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

import 'package:shelf/shelf.dart';

import '../cors_headers.dart';
import '../firebase_auth.dart';
import '../question_source_preferences.dart';
import '../question_source_preferences_db.dart';

const String questionSourcesBasePath = '/v1/me/question-sources';

Handler questionSourceHandler({
  required QuestionSourcePreferencesDb db,
  required FirebaseAuthVerifier auth,
}) {
  return (Request request) async {
    if (request.method == 'OPTIONS') {
      return Response.ok(
        '',
        headers: apiCorsHeaders(methods: 'GET, PUT, OPTIONS'),
      );
    }

    if (request.requestedUri.path != questionSourcesBasePath) {
      return _jsonResponse(404, <String, dynamic>{'error': 'Not found'});
    }

    final String? firebaseUid = await auth.verifyBearerToken(
      request.headers['Authorization'] ?? request.headers['authorization'],
    );
    if (firebaseUid == null) {
      return _jsonResponse(401, <String, dynamic>{'error': 'Unauthorized'});
    }

    try {
      if (request.method == 'GET') {
        final List<ResolvedQuestionSourcePreference> sources =
            await db.getResolved(firebaseUid);
        return _jsonResponse(
          200,
          QuestionSourcePreferences.toApiPayload(sources: sources),
        );
      }

      if (request.method == 'PUT') {
        final String body = await request.readAsString();
        final Map<String, dynamic> json =
            jsonDecode(body) as Map<String, dynamic>;
        final List<Map<String, dynamic>> stored =
            QuestionSourcePreferences.parsePutBody(json);
        final List<ResolvedQuestionSourcePreference> saved =
            await db.save(firebaseUid, stored);
        return _jsonResponse(
          200,
          QuestionSourcePreferences.toApiPayload(
            sources: saved,
            updatedAt: DateTime.now().toUtc(),
          ),
        );
      }

      return _jsonResponse(405, <String, dynamic>{'error': 'Method not allowed'});
    } on QuestionSourceValidationException catch (e) {
      return _jsonResponse(400, <String, dynamic>{'error': e.message});
    } catch (e, st) {
      stderr.writeln('Question source handler error: $e\n$st');
      return _jsonResponse(500, <String, dynamic>{'error': 'Internal error'});
    }
  };
}

Response _jsonResponse(int status, Map<String, dynamic> body) {
  return Response(
    status,
    body: jsonEncode(body),
    headers: <String, String>{
      ...apiCorsHeaders(methods: 'GET, PUT, OPTIONS'),
      'Content-Type': 'application/json',
    },
  );
}