source: WineTrackerFinal/WineTrackerWebApi/Controllers/VehicleTypeController.cs

using System.Data;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Npgsql;
using Dapper;
using WineTrackerWebApi.Models.VehicleType;
using WineTrackerWebApi.Models.WineType;
using WineTrackerWebApi.Models.ErrorHandle;
using WineTrackerWebApi.Helpers;

namespace WineTrackerWebApi.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class VehicleTypeController : ControllerBase
    {
        private readonly string _connectionString;

        public VehicleTypeController(IConfiguration configuration)
        {
            _connectionString = configuration.GetConnectionString("DefaultConnection");
        }

        // GET: api/VehicleType
        [HttpGet]
        public async Task<ActionResult<IEnumerable<VehicleType>>> GetVehicleType()
        {
            using (IDbConnection db = new NpgsqlConnection(_connectionString)) // Use NpgsqlConnection for PostgreSQL
            {
                const string query = $@"select vehicle_type_id as VehicleTypeId, vehicle_type_name as VehicleTypeName from vehicle_type vt";
                var vehicleTypes = await db.QueryAsync<VehicleType>(query);
                return Ok(vehicleTypes);
            }
        }

        // GET: api/VehicleType/5
        [HttpGet("{id}")]
        public async Task<ActionResult<WineType>> GetVehicleType(int id)
        {
            using (IDbConnection db = new NpgsqlConnection(_connectionString)) // Use NpgsqlConnection for PostgreSQL
            {
                var parameters = new { id = id };

                string query = $@"select vehicle_type_id as VehicleTypeId, vehicle_type_name as VehicleTypeName from vehicle_type vt where vehicle_type_id = @id";
                var vehicleType = await db.QueryFirstAsync<VehicleType>(query, parameters);
                return Ok(vehicleType);
            }
        }

        // PUT: api/VehicleType/5
        // To protect from overposting attacks, see https://go.microsoft.com/fwlink/?linkid=2123754
        [HttpPut]
        public async Task<IActionResult> PutVehicleType([FromBody] VehicleType vehicleType)
        {
            try
            {
                using (IDbConnection db = new NpgsqlConnection(_connectionString)) // Use NpgsqlConnection for PostgreSQL
                {
                    db.Open();
                    using (var transaction = db.BeginTransaction()) // Start a transaction
                    {
                        var parameters = new { VehicleTypeName = vehicleType.VehicleTypeName.Trim(), VehicleTypeId = vehicleType.VehicleTypeId };

                        await ModelValidation.DoesEntityExistByName((NpgsqlConnection)db, (NpgsqlTransaction)transaction, "Vehicle_Type", parameters.VehicleTypeName, entityId: parameters.VehicleTypeId);

                        string query = $@"update vehicle_type set vehicle_type_name = @VehicleTypeName where vehicle_type_id = @VehicleTypeId";
                        await db.ExecuteAsync(query, parameters, transaction: transaction);

                        transaction.Commit();
                        return Ok();
                    }
                }
            }
            catch (Exception ex)
            {
                return BadRequest(new ErrorHandler { Name = "Error", Description = ex.Message });
            }
        }

        // POST: api/VehicleType
        // To protect from overposting attacks, see https://go.microsoft.com/fwlink/?linkid=2123754
        [HttpPost]
        public async Task<IActionResult> PostVehicleType([FromBody] VehicleType vehicleType)
        {
            try
            {
                using (IDbConnection db = new NpgsqlConnection(_connectionString)) // Use NpgsqlConnection for PostgreSQL
                {
                    db.Open();
                    using (var transaction = db.BeginTransaction()) // Start a transaction
                    {
                        var parameters = new { VehicleTypeName = vehicleType.VehicleTypeName.Trim() };

                        await ModelValidation.DoesEntityExistByName((NpgsqlConnection)db, (NpgsqlTransaction)transaction, "Vehicle_Type", parameters.VehicleTypeName);

                        string query = "INSERT INTO vehicle_type (vehicle_type_name) VALUES (@VehicleTypeName);";
                        await db.ExecuteAsync(query, parameters, transaction: transaction);

                        transaction.Commit();
                        return Ok();
                    }
                }
            }
            catch (Exception ex)
            {
                return BadRequest(new ErrorHandler { Name = "Error", Description = ex.Message });
            }
        }

        // DELETE: api/VehicleType/5
        [HttpDelete("{id}")]
        public async Task<IActionResult> DeleteVehicleType(int id)
        {
            try
            {
                //Check if there are vehicle details linked to the vehicle type we are trying to delete, if so return a message and dont let the user delete the vehicle type.
                using (IDbConnection db = new NpgsqlConnection(_connectionString)) // Use NpgsqlConnection for PostgreSQL
                {
                    db.Open();
                    using (var transaction = db.BeginTransaction()) // Start a transaction
                    {
                        var parameters = new { id = id };

                        string vehicleTypeLinkToVehicleDetailsQuery = $@"
                    select count(*)
                    from vehicle_type vt 
                    join vehicle_details vd on vd.vehicle_type_id = vt.vehicle_type_id
                    where vt.vehicle_type_id = @id";

                        var isVehicleTypeLinkedToVehicleDetails = await db.QueryFirstAsync<int>(vehicleTypeLinkToVehicleDetailsQuery, parameters, transaction: transaction);
                        if (isVehicleTypeLinkedToVehicleDetails > 0)
                            return BadRequest(new ErrorHandler { Name = "Vehicle Type Cannot Be Deleted", Description = "Vehicle Type cannot be deleted because it is linked to vehicle details" });

                        string query = $@"delete from vehicle_type where vehicle_type_id = @id";
                        await db.ExecuteAsync(query, parameters, transaction: transaction);

                        transaction.Commit();
                        return Ok();
                    }
                }
            }
            catch (Exception ex)
            {
                return BadRequest(new ErrorHandler { Name = "Error", Description = ex.Message });
            }
        }
    }
}