using System;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Sozsoft.Platform.DbStartup;
using Sozsoft.Platform.EntityFrameworkCore;
using Sozsoft.Platform.Permissions;
using Volo.Abp.DistributedLocking;
using Volo.Abp.EntityFrameworkCore;
using Volo.Abp.MultiTenancy;
using Volo.Abp.Uow;

namespace Sozsoft.Platform.Controllers;

/// <summary>
/// Canlı sistemde (tam ABP stack ayaktayken) veritabanı durumunu raporlar ve
/// yetkili host kullanıcısının migration tetiklemesine izin verir.
///
/// Veritabanı hiç yokken bu controller çalışmaz; o durumda
/// <see cref="DbStartup.SetupAppRunner"/> içindeki minimal uygulama devrededir.
/// İki yol da <see cref="SetupMigrationRunner"/> üzerinden aynı migration akışını kullanır.
/// </summary>
[Route("api/setup")]
public class SetupController : ControllerBase
{
    /// <summary>
    /// Yeni izin verilmemiş kurulumlarda kilitlenmemek için tanınan geriye dönük rol.
    /// <see cref="PlatformPermissions.Setup.Migrate"/> rollere atandıktan sonra kaldırılabilir.
    /// </summary>
    private const string LegacyAdminRoleName = "admin";

    private const int DistributedLockTimeoutSeconds = 5;

    private readonly IConfiguration _configuration;
    private readonly IHostEnvironment _env;
    private readonly IHostApplicationLifetime _lifetime;
    private readonly IAuthorizationService _authorizationService;
    private readonly ICurrentTenant _currentTenant;
    private readonly IAbpDistributedLock _distributedLock;
    private readonly IUnitOfWorkManager _unitOfWorkManager;
    private readonly BackgroundWorkerInitializer _backgroundWorkerInitializer;
    private readonly AbpBackgroundWorkerRecurringJobInitializer _abpBackgroundWorkerRecurringJobInitializer;
    private readonly ILogger<SetupController> _logger;

    public SetupController(
        IConfiguration configuration,
        IHostEnvironment env,
        IHostApplicationLifetime lifetime,
        IAuthorizationService authorizationService,
        ICurrentTenant currentTenant,
        IAbpDistributedLock distributedLock,
        IUnitOfWorkManager unitOfWorkManager,
        BackgroundWorkerInitializer backgroundWorkerInitializer,
        AbpBackgroundWorkerRecurringJobInitializer abpBackgroundWorkerRecurringJobInitializer,
        ILogger<SetupController> logger)
    {
        _configuration = configuration;
        _env = env;
        _lifetime = lifetime;
        _authorizationService = authorizationService;
        _currentTenant = currentTenant;
        _distributedLock = distributedLock;
        _unitOfWorkManager = unitOfWorkManager;
        _backgroundWorkerInitializer = backgroundWorkerInitializer;
        _abpBackgroundWorkerRecurringJobInitializer = abpBackgroundWorkerRecurringJobInitializer;
        _logger = logger;
    }

    /// <summary>
    /// Veritabanı durumu. Anonim çağırana yalnızca "hazır mı" bilgisi döner;
    /// bekleyen migration sayısı ve hata detayı sadece yetkili host kullanıcısına verilir.
    /// </summary>
    [HttpGet("application-status")]
    [AllowAnonymous]
    public async Task<SetupStatusDto> StatusAsync(CancellationToken cancellationToken)
    {
        var readiness = DatabaseReadinessChecker.GetStatus(_configuration);
        var canMigrate = await CanMigrateAsync();

        if (canMigrate && readiness.IsReady)
        {
            readiness = readiness.WithPendingMigrations(
                await GetPendingMigrationCountAsync(cancellationToken));
        }

        return SetupStatusDto.From(readiness, includeDiagnostics: canMigrate);
    }

    /// <summary>
    /// Migration + seed çalıştırır ve logları SSE olarak akıtır.
    ///
    /// Yetki: veritabanı ayaktayken host tarafında <see cref="PlatformPermissions.Setup.Migrate"/>
    /// izni (veya geriye dönük olarak admin rolü); veritabanı yokken kurulum parolası.
    /// </summary>
    [HttpPost("migrate")]
    [AllowAnonymous]
    public async Task MigrateAsync()
    {
        var (authorized, denialReason) = await AuthorizeMigrateRequestAsync();
        if (!authorized)
        {
            _logger.LogWarning("Database migration request denied: {Reason}", denialReason);
            Response.StatusCode = StatusCodes.Status403Forbidden;
            Response.ContentType = "text/plain; charset=utf-8";
            await Response.WriteAsync(denialReason);
            return;
        }

        var stream = new SetupEventStream(Response);
        await stream.StartAsync();

