returns {Array}
+   *   Array of `BasicFeature` instances.
+   */
+  get features() {
+    return [...this.#features];
+  }
+
+  get logger() {
+    if (!this.#logger) {
+      this.#logger = lazy.UrlbarUtils.getLogger({
+        prefix: "QuickSuggestRemoteSettings",
+      });
+    }
+    return this.#logger;
+  }
+
+  /**
+   * Registers a quick suggest feature that uses remote settings.
+   *
+   * @param {BaseFeature} feature
+   *   An instance of a `BaseFeature` subclass. See `BaseFeature` for methods
+   *   that the subclass must implement.
+   */
+  register(feature) {
+    this.logger.debug("Registering feature: " + feature.name);
+    this.#features.add(feature);
+    if (this.#features.size == 1) {
+      this.#enableSettings(true);
+    }
+    this.#syncFeature(feature);
+  }
+
+  /**
+   * Unregisters a quick suggest feature that uses remote settings.
+   *
+   * @param {BaseFeature} feature
+   *   An instance of a `BaseFeature` subclass.
+   */
+  unregister(feature) {
+    this.logger.debug("Unregistering feature: " + feature.name);
+    this.#features.delete(feature);
+    if (!this.#features.size) {
+      this.#enableSettings(false);
+    }
+  }
+
+  /**
+   * Queries remote settings suggestions from all registered features.
+   *
+   * @param {string} searchString
+   *   The search string.
+   * @returns {Array}
+   *   The remote settings suggestions. If there are no matches, an empty array
+   *   is returned.
+   */
+  async query(searchString) {
+    let suggestions;
+    let stopwatchInstance = {};
+    TelemetryStopwatch.start(TELEMETRY_LATENCY, stopwatchInstance);
+    try {
+      suggestions = await this.#queryHelper(searchString);
+      TelemetryStopwatch.finish(TELEMETRY_LATENCY, stopwatchInstance);
+    } catch (error) {
+      TelemetryStopwatch.cancel(TELEMETRY_LATENCY, stopwatchInstance);
+      this.logger.error("Query error: " + error);
+    }
+
+    return suggestions || [];
+  }
+
+  async #queryHelper(searchString) {
+    this.logger.info("Handling query: " + JSON.stringify(searchString));
+
+    let results = await Promise.all(
+      [...this.#features].map(async feature => {
+        let suggestions = await feature.queryRemoteSettings(searchString);
+        return [feature, suggestions ?? []];
+      })
+    );
+
+    let allSuggestions = [];
+    for (let [feature, suggestions] of results) {
+      for (let suggestion of suggestions) {
+        suggestion.source = "remote-settings";
+        suggestion.provider = feature.name;
+        if (typeof suggestion.score != "number") {
+          suggestion.score = DEFAULT_SUGGESTION_SCORE;
+        }
+        allSuggestions.push(suggestion);
+      }
+    }
+
+    return allSuggestions;
+  }
+
+  async #enableSettings(enabled) {
+    if (enabled && !this.#rs) {
+      this.logger.debug("Creating RemoteSettings client");
+      this.#onSettingsSync = event => this.#syncAll({ event });
+      this.#rs = lazy.RemoteSettings(RS_COLLECTION);
+      this.#rs.on("sync", this.#onSettingsSync);
+      await this.#syncConfig();
+    } else if (!enabled && this.#rs) {
+      this.logger.debug("Destroying RemoteSettings client");
+      this.#rs.off("sync", this.#onSettingsSync);
+      this.#rs = null;
+      this.#onSettingsSync = null;
+    }
+  }
+
+  async #syncConfig() {
+    this.logger.debug("Syncing config");
+    let rs = this.#rs;
+
+    let configArray = await rs.get({ filters: { type: "configuration" } });
+    if (rs != this.#rs) {
+      return;
+    }
+
+    this.logger.debug("Got config array: " + JSON.stringify(configArray));
+    this.#setConfig(configArray?.[0]?.configuration || {});
+  }
+
+  async #syncFeature(feature) {
+    this.logger.debug("Syncing feature: " + feature.name);
+    await feature.onRemoteSettingsSync(this.#rs);
+  }
+
+  async #syncAll({ event = null } = {}) {
+    this.logger.debug("Syncing all");
+    let rs = this.#rs;
+
+    // Remove local files of deleted records
+    if (event?.data?.deleted) {
+      await Promise.all(
+        event.data.deleted
+          .filter(d => d.attachment)
+          .map(entry =>
+            Promise.all([
+              this.#rs.attachments.deleteDownloaded(entry), // type: data
+              this.#rs.attachments.deleteFromDisk(entry), // type: icon
+            ])
+          )
+      );
+      if (rs != this.#rs) {
+        return;
+      }
+    }
+
+    let promises = [this.#syncConfig()];
+    for (let feature of this.#features) {
+      promises.push(this.#syncFeature(feature));
+    }
+    await Promise.all(promises);
+  }
+
+  /**
+   * Sets the quick suggest config and emits a "config-set" event.
