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

import 'questions_db.dart';
import 'signalr/questions_hub_connections.dart';

/// Creates questions in Postgres and delivers them over SignalR.
class QuestionService {
  QuestionService({
    required QuestionsDb questionsDb,
    required QuestionsHubConnections hubConnections,
  })  : _questionsDb = questionsDb,
        _hubConnections = hubConnections;

  final QuestionsDb _questionsDb;
  final QuestionsHubConnections _hubConnections;

  /// Called at login: ensures a starter question exists when the user has none.
  Future<Map<String, dynamic>> ensureStarterQuestionOnLogin(
    String firebaseUid,
  ) async {
    final Map<String, dynamic> question =
        await _questionsDb.getOrCreateStarterQuestion(firebaseUid);
    final int unansweredCount =
        await _questionsDb.countUnansweredQuestions(firebaseUid);
    final Map<String, dynamic> payload = _questionsDb.toClientPayload(
      question,
      unansweredCount: unansweredCount,
    );
    await _hubConnections.pushQuestion(firebaseUid, payload);
    return payload;
  }

  /// Inserts a question and pushes it to connected SignalR clients.
  Future<Map<String, dynamic>> createAndDeliverQuestion({
    required String assignedUserId,
    required String questionText,
    required num correctAnswer,
    String? sourceTag,
    String? pipelineKey,
    String? pipelineStep,
  }) async {
    final Map<String, dynamic> question = await _questionsDb.createQuestion(
      assignedUserId: assignedUserId,
      questionText: questionText,
      correctAnswer: correctAnswer,
      sourceTag: sourceTag,
      pipelineKey: pipelineKey,
      pipelineStep: pipelineStep,
    );
    final int unansweredCount =
        await _questionsDb.countUnansweredQuestions(assignedUserId);
    final Map<String, dynamic> payload = _questionsDb.toClientPayload(
      question,
      unansweredCount: unansweredCount,
    );
    await _hubConnections.pushQuestion(assignedUserId, payload);
    return payload;
  }

  /// On SignalR connect: deliver an existing unanswered question only (no create).
  Future<void> deliverPendingQuestionOnConnect(
    QuestionsHubConnection connection,
  ) async {
    try {
      final String uid = connection.firebaseUid;
      final Map<String, dynamic>? question =
          await _questionsDb.findUnansweredQuestion(uid);
      if (question == null) {
        return;
      }
      final int unansweredCount =
          await _questionsDb.countUnansweredQuestions(uid);
      final Map<String, dynamic> payload = _questionsDb.toClientPayload(
        question,
        unansweredCount: unansweredCount,
      );
      await _hubConnections.pushQuestionToConnection(connection, payload);
    } catch (e, st) {
      stderr.writeln(
        'Failed to deliver pending question for ${connection.firebaseUid}: $e\n$st',
      );
    }
  }
}