1 files changed, 104 insertions, 0 deletions
diff --git a/toolkit/components/normandy/actions/PreferenceRollbackAction.sys.mjs b/toolkit/components/normandy/actions/PreferenceRollbackAction.sys.mjs
new file mode 100644
index 0000000000..cc86ad8f70
--- /dev/null
+++ b/toolkit/components/normandy/actions/PreferenceRollbackAction.sys.mjs
@@ -0,0 +1,104 @@
+/* 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 { BaseAction } from "resource://normandy/actions/BaseAction.sys.mjs";
+
+const lazy = {};
+ChromeUtils.defineESModuleGetters(lazy, {
+  ActionSchemas: "resource://normandy/actions/schemas/index.sys.mjs",
+  PrefUtils: "resource://normandy/lib/PrefUtils.sys.mjs",
+  PreferenceRollouts: "resource://normandy/lib/PreferenceRollouts.sys.mjs",
+  TelemetryEnvironment: "resource://gre/modules/TelemetryEnvironment.sys.mjs",
+  TelemetryEvents: "resource://normandy/lib/TelemetryEvents.sys.mjs",
+});
+
+export class PreferenceRollbackAction extends BaseAction {
+  get schema() {
+    return lazy.ActionSchemas["preference-rollback"];
+  }
+
+  async _run(recipe) {
+    const { rolloutSlug } = recipe.arguments;
+    const rollout = await lazy.PreferenceRollouts.get(rolloutSlug);
+
+    if (lazy.PreferenceRollouts.GRADUATION_SET.has(rolloutSlug)) {
+      // graduated rollouts can't be rolled back
+      lazy.TelemetryEvents.sendEvent(
+        "unenrollFailed",
+        "preference_rollback",
+        rolloutSlug,
+        {
+          reason: "in-graduation-set",
+          enrollmentId:
+            rollout?.enrollmentId ??
+            lazy.TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
+        }
+      );
+      throw new Error(
+        `Cannot rollback rollout in graduation set "${rolloutSlug}".`
+      );
+    }
+
+    if (!rollout) {
+      this.log.debug(`Rollback ${rolloutSlug} not applicable, skipping`);
+      return;
+    }
+
+    switch (rollout.state) {
+      case lazy.PreferenceRollouts.STATE_ACTIVE: {
+        this.log.info(`Rolling back ${rolloutSlug}`);
+        rollout.state = lazy.PreferenceRollouts.STATE_ROLLED_BACK;
+        for (const { preferenceName, previousValue } of rollout.preferences) {
+          lazy.PrefUtils.setPref(preferenceName, previousValue, {
+            branch: "default",
+          });
+        }
+        await lazy.PreferenceRollouts.update(rollout);
+        lazy.TelemetryEvents.sendEvent(
+          "unenroll",
+          "preference_rollback",
+          rolloutSlug,
+          {
+            reason: "rollback",
+            enrollmentId:
+              rollout.enrollmentId ||
+              lazy.TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
+          }
+        );
+        lazy.TelemetryEnvironment.setExperimentInactive(rolloutSlug);
+        break;
+      }
+      case lazy.PreferenceRollouts.STATE_ROLLED_BACK: {
+        // The rollout has already been rolled back, so nothing to do here.
+        break;
+      }
+      case lazy.PreferenceRollouts.STATE_GRADUATED: {
+        // graduated rollouts can't be rolled back
+        lazy.TelemetryEvents.sendEvent(
+          "unenrollFailed",
+          "preference_rollback",
+          rolloutSlug,
+          {
+            reason: "graduated",
+            enrollmentId:
+              rollout.enrollmentId ||
+              lazy.TelemetryEvents.NO_ENROLLMENT_ID_MARKER,
+          }
+        );
+        throw new Error(
+          `Cannot rollback already graduated rollout ${rolloutSlug}`
+        );
+      }
+      default: {
+        throw new Error(
+          `Unexpected state when rolling back ${rolloutSlug}: ${rollout.state}`
+        );
+      }
+    }
+  }
+
+  async _finalize() {
+    await lazy.PreferenceRollouts.saveStartupPrefs();
+  }
+}