// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

/**
 * `usage` is a wrapper around Google Analytics for both command-line apps
 * and web apps.
 *
 * In order to use this library as a web app, import the `analytics_html.dart`
 * library and instantiate the [AnalyticsHtml] class.
 *
 * In order to use this library as a command-line app, import the
 * `analytics_io.dart` library and instantiate the [AnalyticsIO] class.
 *
 * For both classes, you need to provide a Google Analytics tracking ID, the
 * application name, and the application version.
 *
 * Your application should provide an opt-in option for the user. If they
 * opt-in, set the [optIn] field to `true`. This setting will persist across
 * sessions automatically.
 *
 * For more information, please see the Google Analytics Measurement Protocol
 * [Policy](https://developers.google.com/analytics/devguides/collection/protocol/policy).
 */
library usage;

import 'dart:async';

// Matches file:/, non-ws, /, non-ws, .dart
final RegExp _pathRegex = new RegExp(r'file:/\S+/(\S+\.dart)');

// Match multiple tabs or spaces.
final RegExp _tabOrSpaceRegex = new RegExp(r'[\t ]+');

/**
 * An interface to a Google Analytics session. [AnalyticsHtml] and [AnalyticsIO]
 * are concrete implementations of this interface. [AnalyticsMock] can be used
 * for testing or for some variants of an opt-in workflow.
 *
 * The analytics information is sent on a best-effort basis. So, failures to
 * send the GA information will not result in errors from the asynchronous
 * `send` methods.
 */
abstract class Analytics {
  /**
   * Tracking ID / Property ID.
   */
  String get trackingId;

  /**
   * Is this the first time the tool has run?
   */
  bool get firstRun;

  /**
   * Whether the [Analytics] instance is configured in an opt-in or opt-out manner.
   */
  AnalyticsOpt analyticsOpt = AnalyticsOpt.optOut;

  /**
   * Will analytics data be sent.
   */
  bool get enabled;

  /**
   * Enable or disable sending of analytics data.
   */
  set enabled(bool value);

  /**
   * Anonymous client ID in UUID v4 format.
   *
   * The value is randomly-generated and should be reasonably stable for the
   * computer sending analytics data.
   */
  String get clientId;

  /**
   * Sends a screen view hit to Google Analytics.
   * 
   * [parameters] can be any analytics key/value pair. Useful
   * for custom dimensions, etc.
   */
  Future sendScreenView(String viewName, { Map<String, String> parameters });

  /**
   * Sends an Event hit to Google Analytics. [label] specifies the event label.
   * [value] specifies the event value. Values must be non-negative.
   */
  Future sendEvent(String category, String action, {String label, int value});

  /**
   * Sends a Social hit to Google Analytics. [network] specifies the social
   * network, for example Facebook or Google Plus. [action] specifies the social
   * interaction action. For example on Google Plus when a user clicks the +1
   * button, the social action is 'plus'. [target] specifies the target of a
   * social interaction. This value is typically a URL but can be any text.
   */
  Future sendSocial(String network, String action, String target);

  /**
   * Sends a Timing hit to Google Analytics. [variableName] specifies the
   * variable name of the timing. [time] specifies the user timing value (in
   * milliseconds). [category] specifies the category of the timing. [label]
   * specifies the label of the timing.
   */
  Future sendTiming(String variableName, int time,
      {String category, String label});

  /**
   * Start a timer. The time won't be calculated, and the analytics information
   * sent, until the [AnalyticsTimer.finish] method is called.
   */
  AnalyticsTimer startTimer(String variableName,
      {String category, String label});

  /**
   * In order to avoid sending any personally identifying information, the
   * [description] field must not contain the exception message. In addition,
   * only the first 100 chars of the description will be sent.
   */
  Future sendException(String description, {bool fatal});

  /**
   * Gets a session variable value.
   */
  dynamic getSessionValue(String param);

  /**
   * Sets a session variable value. The value is persistent for the life of the
   * [Analytics] instance. This variable will be sent in with every analytics
   * hit. A list of valid variable names can be found here:
   * https://developers.google.com/analytics/devguides/collection/protocol/v1/parameters.
   */
  void setSessionValue(String param, dynamic value);

  /**
   * Fires events when the usage library sends any data over the network. This
   * will not fire if analytics has been disabled or if the throttling algorithm
   * has been engaged.
   *
   * This method is public to allow library clients to more easily test their
   * analytics implementations.
   */
  Stream<Map<String, dynamic>> get onSend;