+   *
+   * @param {object} config
+   *   The config object.
+   */
+  #setConfig(config) {
+    config ??= {};
+    this.logger.debug("Setting config: " + JSON.stringify(config));
+    this.#config = config;
+    this.#emitter.emit("config-set");
+  }
+
+  // The `RemoteSettings` client.
+  #rs = null;
+
+  // Registered `BaseFeature` instances.
+  #features = new Set();
+
+  // Configuration data synced from remote settings. See the `config` getter.
+  #config = {};
+
+  #emitter = null;
+  #logger = null;
+  #onSettingsSync = null;
+}
+
+export var QuickSuggestRemoteSettings = new _QuickSuggestRemoteSettings();
+
+/**
+ * A wrapper around `Map` that handles quick suggest suggestions from remote
+ * settings. It maps keywords to suggestions. It has two benefits over `Map`:
+ *
+ * - The main benefit is that map entries are added in batches on idle to avoid
+ *   blocking the main thread for too long, since there can be many suggestions
+ *   and keywords.
+ * - A secondary benefit is that the interface is tailored to quick suggest
+ *   suggestions, which have a `keywords` property.
+ */
+export class SuggestionsMap {
+  /**
+   * Returns the list of suggestions for a keyword.
+   *
+   * @param {string} keyword
+   *   The keyword.
+   * @returns {Array}
+   *   The array of suggestions for the keyword. If the keyword isn't in the
+   *   map, the array will be empty.
+   */
+  get(keyword) {
+    let object = this.#suggestionsByKeyword.get(keyword.toLocaleLowerCase());
+    if (!object) {
+      return [];
+    }
+    return Array.isArray(object) ? object : [object];
+  }
+
+  /**
+   * Adds a list of suggestion objects to the results map. Each suggestion must
+   * have a `keywords` property whose value is an array of keyword strings. The
+   * suggestion's keywords will be taken from this array either exactly as they
+   * are specified or by generating new keywords from them; see `mapKeyword`.
+   *
+   * @param {Array} suggestions
+   *   Array of suggestion objects.
+   * @param {Function} mapKeyword
+   *   If null, each suggestion's keywords will be taken from its `keywords`
+   *   array exactly as they are specified. Otherwise, as each suggestion is
+   *   processed, this function will be called for each string in its `keywords`
+   *   array. The function should return an array of strings. The suggestion's
+   *   final list of keywords will be all the keywords returned by this function
+   *   as it is called for each string in `keywords`.
+   */
+  async add(suggestions, mapKeyword = null) {
+    // There can be many suggestions, and each suggestion can have many
+    // keywords. To avoid blocking the main thread for too long, update the map
+    // in chunks, and to avoid blocking the UI and other higher priority work,
+    // do each chunk only when the main thread is idle. During each chunk, we'll
+    // add at most `chunkSize` entries to the map.
+    let suggestionIndex = 0;
+    let keywordIndex = 0;
+
+    // Keep adding chunks until all suggestions have been fully added.
+    while (suggestionIndex < suggestions.length) {
+      await new Promise(resolve => {
+        Services.tm.idleDispatchToMainThread(() => {
+          // Keep updating the map until the current chunk is done.
