using System.Text.Json;
using Microsoft.Extensions.Configuration;
using UtopiaCanteenSystem.Data;
using UtopiaCanteenSystem.Models;
using UtopiaCanteenSystem.Services;

namespace UtopiaCanteen.BackendService;

/// <summary>
/// Backend service configuration: appsettings.json + persisted JSON under LocalApplicationData.
/// </summary>
public sealed class BackendHostConfigService : IConfigService
{
    private readonly IConfiguration _configuration;
    private readonly string _persistedPath;
    private PersistedConfig _persisted;

    public BackendHostConfigService(IConfiguration configuration)
    {
        _configuration = configuration;
        _persistedPath = Path.Combine(DatabasePath.GetAppDataFolder(), "backend-settings.json");
        _persisted = LoadPersisted();
        MergeFromAppSettingsIfNeeded();
    }

    public string GetListenUrls() =>
        _configuration["ListenUrls"] ?? "http://0.0.0.0:5000";

    public string GetSyncApiEndpoint() => _configuration["SyncApiEndpoint"] ?? _persisted.SyncApiEndpoint ?? string.Empty;
    public void SetSyncApiEndpoint(string endpoint) { _persisted.SyncApiEndpoint = endpoint ?? string.Empty; SavePersisted(); }

    public bool GetSyncServiceEnabled() =>
        _configuration.GetValue("SyncServiceEnabled", _persisted.SyncServiceEnabled);

    public void SetSyncServiceEnabled(bool enabled) { _persisted.SyncServiceEnabled = enabled; SavePersisted(); }

    public bool GetScannerConnected() => false;
    public void SetScannerConnected(bool connected) { }

    public int GetScanIntervalDays() => 0;
    public void SetScanIntervalDays(int value) { }
    public int GetScanIntervalHours() => 0;
    public void SetScanIntervalHours(int value) { }
    public int GetScanIntervalMinutes() => 1;
    public void SetScanIntervalMinutes(int value) { }
    public int GetScanIntervalSeconds() => 0;
    public void SetScanIntervalSeconds(int value) { }
    public TimeSpan GetScanInterval() => TimeSpan.FromMinutes(1);

    public string GetAdminCardId() => "ADMIN";
    public void SetAdminCardId(string cardId) { }

    public string GetSiteId() => _persisted.SiteId ?? "02";
    public void SetSiteId(string siteId) { _persisted.SiteId = siteId ?? string.Empty; SavePersisted(); }

    public void ApplyLocationSiteIdFromAuth(string? locationSiteId) { }

    public string GetDeviceId()
    {
        if (!string.IsNullOrWhiteSpace(_persisted.DeviceId))
            return _persisted.DeviceId.Trim();

        _persisted.DeviceId = ResolveMachineDeviceId();
        SavePersisted();
        return _persisted.DeviceId;
    }

    public void SetDeviceId(string deviceId)
    {
        _persisted.DeviceId = string.IsNullOrWhiteSpace(deviceId)
            ? ResolveMachineDeviceId()
            : deviceId.Trim();
        SavePersisted();
    }

    public bool GetRememberAdminCredentials() => false;
    public void SetRememberAdminCredentials(bool remember) { }
    public string GetSavedAdminUsername() => string.Empty;
    public void SetSavedAdminUsername(string username) { }
    public string GetSavedAdminPassword() => string.Empty;
    public void SetSavedAdminPassword(string password) { }

    public string GetMySqlConnectionString() =>
        FirstNonEmpty(_configuration["MySqlConnectionString"], _persisted.MySqlConnectionString);

    public void SetMySqlConnectionString(string connectionString)
    {
        _persisted.MySqlConnectionString = connectionString ?? string.Empty;
        SavePersisted();
    }

    public string GetHrmsLookupConnectionString() =>
        ConfigConnectionHelper.GetHrmsOrProductionConnectionString(
            FirstNonEmpty(_configuration["HrmsLookupConnectionString"], _persisted.HrmsLookupConnectionString),
            GetMySqlConnectionString());

