1 files changed, 201 insertions, 0 deletions
diff --git a/toolkit/mozapps/extensions/content/view-controller.js b/toolkit/mozapps/extensions/content/view-controller.js
new file mode 100644
index 0000000000..7e9516024c
--- /dev/null
+++ b/toolkit/mozapps/extensions/content/view-controller.js
@@ -0,0 +1,201 @@
+/* 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/. */
+
+"use strict";
+
+/* import-globals-from /toolkit/content/customElements.js */
+/* import-globals-from aboutaddonsCommon.js */
+/* exported loadView */
+
+// Used by external callers to load a specific view into the manager
+function loadView(viewId) {
+  if (!gViewController.readyForLoadView) {
+    throw new Error("loadView called before about:addons is initialized");
+  }
+  gViewController.loadView(viewId);
+}
+
+/**
+ * Helper for saving and restoring the scroll offsets when a previously loaded
+ * view is accessed again.
+ */
+var ScrollOffsets = {
+  _key: null,
+  _offsets: new Map(),
+  canRestore: true,
+
+  setView(historyEntryId) {
+    this._key = historyEntryId;
+    this.canRestore = true;
+  },
+
+  getPosition() {
+    if (!this.canRestore) {
+      return { top: 0, left: 0 };
+    }
+    let { scrollTop: top, scrollLeft: left } = document.documentElement;
+    return { top, left };
+  },
+
+  save() {
+    if (this._key) {
+      this._offsets.set(this._key, this.getPosition());
+    }
+  },
+
+  restore() {
+    let { top = 0, left = 0 } = this._offsets.get(this._key) || {};
+    window.scrollTo({ top, left, behavior: "auto" });
+  },
+};
+
+var gViewController = {
+  currentViewId: null,
+  readyForLoadView: false,
+  get defaultViewId() {
+    if (!isDiscoverEnabled()) {
+      return "addons://list/extension";
+    }
+    return "addons://discover/";
+  },
+  isLoading: true,
+  // All historyEntryId values must be unique within one session, because the
+  // IDs are used to map history entries to page state. It is not possible to
+  // see whether a historyEntryId was used in history entries before this page
+  // was loaded, so start counting from a random value to avoid collisions.
+  // This is used for scroll offsets in aboutaddons.js
+  nextHistoryEntryId: Math.floor(Math.random() * 2 ** 32),
+  views: {},
+
+  initialize(container) {
+    this.container = container;
+
+    window.addEventListener("popstate", this);
+    window.addEventListener("unload", this, { once: true });
+    Services.obs.addObserver(this, "EM-ping");
+  },
+
+  handleEvent(e) {
+    if (e.type == "popstate") {
+      this.renderState(e.state);
+      return;
+    }
+
+    if (e.type == "unload") {
+      Services.obs.removeObserver(this, "EM-ping");
+      // eslint-disable-next-line no-useless-return
+      return;
+    }
+  },
+
+  observe(subject, topic, data) {
+    if (topic == "EM-ping") {
+      this.readyForLoadView = true;
+      Services.obs.notifyObservers(window, "EM-pong");
+    }
+  },
+
+  notifyEMLoaded() {
+    this.readyForLoadView = true;
+    Services.obs.notifyObservers(window, "EM-loaded");
+  },
+
+  notifyEMUpdateCheckFinished() {
+    // Notify the observer about a completed update check (currently only used in tests).
+    Services.obs.notifyObservers(null, "EM-update-check-finished");
+  },
+
+  defineView(viewName, renderFunction) {
+    if (this.views[viewName]) {
+      throw new Error(
+        `about:addons view ${viewName} should not be defined twice`
+      );
+    }
+    this.views[viewName] = renderFunction;
+  },
+
+  parseViewId(viewId) {
+    const matchRegex = /^addons:\/\/([^\/]+)\/(.*)$/;
+    const [, viewType, viewParam] = viewId.match(matchRegex) || [];
+    return { type: viewType, param: decodeURIComponent(viewParam) };
+  },
+
+  loadView(viewId, replace = false) {
+    viewId = viewId.startsWith("addons://") ? viewId : `addons://${viewId}`;
+    if (viewId == this.currentViewId) {
+      return Promise.resolve();
+    }
+
+    // Always rewrite history state instead of pushing incorrect state for initial load.
+    replace = replace || !this.currentViewId;
+
+    const state = {
+      view: viewId,
+      previousView: replace ? null : this.currentViewId,
+      historyEntryId: ++this.nextHistoryEntryId,
+    };
+    if (replace) {
+      history.replaceState(state, "");
+    } else {
+      history.pushState(state, "");
+    }
+    return this.renderState(state);
+  },
+
+  async renderState(state) {
+    let { param, type } = this.parseViewId(state.view);
+
+    if (!type || this.views[type] == null) {
+      console.warn(`No view for ${type} ${param}, switching to default`);
+      this.resetState();
+      return;
+    }
+
+    this.currentViewId = state.view;
+    this.isLoading = true;
+
+    // Perform tasks before view load
+    document.dispatchEvent(
+      new CustomEvent("view-selected", {
+        detail: { id: state.view, param, type },
+      })
+    );
+
+    // Render the fragment
+    this.container.setAttribute("current-view", type);
+    let fragment = await this.views[type](param);
+
+    // Clear and append the fragment
+    if (fragment) {
+      ScrollOffsets.save();
+      ScrollOffsets.setView(state.historyEntryId);
+
+      this.container.textContent = "";
+      this.container.append(fragment);
+
+      // Most content has been rendered at this point. The only exception are
+      // recommendations in the discovery pane and extension/theme list, because
+      // they rely on remote data. If loaded before, then these may be rendered
+      // within one tick, so wait a frame before restoring scroll offsets.
+      await new Promise(resolve => {
+        window.requestAnimationFrame(() => {
+          ScrollOffsets.restore();
+          resolve();
+        });
+      });
+    } else {
+      // Reset to default view if no given content
+      this.resetState();
+      return;
+    }
+
+    this.isLoading = false;
+
+    document.dispatchEvent(new CustomEvent("view-loaded"));
+  },
+
+  resetState() {
+    return this.loadView(this.defaultViewId, true);
+  },
+};