+          let indexInChunk = 0;
+          while (
+            indexInChunk < SuggestionsMap.chunkSize &&
+            suggestionIndex < suggestions.length
+          ) {
+            let suggestion = suggestions[suggestionIndex];
+            if (keywordIndex == suggestion.keywords.length) {
+              // We've added entries for all keywords of the current suggestion.
+              // Move on to the next suggestion.
+              suggestionIndex++;
+              keywordIndex = 0;
+              continue;
+            }
+
+            let originalKeyword = suggestion.keywords[keywordIndex];
+            let keywords = mapKeyword?.(originalKeyword) ?? [originalKeyword];
+            for (let keyword of keywords) {
+              // If the keyword's only suggestion is `suggestion`, store it
+              // directly as the value. Otherwise store an array of unique
+              // suggestions. See the `#suggestionsByKeyword` comment.
+              let object = this.#suggestionsByKeyword.get(keyword);
+              if (!object) {
+                this.#suggestionsByKeyword.set(keyword, suggestion);
+              } else {
+                let isArray = Array.isArray(object);
+                if (!isArray && object != suggestion) {
+                  this.#suggestionsByKeyword.set(keyword, [object, suggestion]);
+                } else if (isArray && !object.includes(suggestion)) {
+                  object.push(suggestion);
+                }
+              }
+            }
+
+            keywordIndex++;
+            indexInChunk++;
+          }
+
+          // The current chunk is done.
+          resolve();
+        });
+      });
+    }
+  }
+
+  clear() {
+    this.#suggestionsByKeyword.clear();
+  }
+
+  // Maps each keyword in the dataset to one or more suggestions for the
+  // keyword. If only one suggestion uses a keyword, the keyword's value in the
+  // map will be the suggestion object. If more than one suggestion uses the
+  // keyword, the value will be an array of the suggestions. The reason for not
+  // always using an array is that we expect the vast majority of keywords to be
+  // used by only one suggestion, and since there are potentially very many
+  // keywords and suggestions and we keep them in memory all the time, we want
+  // to save as much memory as possible.
+  #suggestionsByKeyword = new Map();
+
+  // This is only defined as a property so that tests can override it.
+  static chunkSize = SUGGESTIONS_MAP_CHUNK_SIZE;
+}
diff --git a/browser/components/urlbar/private/Weather.sys.mjs b/browser/components/urlbar/private/Weather.sys.mjs
new file mode 100644
index 0000000000..ea9eddfa2c
--- /dev/null
+++ b/browser/components/urlbar/private/Weather.sys.mjs
@@ -0,0 +1,499 @@
+/* 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/. */
+
+import { BaseFeature } from "resource:///modules/urlbar/private/BaseFeature.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  clearTimeout: "resource://gre/modules/Timer.sys.mjs",
+  MerinoClient: "resource:///modules/MerinoClient.sys.mjs",
+  PromiseUtils: "resource://gre/modules/PromiseUtils.sys.mjs",
+  QuickSuggestRemoteSettings:
+    "resource:///modules/urlbar/private/QuickSuggestRemoteSettings.sys.mjs",
+  setTimeout: "resource://gre/modules/Timer.sys.mjs",
+  UrlbarPrefs: "resource:///modules/UrlbarPrefs.sys.mjs",
+});
+
+const FETCH_DELAY_AFTER_COMING_ONLINE_MS = 3000; // 3s
+const FETCH_INTERVAL_MS = 30 * 60 * 1000; // 30 minutes
+const MERINO_PROVIDER = "accuweather";
+const MERINO_TIMEOUT_MS = 5000; // 5s
+
+const HISTOGRAM_LATENCY = "FX_URLBAR_MERINO_LATENCY_WEATHER_MS";
+const HISTOGRAM_RESPONSE = "FX_URLBAR_MERINO_RESPONSE_WEATHER";
+
+const NOTIFICATIONS = {
+  CAPTIVE_PORTAL_LOGIN: "captive-portal-login-success",
+  LINK_STATUS_CHANGED: "network:link-status-changed",
+  OFFLINE_STATUS_CHANGED: "network:offline-status-changed",
+  WAKE: "wake_notification",
+};
+
+/**
+ * A feature that periodically fetches weather suggestions from Merino.
