1 files changed, 208 insertions, 0 deletions
diff --git a/browser/components/newtab/lib/WeatherFeed.sys.mjs b/browser/components/newtab/lib/WeatherFeed.sys.mjs
new file mode 100644
index 0000000000..16aa8196af
--- /dev/null
+++ b/browser/components/newtab/lib/WeatherFeed.sys.mjs
@@ -0,0 +1,208 @@
+/* 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, {
+  MerinoClient: "resource:///modules/MerinoClient.sys.mjs",
+  clearTimeout: "resource://gre/modules/Timer.sys.mjs",
+  setTimeout: "resource://gre/modules/Timer.sys.mjs",
+  PersistentCache: "resource://activity-stream/lib/PersistentCache.sys.mjs",
+});
+
+import {
+  actionTypes as at,
+  actionCreators as ac,
+} from "resource://activity-stream/common/Actions.mjs";
+
+const CACHE_KEY = "weather_feed";
+const WEATHER_UPDATE_TIME = 10 * 60 * 1000; // 10 minutes
+const MERINO_PROVIDER = "accuweather";
+
+const PREF_WEATHER_QUERY = "weather.query";
+const PREF_SHOW_WEATHER = "showWeather";
+const PREF_SYSTEM_SHOW_WEATHER = "system.showWeather";
+
+/**
+ * A feature that periodically fetches weather suggestions from Merino for HNT.
+ */
+export class WeatherFeed {
+  constructor() {
+    this.loaded = false;
+    this.merino = null;
+    this.suggestions = [];
+    this.lastUpdated = null;
+    this.fetchTimer = null;
+    this.fetchIntervalMs = 30 * 60 * 1000; // 30 minutes
+    this.timeoutMS = 5000;
+    this.lastFetchTimeMs = 0;
+    this.fetchDelayAfterComingOnlineMs = 3000; // 3s
+    this.cache = this.PersistentCache(CACHE_KEY, true);
+  }
+
+  async resetCache() {
+    if (this.cache) {
+      await this.cache.set("weather", {});
+    }
+  }
+
+  async resetWeather() {
+    await this.resetCache();
+    this.suggestions = [];
+    this.lastUpdated = null;
+  }
+
+  isEnabled() {
+    return (
+      this.store.getState().Prefs.values[PREF_SHOW_WEATHER] &&
+      this.store.getState().Prefs.values[PREF_SYSTEM_SHOW_WEATHER]
+    );
+  }
+
+  async init() {
+    await this.loadWeather(true /* isStartup */);
+  }
+
+  stopFetching() {
+    if (!this.merino) {
+      return;
+    }
+
+    lazy.clearTimeout(this.fetchTimer);
+    this.merino = null;
+    this.suggestions = null;
+    this.fetchTimer = 0;
+  }
+
+  /**
+   * This thin wrapper around the fetch call makes it easier for us to write
+   * automated tests that simulate responses.
+   */
+  async fetchHelper() {
+    this.restartFetchTimer();
+    const weatherQuery = this.store.getState().Prefs.values[PREF_WEATHER_QUERY];
+    let suggestions = [];
+    try {
+      suggestions = await this.merino.fetch({
+        query: weatherQuery || "",
+        providers: [MERINO_PROVIDER],
+        timeoutMs: 5000,
+      });
+    } catch (error) {
+      // We don't need to do anything with this right now.
+    }
+
+    // results from the API or empty array if null
+    this.suggestions = suggestions ?? [];
+  }
+
+  async fetch(isStartup) {
+    // Keep a handle on the `MerinoClient` instance that exists at the start of
+    // this fetch. If fetching stops or this `Weather` instance is uninitialized
+    // during the fetch, `#merino` will be nulled, and the fetch should stop. We
+    // can compare `merino` to `this.merino` to tell when this occurs.
+    this.merino = await this.MerinoClient("HNT_WEATHER_FEED");
+    await this.fetchHelper();
+
+    if (this.suggestions.length) {
+      this.lastUpdated = this.Date().now();
+      await this.cache.set("weather", {
+        suggestions: this.suggestions,
+        lastUpdated: this.lastUpdated,
+      });
+    }
+
+    this.update(isStartup);
+  }
+
+  async loadWeather(isStartup = false) {
+    const cachedData = (await this.cache.get()) || {};
+    const { weather } = cachedData;
+
+    // If we have nothing in cache, or cache has expired, we can make a fresh fetch.
+    if (
+      !weather?.lastUpdated ||
+      !(this.Date().now() - weather.lastUpdated < WEATHER_UPDATE_TIME)
+    ) {
+      await this.fetch(isStartup);
+    } else if (!this.lastUpdated) {
+      this.suggestions = weather.suggestions;
+      this.lastUpdated = weather.lastUpdated;
+      this.update(isStartup);
+    }
+  }
+
+  update(isStartup) {
+    this.store.dispatch(
+      ac.BroadcastToContent({
+        type: at.WEATHER_UPDATE,
+        data: {
+          suggestions: this.suggestions,
+          lastUpdated: this.lastUpdated,
+        },
+        meta: {
+          isStartup,
+        },
+      })
+    );
+  }
+
+  restartFetchTimer(ms = this.fetchIntervalMs) {
+    lazy.clearTimeout(this.fetchTimer);
+    this.fetchTimer = lazy.setTimeout(() => {
+      this.fetch();
+    }, ms);
+  }
+
+  async onPrefChangedAction(action) {
+    switch (action.data.name) {
+      case PREF_WEATHER_QUERY:
+        await this.loadWeather();
+        break;
+      case PREF_SHOW_WEATHER:
+      case PREF_SYSTEM_SHOW_WEATHER:
+        if (this.isEnabled() && action.data.value) {
+          await this.loadWeather();
+        } else {
+          await this.resetWeather();
+        }
+        break;
+    }
+  }
+
+  async onAction(action) {
+    switch (action.type) {
+      case at.INIT:
+        if (this.isEnabled()) {
+          await this.init();
+        }
+        break;
+      case at.UNINIT:
+        await this.resetWeather();
+        break;
+      case at.DISCOVERY_STREAM_DEV_SYSTEM_TICK:
+      case at.SYSTEM_TICK:
+        if (this.isEnabled()) {
+          await this.loadWeather();
+        }
+        break;
+      case at.PREF_CHANGED:
+        await this.onPrefChangedAction(action);
+        break;
+    }
+  }
+}
+
+/**
+ * Creating a thin wrapper around MerinoClient, PersistentCache, and Date.
+ * This makes it easier for us to write automated tests that simulate responses.
+ */
+WeatherFeed.prototype.MerinoClient = (...args) => {
+  return new lazy.MerinoClient(...args);
+};
+WeatherFeed.prototype.PersistentCache = (...args) => {
+  return new lazy.PersistentCache(...args);
+};
+WeatherFeed.prototype.Date = () => {
+  return Date;
+};