using Microsoft.EntityFrameworkCore;
using System;
using System.Linq;
using System.Text.Json;
using System.Security.Principal;
using System.Threading.Tasks;

namespace Inventory.Core
{
    public class DatabaseUpdater
    {
        private readonly InventoryContext _db;
        private readonly SystemInfoCollector _collector;
        private readonly HealthMonitor _healthMonitor;
        private readonly ConsumerType _consumerType;

        private static readonly TimeZoneInfo ManilaTimeZone = GetManilaTimeZone();

        private string? _existingPrinters;

        private static TimeZoneInfo GetManilaTimeZone()
        {
            try
            {
                return TimeZoneInfo.FindSystemTimeZoneById("Asia/Manila"); // IANA ID for Linux/macOS
            }
            catch (TimeZoneNotFoundException)
            {
                return TimeZoneInfo.FindSystemTimeZoneById("Singapore Standard Time"); // Windows ID
            }
        }
        public DatabaseUpdater(InventoryContext db, SystemInfoCollector collector, HealthMonitor healthMonitor, ConsumerType consumerType)
        {
            _db = db;
            _collector = collector;
            _healthMonitor = healthMonitor;
            _consumerType = consumerType;
        }

        public async Task UpsertDevice()
        {
            // --- Step 1: Data Collection ---
            string? localIdentifier = GetLocalIdentifier();
            if (string.IsNullOrWhiteSpace(localIdentifier))
            {
                return;
            }

            var healthReport = _healthMonitor.CollectHealthMetrics();

            // --- Step 2: Data Persistence ---
            var existingDevice = await _db.Devices.FirstOrDefaultAsync(d => d.HardwareIdentifier == localIdentifier);

            // The agent service (running as SYSTEM) cannot access user-specific printer info.
            // We only collect and update printer data if we are NOT running as the system service.

            if (existingDevice != null)
            {
                // Update existing device
                _existingPrinters = existingDevice.Printers;
                UpdateDeviceProperties(existingDevice, healthReport);
            }
            else
            {
                // Create new device
                var newDevice = new Device();
                newDevice.HardwareIdentifier = localIdentifier;
                UpdateDeviceProperties(newDevice, healthReport); // Update all properties
                _db.Devices.Add(newDevice);
            }

            await _db.SaveChangesAsync();
        }


        private void UpdateDeviceProperties(Device device, HealthMetricsReport healthReport)
        {
            var (ipAddresses, macAddress) = _collector.GetNetworkInfo();

            device.ComputerName = _collector.GetComputerName();
            device.DeviceType = _collector.GetDeviceType();
            device.SerialNumber = _collector.GetSystemSerialNumber();
            device.MotherboardSerialNumber = _collector.GetMotherboardSerialNumber();
            device.SystemUUID = _collector.GetSystemUUID();
            device.Processor = _collector.GetProcessor();
            device.RAM = _collector.GetTotalRAM();
            device.GPUs = JsonSerializer.Serialize(_collector.GetGPUs()); // Save as JSON array
            device.HasOpticalDrive = _collector.HasOpticalDrive();
            device.OSVersion = _collector.GetOSVersion();
            device.OsInstallDate = _collector.GetOSInstallDate();
            device.OSLicenseKey = _collector.GetOSLicenseKey();
            device.IPAddress = JsonSerializer.Serialize(ipAddresses);
            device.MACAddress = macAddress;

            // Health Metrics
            device.CpuTemperature = healthReport.CpuTemp;
            device.GpuTemperature = healthReport.GpuTemp;
            device.BatteryHealthPercent = healthReport.BatteryHealth;

            device.Monitors = JsonSerializer.Serialize(_collector.GetMonitors());
            device.StorageDevices = JsonSerializer.Serialize(_collector.GetStorage());
            device.DriveHealth = JsonSerializer.Serialize(healthReport.DriveHealth);
            device.HealthMetrics = JsonSerializer.Serialize(healthReport);
            device.LocalAdmins = JsonSerializer.Serialize(_collector.GetLocalAdmins());

            if (_consumerType == ConsumerType.AdminTool)
            {
                // Only the Admin Tool should ever collect and save printer information.
                device.Printers = JsonSerializer.Serialize(_collector.GetPrinters());
            } else if (!string.IsNullOrEmpty(_existingPrinters))
            {
                // If running as Agent, preserve existing printer data if available.
                device.Printers = _existingPrinters;
            }

            device.LastSeen = TimeZoneInfo.ConvertTimeFromUtc(DateTime.UtcNow, ManilaTimeZone);
        }

        public string? GetLocalIdentifier()
        {
            string? motherboardSerial = _collector.GetMotherboardSerialNumber();
            if (IsValidIdentifier(motherboardSerial))
            {
                return motherboardSerial;
            }

            string? systemUuid = _collector.GetSystemUUID();
            if (IsValidIdentifier(systemUuid))
            {
                return systemUuid;
            }

            var (_, macAddress) = _collector.GetNetworkInfo();
            if (IsValidIdentifier(macAddress))
            {
                return macAddress;
            }

            var computerName = _collector.GetComputerName();
            if (IsValidIdentifier(computerName))
            {
                return computerName;
            }

            return null;
        }

        private bool IsValidIdentifier(string? identifier)
        {
            return !string.IsNullOrWhiteSpace(identifier) && 
                   !identifier.Equals("Unknown", StringComparison.OrdinalIgnoreCase) &&
                   !identifier.Equals("N/A", StringComparison.OrdinalIgnoreCase) &&
                   !identifier.Equals("Not Available", StringComparison.OrdinalIgnoreCase) &&
                   !identifier.Equals("To be filled by O.E.M.", StringComparison.OrdinalIgnoreCase) &&
                   !identifier.Equals("Default string", StringComparison.OrdinalIgnoreCase);
        }
    }
}