  /**
   * Wait for all of the outstanding analytics pings to complete. The returned
   * `Future` will always complete without errors. You can pass in an optional
   * `Duration` to specify to only wait for a certain amount of time.
   *
   * This method is particularly useful for command-line clients. Outstanding
   * I/O requests will cause the VM to delay terminating the process. Generally,
   * users won't want their CLI app to pause at the end of the process waiting
   * for Google analytics requests to complete. This method allows CLI apps to
   * delay for a short time waiting for GA requests to complete, and then do
   * something like call `exit()` explicitly themselves.
   */
  Future waitForLastPing({Duration timeout});
}

enum AnalyticsOpt {
  /**
   * Users must opt-in before any analytics data is sent.
   */
  optIn,

  /**
   * Users must opt-out for analytics data to not be sent.
   */
  optOut
}

/**
 * An object, returned by [Analytics.startTimer], that is used to measure an
 * asynchronous process.
 */
class AnalyticsTimer {
  final Analytics analytics;
  final String variableName;
  final String category;
  final String label;

  int _startMillis;
  int _endMillis;

  AnalyticsTimer(this.analytics, this.variableName,
      {this.category, this.label}) {
    _startMillis = new DateTime.now().millisecondsSinceEpoch;
  }

  int get currentElapsedMillis {
    if (_endMillis == null) {
      return new DateTime.now().millisecondsSinceEpoch - _startMillis;
    } else {
      return _endMillis - _startMillis;
    }
  }

  /**
   * Finish the timer, calculate the elapsed time, and send the information to
   * analytics. Once this is called, any future invocations are no-ops.
   */
  Future finish() {
    if (_endMillis != null) return new Future.value();

    _endMillis = new DateTime.now().millisecondsSinceEpoch;
    return analytics.sendTiming(variableName, currentElapsedMillis,
        category: category, label: label);
  }
}

/**
 * A no-op implementation of the [Analytics] class. This can be used as a
 * stand-in for that will never ping the GA server, or as a mock in test code.
 */
class AnalyticsMock implements Analytics {
  String get trackingId => 'UA-0';
  final bool logCalls;

  /**
   * Events are never added to this controller for the mock implementation.
   */
  StreamController<Map<String, dynamic>> _sendController =
      new StreamController.broadcast();

  /**
   * Create a new [AnalyticsMock]. If [logCalls] is true, all calls will be
   * logged to stdout.
   */
  AnalyticsMock([this.logCalls = false]);

  bool get firstRun => false;

  AnalyticsOpt analyticsOpt = AnalyticsOpt.optOut;

  bool enabled = true;

  @override
  String get clientId => '00000000-0000-4000-0000-000000000000';

  Future sendScreenView(String viewName, { Map<String, String> parameters }) {
    if (parameters == null) {
      parameters = <String, String>{};
    }
    parameters['viewName'] = viewName;
    _log('screenView', parameters);
  }

  Future sendEvent(String category, String action, {String label, int value}) {
    return _log('event', {
      'category': category,
      'action': action,
      'label': label,
      'value': value
    });
  }

  Future sendSocial(String network, String action, String target) =>
      _log('social', {'network': network, 'action': action, 'target': target});

  Future sendTiming(String variableName, int time,
      {String category, String label}) {
    return _log('timing', {
      'variableName': variableName,
      'time': time,
      'category': category,
      'label': label
    });
  }

  AnalyticsTimer startTimer(String variableName,
      {String category, String label}) {
    return new AnalyticsTimer(this, variableName,
        category: category, label: label);
  }

  Future sendException(String description, {bool fatal}) =>
      _log('exception', {'description': description, 'fatal': fatal});

  dynamic getSessionValue(String param) => null;

  void setSessionValue(String param, dynamic value) {}

  Stream<Map<String, dynamic>> get onSend => _sendController.stream;

  Future waitForLastPing({Duration timeout}) => new Future.value();

  Future _log(String hitType, Map m) {
    if (logCalls) {
      print('analytics: ${hitType} ${m}');
    }

    return new Future.value();
  }
}

/**
 * Sanitize a stacktrace. This will shorten file paths in order to remove any
 * PII that may be contained in the full file path. For example, this will
 * shorten `file:///Users/foobar/tmp/error.dart` to `error.dart`.
 *
 * If [shorten] is `true`, this method will also attempt to compress the text
 * of the stacktrace. GA has a 100 char limit on the text that can be sent for
 * an exception. This will try and make those first 100 chars contain
 * information useful to debugging the issue.
 */
String sanitizeStacktrace(dynamic st, {bool shorten: true}) {
  String str = '${st}';

  Iterable<Match> iter = _pathRegex.allMatches(str);
  iter = iter.toList().reversed;

  for (Match match in iter) {
    String replacement = match.group(1);
    str =
        str.substring(0, match.start) + replacement + str.substring(match.end);
  }

  if (shorten) {
    // Shorten the stacktrace up a bit.
    str = str.replaceAll(_tabOrSpaceRegex, ' ');
  }

  return str;
}