+ */
+export class Weather extends BaseFeature {
+  get shouldEnable() {
+    // The feature itself is enabled by setting these prefs regardless of
+    // whether any config is defined. This is necessary to allow the feature to
+    // sync the config from remote settings and Nimbus. Suggestion fetches will
+    // not start until the config has been either synced from remote settings or
+    // set by Nimbus.
+    return (
+      lazy.UrlbarPrefs.get("weatherFeatureGate") &&
+      lazy.UrlbarPrefs.get("suggest.weather") &&
+      lazy.UrlbarPrefs.get("merinoEnabled")
+    );
+  }
+
+  get enablingPreferences() {
+    return ["suggest.weather"];
+  }
+
+  /**
+   * @returns {object}
+   *   The last weather suggestion fetched from Merino or null if none.
+   */
+  get suggestion() {
+    return this.#suggestion;
+  }
+
+  /**
+   * @returns {Set}
+   *   The set of keywords that should trigger the weather suggestion. This will
+   *   be null when no config is defined.
+   */
+  get keywords() {
+    return this.#keywords;
+  }
+
+  /**
+   * @returns {number}
+   *   The minimum prefix length of a weather keyword the user must type to
+   *   trigger the suggestion. Note that the strings returned from `keywords`
+   *   already take this into account. The min length is determined from the
+   *   first config source below whose value is non-zero. If no source has a
+   *   non-zero value, zero will be returned, and `this.keywords` will contain
+   *   only full keywords.
+   *
+   *   1. The `weather.minKeywordLength` pref, which is set when the user
+   *      increments the min length
+   *   2. `weatherKeywordsMinimumLength` in Nimbus
+   *   3. `min_keyword_length` in remote settings
+   */
+  get minKeywordLength() {
+    let minLength =
+      lazy.UrlbarPrefs.get("weather.minKeywordLength") ||
+      lazy.UrlbarPrefs.get("weatherKeywordsMinimumLength") ||
+      this.#rsData?.min_keyword_length ||
+      0;
+    return Math.max(minLength, 0);
+  }
+
+  /**
+   * @returns {boolean}
+   *   Weather the min keyword length can be incremented. A cap on the min
+   *   length can be set in remote settings and Nimbus.
+   */
+  get canIncrementMinKeywordLength() {
+    let cap =
+      lazy.UrlbarPrefs.get("weatherKeywordsMinimumLengthCap") ||
+      this.#rsData?.min_keyword_length_cap ||
+      0;
+    return !cap || this.minKeywordLength < cap;
+  }
+
+  update() {
+    let wasEnabled = this.isEnabled;
+    super.update();
+
+    // This method is called by `QuickSuggest` in a
+    // `NimbusFeatures.urlbar.onUpdate()` callback, when a change occurs to a
+    // Nimbus variable or to a pref that's a fallback for a Nimbus variable. A
+    // config-related variable or pref may have changed, so update it, but only
+    // if the feature was already enabled because if it wasn't, `enable(true)`
+    // was just called, which calls `#init()`, which calls `#updateConfig()`.
+    if (wasEnabled && this.isEnabled) {
+      this.#updateConfig();
+    }
+  }
+
+  enable(enabled) {
+    if (enabled) {
+      this.#init();
+    } else {
+      this.#uninit();
+    }
+  }
+
+  /**
+   * Increments the minimum prefix length of a weather keyword the user must
+   * type to trigger the suggestion, if possible. A cap on the min length can be
+   * set in remote settings and Nimbus, and if the cap has been reached, the
+   * length is not incremented.
+   */
+  incrementMinKeywordLength() {
+    if (this.canIncrementMinKeywordLength) {
+      lazy.UrlbarPrefs.set(
+        "weather.minKeywordLength",
+        this.minKeywordLength + 1
+      );
+    }
+  }
+
+  /**
+   * Returns a promise that resolves when all pending fetches finish, if there
+   * are pending fetches. If there aren't, the promise resolves when all pending
+   * fetches starting with the next fetch finish.
