parking-webapi/WebApi_data_value/Services/BackgroundService.cs

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.EntityFrameworkCore;
using System;
using System.Globalization;
using System.Threading;
using System.Threading.Tasks;
using Parking_space_WebAPI.Services;
using WebApi_data_value.Models; 
// 執行計算剩餘車位並不為負數存入資料庫ParkingLogs
public class ParkingUpdateService : BackgroundService
{
    private readonly IServiceScopeFactory _scopeFactory;

    public ParkingUpdateService(IServiceScopeFactory scopeFactory)
    {
        _scopeFactory = scopeFactory;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        while (!stoppingToken.IsCancellationRequested)
        {
            using (var scope = _scopeFactory.CreateScope())
            {
                var _context = scope.ServiceProvider.GetRequiredService<SqlContext>();

                try
                {
                    var yuntech_parking = await _context.yuntech_parking.FirstOrDefaultAsync();
                    if (yuntech_parking != null)
                    {
                        
                        if (Int32.TryParse(yuntech_parking.all_num, out int totalParkingSpaces))
                        {
                           
                            var monthly_rent_data = await _context.yuntech_monthly_rent_number
                                .FirstOrDefaultAsync(rent => rent.category == "月租");
                            int monthlyRentNumber = 0;
                            if (monthly_rent_data != null)
                            {
                                Int32.TryParse(monthly_rent_data.number, out monthlyRentNumber);
                            }

                            
                            var temporary_rent_data = await _context.yuntech_monthly_rent_number
                                .FirstOrDefaultAsync(rent => rent.category == "臨停");
                            int temporaryRentNumber = 0;
                            if (temporary_rent_data != null)
                            {
                                Int32.TryParse(temporary_rent_data.number, out temporaryRentNumber);
                            }

                            
                            int totalOccupiedSpaces = monthlyRentNumber + Math.Abs(temporaryRentNumber); //確保絕對值
                            int remainingSpaces = totalParkingSpaces - totalOccupiedSpaces;

                            // 確保剩餘車位數不為負數
                            yuntech_parking.now_num = Math.Max(remainingSpaces, 0).ToString();

                           
                            await _context.SaveChangesAsync();

                            
                            var log = new ParkingLog
                            {
                                Timestamp = DateTime.Now,
                                TotalParkingSpaces = totalParkingSpaces,
                                RemainingSpaces = Math.Max(remainingSpaces, 0),  // 確保儲存時不為負數
                                MonthlyRentSpaces = monthlyRentNumber,
                                TemporaryRentSpaces = Math.Abs(temporaryRentNumber),
                                DayOfWeek = DateTime.Now.ToString("dddd", new CultureInfo("zh-TW"))
                            };

                            // 儲存資料庫ParkingLogs
                            _context.ParkingLogs.Add(log);
                            await _context.SaveChangesAsync();
                        }
                    }
                }
                catch (Exception ex)
                {
                    // 錯誤顯示
                    Console.WriteLine($"An error occurred: {ex.Message}");
                }
            }

            // 每分鐘執行一次
            await Task.Delay(TimeSpan.FromMinutes(1), stoppingToken);
        }
    }
}