// Copyright (c) 2023, 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.

import 'dart:convert';

import 'package:clock/clock.dart';
import 'package:file/file.dart';

import 'constants.dart';
import 'event.dart';
import 'initializer.dart';

/// Data class that will be returned when analyzing the
/// persisted log file on the client's machine.
class LogFileStats {
  /// The oldest timestamp in the log file.
  final DateTime startDateTime;

  /// Number of minutes from [startDateTime] to now using [clock].
  final int minsFromStartDateTime;

  /// The latest timestamp in the log file.
  final DateTime endDateTime;

  /// Number of minutes from [endDateTime] to now using [clock].
  final int minsFromEndDateTime;

  /// The number of unique session ids found in the log file.
  final int sessionCount;

  /// The map containing all of the flutter channels and a count
  /// of how many events were under each channel.
  ///
  /// ```
  /// {
  ///   'stable': 123,
  ///   'beta': 50,
  ///   'master': 5,
  /// }
  /// ```
  final Map<String, int> flutterChannelCount;

  /// The map containing all of the tools that have sent events
  /// and how many events were sent by each tool.
  ///
  /// ```
  /// {
  ///   'flutter-tool': 500,
  ///   'dart-tool': 45,
  ///   'vscode-plugins': 321,
  /// }
  /// ```
  final Map<String, int> toolCount;

  /// The map containing all of the events in the file along with
  /// how many times they have occured.
  ///
  /// ```
  /// {
  ///   'client_request': 345,
  ///   'hot_reload_time': 765,
  ///   'memory_info': 90,
  /// }
  /// ```
  final Map<String, int> eventCount;

  /// Total number of records in the log file.
  final int recordCount;

  /// Contains the data from the [LogHandler.logFileStats] method.
  const LogFileStats({
    required this.startDateTime,
    required this.minsFromStartDateTime,
    required this.endDateTime,
    required this.minsFromEndDateTime,
    required this.sessionCount,
    required this.flutterChannelCount,
    required this.toolCount,
    required this.recordCount,
    required this.eventCount,
  });

  /// Pass in a string label for one of the instance variables
  /// and return the integer value of that label.
  ///
  /// If label passed for [DateTime] instance variable, integer
  /// in the form of [DateTime.millisecondsSinceEpoch] will be
  /// returned.
  ///
  /// Returns null if the label passed does not match anything.
  int? getValueByString(String label) {
    // When querying counts, the label will include the
    // key for the appropriate map
    //
    // Example: logFileStats.toolCount.flutter-tool is asking
    //   for the number of events sent via flutter cli
    final parts = label.split('.');
    String? key;
    if (parts.length >= 3) {
      // Assign the first two parts of the string as the label
      // ie. logFileStats.toolCount.flutter-tool -> logFileStats.toolCount
      label = parts.sublist(0, 2).join('.');
      key = parts.sublist(2, parts.length).join('.');
    }

    switch (label) {
      case 'logFileStats.startDateTime':
        return startDateTime.millisecondsSinceEpoch;
      case 'logFileStats.minsFromStartDateTime':
        return minsFromStartDateTime;
      case 'logFileStats.endDateTime':
        return endDateTime.millisecondsSinceEpoch;
      case 'logFileStats.minsFromEndDateTime':
        return minsFromEndDateTime;
      case 'logFileStats.sessionCount':
        return sessionCount;
      case 'logFileStats.recordCount':
        return recordCount;
      case 'logFileStats.flutterChannelCount':
        if (key != null && flutterChannelCount.containsKey(key)) {
          return flutterChannelCount[key];
        }
      case 'logFileStats.toolCount':
        if (key != null && toolCount.containsKey(key)) {
          return toolCount[key];
        }
      case 'logFileStats.eventCount':
        if (key != null && eventCount.containsKey(key)) {
          return eventCount[key];
        }
    }

    return null;
  }

  @override
  String toString() {
    const encoder = JsonEncoder.withIndent('  ');
    return encoder.convert({
      'startDateTime': startDateTime.toString(),
      'minsFromStartDateTime': minsFromStartDateTime,
      'endDateTime': endDateTime.toString(),
      'minsFromEndDateTime': minsFromEndDateTime,
      'sessionCount': sessionCount,
      'recordCount': recordCount,
      'eventCount': eventCount,
      'toolCount': toolCount,
      'flutterChannelCount': flutterChannelCount,
    });
  }
}

/// This class is responsible for writing to a log
/// file that has been initialized by the [createLogFile].
///
/// It will be treated as an append only log and will be limited
/// to have has many data records as specified by [kLogFileLength].
class LogHandler {
  final File logFile;

