import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:infinite_scroll_pagination/infinite_scroll_pagination.dart';
import 'package:provider/provider.dart';
import 'package:solian/models/channel.dart';
import 'package:solian/models/message.dart';
import 'package:solian/models/pagination.dart';
import 'package:solian/providers/auth.dart';
import 'package:solian/utils/service_url.dart';
import 'package:solian/widgets/chat/maintainer.dart';
import 'package:solian/widgets/chat/message.dart';
import 'package:solian/widgets/chat/message_editor.dart';
import 'package:solian/widgets/indent_wrapper.dart';
import 'package:http/http.dart' as http;

class ChatScreen extends StatefulWidget {
  final String alias;

  const ChatScreen({super.key, required this.alias});

  @override
  State<ChatScreen> createState() => _ChatScreenState();
}

class _ChatScreenState extends State<ChatScreen> {
  Channel? _channelMeta;

  final PagingController<int, Message> _pagingController = PagingController(firstPageKey: 0);

  final http.Client _client = http.Client();

  Future<void> fetchMetadata(BuildContext context) async {
    var uri = getRequestUri('messaging', '/api/channels/${widget.alias}');
    var res = await _client.get(uri);
    if (res.statusCode == 200) {
      final result = jsonDecode(utf8.decode(res.bodyBytes));
      setState(() => _channelMeta = Channel.fromJson(result));
    } else {
      var message = utf8.decode(res.bodyBytes);
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text("Something went wrong... $message")),
      );
    }
  }

  Future<void> fetchMessages(int pageKey, BuildContext context) async {
    final auth = context.read<AuthProvider>();
    if (!await auth.isAuthorized()) return;

    final offset = pageKey;
    const take = 5;

    var uri = getRequestUri(
      'messaging',
      '/api/channels/${widget.alias}/messages?take=$take&offset=$offset',
    );

    var res = await auth.client!.get(uri);
    if (res.statusCode == 200) {
      final result = PaginationResult.fromJson(jsonDecode(utf8.decode(res.bodyBytes)));
      final items = result.data?.map((x) => Message.fromJson(x)).toList() ?? List.empty();
      final isLastPage = (result.count - pageKey) < take;
      if (isLastPage || result.data == null) {
        _pagingController.appendLastPage(items);
      } else {
        final nextPageKey = pageKey + items.length;
        _pagingController.appendPage(items, nextPageKey);
      }
    } else {
      _pagingController.error = utf8.decode(res.bodyBytes);
    }
  }

  bool getMessageMergeable(Message? a, Message? b) {
    if (a == null || b == null) return false;
    if (a.senderId != b.senderId) return false;
    return a.createdAt.difference(b.createdAt).inMinutes <= 5;
  }

  void addMessage(Message item) {
    setState(() {
      _pagingController.itemList?.insert(0, item);
    });
  }

  void updateMessage(Message item) {
    setState(() {
      _pagingController.itemList = _pagingController.itemList?.map((x) => x.id == item.id ? item : x).toList();
    });
  }

  void deleteMessage(Message item) {
    setState(() {
      _pagingController.itemList = _pagingController.itemList?.where((x) => x.id != item.id).toList();
    });
  }

  @override
  void initState() {
    Future.delayed(Duration.zero, () {
      fetchMetadata(context);
    });

    _pagingController.addPageRequestListener((pageKey) => fetchMessages(pageKey, context));

    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return IndentWrapper(
      hideDrawer: true,
      title: _channelMeta?.name ?? "Loading...",
      child: ChatMaintainer(
        child: Column(
          children: [
            Expanded(
              child: PagedListView<int, Message>(
                reverse: true,
                pagingController: _pagingController,
                builderDelegate: PagedChildBuilderDelegate<Message>(
                  itemBuilder: (context, item, index) {
                    bool isMerged = false, hasMerged = false;
                    if (index > 0) {
                      hasMerged = getMessageMergeable(_pagingController.itemList?[index - 1], item);
                    }
                    if (index + 1 < (_pagingController.itemList?.length ?? 0)) {
                      isMerged = getMessageMergeable(item, _pagingController.itemList?[index + 1]);
                    }
                    return Container(
                      padding: EdgeInsets.only(
                        top: !isMerged ? 8 : 0,
                        bottom: !hasMerged ? 8 : 0,
                        left: 12,
                        right: 12,
                      ),
                      child: ChatMessage(
                        key: Key('m${item.id}'),
                        item: item,
                        underMerged: isMerged,
                      ),
                    );
                  },
                ),
              ),
            ),
            ChatMessageEditor(channel: widget.alias),
          ],
        ),
        onInsertMessage: (message) => addMessage(message),
        onUpdateMessage: (message) => updateMessage(message),
        onDeleteMessage: (message) => deleteMessage(message),
      ),
    );
  }
}