import 'dart:async';
import 'dart:convert';
import 'dart:io';

import 'package:friendly_map/modules/core/core.dart';

/// 외부 보관함 서버로 봉투를 주고받는다. 보관함은 잠긴 봉투를 잠시 맡아 두기만 한다.
///
/// 서버 쪽 약속 (server/mailbox_server.py):
///   POST /v1/send   봉투 JSON            → {"ok":true}
///   GET  /v1/fetch?to=<번호>             → {"items":[봉투 JSON ...]}   (헤더 X-Fm-Token)
///   POST /v1/ack    {"to":..,"ids":[..]} → {"ok":true}                 (헤더 X-Fm-Token)
///   GET  /v1/time                        → {"stamp": 1/100초}
class MailboxTransport implements Transport, TimeSource {
  MailboxTransport({
    required this.baseUrl,
    required this.myPhone,
    required this.token,
    this.timeout = const Duration(seconds: 8),
  });

  final String baseUrl;
  final String myPhone;

  /// 이 기기가 보관함에서 내 우편함을 열 때 내는 비밀값 (처음 쓴 기기에 묶인다).
  final String token;
  final Duration timeout;

  final StreamController<Envelope> _in = StreamController<Envelope>.broadcast(sync: true);
  final HttpClient _http = HttpClient();

  @override
  Stream<Envelope> get incoming => _in.stream;

  @override
  Future<void> start() async {}

  @override
  Future<void> stop() async => _http.close(force: true);

  Future<Map<String, Object?>?> _call(String method, String path,
      {Object? body, Map<String, String>? query, bool auth = false}) async {
    try {
      final uri = Uri.parse('$baseUrl$path').replace(queryParameters: query);
      final req = await _http.openUrl(method, uri).timeout(timeout);
      req.headers.contentType = ContentType.json;
      if (auth) req.headers.set('X-Fm-Token', token);
      final bytes = utf8.encode(body == null ? '{}' : jsonEncode(body));
      if (method == 'POST') {
        req.contentLength = bytes.length; // 서버가 길이를 요구한다
        req.add(bytes);
      }
      final res = await req.close().timeout(timeout);
      final text = await utf8.decodeStream(res).timeout(timeout);
      if (res.statusCode != 200) return null;
      return (jsonDecode(text) as Map).cast<String, Object?>();
    } on Object {
      return null; // 연결 실패는 "못 보냄"으로 다룬다.
    }
  }

  @override
  Future<bool> send(Envelope envelope) async {
    final r = await _call('POST', '/v1/send', body: envelope.toJson());
    return r != null && r['ok'] == true;
  }

  @override
  Future<int> fetchPending() async {
    final r = await _call('GET', '/v1/fetch', query: {'to': myPhone}, auth: true);
    if (r == null) return 0;
    final items = (r['items'] as List? ?? const []).cast<Object?>();
    final ids = <String>[];
    for (final raw in items) {
      try {
        final e = Envelope.fromJson((raw as Map).cast<String, Object?>());
        ids.add(e.id);
        _in.add(e);
      } catch (_) {
        // 읽을 수 없는 봉투는 건너뛴다.
      }
    }
    if (ids.isNotEmpty) {
      await _call('POST', '/v1/ack', body: {'to': myPhone, 'ids': ids}, auth: true);
    }
    return ids.length;
  }

  @override
  Future<int?> referenceStamp() async {
    final r = await _call('GET', '/v1/time');
    final v = r?['stamp'];
    return v is int ? v : null;
  }
}