  /// Contains instances of [Event.analyticsException] that were encountered
  /// during a workflow and will be sent to GA4 for collection.
  final Set<Event> errorSet = {};

  /// A log handler constructor that will delegate saving
  /// logs and retrieving stats from the persisted log.
  LogHandler({required this.logFile});

  /// Get stats from the persisted log file.
  ///
  /// Note that some developers may only be Dart
  /// developers and will not have any data for flutter
  /// related metrics.
  LogFileStats? logFileStats() {
    // Parse each line of the log file through [LogItem],
    // some returned records may be null if malformed, they will be
    // removed later through `whereType<LogItem>`
    final records = logFile
        .readAsLinesSync()
        .map((String e) {
          try {
            return LogItem.fromRecord(jsonDecode(e) as Map<String, Object?>);
          } on FormatException catch (err) {
            errorSet.add(Event.analyticsException(
              workflow: 'LogFileStats.logFileStats',
              error: err.runtimeType.toString(),
              description: 'message: ${err.message}\nsource: ${err.source}',
            ));

            return null;
            // ignore: avoid_catching_errors
          } on TypeError catch (err) {
            errorSet.add(Event.analyticsException(
              workflow: 'LogFileStats.logFileStats',
              error: err.runtimeType.toString(),
            ));

            return null;
          }
        })
        .whereType<LogItem>()
        .toList();

    if (records.isEmpty) return null;

    // Get the start and end dates for the log file
    final startDateTime = records.first.localTime;
    final endDateTime = records.last.localTime;

    // Map with counters for user properties
    final counter = <String, Set<Object>>{
      'sessions': <int>{},
      'flutter_channel': <String>{},
      'tool': <String>{},
    };

    // Map of counters for each event
    final eventCount = <String, int>{};
    final flutterChannelCount = <String, int>{};
    final toolCount = <String, int>{};
    for (final record in records) {
      counter['sessions']!.add(record.sessionId);
      counter['tool']!.add(record.tool);
      if (record.flutterChannel != null) {
        counter['flutter_channel']!.add(record.flutterChannel!);
      }

      // Count each event, if it doesn't exist in the [eventCount]
      // it will be added first
      if (!eventCount.containsKey(record.eventName)) {
        eventCount[record.eventName] = 0;
      }
      eventCount[record.eventName] = eventCount[record.eventName]! + 1;

      // Counting how many events were recorded for each tool
      if (!toolCount.containsKey(record.tool)) {
        toolCount[record.tool] = 0;
      }
      toolCount[record.tool] = toolCount[record.tool]! + 1;

      // Necessary to perform a null check for flutter channel because
      // not all events will have information about flutter
      if (record.flutterChannel != null) {
        final flutterChannel = record.flutterChannel!;
        if (!flutterChannelCount.containsKey(flutterChannel)) {
          flutterChannelCount[flutterChannel] = 0;
        }

        flutterChannelCount[flutterChannel] =
            flutterChannelCount[flutterChannel]! + 1;
      }
    }

    final now = clock.now();

    return LogFileStats(
      startDateTime: startDateTime,
      minsFromStartDateTime: now.difference(startDateTime).inMinutes,
      endDateTime: endDateTime,
      minsFromEndDateTime: now.difference(endDateTime).inMinutes,
      sessionCount: counter['sessions']!.length,
      flutterChannelCount: flutterChannelCount,
      toolCount: toolCount,
      eventCount: eventCount,
      recordCount: records.length,
    );
  }

  /// Saves the data passed in as a single line in the log file.
  ///
  /// This will keep the max number of records limited to equal to
  /// or less than [kLogFileLength] records.
  void save({required Map<String, Object?> data}) {
    try {
      final stat = logFile.statSync();
      List<String> records;
      if (stat.size > kMaxLogFileSize) {
        logFile.deleteSync();
        logFile.createSync();
        records = [];
      } else {
        records = logFile.readAsLinesSync();
      }
      final content = '${jsonEncode(data)}\n';

      // When the record count is less than the max, add as normal;
      // else drop the oldest records until equal to max
      if (records.length < kLogFileLength) {
        logFile.writeAsStringSync(content, mode: FileMode.writeOnlyAppend);
      } else {
        records.add(content);
        records = records.skip(records.length - kLogFileLength).toList();

        logFile.writeAsStringSync(records.join('\n'));
      }
    } on FileSystemException {
      // Logging isn't important enough to warrant raising a
      // FileSystemException that will surprise consumers of this package.
    }
  }
}

/// Data class for each record persisted on the client's machine.
class LogItem {
  final String eventName;
  final int sessionId;
  final String? flutterChannel;
  final String host;
  final String? flutterVersion;
  final String dartVersion;
  final String tool;
  final DateTime localTime;
  final String hostOsVersion;
  final String locale;
  final String? clientIde;

