1 files changed, 106 insertions, 0 deletions
diff --git a/application/basilisk/components/sessionstore/SessionMigration.jsm b/application/basilisk/components/sessionstore/SessionMigration.jsm
new file mode 100644
index 0000000000..1aa22f1a9d
--- /dev/null
+++ b/application/basilisk/components/sessionstore/SessionMigration.jsm
@@ -0,0 +1,106 @@
+/* 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";
+
+this.EXPORTED_SYMBOLS = ["SessionMigration"];
+
+const Cu = Components.utils;
+Cu.import("resource://gre/modules/XPCOMUtils.jsm", this);
+Cu.import("resource://gre/modules/Task.jsm", this);
+Cu.import("resource://gre/modules/osfile.jsm", this);
+
+XPCOMUtils.defineLazyModuleGetter(this, "Utils",
+  "resource://gre/modules/sessionstore/Utils.jsm");
+
+// An encoder to UTF-8.
+XPCOMUtils.defineLazyGetter(this, "gEncoder", function () {
+  return new TextEncoder();
+});
+
+// A decoder.
+XPCOMUtils.defineLazyGetter(this, "gDecoder", function () {
+  return new TextDecoder();
+});
+
+var SessionMigrationInternal = {
+  /**
+   * Convert the original session restore state into a minimal state. It will
+   * only contain:
+   * - open windows
+   *   - with tabs
+   *     - with history entries with only title, url, triggeringPrincipal
+   *     - with pinned state
+   *     - with tab group info (hidden + group id)
+   *     - with selected tab info
+   *   - with selected window info
+   *
+   * The complete state is then wrapped into the "about:welcomeback" page as
+   * form field info to be restored when restoring the state.
+   */
+  convertState: function(aStateObj) {
+    let state = {
+      selectedWindow: aStateObj.selectedWindow,
+      _closedWindows: []
+    };
+    state.windows = aStateObj.windows.map(function(oldWin) {
+      var win = {extData: {}};
+      win.tabs = oldWin.tabs.map(function(oldTab) {
+        var tab = {};
+        // Keep only titles, urls and triggeringPrincipals for history entries
+        tab.entries = oldTab.entries.map(function(entry) {
+          return { url: entry.url,
+                   triggeringPrincipal_base64: entry.triggeringPrincipal_base64,
+                   title: entry.title };
+        });
+        tab.index = oldTab.index;
+        tab.hidden = oldTab.hidden;
+        tab.pinned = oldTab.pinned;
+        return tab;
+      });
+      win.selected = oldWin.selected;
+      win._closedTabs = [];
+      return win;
+    });
+    let url = "about:welcomeback";
+    let formdata = {id: {sessionData: state}, url};
+    let entry = { url, triggeringPrincipal_base64: Utils.SERIALIZED_SYSTEMPRINCIPAL };
+    return { windows: [{ tabs: [{ entries: [ entry ], formdata}]}]};
+  },
+  /**
+   * Asynchronously read session restore state (JSON) from a path
+   */
+  readState: function(aPath) {
+    return Task.spawn(function() {
+      let bytes = yield OS.File.read(aPath);
+      let text = gDecoder.decode(bytes);
+      let state = JSON.parse(text);
+      throw new Task.Result(state);
+    });
+  },
+  /**
+   * Asynchronously write session restore state as JSON to a path
+   */
+  writeState: function(aPath, aState) {
+    let bytes = gEncoder.encode(JSON.stringify(aState));
+    return OS.File.writeAtomic(aPath, bytes, {tmpPath: aPath + ".tmp"});
+  }
+}
+
+var SessionMigration = {
+  /**
+   * Migrate a limited set of session data from one path to another.
+   */
+  migrate: function(aFromPath, aToPath) {
+    return Task.spawn(function() {
+      let inState = yield SessionMigrationInternal.readState(aFromPath);
+      let outState = SessionMigrationInternal.convertState(inState);
+      // Unfortunately, we can't use SessionStore's own SessionFile to
+      // write out the data because it has a dependency on the profile dir
+      // being known. When the migration runs, there is no guarantee that
+      // that's true.
+      yield SessionMigrationInternal.writeState(aToPath, outState);
+    });
+  }
+};