/*
 *   Famedly Matrix SDK
 *   Copyright (C) 2019, 2020, 2021 Famedly GmbH
 *
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU Affero General Public License as
 *   published by the Free Software Foundation, either version 3 of the
 *   License, or (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 *   GNU Affero General Public License for more details.
 *
 *   You should have received a copy of the GNU Affero General Public License
 *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

import '../matrix.dart';

/// Represents a Matrix User which may be a participant in a Matrix Room.
class User extends Event {
  factory User(
    String id, {
    String? membership,
    String? displayName,
    String? avatarUrl,
    required Room room,
  }) {
    return User.fromState(
      stateKey: id,
      content: {
        if (membership != null) 'membership': membership,
        if (displayName != null) 'displayname': displayName,
        if (avatarUrl != null) 'avatar_url': avatarUrl,
      },
      typeKey: EventTypes.RoomMember,
      roomId: room.id,
      room: room,
      originServerTs: DateTime.now(),
    );
  }

  User.fromState({
    dynamic prevContent,
    required String stateKey,
    dynamic content,
    required String typeKey,
    String eventId = 'fakevent',
    String? roomId,
    String senderId = 'fakesender',
    required DateTime originServerTs,
    dynamic unsigned,
    required Room room,
  }) : super(
          stateKey: stateKey,
          prevContent: prevContent,
          content: content,
          type: typeKey,
          eventId: eventId,
          senderId: senderId,
          originServerTs: originServerTs,
          unsigned: unsigned,
          room: room,
        );

  /// The full qualified Matrix ID in the format @username:server.abc.
  String get id => stateKey ?? '@unknown:unknown';

  /// The displayname of the user if the user has set one.
  String? get displayName =>
      content.tryGet<String>('displayname') ??
      prevContent?.tryGet<String>('displayname');

  /// Returns the power level of this user.
  int get powerLevel => room.getPowerLevelByUserId(id);

  /// The membership status of the user. One of:
  /// join
  /// invite
  /// leave
  /// ban
  Membership get membership => Membership.values.firstWhere((e) {
        if (content['membership'] != null) {
          return e.toString() == 'Membership.' + content['membership'];
        }
        return false;
      }, orElse: () => Membership.join);

  /// The avatar if the user has one.
  Uri? get avatarUrl {
    final prevContent = this.prevContent;
    return content.containsKey('avatar_url')
        ? (content['avatar_url'] is String
            ? Uri.tryParse(content['avatar_url'])
            : null)
        : (prevContent != null && prevContent['avatar_url'] is String
            ? Uri.tryParse(prevContent['avatar_url'])
            : null);
  }

  /// Returns the displayname or the local part of the Matrix ID if the user
  /// has no displayname. If [formatLocalpart] is true, then the localpart will
  /// be formatted in the way, that all "_" characters are becomming white spaces and
  /// the first character of each word becomes uppercase.
  /// If [mxidLocalPartFallback] is true, then the local part of the mxid will be shown
  /// if there is no other displayname available. If not then this will return "Unknown user".
  String calcDisplayname({
    bool? formatLocalpart,
    bool? mxidLocalPartFallback,
  }) {
    formatLocalpart ??= room.client.formatLocalpart;
    mxidLocalPartFallback ??= room.client.mxidLocalPartFallback;
    final displayName = this.displayName;
    if (displayName != null && displayName.isNotEmpty) {
      return displayName;
    }
    final stateKey = this.stateKey;
    if (stateKey != null && mxidLocalPartFallback) {
      if (!formatLocalpart) {
        return stateKey.localpart ?? '';
      }
      final words = stateKey.localpart?.replaceAll('_', ' ').split(' ') ?? [];
      for (var i = 0; i < words.length; i++) {
        if (words[i].isNotEmpty) {
          words[i] = words[i][0].toUpperCase() + words[i].substring(1);
        }
      }
      return words.join(' ').trim();
    }
    return 'Unknown user';
  }

  /// Call the Matrix API to kick this user from this room.
  Future<void> kick() async => await room.kick(id);

  /// Call the Matrix API to ban this user from this room.
  Future<void> ban() async => await room.ban(id);

  /// Call the Matrix API to unban this banned user from this room.
  Future<void> unban() async => await room.unban(id);

  /// Call the Matrix API to change the power level of this user.
  Future<void> setPower(int power) async => await room.setPower(id, power);

  /// Returns an existing direct chat ID with this user or creates a new one.
  /// Returns null on error.
  Future<String> startDirectChat({
    bool? enableEncryption,
    List<StateEvent>? initialState,
    bool waitForSync = true,
  }) async =>
      room.client.startDirectChat(
        id,
        enableEncryption: enableEncryption,
        initialState: initialState,
        waitForSync: waitForSync,
      );

  /// The newest presence of this user if there is any and null if not.
  Presence? get presence => room.client.presences[id];

  /// Whether the client is able to ban/unban this user.
  bool get canBan => room.canBan && powerLevel < room.ownPowerLevel;

  /// Whether the client is able to kick this user.
  bool get canKick =>
      [Membership.join, Membership.invite].contains(membership) &&
      room.canKick &&
      powerLevel < room.ownPowerLevel;

  /// Whether the client is allowed to change the power level of this user.
  /// Please be aware that you can only set the power level to at least your own!
  bool get canChangePowerLevel =>
      room.canChangePowerLevel && powerLevel < room.ownPowerLevel;

  @override
  bool operator ==(dynamic other) => (other is User &&
      other.id == id &&
      other.room == room &&
      other.membership == membership);

  /// Get the mention text to use in a plain text body to mention this specific user
  /// in this specific room
  String get mention {
    // if the displayname has [ or ] or : we can't build our more fancy stuff, so fall back to the id
    // [] is used for the delimitors
    // If we allowed : we could get collissions with the mxid fallbacks
    final displayName = this.displayName;
    if (displayName == null ||
        displayName.isEmpty ||
        {'[', ']', ':'}.any(displayName.contains)) {
      return id;
    }

    final identifier = '@' +
        // if we have non-word characters we need to surround with []
        (RegExp(r'^\w+$').hasMatch(displayName)
            ? displayName
            : '[$displayName]');

    // get all the users with the same display name
    final allUsersWithSameDisplayname = room.getParticipants();
    allUsersWithSameDisplayname.removeWhere((user) =>
        user.id == id ||
        (user.displayName?.isEmpty ?? true) ||
        user.displayName != displayName);
    if (allUsersWithSameDisplayname.isEmpty) {
      return identifier;
    }
    // ok, we have multiple users with the same display name....time to calculate a hash
    final hashes = allUsersWithSameDisplayname.map((u) => _hash(u.id));
    final ourHash = _hash(id);
    // hash collission...just return our own mxid again
    if (hashes.contains(ourHash)) {
      return id;
    }
    return '$identifier#$ourHash';
  }

  /// Get the mention fragments for this user.
  Set<String> get mentionFragments {
    final displayName = this.displayName;
    if (displayName == null ||
        displayName.isEmpty ||
        {'[', ']', ':'}.any(displayName.contains)) {
      return {};
    }
    final identifier = '@' +
        // if we have non-word characters we need to surround with []
        (RegExp(r'^\w+$').hasMatch(displayName)
            ? displayName
            : '[$displayName]');

    final hash = _hash(id);
    return {identifier, '$identifier#$hash'};
  }
}

const _maximumHashLength = 10000;
String _hash(String s) =>
    (s.codeUnits.fold<int>(0, (a, b) => a + b) % _maximumHashLength).toString();