1 files changed, 175 insertions, 0 deletions
diff --git a/remote/marionette/prefs.sys.mjs b/remote/marionette/prefs.sys.mjs
new file mode 100644
index 0000000000..17df13d0fd
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+++ b/remote/marionette/prefs.sys.mjs
@@ -0,0 +1,175 @@
+/* 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 { PREF_BOOL, PREF_INT, PREF_INVALID, PREF_STRING } = Ci.nsIPrefBranch;
+
+export class Branch {
+  /**
+   * @param {string=} branch
+   *     Preference subtree.  Uses root tree given `null`.
+   */
+  constructor(branch) {
+    this._branch = Services.prefs.getBranch(branch);
+  }
+
+  /**
+   * Gets value of `pref` in its known type.
+   *
+   * @param {string} pref
+   *     Preference name.
+   * @param {*=} fallback
+   *     Fallback value to return if `pref` does not exist.
+   *
+   * @returns {(string|boolean|number)}
+   *     Value of `pref`, or the `fallback` value if `pref` does
+   *     not exist.
+   *
+   * @throws {TypeError}
+   *     If `pref` is not a recognised preference and no `fallback`
+   *     value has been provided.
+   */
+  get(pref, fallback = null) {
+    switch (this._branch.getPrefType(pref)) {
+      case PREF_STRING:
+        return this._branch.getStringPref(pref);
+
+      case PREF_BOOL:
+        return this._branch.getBoolPref(pref);
+
+      case PREF_INT:
+        return this._branch.getIntPref(pref);
+
+      case PREF_INVALID:
+      default:
+        if (fallback != null) {
+          return fallback;
+        }
+        throw new TypeError(`Unrecognised preference: ${pref}`);
+    }
+  }
+
+  /**
+   * Sets the value of `pref`.
+   *
+   * @param {string} pref
+   *     Preference name.
+   * @param {(string|boolean|number)} value
+   *     `pref`'s new value.
+   *
+   * @throws {TypeError}
+   *     If `value` is not the correct type for `pref`.
+   */
+  set(pref, value) {
+    let typ;
+    if (typeof value != "undefined" && value != null) {
+      typ = value.constructor.name;
+    }
+
+    switch (typ) {
+      case "String":
+        // Unicode compliant
+        return this._branch.setStringPref(pref, value);
+
+      case "Boolean":
+        return this._branch.setBoolPref(pref, value);
+
+      case "Number":
+        return this._branch.setIntPref(pref, value);
+
+      default:
+        throw new TypeError(`Illegal preference type value: ${typ}`);
+    }
+  }
+}
+
+/**
+ * Provides shortcuts for lazily getting and setting typed Marionette
+ * preferences.
+ *
+ * Some of Marionette's preferences are stored using primitive values
+ * that internally are represented by complex types.
+ *
+ * Because we cannot trust the input of many of these preferences,
+ * this class provides abstraction that lets us safely deal with
+ * potentially malformed input.
+ *
+ * A further complication is that we cannot rely on `Preferences.sys.mjs`
+ * in Marionette.  See https://bugzilla.mozilla.org/show_bug.cgi?id=1357517
+ * for further details.
+ */
+class MarionetteBranch extends Branch {
+  constructor(branch = "marionette.") {
+    super(branch);
+  }
+
+  /**
+   * The `marionette.debugging.clicktostart` preference delays
+   * server startup until a modal dialogue has been clicked to allow
+   * time for user to set breakpoints in the Browser Toolbox.
+   *
+   * @returns {boolean}
+   */
+  get clickToStart() {
+    return this.get("debugging.clicktostart", false);
+  }
+
+  /**
+   * The `marionette.port` preference, detailing which port
+   * the TCP server should listen on.
+   *
+   * @returns {number}
+   */
+  get port() {
+    return this.get("port", 2828);
+  }
+
+  set port(newPort) {
+    this.set("port", newPort);
+  }
+
+  /**
+   * Gets the `marionette.setpermission.enabled` preference, should
+   * only be used for testdriver's set_permission API.
+   *
+   * @returns {boolean}
+   */
+  get setPermissionEnabled() {
+    return this.get("setpermission.enabled", false);
+  }
+}
+
+/** Reads a JSON serialised blob stored in the environment. */
+export class EnvironmentPrefs {
+  /**
+   * Reads the environment variable `key` and tries to parse it as
+   * JSON Object, then provides an iterator over its keys and values.
+   *
+   * If the environment variable is not set, this function returns empty.
+   *
+   * @param {string} key
+   *     Environment variable.
+   *
+   * @returns {Iterable.<string, (string|boolean|number)>}
+   */
+  static *from(key) {
+    if (!Services.env.exists(key)) {
+      return;
+    }
+
+    let prefs;
+    try {
+      prefs = JSON.parse(Services.env.get(key));
+    } catch (e) {
+      throw new TypeError(`Unable to parse prefs from ${key}`, e);
+    }
+
+    for (let prefName of Object.keys(prefs)) {
+      yield [prefName, prefs[prefName]];
+    }
+  }
+}
+
+// There is a future potential of exposing this as Marionette.prefs.port
+// if we introduce a Marionette.jsm module.
+export const MarionettePrefs = new MarionetteBranch();