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

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

import '../api_request.dart';
import '../errors/network_exception.dart';
import '../errors/parse_exception.dart';
import '../errors/server_exception.dart';
import 'connect_auth_store.dart';
import 'connect_endpoint.dart';
import 'errors/connect_exception.dart';
import 'errors/rmv_rate_limited_exception.dart';
import 'errors/rmv_upstream_exception.dart';

enum ConnectHttpMethod { get, post }

/// Mirrors the [MhslApi] pattern: each endpoint subclasses this, declares the
/// subpath/query/body, and implements [assemble]. Handles bearer-token
/// injection (via [ConnectAuthStore]), one transparent 401-retry after a
/// fresh login, and turns the structured `RmvController.wrap` error strings
/// into typed exceptions.
abstract class ConnectApi<T> extends ApiRequest {
  final String subpath;

  ConnectApi(this.subpath);

  /// Override to `false` for endpoints that must NOT receive a bearer token
  /// (currently only login itself, to avoid an infinite refresh loop).
  bool get requiresAuth => true;

  ConnectHttpMethod get method => ConnectHttpMethod.get;

  Map<String, String>? get queryParameters => null;

  /// Returns the body to send for POST requests. Should be JSON-encodable.
  Object? get body => null;

  T assemble(String raw);

  Future<T> run() async {
    final response = await _runOnce(forceTokenRefresh: false);
    if (response.statusCode == 401 && requiresAuth) {
      // Single transparent retry after a forced refresh, then bail.
      await ConnectAuthStore.instance.invalidate();
      final retry = await _runOnce(forceTokenRefresh: true);
      if (retry.statusCode == 401) {
        throw ConnectException.authFailed(
          technicalDetails:
              'connect $subpath HTTP 401 after token refresh: ${_safeBody(retry)}',
        );
      }
      return _handleResponse(retry);
    }
    return _handleResponse(response);
  }

  Future<http.Response> _runOnce({required bool forceTokenRefresh}) async {
    final uri = ConnectEndpoint.resolve(subpath).replace(
      queryParameters: _normaliseQuery(queryParameters),
    );

    final headers = <String, String>{
      if (method == ConnectHttpMethod.post) 'Content-Type': 'application/json',
      'Accept': 'application/json',
    };
    if (requiresAuth) {
      final token = await ConnectAuthStore.instance.getToken(
        forceRefresh: forceTokenRefresh,
      );
      headers['Authorization'] = 'Bearer $token';
    }

    try {
      switch (method) {
        case ConnectHttpMethod.get:
          return await http.get(uri, headers: headers);
        case ConnectHttpMethod.post:
          final payload = body;
          return await http.post(
            uri,
            headers: headers,
            body: payload == null ? null : jsonEncode(payload),
          );
      }
    } on SocketException catch (e) {
      throw NetworkException(
        technicalDetails: 'connect $subpath: ${e.message}',
      );
    } on TimeoutException catch (e) {
      throw NetworkException.timeout(
        technicalDetails: 'connect $subpath: $e',
      );
    } on http.ClientException catch (e) {
      throw NetworkException(
        technicalDetails: 'connect $subpath: ${e.message}',
      );
    } on HandshakeException catch (e) {
      throw NetworkException(
        technicalDetails: 'connect $subpath TLS: ${e.message}',
      );
    }
  }

  T _handleResponse(http.Response response) {
    final status = response.statusCode;
    final bodyText = _safeBody(response);

    if (status == 503) {
      final retryAfter = _parseRetryAfter(bodyText);
      throw RmvRateLimitedException(
        retryAfter: retryAfter,
        technicalDetails: 'connect $subpath HTTP 503: $bodyText',
      );
    }
    if (status == 502) {
      final code = _parseUpstreamErrorCode(bodyText);
      throw RmvUpstreamException(
        errorCode: code,
        technicalDetails: 'connect $subpath HTTP 502: $bodyText',
      );
    }
    if (status > 299) {
      throw ServerException(
        statusCode: status,
        technicalDetails: 'connect $subpath HTTP $status: $bodyText',
      );
    }

    try {
      return assemble(bodyText);
    } catch (e, st) {
      final preview = bodyText.length > 1024
          ? '${bodyText.substring(0, 1024)}…'
          : bodyText;
      log(
        'connect $subpath assemble failed: $e\nbody: $preview',
        stackTrace: st,
      );
      throw ParseException(
        technicalDetails: 'connect $subpath assemble: $e',
      );
    }
  }

  String _safeBody(http.Response response) {
    try {
      return utf8.decode(response.bodyBytes);
    } catch (_) {
      return response.body;
    }
  }

  /// Body format from `RmvController.wrap`: `upstream_rate_limited|retryAfter=60`.
  Duration _parseRetryAfter(String body) {
    final match = RegExp(r'retryAfter=(\d+)').firstMatch(body);
    final seconds = match == null ? 60 : int.tryParse(match.group(1)!) ?? 60;
    return Duration(seconds: seconds);
  }

  /// Body format: `upstream_error|H390` — the segment after the pipe is the
  /// RMV/HaFAS error code.
  String? _parseUpstreamErrorCode(String body) {
    final idx = body.indexOf('|');
    if (idx < 0 || idx >= body.length - 1) return null;
    return body.substring(idx + 1).trim();
  }

  Map<String, String>? _normaliseQuery(Map<String, String>? raw) {
    if (raw == null) return null;
    final cleaned = <String, String>{};
    raw.forEach((key, value) {
      if (value.isNotEmpty) cleaned[key] = value;
    });
    return cleaned.isEmpty ? null : cleaned;
  }
}