+   *
+   * @returns {Promise}
+   */
+  waitForFetches() {
+    if (!this.#waitForFetchesDeferred) {
+      this.#waitForFetchesDeferred = lazy.PromiseUtils.defer();
+    }
+    return this.#waitForFetchesDeferred.promise;
+  }
+
+  async onRemoteSettingsSync(rs) {
+    this.logger.debug("Loading weather config from remote settings");
+    let records = await rs.get({ filters: { type: "weather" } });
+    if (rs != lazy.QuickSuggestRemoteSettings.rs) {
+      return;
+    }
+
+    this.logger.debug("Got weather records: " + JSON.stringify(records));
+    this.#rsData = records?.[0]?.weather;
+    this.#updateConfig();
+  }
+
+  get #vpnDetected() {
+    if (lazy.UrlbarPrefs.get("weather.ignoreVPN")) {
+      return false;
+    }
+
+    let linkService =
+      this._test_linkService ||
+      Cc["@mozilla.org/network/network-link-service;1"].getService(
+        Ci.nsINetworkLinkService
+      );
+
+    // `platformDNSIndications` throws `NS_ERROR_NOT_IMPLEMENTED` on all
+    // platforms except Windows, so we can't detect a VPN on any other platform.
+    try {
+      return (
+        linkService.platformDNSIndications &
+        Ci.nsINetworkLinkService.VPN_DETECTED
+      );
+    } catch (e) {}
+    return false;
+  }
+
+  #init() {
+    // On feature init, we only update the config and listen for changes that
+    // affect the config. Suggestion fetches will not start until a config has
+    // been either synced from remote settings or set by Nimbus.
+    this.#updateConfig();
+    lazy.UrlbarPrefs.addObserver(this);
+    lazy.QuickSuggestRemoteSettings.register(this);
+  }
+
+  #uninit() {
+    this.#stopFetching();
+    lazy.QuickSuggestRemoteSettings.unregister(this);
+    lazy.UrlbarPrefs.removeObserver(this);
+    this.#keywords = null;
+  }
+
+  #startFetching() {
+    if (this.#merino) {
+      this.logger.debug("Suggestion fetching already started");
+      return;
+    }
+
+    this.logger.debug("Starting suggestion fetching");
+
+    this.#merino = new lazy.MerinoClient(this.constructor.name);
+    this.#fetch();
+    for (let notif of Object.values(NOTIFICATIONS)) {
+      Services.obs.addObserver(this, notif);
+    }
+  }
+
+  #stopFetching() {
+    if (!this.#merino) {
+      this.logger.debug("Suggestion fetching already stopped");
+      return;
+    }
+
+    this.logger.debug("Stopping suggestion fetching");
+
+    for (let notif of Object.values(NOTIFICATIONS)) {
+      Services.obs.removeObserver(this, notif);
+    }
+    lazy.clearTimeout(this.#fetchTimer);
+    this.#merino = null;
+    this.#suggestion = null;
+    this.#fetchTimer = 0;
+  }
+
+  async #fetch() {
+    this.logger.info("Fetching suggestion");
+
+    if (this.#vpnDetected) {
+      // A VPN is detected, so Merino will not be able to accurately determine
+      // the user's location. Set the suggestion to null. We treat this as if
+      // the network is offline (see below). When the VPN is disconnected, a
+      // `network:link-status-changed` notification will be sent, triggering a
+      // new fetch.
+      this.logger.info("VPN detected, not fetching");
+      this.#suggestion = null;
+      if (!this.#pendingFetchCount) {
+        this.#waitForFetchesDeferred?.resolve();
+        this.#waitForFetchesDeferred = null;
+      }
+      return;
+    }
+
+    // This `Weather` instance may be uninitialized while awaiting the fetch or
+    // even uninitialized and re-initialized a number of times. Multiple fetches
+    // may also happen at once. Ignore the fetch below if `#merino` changes or
+    // another fetch happens in the meantime.
