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

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

  ProspectiveGuessAssignmentsDb get _assignmentsDb =>
      ProspectiveGuessAssignmentsDb(_questionsDb.connection);

  /// Called at login: ensures one unanswered prospective question when possible.
  Future<Map<String, dynamic>?> bootstrapOnLogin(
    String firebaseUid,
  ) async {
    await _questionsDb.ensureUserExists(firebaseUid);
    return ensureProspectiveQuestionQueued(firebaseUid);
  }

  /// Creates the next slot-based prospective question when the queue is empty.
  Future<Map<String, dynamic>?> ensureProspectiveQuestionQueued(
    String firebaseUid, {
    DateTime? now,
  }) async {
    await _questionsDb.ensureUserExists(firebaseUid);

    final String? pendingQuestionId =
        await _assignmentsDb.findPendingQuestionId(firebaseUid);
    if (pendingQuestionId != null) {
      final Map<String, dynamic>? question = await _questionsDb.findQuestionById(
        questionId: pendingQuestionId,
        assignedUserId: firebaseUid,
      );
      if (question != null && question['userResponse'] == null) {
        final int unansweredCount =
            await _questionsDb.countUnansweredQuestions(firebaseUid);
        return _questionsDb.toClientPayload(
          question,
          unansweredCount: unansweredCount > 0 ? unansweredCount : 1,
        );
      }
    }

    final int queued =
        await _questionsDb.countUnansweredQuestions(firebaseUid);
    if (queued > 0) {
      final Map<String, dynamic>? existing =
          await _questionsDb.findUnansweredQuestion(firebaseUid);
      if (existing == null) {
        return null;
      }
      return _questionsDb.toClientPayload(
        existing,
        unansweredCount: queued,
      );
    }

    final Map<String, dynamic>? prospective =
        await _createProspectiveQuestionWithAssignment(
      firebaseUid,
      now: now,
    );
    if (prospective == null) {
      return null;
    }

    return prospective;
  }

  /// Picks, creates, and records one prospective question when none is queued.
  ///
  /// Retries when a concurrent request claims the same user/slot/symbol first.
  Future<Map<String, dynamic>?> _createProspectiveQuestionWithAssignment(
    String firebaseUid, {
    DateTime? now,
  }) async {
    for (var attempt = 0; attempt < 8; attempt++) {
      final Map<String, dynamic>? picked =
          await _questionsDb.pickProspectiveQuestionForUser(
        firebaseUid,
        now: now,
      );
      if (picked == null) {
        return null;
      }

      final DateTime olderSlotStart = DateTime.parse(
        picked['olderSlotStart']! as String,
      );
      final DateTime newerSlotStart = DateTime.parse(
        picked['newerSlotStart']! as String,
      );
      final String symbol = picked['symbol']! as String;

      if (await _assignmentsDb.hasAssignmentForSymbolSlotPair(
        firebaseUid: firebaseUid,
        olderSlotStart: olderSlotStart,
        newerSlotStart: newerSlotStart,
        symbol: symbol,
      )) {
        continue;
      }

      final Map<String, dynamic> question = await _questionsDb.createQuestion(
        assignedUserId: firebaseUid,
        questionText: picked['questionText']! as String,
        correctAnswer: picked['correctAnswer']! as num,
        sourceTag: 'market_history:prospective',
        pipelineKey: 'trading',
        pipelineStep: 'guess_weekly_move:await_answer',
        metadata: <String, dynamic>{
          'prospective_question_id': picked['id'],
          'symbol': symbol,
          'older_slot_start': picked['olderSlotStart'],
          'newer_slot_start': picked['newerSlotStart'],
          'price_delta_pct': picked['priceDeltaPct'],
        },
      );

      final bool assigned = await _assignmentsDb.insertPendingIfAbsent(
        firebaseUid: firebaseUid,
        olderSlotStart: olderSlotStart,
        newerSlotStart: newerSlotStart,
        symbol: symbol,
        prospectiveQuestionId: picked['id']! as String,
        questionId: question['id']! as String,
      );
      if (!assigned) {
        await _questionsDb.deleteUnansweredQuestion(
          questionId: question['id']! as String,
          assignedUserId: firebaseUid,
        );
        continue;
      }

      return _questionsDb.toClientPayload(
        question,
        unansweredCount: 1,
      );
    }
    return null;
  }

  /// 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,
    Map<String, dynamic>? metadata,
  }) async {
    final Map<String, dynamic> question = await _questionsDb.createQuestion(
      assignedUserId: assignedUserId,
      questionText: questionText,
      correctAnswer: correctAnswer,
      sourceTag: sourceTag,
      pipelineKey: pipelineKey,
      pipelineStep: pipelineStep,
      metadata: metadata,
    );
    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',
      );
    }
  }
}