import 'package:postgres/postgres.dart';

import 'spelling_progress_policy.dart';

/// Per-user familiarity with shared [spelling_items].
class UserSpellingProgressDb {
  UserSpellingProgressDb(this._connection);

  final Connection _connection;

  /// Ensures a per-user link to [spellingItemId] with scores starting at zero.
  Future<void> ensureLink({
    required String firebaseUid,
    required String spellingItemId,
  }) async {
    await _connection.execute(
      Sql.named(
        '''
        INSERT INTO user_spelling_progress (
          firebase_uid,
          spelling_item_id,
          familiarity_score,
          attempt_count,
          correct_count
        ) VALUES (
          @uid,
          @item_id::uuid,
          0,
          0,
          0
        )
        ON CONFLICT (firebase_uid, spelling_item_id) DO NOTHING
        ''',
      ),
      parameters: <String, dynamic>{
        'uid': firebaseUid,
        'item_id': spellingItemId,
      },
    );
  }

  Future<void> recordQuizOutcome({
    required String firebaseUid,
    required String spellingItemId,
    required bool correct,
  }) async {
    final DateTime now = DateTime.now().toUtc();
    final String outcome = correct ? 'correct' : 'incorrect';
    final int delta = correct
        ? SpellingProgressPolicy.correctDelta
        : -SpellingProgressPolicy.incorrectDelta;

    await _connection.execute(
      Sql.named(
        '''
        INSERT INTO user_spelling_progress (
          firebase_uid,
          spelling_item_id,
          familiarity_score,
          attempt_count,
          correct_count,
          last_attempted_at,
          last_outcome
        ) VALUES (
          @uid,
          @item_id::uuid,
          @delta,
          1,
          @correct_inc,
          @now,
          @outcome
        )
        ON CONFLICT (firebase_uid, spelling_item_id) DO UPDATE SET
          familiarity_score = user_spelling_progress.familiarity_score + @delta,
          attempt_count = user_spelling_progress.attempt_count + 1,
          correct_count = user_spelling_progress.correct_count + @correct_inc,
          last_attempted_at = @now,
          last_outcome = @outcome
        ''',
      ),
      parameters: <String, dynamic>{
        'uid': firebaseUid,
        'item_id': spellingItemId,
        'delta': delta,
        'correct_inc': correct ? 1 : 0,
        'now': now,
        'outcome': outcome,
      },
    );
  }

  Future<int?> familiarityScore({
    required String firebaseUid,
    required String spellingItemId,
  }) async {
    final Result result = await _connection.execute(
      Sql.named(
        '''
        SELECT familiarity_score
        FROM user_spelling_progress
        WHERE firebase_uid = @uid AND spelling_item_id = @item_id::uuid
        ''',
      ),
      parameters: <String, dynamic>{
        'uid': firebaseUid,
        'item_id': spellingItemId,
      },
    );
    if (result.isEmpty) {
      return null;
    }
    return (result.first[0]! as num).toInt();
  }
}