+    let merino = this.#merino;
+    let instance = (this.#fetchInstance = {});
+
+    this.#restartFetchTimer();
+    this.#lastFetchTimeMs = Date.now();
+    this.#pendingFetchCount++;
+
+    let suggestions;
+    try {
+      suggestions = await merino.fetch({
+        query: "",
+        providers: [MERINO_PROVIDER],
+        timeoutMs: this.#timeoutMs,
+        extraLatencyHistogram: HISTOGRAM_LATENCY,
+        extraResponseHistogram: HISTOGRAM_RESPONSE,
+      });
+    } finally {
+      this.#pendingFetchCount--;
+    }
+
+    // Reset the Merino client's session so different fetches use different
+    // sessions. A single session is intended to represent a single user
+    // engagement in the urlbar, which this is not. Practically this isn't
+    // necessary since the client automatically resets the session on a timer
+    // whose period is much shorter than our fetch period, but there's no reason
+    // to keep it ticking in the meantime.
+    merino.resetSession();
+
+    if (merino != this.#merino || instance != this.#fetchInstance) {
+      this.logger.info("Fetch finished but is out of date, ignoring");
+    } else {
+      let suggestion = suggestions?.[0];
+      if (!suggestion) {
+        // No suggestion was received. The network may be offline or there may
+        // be some other problem. Set the suggestion to null: Better to show
+        // nothing than outdated weather information. When the network comes
+        // back online, one or more network notifications will be sent,
+        // triggering a new fetch.
+        this.logger.info("No suggestion received");
+        this.#suggestion = null;
+      } else {
+        this.logger.info("Got suggestion");
+        this.logger.debug(JSON.stringify({ suggestion }));
+        this.#suggestion = { ...suggestion, source: "merino" };
+      }
+    }
+
+    if (!this.#pendingFetchCount) {
+      this.#waitForFetchesDeferred?.resolve();
+      this.#waitForFetchesDeferred = null;
+    }
+  }
+
+  #restartFetchTimer(ms = this.#fetchIntervalMs) {
+    this.logger.debug(
+      "Restarting fetch timer: " +
+        JSON.stringify({ ms, fetchIntervalMs: this.#fetchIntervalMs })
+    );
+
+    lazy.clearTimeout(this.#fetchTimer);
+    this.#fetchTimer = lazy.setTimeout(() => {
+      this.logger.debug("Fetch timer fired");
+      this.#fetch();
+    }, ms);
+    this._test_fetchTimerMs = ms;
+  }
+
+  #onMaybeCameOnline() {
+    this.logger.debug("Maybe came online");
+
+    // If the suggestion is null, we were offline the last time we tried to
+    // fetch, at the start of the current fetch period. Otherwise the suggestion
+    // was fetched successfully at the start of the current fetch period and is
+    // therefore still fresh.
+    if (!this.suggestion) {
+      // Multiple notifications can occur at once when the network comes online,
+      // and we don't want to do separate fetches for each. Start the timer with
+      // a small timeout. If another notification happens in the meantime, we'll
+      // start it again.
+      this.#restartFetchTimer(this.#fetchDelayAfterComingOnlineMs);
+    }
+  }
+
+  #onWake() {
+    // Calculate the elapsed time between the last fetch and now, and the
+    // remaining interval in the current fetch period.
+    let elapsedMs = Date.now() - this.#lastFetchTimeMs;
+    let remainingIntervalMs = this.#fetchIntervalMs - elapsedMs;
+    this.logger.debug(
+      "Wake: " +
+        JSON.stringify({
+          elapsedMs,
+          remainingIntervalMs,
+          fetchIntervalMs: this.#fetchIntervalMs,
+        })
+    );
+
+    // Regardless of the elapsed time, we need to restart the fetch timer
+    // because it didn't tick while the computer was asleep. If the elapsed time
+    // >= the fetch interval, the remaining interval will be negative and we
+    // need to fetch now, but do it after a brief delay in case other
+    // notifications occur soon when the network comes online. If the elapsed
+    // time < the fetch interval, the suggestion is still fresh so there's no
+    // need to fetch. Just restart the timer with the remaining interval.
+    if (remainingIntervalMs <= 0) {
+      remainingIntervalMs = this.#fetchDelayAfterComingOnlineMs;
+    }
+    this.#restartFetchTimer(remainingIntervalMs);
+  }
+
+  #updateConfig() {
+    this.logger.debug("Starting config update");
+
+    // Get the full keywords, preferring Nimbus over remote settings.
