1 files changed, 329 insertions, 0 deletions
diff --git a/remote/marionette/message.sys.mjs b/remote/marionette/message.sys.mjs
new file mode 100644
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+++ b/remote/marionette/message.sys.mjs
@@ -0,0 +1,329 @@
+/* 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 lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  assert: "chrome://remote/content/shared/webdriver/Assert.sys.mjs",
+  error: "chrome://remote/content/shared/webdriver/Errors.sys.mjs",
+  truncate: "chrome://remote/content/shared/Format.sys.mjs",
+});
+
+/** Representation of the packets transproted over the wire. */
+export class Message {
+  /**
+   * @param {number} messageID
+   *     Message ID unique identifying this message.
+   */
+  constructor(messageID) {
+    this.id = lazy.assert.integer(messageID);
+  }
+
+  toString() {
+    function replacer(key, value) {
+      if (typeof value === "string") {
+        return lazy.truncate`${value}`;
+      }
+      return value;
+    }
+
+    return JSON.stringify(this.toPacket(), replacer);
+  }
+
+  /**
+   * Converts a data packet into a {@link Command} or {@link Response}.
+   *
+   * @param {Array.<number, number, ?, ?>} data
+   *     A four element array where the elements, in sequence, signifies
+   *     message type, message ID, method name or error, and parameters
+   *     or result.
+   *
+   * @return {Message}
+   *     Based on the message type, a {@link Command} or {@link Response}
+   *     instance.
+   *
+   * @throws {TypeError}
+   *     If the message type is not recognised.
+   */
+  static fromPacket(data) {
+    const [type] = data;
+
+    switch (type) {
+      case Command.Type:
+        return Command.fromPacket(data);
+
+      case Response.Type:
+        return Response.fromPacket(data);
+
+      default:
+        throw new TypeError(
+          "Unrecognised message type in packet: " + JSON.stringify(data)
+        );
+    }
+  }
+}
+
+/**
+ * Messages may originate from either the server or the client.
+ * Because the remote protocol is full duplex, both endpoints may be
+ * the origin of both commands and responses.
+ *
+ * @enum
+ * @see {@link Message}
+ */
+Message.Origin = {
+  /** Indicates that the message originates from the client. */
+  Client: 0,
+  /** Indicates that the message originates from the server. */
+  Server: 1,
+};
+
+/**
+ * A command is a request from the client to run a series of remote end
+ * steps and return a fitting response.
+ *
+ * The command can be synthesised from the message passed over the
+ * Marionette socket using the {@link fromPacket} function.  The format of
+ * a message is:
+ *
+ * <pre>
+ *     [<var>type</var>, <var>id</var>, <var>name</var>, <var>params</var>]
+ * </pre>
+ *
+ * where
+ *
+ * <dl>
+ *   <dt><var>type</var> (integer)
+ *   <dd>
+ *     Must be zero (integer).  Zero means that this message is
+ *     a command.
+ *
+ *   <dt><var>id</var> (integer)
+ *   <dd>
+ *     Integer used as a sequence number.  The server replies with
+ *     the same ID for the response.
+ *
+ *   <dt><var>name</var> (string)
+ *   <dd>
+ *     String representing the command name with an associated set
+ *     of remote end steps.
+ *
+ *   <dt><var>params</var> (JSON Object or null)
+ *   <dd>
+ *     Object of command function arguments.  The keys of this object
+ *     must be strings, but the values can be arbitrary values.
+ * </dl>
+ *
+ * A command has an associated message <var>id</var> that prevents
+ * the dispatcher from sending responses in the wrong order.
+ *
+ * The command may also have optional error- and result handlers that
+ * are called when the client returns with a response.  These are
+ * <code>function onerror({Object})</code>,
+ * <code>function onresult({Object})</code>, and
+ * <code>function onresult({Response})</code>:
+ *
+ * @param {number} messageID
+ *     Message ID unique identifying this message.
+ * @param {string} name
+ *     Command name.
+ * @param {Object.<string, ?>} params
+ *     Command parameters.
+ */
+export class Command extends Message {
+  constructor(messageID, name, params = {}) {
+    super(messageID);
+
+    this.name = lazy.assert.string(name);
+    this.parameters = lazy.assert.object(params);
+
+    this.onerror = null;
+    this.onresult = null;
+
+    this.origin = Message.Origin.Client;
+    this.sent = false;
+  }
+
+  /**
+   * Calls the error- or result handler associated with this command.
+   * This function can be replaced with a custom response handler.
+   *
+   * @param {Response} resp
+   *     The response to pass on to the result or error to the
+   *     <code>onerror</code> or <code>onresult</code> handlers to.
