components/sync/driver/resources/sync_log.ts

// Copyright 2011 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import {addWebUiListener} from 'chrome://resources/js/cr.js';

interface LogEntry {
  submodule: string;
  event: string;
  date: Date;
  details: object;
  textDetails: string;
}

/**
 * Creates a new log object which then immediately starts recording sync
 * protocol events.  Recorded entries are available in the 'entries'
 * property and there is an 'append' event which can be listened to.
 */
class Log extends EventTarget {
  /** Must match the value in SyncInternalsMessageHandler::OnProtocolEvent(). */
  private protocolEventName_: string = 'onProtocolEvent';

  /** The recorded log entries. */
  entries: LogEntry[] = [];

  constructor() {
    super();

    addWebUiListener(this.protocolEventName_, (response: object) => {
      this.log_(response);
    });
  }

  /**
   * Records a single event with the given parameters and fires the
   * 'append' event with the newly-created event as the 'detail'
   * field of a custom event.
   * @param details A dictionary of event-specific details.
   */
  private log_(details: object) {
    const entry = {
      submodule: 'protocol',
      event: this.protocolEventName_,
      date: new Date(),
      details: details,
      textDetails: '',
    };
    entry.textDetails = JSON.stringify(entry.details, null, 2);
    this.entries.push(entry);
    // Fire append event.
    const e = new CustomEvent(
        'append', {bubbles: false, cancelable: false, detail: entry});
    this.dispatchEvent(e);
  }
}

export const log = new Log();