read the best solution for each task in contest

internal/tester/repository/pg_contests_repository.go

@@ -626,3 +626,65 @@ func (r *ContestRepository) ReadMonitor(ctx context.Context, contestId int32) (*
 
 	return &monitor, nil
 }
+
+const (
+	// state=5 - AC
+	readBestSolutions = `
+		WITH contest_tasks AS (
+    SELECT t.id AS task_id,
+           t.position AS task_position,
+           t.contest_id,
+           t.problem_id,
+           t.created_at,
+           t.updated_at,
+           p.title AS task_title,
+           c.title AS contest_title
+    FROM tasks t
+             LEFT JOIN problems p ON p.id = t.problem_id
+             LEFT JOIN  contests c ON c.id = t.contest_id
+    WHERE t.contest_id = ?
+),
+     best_solutions AS (
+         SELECT DISTINCT ON (s.task_id)
+             *
+         FROM solutions s
+         WHERE s.participant_id = ?
+         ORDER BY s.task_id, s.score DESC, s.created_at DESC
+     )
+SELECT
+    s.id,
+    s.participant_id,
+    p.name AS participant_name,
+    s.solution,
+    s.state,
+    s.score,
+    s.penalty,
+    s.time_stat,
+    s.memory_stat,
+    s.language,
+    ct.task_id,
+    ct.task_position,
+    ct.task_title,
+    ct.contest_id,
+    ct.contest_title,
+    s.updated_at,
+    s.created_at
+FROM contest_tasks ct
+         LEFT JOIN best_solutions s ON s.task_id = ct.task_id
+         LEFT JOIN participants p ON p.id = s.participant_id WHERE s.id IS NOT NULL
+ORDER BY ct.task_position
+`
+)
+
+func (r *ContestRepository) ReadBestSolutions(ctx context.Context, contestId int32, participantId int32) ([]*models.Solution, error) {
+	const op = "ContestRepository.ReadBestSolutions"
+	var solutions []*models.Solution
+	query := r.db.Rebind(readBestSolutions)
+	err := r.db.SelectContext(ctx, &solutions, query, contestId, participantId)
+
+	if err != nil {
+		return nil, handlePgErr(err, op)
+	}
+
+	return solutions, nil
+}