using System.Globalization;
using line_gestao_api.Data;
using line_gestao_api.Models;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Options;

namespace line_gestao_api.Services;

public class VigenciaNotificationBackgroundService : BackgroundService
{
    private readonly IServiceScopeFactory _scopeFactory;
    private readonly ILogger<VigenciaNotificationBackgroundService> _logger;
    private readonly NotificationOptions _options;

    public VigenciaNotificationBackgroundService(
        IServiceScopeFactory scopeFactory,
        IOptions<NotificationOptions> options,
        ILogger<VigenciaNotificationBackgroundService> logger)
    {
        _scopeFactory = scopeFactory;
        _logger = logger;
        _options = options.Value;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        var intervalMinutes = _options.CheckIntervalMinutes <= 0 ? 60 : _options.CheckIntervalMinutes;
        using var timer = new PeriodicTimer(TimeSpan.FromMinutes(intervalMinutes));

        await RunOnceAsync(stoppingToken);

        while (await timer.WaitForNextTickAsync(stoppingToken))
        {
            await RunOnceAsync(stoppingToken);
        }
    }

    private async Task RunOnceAsync(CancellationToken stoppingToken)
    {
        try
        {
            using var scope = _scopeFactory.CreateScope();
            var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();

            var today = DateTime.UtcNow.Date;
            var reminderDays = _options.ReminderDays
                .Distinct()
                .Where(d => d > 0)
                .OrderBy(d => d)
                .ToList();

            var users = await db.Users.AsNoTracking()
                .Select(u => new { u.Id, u.Name, u.Email })
                .ToListAsync(stoppingToken);

            var userByName = users
                .Where(u => !string.IsNullOrWhiteSpace(u.Name))
                .ToDictionary(u => u.Name.Trim().ToLowerInvariant(), u => u.Id);

            var userByEmail = users
                .Where(u => !string.IsNullOrWhiteSpace(u.Email))
                .ToDictionary(u => u.Email.Trim().ToLowerInvariant(), u => u.Id);

            var vigencias = await db.VigenciaLines.AsNoTracking()
                .Where(v => v.DtTerminoFidelizacao != null)
                .ToListAsync(stoppingToken);

            var candidates = new List<Notification>();
            foreach (var vigencia in vigencias)
            {
                if (vigencia.DtTerminoFidelizacao is null)
                {
                    continue;
                }

                var endDate = vigencia.DtTerminoFidelizacao.Value.Date;
                var usuario = vigencia.Usuario?.Trim();
                var cliente = vigencia.Cliente?.Trim();
                var linha = vigencia.Linha?.Trim();
                var usuarioKey = usuario?.ToLowerInvariant();

                Guid? userId = null;
                if (!string.IsNullOrWhiteSpace(usuarioKey))
                {
                    if (userByEmail.TryGetValue(usuarioKey, out var matchedByEmail))
                    {
                        userId = matchedByEmail;
                    }
                    else if (userByName.TryGetValue(usuarioKey, out var matchedByName))
                    {
                        userId = matchedByName;
                    }
                }

                if (endDate < today)
                {
                    var notification = BuildNotification(
                        tipo: "Vencido",
                        titulo: $"Linha vencida{FormatLinha(linha)}",
                        mensagem: $"A linha{FormatLinha(linha)} do cliente {cliente ?? "(sem cliente)"} venceu em {endDate:dd/MM/yyyy}.",
                        referenciaData: endDate,
                        diasParaVencer: 0,
                        userId: userId,
                        usuario: usuario,
                        cliente: cliente,
                        linha: linha,
                        vigenciaLineId: vigencia.Id);

                    candidates.Add(notification);
                    continue;
                }

                var daysUntil = (endDate - today).Days;
                if (reminderDays.Contains(daysUntil))
                {
                    var notification = BuildNotification(
                        tipo: "AVencer",
                        titulo: $"Linha a vencer em {daysUntil} dias{FormatLinha(linha)}",
                        mensagem: $"A linha{FormatLinha(linha)} do cliente {cliente ?? "(sem cliente)"} vence em {endDate:dd/MM/yyyy}.",
                        referenciaData: endDate,
                        diasParaVencer: daysUntil,
                        userId: userId,
                        usuario: usuario,
                        cliente: cliente,
                        linha: linha,
                        vigenciaLineId: vigencia.Id);

                    candidates.Add(notification);
                }
            }

            if (candidates.Count == 0)
            {
                return;
            }

            var dedupKeys = candidates.Select(c => c.DedupKey).Distinct().ToList();
            var existingKeys = await db.Notifications.AsNoTracking()
                .Where(n => dedupKeys.Contains(n.DedupKey))
                .Select(n => n.DedupKey)
                .ToListAsync(stoppingToken);

            var existingSet = new HashSet<string>(existingKeys);
            var toInsert = candidates
                .Where(c => !existingSet.Contains(c.DedupKey))
                .ToList();

            if (toInsert.Count == 0)
            {
                return;
            }

            await db.Notifications.AddRangeAsync(toInsert, stoppingToken);
            await db.SaveChangesAsync(stoppingToken);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Erro ao gerar notificações de vigência.");
        }
    }

    private static Notification BuildNotification(
        string tipo,
        string titulo,
        string mensagem,
        DateTime referenciaData,
        int diasParaVencer,
        Guid? userId,
        string? usuario,
        string? cliente,
        string? linha,
        Guid vigenciaLineId)
    {
        return new Notification
        {
            Tipo = tipo,
            Titulo = titulo,
            Mensagem = mensagem,
            Data = DateTime.UtcNow,
            ReferenciaData = referenciaData,
            DiasParaVencer = diasParaVencer,
            Lida = false,
            DedupKey = BuildDedupKey(tipo, vigenciaLineId, referenciaData, diasParaVencer, usuario, cliente, linha),
            UserId = userId,
            Usuario = usuario,
            Cliente = cliente,
            Linha = linha,
            VigenciaLineId = vigenciaLineId
        };
    }

    private static string BuildDedupKey(
        string tipo,
        Guid vigenciaLineId,
        DateTime referenciaData,
        int diasParaVencer,
        string? usuario,
        string? cliente,
        string? linha)
    {
        var parts = new[]
        {
            tipo.Trim().ToLowerInvariant(),
            vigenciaLineId.ToString(),
            referenciaData.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture),
            diasParaVencer.ToString(CultureInfo.InvariantCulture),
            (usuario ?? string.Empty).Trim().ToLowerInvariant(),
            (cliente ?? string.Empty).Trim().ToLowerInvariant(),
            (linha ?? string.Empty).Trim().ToLowerInvariant()
        };

        return string.Join('|', parts);
    }

    private static string FormatLinha(string? linha)
    {
        return string.IsNullOrWhiteSpace(linha) ? string.Empty : $" {linha}";
    }
}