1 files changed, 116 insertions, 0 deletions
diff --git a/toolkit/components/normandy/lib/PrefUtils.jsm b/toolkit/components/normandy/lib/PrefUtils.jsm
new file mode 100644
index 0000000000..6118bfc366
--- /dev/null
+++ b/toolkit/components/normandy/lib/PrefUtils.jsm
@@ -0,0 +1,116 @@
+/* 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";
+
+const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
+const { XPCOMUtils } = ChromeUtils.import(
+  "resource://gre/modules/XPCOMUtils.jsm"
+);
+ChromeUtils.defineModuleGetter(
+  this,
+  "LogManager",
+  "resource://normandy/lib/LogManager.jsm"
+);
+
+var EXPORTED_SYMBOLS = ["PrefUtils"];
+
+XPCOMUtils.defineLazyGetter(this, "log", () => {
+  return LogManager.getLogger("preference-experiments");
+});
+
+const kPrefBranches = {
+  user: Services.prefs,
+  default: Services.prefs.getDefaultBranch(""),
+};
+
+var PrefUtils = {
+  /**
+   * Get a preference from the named branch
+   * @param {string} branchName One of "default" or "user"
+   * @param {string} pref
+   * @param {string|boolean|integer|null} [default]
+   *   The value to return if the preference does not exist. Defaults to null.
+   */
+  getPref(branchName, pref, defaultValue = null) {
+    const branch = kPrefBranches[branchName];
+    const type = branch.getPrefType(pref);
+
+    try {
+      switch (type) {
+        case Services.prefs.PREF_BOOL: {
+          return branch.getBoolPref(pref);
+        }
+        case Services.prefs.PREF_STRING: {
+          return branch.getStringPref(pref);
+        }
+        case Services.prefs.PREF_INT: {
+          return branch.getIntPref(pref);
+        }
+        case Services.prefs.PREF_INVALID: {
+          return defaultValue;
+        }
+      }
+    } catch (e) {
+      if (branchName === "default" && e.result === Cr.NS_ERROR_UNEXPECTED) {
+        // There is a value for the pref on the user branch but not on the default branch. This is ok.
+        return defaultValue;
+      }
+      // Unexpected error, re-throw it
+      throw e;
+    }
+
+    // If `type` isn't any of the above, throw an error. Don't do this in a
+    // default branch of switch so that error handling is easier.
+    throw new TypeError(`Unknown preference type (${type}) for ${pref}.`);
+  },
+
+  /**
+   * Set a preference on the named branch
+   * @param {string} branchName One of "default" or "user"
+   * @param {string} pref
+   * @param {string|boolean|integer|null} value
+   *   The value to set. Must match the type named in `type`.
+   */
+  setPref(branchName, pref, value) {
+    if (value === null) {
+      this.clearPref(branchName, pref);
+      return;
+    }
+    const branch = kPrefBranches[branchName];
+    switch (typeof value) {
+      case "boolean": {
+        branch.setBoolPref(pref, value);
+        break;
+      }
+      case "string": {
+        branch.setStringPref(pref, value);
+        break;
+      }
+      case "number": {
+        branch.setIntPref(pref, value);
+        break;
+      }
+      default: {
+        throw new TypeError(
+          `Unexpected value type (${typeof value}) for ${pref}.`
+        );
+      }
+    }
+  },
+
+  /**
+   * Remove a preference from a branch.
+   * @param {string} branchName One of "default" or "user"
+   * @param {string} pref
+   */
+  clearPref(branchName, pref) {
+    if (branchName === "user") {
+      kPrefBranches.user.clearUserPref(pref);
+    } else if (branchName === "default") {
+      log.warn(
+        `Cannot not reset pref ${pref} on the default branch. Pref will be cleared at next restart.`
+      );
+    }
+  },
+};