    public void SetHrmsLookupConnectionString(string connectionString)
    {
        _persisted.HrmsLookupConnectionString = connectionString ?? string.Empty;
        SavePersisted();
    }

    public DateTime? GetLastEmployeeRfidCacheSyncUtc() => _persisted.LastEmployeeRfidCacheSyncUtc;
    public void SetLastEmployeeRfidCacheSyncUtc(DateTime utc)
    {
        _persisted.LastEmployeeRfidCacheSyncUtc = utc;
        SavePersisted();
    }

    public DateTime? GetLastMealMenuCacheSyncUtc() => _persisted.LastMealMenuCacheSyncUtc;
    public void SetLastMealMenuCacheSyncUtc(DateTime utc)
    {
        _persisted.LastMealMenuCacheSyncUtc = utc;
        SavePersisted();
    }

    public AppMode GetAppMode() => AppMode.Server;
    public void SetAppMode(AppMode mode) { }

    public string GetCentralServerBaseUrl() => string.Empty;
    public void SetCentralServerBaseUrl(string url) { }

    public string GetBackendBaseUrl() => DeriveLocalhostApiBaseUrl(GetListenUrls());

    public string GetLocalServerListenUrls() => GetListenUrls();
    public void SetLocalServerListenUrls(string urls) { }

    private static string ResolveMachineDeviceId()
    {
        var machineName = Environment.MachineName;
        return string.IsNullOrWhiteSpace(machineName)
            ? Guid.NewGuid().ToString("N")
            : machineName.Trim();
    }

    private void MergeFromAppSettingsIfNeeded()
    {
        var mysql = _configuration["MySqlConnectionString"];
        if (!string.IsNullOrWhiteSpace(mysql) && string.IsNullOrWhiteSpace(_persisted.MySqlConnectionString))
            _persisted.MySqlConnectionString = mysql;

        var hrms = _configuration["HrmsLookupConnectionString"];
        if (!string.IsNullOrWhiteSpace(hrms) && string.IsNullOrWhiteSpace(_persisted.HrmsLookupConnectionString))
            _persisted.HrmsLookupConnectionString = hrms;

        SavePersisted();
    }

    private static string FirstNonEmpty(params string?[] values)
    {
        foreach (var v in values)
        {
            if (!string.IsNullOrWhiteSpace(v))
                return v!;
        }
        return string.Empty;
    }

    private static string DeriveLocalhostApiBaseUrl(string listenUrls)
    {
        var first = listenUrls
            .Split(new[] { ';', ',' }, StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries)
            .FirstOrDefault() ?? "http://0.0.0.0:5000";
        first = first.TrimEnd('/');
        if (first.Contains("0.0.0.0", StringComparison.Ordinal))
            first = first.Replace("0.0.0.0", "localhost", StringComparison.Ordinal);
        if (first.Contains('+'))
            first = first.Replace("+", "localhost", StringComparison.Ordinal);
        return first;
    }

    private PersistedConfig LoadPersisted()
    {
        try
        {
            if (!File.Exists(_persistedPath))
                return new PersistedConfig();
            var json = File.ReadAllText(_persistedPath);
            return JsonSerializer.Deserialize<PersistedConfig>(json) ?? new PersistedConfig();
        }
        catch
        {
            return new PersistedConfig();
        }
    }

    private void SavePersisted()
    {
        try
        {
            var json = JsonSerializer.Serialize(_persisted, new JsonSerializerOptions { WriteIndented = true });
            File.WriteAllText(_persistedPath, json);
        }
        catch (Exception ex)
        {
            Logger.Log(ex, "BackendHostConfigService.SavePersisted");
        }
    }

    private sealed class PersistedConfig
    {
        public string? SyncApiEndpoint { get; set; }
        public bool SyncServiceEnabled { get; set; } = true;
        public string? MySqlConnectionString { get; set; }
        public string? HrmsLookupConnectionString { get; set; }
        public DateTime? LastEmployeeRfidCacheSyncUtc { get; set; }
        public DateTime? LastMealMenuCacheSyncUtc { get; set; }
        public string? SiteId { get; set; }
        public string? DeviceId { get; set; }
    }
}