// nodes_provider.dart — 节点清单 + 当前选择
//
// 从 GET /v1/nodes 拉取节点列表；认证后自动刷新。
// 未登录 / 加载中时退回演示节点（kDemoNodes）保证 UI 正常显示。
import 'dart:convert';

import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:http/http.dart' as http;

import '../models/node.dart';
import 'auth_provider.dart';

// ── API base URL（由 --dart-define 注入）──────────────────────────

const _kApiUrl = String.fromEnvironment(
  'PANGOLIN_API_URL',
  defaultValue: 'http://localhost:8080',
);

// ── 节点列表 AsyncNotifier ────────────────────────────────────────

class NodesNotifier extends AsyncNotifier<List<Node>> {
  @override
  Future<List<Node>> build() async {
    final auth = ref.watch(authProvider);
    if (!auth.isLoggedIn) return kDemoNodes;
    return _fetchNodes(auth.accessToken!);
  }

  Future<void> refresh() async {
    state = const AsyncLoading();
    final auth = ref.read(authProvider);
    if (!auth.isLoggedIn) {
      state = AsyncData(kDemoNodes);
      return;
    }
    state = await AsyncValue.guard(() => _fetchNodes(auth.accessToken!));
  }

  static Future<List<Node>> _fetchNodes(String accessToken) async {
    final uri = Uri.parse('$_kApiUrl/v1/nodes');
    final resp = await http.get(uri, headers: {
      'Authorization': 'Bearer $accessToken',
    }).timeout(const Duration(seconds: 10));

    if (resp.statusCode != 200) return kDemoNodes;

    final body = jsonDecode(resp.body) as Map<String, dynamic>;
    final rawList = body['nodes'] as List<dynamic>? ?? [];
    return rawList.map((e) {
      final m = e as Map<String, dynamic>;
      return Node(
        uuid: m['id'] as String? ?? '',
        code: m['region'] as String? ?? '??',
        nameZh: m['name_zh'] as String? ?? '',
        nameEn: m['name_en'] as String? ?? '',
        tier: m['tier'] as String? ?? 'free',
        ping: 0, // 延迟由探针数据填充；MVP 默认 0
      );
    }).toList();
  }
}

final nodesProvider =
    AsyncNotifierProvider<NodesNotifier, List<Node>>(NodesNotifier.new);

// ── 当前选中的节点 UUID；'AUTO' 表示智能选择（默认）─────────────────

final selectedNodeCodeProvider = StateProvider<String>((ref) => kSmartNodeCode);

/// 是否处于智能选择。
final isSmartSelectProvider = Provider<bool>(
  (ref) => ref.watch(selectedNodeCodeProvider) == kSmartNodeCode,
);

/// 实际生效的节点：同步拉取 AsyncValue；未就绪时取 kDemoNodes 第一条。
final effectiveNodeProvider = Provider<Node>((ref) {
  final nodesAsync = ref.watch(nodesProvider);
  final nodes = nodesAsync.valueOrNull ?? kDemoNodes;
  if (nodes.isEmpty) return kDemoNodes.first;

  final code = ref.watch(selectedNodeCodeProvider);
  if (code == kSmartNodeCode) {
    // 延迟最小者；MVP 无真实延迟时取第一条
    return nodes.reduce((a, b) => a.ping <= b.ping ? a : b);
  }
  return nodes.firstWhere((n) => n.code == code, orElse: () => nodes.first);
});