import 'package:comunic/helpers/conversations_helper.dart';
import 'package:comunic/helpers/users_helper.dart';
import 'package:comunic/lists/conversation_messages_list.dart';
import 'package:comunic/lists/users_list.dart';
import 'package:comunic/models/new_conversation_message.dart';
import 'package:comunic/ui/tiles/conversation_message_tile.dart';
import 'package:comunic/utils/files_utils.dart';
import 'package:comunic/utils/intl_utils.dart';
import 'package:comunic/utils/list_utils.dart';
import 'package:comunic/utils/ui_utils.dart';
import 'package:flutter/material.dart';

/// Conversation screen
///
/// @author Pierre HUBERT

enum ErrorLevel { NONE, MINOR, MAJOR }

class ConversationScreen extends StatefulWidget {
  final int conversationID;

  const ConversationScreen({Key key, this.conversationID})
      : assert(conversationID != null),
        super(key: key);

  @override
  State<StatefulWidget> createState() => _ConversationScreenState();
}

class _ConversationScreenState extends State<ConversationScreen> {
  //Helpers
  final ConversationsHelper _conversationsHelper = ConversationsHelper();
  final UsersHelper _usersHelper = UsersHelper();

  // Class members
  ConversationMessagesList _messages;
  UsersList _usersInfo = UsersList();
  ErrorLevel _error = ErrorLevel.NONE;
  bool _isMessageValid = false;
  bool _isSendingMessage = false;
  TextEditingController _textEditingController = TextEditingController();

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

  void _setError(ErrorLevel err) => setState(() => _error = err);

  void _setSending(bool sending) => setState(() => _isSendingMessage = sending);

  /// Method called when an error occurred while loading messages
  void _errorLoading() {
    _setError(_messages == null ? ErrorLevel.MAJOR : ErrorLevel.MINOR);
  }

  /// Load a list of messages
  Future<void> _loadMessages() async {
    //First, get the messages
    final messages = await _conversationsHelper
        .downloadNewMessagesSingle(widget.conversationID);

    if (messages == null) return _errorLoading();

    //Then get information about users
    final usersToGet =
        findMissingFromList(_usersInfo.usersID, messages.getUsersID());

    final users = await _usersHelper.getUsersInfo(usersToGet);

    if (users == null) _errorLoading();

    // Save the new list of messages
    setState(() {
      _usersInfo.addAll(users);
      if (_messages == null)
        _messages = messages;
      else
        _messages.addAll(messages);

      //Reverse the order of the messages
      _messages.sort();
      final reverse =_messages.reversed;
      _messages = ConversationMessagesList();
      _messages.addAll(reverse);
    });
  }

  /// Pick and send an image
  Future<void> _sendImage(BuildContext context) async {
    final image = await pickImage(context);

    if (image == null) return null;

    _submitMessage(
      context,
      NewConversationMessage(
        conversationID: widget.conversationID,
        message: null,
        image: image,
      ),
    );

    // In case a message was already written in the input
    _updatedText(_textEditingController.text);
  }

  /// Send a new text message
  Future<void> _submitTextMessage(BuildContext context, String content) async {
    if (await _submitMessage(
            context,
            NewConversationMessage(
              conversationID: widget.conversationID,
              message: content,
            )) ==
        SendMessageResult.SUCCESS) _clearSendMessageForm();
  }

  /// Submit a new message
  Future<SendMessageResult> _submitMessage(
      BuildContext context, NewConversationMessage message) async {
    //Send the message
    _setSending(true);
    final result = await _conversationsHelper.sendMessage(message);
    _setSending(false);

    //Check the result of the operation
    if (result != SendMessageResult.SUCCESS)
      Scaffold.of(context).showSnackBar(
        SnackBar(
          content: Text(
            result == SendMessageResult.MESSAGE_REJECTED
                ? tr("Message rejected by the server!")
                : tr("Could not send message!"),
          ),
          duration: Duration(milliseconds: 500),
        ),
      );

    return result;
  }

  void _updatedText(String text) {
    setState(() {
      _isMessageValid = text.length > 4;
    });
  }

  /// Clear send message form
  void _clearSendMessageForm() {
    setState(() {
      _textEditingController = TextEditingController();
      _isMessageValid = false;
    });
  }

  /// Check if a message is the last message of a user or not
  bool _isLastMessage(int index) {
    return index == 0 ||
        (index > 0 && _messages[index - 1].userID != _messages[index].userID);
  }

  /// Check if a message is the first message of a user or not
  bool _isFirstMessage(int index) {
    return index == _messages.length - 1 ||
        (index < _messages.length - 1 && _messages[index + 1].userID != _messages[index].userID);
  }

  /// Error handling
  Widget _buildError() {
    return buildErrorCard(tr("Could not load the list of messages!"));
  }

  /// Messages list
  Widget _buildMessagesList() {
    return Expanded(
      child: ListView.builder(
        reverse: true,
          itemCount: _messages.length,
          itemBuilder: (c, i) {
            return ConversationMessageTile(
              message: _messages.elementAt(i),
              userInfo: _usersInfo.getUser(_messages[i].userID),
              isLastMessage: _isLastMessage(i),
              isFirstMessage: _isFirstMessage(i),
            );
          }),
    );
  }

  /// Send message from
  Widget _buildSendMessageForm() {
    return new Container(
      margin: const EdgeInsets.symmetric(horizontal: 8.0),
      child: new Row(
        children: <Widget>[
          // Image area
          new Container(
            margin: new EdgeInsets.symmetric(horizontal: 4.0),
            child: new IconButton(
              icon: new Icon(
                Icons.photo_camera,
                color: _isSendingMessage
                    ? Theme.of(context).disabledColor
                    : Theme.of(context).accentColor,
              ),
              onPressed: () => _sendImage(context),
            ),
          ),

          // Message area
          new Flexible(
            child: new TextField(
              enabled: !_isSendingMessage,
              controller: _textEditingController,
              onChanged: _updatedText,
              onSubmitted: _isMessageValid
                  ? (s) => _submitTextMessage(context, s)
                  : null,
              decoration:
                  new InputDecoration.collapsed(hintText: tr("Send a message")),
            ),
          ),

          // Send button
          new Container(
            margin: const EdgeInsets.symmetric(horizontal: 4.0),
            child: new IconButton(
              icon: new Icon(
                Icons.send,
                color: !_isSendingMessage && _isMessageValid
                    ? Theme.of(context).accentColor
                    : Theme.of(context).disabledColor,
              ),
              onPressed: !_isSendingMessage && _isMessageValid
                  ? () =>
                      _submitTextMessage(context, _textEditingController.text)
                  : null,
            ),
          ),
        ],
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    if (_error == ErrorLevel.MAJOR) return _buildError();

    if (_messages == null) return buildCenteredProgressBar();

    return Column(
      children: <Widget>[
        _buildMessagesList(),
        Divider(),
        _buildSendMessageForm()
      ],
    );
  }
}