+    let fullKeywords =
+      lazy.UrlbarPrefs.get("weatherKeywords") ?? this.#rsData?.keywords;
+    if (!fullKeywords) {
+      this.logger.debug("No keywords defined, stopping suggestion fetching");
+      this.#keywords = null;
+      this.#stopFetching();
+      return;
+    }
+
+    let minLength = this.minKeywordLength;
+    this.logger.debug(
+      "Updating keywords: " + JSON.stringify({ fullKeywords, minLength })
+    );
+
+    if (!minLength) {
+      this.logger.debug("Min length is undefined or zero, using full keywords");
+      this.#keywords = new Set(fullKeywords);
+    } else {
+      // Create keywords that are prefixes of the full keywords starting at the
+      // specified minimum length.
+      this.#keywords = new Set();
+      for (let full of fullKeywords) {
+        for (let i = minLength; i <= full.length; i++) {
+          this.#keywords.add(full.substring(0, i));
+        }
+      }
+    }
+
+    this.#startFetching();
+  }
+
+  onPrefChanged(pref) {
+    if (pref == "weather.minKeywordLength") {
+      this.#updateConfig();
+    }
+  }
+
+  observe(subject, topic, data) {
+    this.logger.debug(
+      "Observed notification: " + JSON.stringify({ topic, data })
+    );
+
+    switch (topic) {
+      case NOTIFICATIONS.CAPTIVE_PORTAL_LOGIN:
+        this.#onMaybeCameOnline();
+        break;
+      case NOTIFICATIONS.LINK_STATUS_CHANGED:
+        // This notificaton means the user's connection status changed. See
+        // nsINetworkLinkService.
+        if (data != "down") {
+          this.#onMaybeCameOnline();
+        }
+        break;
+      case NOTIFICATIONS.OFFLINE_STATUS_CHANGED:
+        // This notificaton means the user toggled the "Work Offline" pref.
+        // See nsIIOService.
+        if (data != "offline") {
+          this.#onMaybeCameOnline();
+        }
+        break;
+      case NOTIFICATIONS.WAKE:
+        this.#onWake();
+        break;
+    }
+  }
+
+  get _test_fetchDelayAfterComingOnlineMs() {
+    return this.#fetchDelayAfterComingOnlineMs;
+  }
+  set _test_fetchDelayAfterComingOnlineMs(ms) {
+    this.#fetchDelayAfterComingOnlineMs =
+      ms < 0 ? FETCH_DELAY_AFTER_COMING_ONLINE_MS : ms;
+  }
+
+  get _test_fetchIntervalMs() {
+    return this.#fetchIntervalMs;
+  }
+  set _test_fetchIntervalMs(ms) {
+    this.#fetchIntervalMs = ms < 0 ? FETCH_INTERVAL_MS : ms;
+  }
+
+  get _test_fetchTimer() {
+    return this.#fetchTimer;
+  }
+
+  get _test_lastFetchTimeMs() {
+    return this.#lastFetchTimeMs;
+  }
+
+  get _test_merino() {
+    return this.#merino;
+  }
+
+  get _test_pendingFetchCount() {
+    return this.#pendingFetchCount;
+  }
+
+  async _test_fetch() {
+    await this.#fetch();
+  }
+
+  _test_setSuggestionToNull() {
+    this.#suggestion = null;
+  }
+
+  _test_setTimeoutMs(ms) {
+    this.#timeoutMs = ms < 0 ? MERINO_TIMEOUT_MS : ms;
+  }
+
+  #fetchDelayAfterComingOnlineMs = FETCH_DELAY_AFTER_COMING_ONLINE_MS;
+  #fetchInstance = null;
+  #fetchIntervalMs = FETCH_INTERVAL_MS;
+  #fetchTimer = 0;
+  #keywords = null;
+  #lastFetchTimeMs = 0;
+  #merino = null;
+  #pendingFetchCount = 0;
+  #rsData = null;
+  #suggestion = null;
+  #timeoutMs = MERINO_TIMEOUT_MS;
+  #waitForFetchesDeferred = null;
+}