  LogItem({
    required this.eventName,
    required this.sessionId,
    this.flutterChannel,
    required this.host,
    this.flutterVersion,
    required this.dartVersion,
    required this.tool,
    required this.localTime,
    required this.hostOsVersion,
    required this.locale,
    required this.clientIde,
  });

  /// Serves a parser for each record in the log file.
  ///
  /// Using this method guarantees that we have parsed out
  /// fields that are necessary for the [LogHandler.logFileStats]
  /// method.
  ///
  /// If the returned value is null, that indicates a malformed
  /// record which can be discarded during analysis.
  ///
  /// Example of what a record looks like:
  /// ```
  /// {
  ///     "client_id": "ffcea97b-db5e-4c66-98c2-3942de4fac40",
  ///     "events": [
  ///         {
  ///             "name": "hot_reload_time",
  ///             "params": {
  ///                 "timeMs": 135
  ///             }
  ///         }
  ///     ],
  ///     "user_properties": {
  ///         "session_id": {
  ///             "value": 1699385899950
  ///         },
  ///         "flutter_channel": {
  ///             "value": "ey-test-channel"
  ///         },
  ///         "host": {
  ///             "value": "macOS"
  ///         },
  ///         "flutter_version": {
  ///             "value": "Flutter 3.6.0-7.0.pre.47"
  ///         },
  ///         "dart_version": {
  ///             "value": "Dart 2.19.0"
  ///         },
  ///         "analytics_pkg_version": {
  ///             "value": "5.2.0"
  ///         },
  ///         "tool": {
  ///             "value": "flutter-tool"
  ///         },
  ///         "local_time": {
  ///             "value": "2023-11-07 15:09:03.025559 -0500"
  ///         },
  ///         "host_os_version": {
  ///             "value": "Version 14.1 (Build 23B74)"
  ///         },
  ///         "locale": {
  ///             "value": "en"
  ///         },
  ///         "clientIde": {
  ///             "value": "VSCode"
  ///         }
  ///     }
  /// }
  /// ```
  static LogItem? fromRecord(Map<String, Object?> record) {
    if (!record.containsKey('user_properties') ||
        !record.containsKey('events')) {
      return null;
    }

    // Parse out values from the top level key = 'events' and return
    // a map for the one event in the value
    final eventProp =
        (record['events']! as List<Object?>).first as Map<String, Object?>;
    final eventName = eventProp['name'] as String;

    // Parse the data out of the `user_properties` value
    final userProps = record['user_properties'] as Map<String, Object?>;

    // Parse out the values from the top level key = 'user_properties`
    final sessionId =
        (userProps['session_id']! as Map<String, Object?>)['value'] as int?;
    final flutterChannel = (userProps['flutter_channel']!
        as Map<String, Object?>)['value'] as String?;
    final host =
        (userProps['host']! as Map<String, Object?>)['value'] as String?;
    final flutterVersion = (userProps['flutter_version']!
        as Map<String, Object?>)['value'] as String?;
    final dartVersion = (userProps['dart_version']!
        as Map<String, Object?>)['value'] as String?;
    final tool =
        (userProps['tool']! as Map<String, Object?>)['value'] as String?;
    final localTimeString =
        (userProps['local_time']! as Map<String, Object?>)['value'] as String?;
    final hostOsVersion = (userProps['host_os_version']!
        as Map<String, Object?>)['value'] as String?;
    final locale =
        (userProps['locale']! as Map<String, Object?>)['value'] as String?;
    final clientIde =
        (userProps['client_ide']! as Map<String, Object?>)['value'] as String?;

    // If any of the above values are null, return null since that
    // indicates the record is malformed; note that `flutter_version`,
    // `flutter_channel`, and `client_ide` are nullable fields in the log file
    final values = <Object?>[
      // Values associated with the top level key = 'events'
      eventName,

      // Values associated with the top level key = 'events'
      sessionId,
      host,
      dartVersion,
      tool,
      localTimeString,
      hostOsVersion,
      locale,
    ];
    for (final value in values) {
      if (value == null) return null;
    }

    // Parse the local time from the string extracted
    final localTime = DateTime.parse(localTimeString!).toLocal();

    return LogItem(
      eventName: eventName,
      sessionId: sessionId!,
      flutterChannel: flutterChannel,
      host: host!,
      flutterVersion: flutterVersion,
      dartVersion: dartVersion!,
      tool: tool!,
      localTime: localTime,
      hostOsVersion: hostOsVersion!,
      locale: locale!,
      clientIde: clientIde,
    );
  }
}