+   */
+  onresponse(resp) {
+    if (this.onerror && resp.error) {
+      this.onerror(resp.error);
+    } else if (this.onresult && resp.body) {
+      this.onresult(resp.body);
+    }
+  }
+
+  /**
+   * Encodes the command to a packet.
+   *
+   * @return {Array}
+   *     Packet.
+   */
+  toPacket() {
+    return [Command.Type, this.id, this.name, this.parameters];
+  }
+
+  /**
+   * Converts a data packet into {@link Command}.
+   *
+   * @param {Array.<number, number, ?, ?>} data
+   *     A four element array where the elements, in sequence, signifies
+   *     message type, message ID, command name, and parameters.
+   *
+   * @return {Command}
+   *     Representation of packet.
+   *
+   * @throws {TypeError}
+   *     If the message type is not recognised.
+   */
+  static fromPacket(payload) {
+    let [type, msgID, name, params] = payload;
+    lazy.assert.that(n => n === Command.Type)(type);
+
+    // if parameters are given but null, treat them as undefined
+    if (params === null) {
+      params = undefined;
+    }
+
+    return new Command(msgID, name, params);
+  }
+}
+
+Command.Type = 0;
+
+/**
+ * @callback ResponseCallback
+ *
+ * @param {Response} resp
+ *     Response to handle.
+ */
+
+/**
+ * Represents the response returned from the remote end after execution
+ * of its corresponding command.
+ *
+ * The response is a mutable object passed to each command for
+ * modification through the available setters.  To send data in a response,
+ * you modify the body property on the response.  The body property can
+ * also be replaced completely.
+ *
+ * The response is sent implicitly by
+ * {@link server.TCPConnection#execute when a command has finished
+ * executing, and any modifications made subsequent to that will have
+ * no effect.
+ *
+ * @param {number} messageID
+ *     Message ID tied to the corresponding command request this is
+ *     a response for.
+ * @param {ResponseHandler} respHandler
+ *     Function callback called on sending the response.
+ */
+export class Response extends Message {
+  constructor(messageID, respHandler = () => {}) {
+    super(messageID);
+
+    this.respHandler_ = lazy.assert.callable(respHandler);
+
+    this.error = null;
+    this.body = { value: null };
+
+    this.origin = Message.Origin.Server;
+    this.sent = false;
+  }
+
+  /**
+   * Sends response conditionally, given a predicate.
+   *
+   * @param {function(Response): boolean} predicate
+   *     A predicate taking a Response object and returning a boolean.
+   */
+  sendConditionally(predicate) {
+    if (predicate(this)) {
+      this.send();
+    }
+  }
+
+  /**
+   * Sends response using the response handler provided on
+   * construction.
+   *
+   * @throws {RangeError}
+   *     If the response has already been sent.
+   */
+  send() {
+    if (this.sent) {
+      throw new RangeError("Response has already been sent: " + this);
+    }
+    this.respHandler_(this);
+    this.sent = true;
+  }
+
+  /**
+   * Send error to client.
+   *
+   * Turns the response into an error response, clears any previously
+   * set body data, and sends it using the response handler provided
+   * on construction.
+   *
+   * @param {Error} err
+   *     The Error instance to send.
+   *
+   * @throws {Error}
+   *     If <var>err</var> is not a {@link WebDriverError}, the error
+   *     is propagated, i.e. rethrown.
+   */
+  sendError(err) {
+    this.error = lazy.error.wrap(err).toJSON();
+    this.body = null;
+    this.send();
+
+    // propagate errors which are implementation problems
+    if (!lazy.error.isWebDriverError(err)) {
+      throw err;
+    }
+  }
+
+  /**
+   * Encodes the response to a packet.
+   *
+   * @return {Array}
+   *     Packet.
+   */
+  toPacket() {
+    return [Response.Type, this.id, this.error, this.body];
+  }
+
+  /**
+   * Converts a data packet into {@link Response}.
+   *
+   * @param {Array.<number, number, ?, ?>} data
+   *     A four element array where the elements, in sequence, signifies
+   *     message type, message ID, error, and result.
+   *
+   * @return {Response}
+   *     Representation of packet.
+   *
+   * @throws {TypeError}
+   *     If the message type is not recognised.
+   */
+  static fromPacket(payload) {
+    let [type, msgID, err, body] = payload;
+    lazy.assert.that(n => n === Response.Type)(type);
+
+    let resp = new Response(msgID);
+    resp.error = lazy.assert.string(err);
+
+    resp.body = body;
+    return resp;
+  }
+}
+
+Response.Type = 1;