import 'package:comunic/enums/load_error_level.dart';
import 'package:comunic/helpers/conversations_helper.dart';
import 'package:comunic/helpers/users_helper.dart';
import 'package:comunic/lists/conversations_list.dart';
import 'package:comunic/ui/tiles/conversation_tile.dart';
import 'package:comunic/utils/intl_utils.dart';
import 'package:comunic/utils/ui_utils.dart';
import 'package:flutter/material.dart';

/// Conversations screen
///
/// @author Pierre HUBERT

class ConversationsScreen extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => _ConversationScreenState();
}

class _ConversationScreenState extends State<ConversationsScreen> {
  final ConversationsHelper _conversationsHelper = ConversationsHelper();
  final UsersHelper _usersHelper = UsersHelper();
  ConversationsList _list;
  LoadErrorLevel _error = LoadErrorLevel.NONE;
  bool _loading = true;

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    _loadConversations();
  }

  void setError(LoadErrorLevel err) => setState(() => _error = err);

  void setLoading(bool loading) => setState(() => _loading = loading);

  /// Get the list of conversations, once from the cache, once from the server
  Future<void> _loadConversations() async {
    await _loadConversationsList(true);
    await _loadConversationsList(false);
  }

  void _gotLoadingError() {
    setLoading(false);
    setError(_list == null ? LoadErrorLevel.MAJOR : LoadErrorLevel.MINOR);
  }

  /// Load the list of conversations
  Future<void> _loadConversationsList(bool cached) async {
    setError(LoadErrorLevel.NONE);
    setLoading(true);

    //Get the list of conversations
    var list;
    if(cached)
      list = await _conversationsHelper.getCachedList();
    else
      list = await _conversationsHelper.downloadList();

    if (list == null) return _gotLoadingError();

    //Get information about the members of the conversations
    list.users = await _usersHelper.getUsersInfo(list.allUsersID);
    if (list.users == null) return _gotLoadingError();

    //Save list
    setState(() {
      _list = list;
    });

    setLoading(false);
  }

  /// Build an error card
  Widget _buildErrorCard() {
    return buildErrorCard(
      tr("Could not retrieve the list of conversations!"),
      actions: <Widget>[
        FlatButton(
          onPressed: () => _loadConversationsList(true),
          child: Text(
            tr("Retry").toUpperCase(),
            style: TextStyle(
              color: Colors.white,
            ),
          ),
        )
      ],
    );
  }

  @override
  Widget build(BuildContext context) {
    if (_error == LoadErrorLevel.MAJOR) return _buildErrorCard();
    if (_list == null) return buildCenteredProgressBar();

    // Show the list of conversations
    return Stack(
      children: <Widget>[
        Column(
          children: <Widget>[
            Container(
              child: _error == LoadErrorLevel.MINOR ? _buildErrorCard() : null,
            ),
            Expanded(
              child: ListView.builder(
                itemBuilder: (context, index) {
                  return ConversationTile(
                    conversation: _list.elementAt(index),
                    usersList: _list.users,
                  );
                },
                itemCount: _list.length,
              ),
            ),
          ],
        ),
        Positioned(
          top: 8.0,
          left: 0.0,
          right: 0.0,
          child: Container(
            child: !_loading
                ? null
                : Center(
                    child: CircularProgressIndicator(),
                  ),
          ),
        )
      ],
    );
  }
}