PIbd-21_Rodionov_I.A._SUBD/ElectronicDiary/ElectronicDiaryPostgresImplementation/WorkImplementation/TeacherWork.cs

using ElectronicDiaryAbstractions.Models;
using ElectronicDiaryAbstractions.WorkAbstractions;
using Npgsql;

namespace ElectronicDiaryPostgresImplementation.WorkImplementation
{
    public class TeacherWork : ITeacherWork
    {
        private readonly SubjectWork _subjectWork;

        public TeacherWork(SubjectWork subjectWork)
        {
            _subjectWork = subjectWork;
        }

        public List<Teacher> GetAll()
        {
            var teachers = new List<Teacher>();
            using var con = SqlConnection.GetConnection();
            con.Open();
            using var cmd = new NpgsqlCommand("SELECT * FROM teacher order by teacher_id", con);
            using var reader = cmd.ExecuteReader();
            while (reader.Read())
            {
                teachers.Add(new Teacher
                {
                    Id = reader.GetInt32(0),
                    LastName = reader.GetString(1),
                    FirstName = reader.GetString(2),
                    Patronymic = reader.GetString(3),
                    UserId = reader.GetInt32(4),
                });
            }
            return teachers;
        }

        public Teacher? Get(int id)
        {
            using var con = SqlConnection.GetConnection();
            con.Open();
            using var cmd = new NpgsqlCommand($"SELECT * FROM teacher WHERE teacher_id = {id}", con);
            using var reader = cmd.ExecuteReader();
            if (reader.Read())
            {
                return new Teacher
                {
                    Id = reader.GetInt32(0),
                    LastName = reader.GetString(1),
                    FirstName = reader.GetString(2),
                    Patronymic = reader.GetString(3),
                    UserId = reader.GetInt32(4),
                };
            }
            return null;
        }

        public Teacher? Create(Teacher teacher)
        {
            using var con = SqlConnection.GetConnection();
            con.Open();
            using var cmd = new NpgsqlCommand("INSERT INTO teacher (last_name, first_name, patronymic, fk_user_id) VALUES (@LastName, @FirstName, @Patronymic, @UserId)", con);
            cmd.Parameters.AddWithValue("@LastName", teacher.LastName);
            cmd.Parameters.AddWithValue("@FirstName", teacher.FirstName);
            cmd.Parameters.AddWithValue("@Patronymic", teacher.Patronymic);
            cmd.Parameters.AddWithValue("@UserId", teacher.UserId);
            cmd.ExecuteNonQuery();
            return teacher;
        }

        public Teacher? Update(Teacher teacher)
        {
            using var con = SqlConnection.GetConnection();
            con.Open();
            using var cmd = new NpgsqlCommand($"UPDATE teacher SET last_name = '{teacher.LastName}', first_name = '{teacher.FirstName}', patronymic = '{teacher.Patronymic}', fk_user_id = {teacher.UserId} WHERE teacher_id = {teacher.Id}", con);
            cmd.ExecuteNonQuery();
            var element = Get(teacher.Id);
            return element;
        }

        public Teacher? Delete(int id)
        {
            var element = Get(id);
            using var con = SqlConnection.GetConnection();
            con.Open();
            using var cmd = new NpgsqlCommand($"DELETE FROM teacher WHERE teacher_id = {id}", con);
            cmd.ExecuteNonQuery();
            return element;
        }

        public List<Subject> GetAllTeacherSubjects(int teacherId)
        {
            var subjects = new List<Subject>();
            using var con = SqlConnection.GetConnection();
            con.Open();
            using var cmd = new NpgsqlCommand($"SELECT s.subject_id, s.subject_name FROM teacher_subject ts JOIN subject s ON ts.fk_subject_id = s.subject_id WHERE ts.fk_teacher_id = {teacherId}", con);
            using var reader = cmd.ExecuteReader();
            while (reader.Read())
            {
                subjects.Add(new Subject()
                {
                    Id = reader.GetInt32(0),
                    Name = reader.GetString(1),
                });
            }
            return subjects;
        }

        public Subject? AddTeacherSubject(int teacherId, int subjectId)
        {
            using var con = SqlConnection.GetConnection();
            con.Open();
            using var cmd = new NpgsqlCommand("INSERT INTO teacher_subject (fk_teacher_id, fk_subject_id) VALUES (@TeacherId, @SubjectId)", con);
            cmd.Parameters.AddWithValue("@TeacherId", teacherId);
            cmd.Parameters.AddWithValue("@SubjectId", subjectId);
            cmd.ExecuteNonQuery();
            return _subjectWork.Get(subjectId);
        }

        public Subject? DeleteTeacherSubject(int teacherId, int subjectId)
        {
            using var con = SqlConnection.GetConnection();
            con.Open();
            using var cmd = new NpgsqlCommand($"DELETE FROM teacher_subject WHERE fk_teacher_id = {teacherId} AND fk_subject_id = {subjectId}", con);
            cmd.ExecuteNonQuery();
            return _subjectWork.Get(subjectId);
        }

        public List<Subject> DeleteAllTeacherSubjects(int teacherId)
        {
            var subjects = GetAllTeacherSubjects(teacherId);
            using var con = SqlConnection.GetConnection();
            con.Open();
            using var cmd = new NpgsqlCommand($"DELETE FROM teacher_subject WHERE fk_teacher_id = {teacherId}", con);
            cmd.ExecuteNonQuery();
            return subjects;
        }
    }
}