import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';

import '../components/chat_bubble.dart';
import '../components/my_textfield.dart';
import '../constants.dart';
import '../services/auth/auth_service.dart';
import '../services/chat/chat_service.dart';

class ChatPage extends StatefulWidget {
  final String receiverEmail;
  final String receiverID;
  final String chatTitle;

  const ChatPage({
    super.key,
    required this.receiverEmail,
    required this.receiverID,
    required this.chatTitle,
  });

  @override
  State<ChatPage> createState() => _ChatPageState();
}

class _ChatPageState extends State<ChatPage> {
  final TextEditingController _messageController = TextEditingController();

  final ChatService _chatService = ChatService();
  final AuthService _authService = AuthService();

  // for textfield focus
  FocusNode myFocusNode = FocusNode();

  @override
  void initState() {
    super.initState();

    // add listener to focus node
    myFocusNode.addListener(() {
      if (myFocusNode.hasFocus) {
        // cause a delay so that the keyboard has time to show up
        // then the amount of remaining space will be calculated
        // then scroll down
        Future.delayed(
          const Duration(milliseconds: 500),
          () => scrollDown(),
        );
      }
    });

    // wait a bit for listview to be built, then scroll to bottom
    Future.delayed(
      const Duration(milliseconds: 500),
      () => scrollDown(),
    );
  }

  @override
  void dispose() {
    myFocusNode.dispose();
    _messageController.dispose();
    super.dispose();
  }

  // scroll controller
  final ScrollController _scrollController = ScrollController();
  void scrollDown() {
    _scrollController.animateTo(
      _scrollController.position.maxScrollExtent,
      duration: const Duration(seconds: 1),
      curve: Curves.fastOutSlowIn,
    );
  }

  void sendMessage() async {
    // send message if not empty
    if (_messageController.text.isNotEmpty) {
      await _chatService.sendMessage(
        widget.receiverID,
        _messageController.text,
      );

      // clear text controller
      _messageController.clear();
    }

    scrollDown();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text(widget.chatTitle)),
      body: Column(
        children: [
          // display all messages
          Expanded(child: _buildMessageList()),
          // user input
          _buildUserInput(),
        ],
      ),
    );
  }

  Widget _buildMessageList() {
    String senderID = _authService.getCurrentUser()!.uid;
    return StreamBuilder(
      stream: _chatService.getMessages(senderID, widget.receiverID),
      builder: (context, snapshot) {
        // errors
        if (snapshot.hasError) {
          return Text('Error: ${snapshot.error}');
        }

        // loading
        if (snapshot.connectionState == ConnectionState.waiting) {
          return const Text('Loading..');
        }

        // return list view
        return ListView(
          controller: _scrollController,
          children:
              snapshot.data!.docs.map((doc) => _buildMessageItem(doc)).toList(),
        );
      },
    );
  }

  Widget _buildMessageItem(DocumentSnapshot doc) {
    Map<String, dynamic> data = doc.data() as Map<String, dynamic>;

    // align message to the right if sender is current user, otherwise left
    bool isCurrentUser = data[Constants.dbFieldMessageSenderId] ==
        _authService.getCurrentUser()!.uid;
    var alignment =
        isCurrentUser ? Alignment.centerRight : Alignment.centerLeft;

    List<String> msgDate =
        (data[Constants.dbFieldMessageTimestamp] as Timestamp)
            .toDate()
            .toIso8601String()
            .split("T");

    return Container(
      alignment: alignment,
      child: Column(
        crossAxisAlignment:
            isCurrentUser ? CrossAxisAlignment.end : CrossAxisAlignment.start,
        children: [
          Padding(
            padding: const EdgeInsets.symmetric(horizontal: 25.0),
            child: Text(
              '${msgDate[0]} ${msgDate[1].substring(0, 5)}',
              style: const TextStyle(color: Colors.grey, fontSize: 10),
            ),
          ),
          ChatBubble(
            message: data[Constants.dbFieldMessageText],
            isCurrentUser: isCurrentUser,
          ),
        ],
      ),
    );
  }

  Widget _buildUserInput() {
    return Padding(
      padding: const EdgeInsets.only(bottom: 10.0),
      child: Row(
        children: [
          // text should take up most of space
          Expanded(
            child: MyTextField(
              controller: _messageController,
              hintText: 'Type a message',
              obscureText: false,
              focusNode: myFocusNode,
            ),
          ),

          // send button
          Container(
            decoration: const BoxDecoration(
              color: Colors.green,
              shape: BoxShape.circle,
            ),
            margin: const EdgeInsets.only(right: 25),
            child: IconButton(
              onPressed: sendMessage,
              icon: const Icon(Icons.send),
              color: Colors.white,
            ),
          )
        ],
      ),
    );
  }
}