        // Çok örnekli (multi-instance) dağıtımlarda aynı anda tek migration çalışsın.
        await using var lockHandle = await _distributedLock.TryAcquireAsync(
            "Sozsoft.Platform.SetupMigration",
            TimeSpan.FromSeconds(DistributedLockTimeoutSeconds),
            _lifetime.ApplicationStopping);

        if (lockHandle is null)
        {
            await stream.ErrorAsync("Another migration is already in progress. Please try again later.");
            await stream.DoneAsync("Failed.");
            return;
        }

        _logger.LogWarning(
            "Database migration triggered via /api/setup/migrate by user {UserId}.",
            User?.Identity?.Name ?? "(setup password)");

        // ApplicationStopping kullanılıyor: istemci sekmesini kapatsa da migration tamamlanır.
        var outcome = await SetupMigrationRunner.ExecuteAsync(
            _configuration, _env.ContentRootPath, stream, _lifetime.ApplicationStopping);

        if (outcome != MigrationOutcome.Succeeded)
        {
            _logger.LogWarning("Database migration finished with outcome {Outcome}.", outcome);
            return;
        }

        await stream.InfoAsync("Migration and seed completed successfully.");

        // Yeni/değişen tanımlar Hangfire'a yansısın diye worker'lar tazelenir.
        try
        {
            await stream.InfoAsync("Loading background workers into Hangfire...");
            await _abpBackgroundWorkerRecurringJobInitializer.RunAsync(_lifetime.ApplicationStopping);
            await _backgroundWorkerInitializer.RunAsync();
            await stream.SuccessAsync("Background workers loaded successfully.");
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Background workers could not be reloaded after migration.");
            await stream.ErrorAsync($"Background workers could not be loaded: {ex.Message}");
            await stream.DoneAsync("Failed.");
            return;
        }

        await stream.DoneAsync("Completed.");
    }

    // Yetkilendirme

    /// <summary>
    /// İki geçerli kimlik yolu vardır:
    ///
    /// 1. <c>X-Setup-Password</c> header'ı — veritabanına hiç ihtiyaç duymaz, bu yüzden
    ///    veritabanı düşmüşken de çalışır.
    /// 2. Oturum açmış host kullanıcısı + <see cref="PlatformPermissions.Setup.Migrate"/> izni —
    ///    izin kontrolü veritabanı okuması gerektirdiği için yalnızca veritabanı ayaktayken
    ///    (örn. yalnızca bekleyen migration varken) kullanılabilir.
    ///
    /// Reddetme nedeni çağırana döndürülür; aksi halde "yetkisiz" hatası teşhis edilemez oluyordu.
    /// Nedenler yapılandırma/izin adından fazlasını sızdırmaz.
    /// </summary>
    private async Task<(bool Authorized, string Reason)> AuthorizeMigrateRequestAsync()
    {
        if (Request.Headers.ContainsKey(SetupPasswordValidator.HeaderName))
        {
            if (!SetupPasswordValidator.IsConfigured(_configuration))
            {
                return (false, "Setup password is not configured on the server (Setup:MigrationPassword).");
            }

            return SetupPasswordValidator.IsValid(_configuration, Request.Headers)
                ? (true, string.Empty)
                : (false, "Invalid setup password.");
        }

        if (!DatabaseReadinessChecker.GetStatus(_configuration).IsReady)
        {
            return (false,
                "The database is not available, so permissions cannot be verified. " +
                $"Send the {SetupPasswordValidator.HeaderName} header to run migration.");
        }

        if (User?.Identity?.IsAuthenticated != true)
        {
            return (false, "Authentication is required to run database migration.");
        }

        if (_currentTenant.Id is not null)
        {
            return (false, "Database migration can only be run by a host user.");
        }

        return await CanMigrateAsync()
            ? (true, string.Empty)
            : (false, $"The '{PlatformPermissions.Setup.Migrate}' permission is required.");
    }

    private async Task<bool> CanMigrateAsync()
    {
        if (User?.Identity?.IsAuthenticated != true)
        {
            return false;
        }

        // Host veritabanına migration uygulanır — tenant kullanıcıları tetikleyemez.
        if (_currentTenant.Id is not null)
        {
            return false;
        }

        if ((await _authorizationService.AuthorizeAsync(User, PlatformPermissions.Setup.Migrate)).Succeeded)
        {
            return true;
        }

        return User.IsInRole(LegacyAdminRoleName);
    }

    // Bekleyen migration sayısı

    private async Task<int?> GetPendingMigrationCountAsync(CancellationToken cancellationToken)
    {
        try
        {
            using var uow = _unitOfWorkManager.Begin(requiresNew: true, isTransactional: false);

            var dbContext = await uow.ServiceProvider
                .GetRequiredService<IDbContextProvider<PlatformDbContext>>()
                .GetDbContextAsync();

            var pending = await dbContext.Database.GetPendingMigrationsAsync(cancellationToken);
            return pending.Count();
        }
        catch (Exception ex)
        {
            // Bu bilgi opsiyonel — alınamıyorsa durum raporu yine de dönmeli.
            _logger.LogDebug(ex, "Pending migration count could not be determined.");
            return null;
        }
    }
}