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 VigenciaNotificationSyncService : IVigenciaNotificationSyncService
{
    private readonly AppDbContext _db;
    private readonly ITenantProvider _tenantProvider;
    private readonly NotificationOptions _options;
    private readonly ILogger<VigenciaNotificationSyncService> _logger;

    public VigenciaNotificationSyncService(
        AppDbContext db,
        ITenantProvider tenantProvider,
        IOptions<NotificationOptions> options,
        ILogger<VigenciaNotificationSyncService> logger)
    {
        _db = db;
        _tenantProvider = tenantProvider;
        _options = options.Value;
        _logger = logger;
    }

    public async Task SyncCurrentTenantAsync(CancellationToken cancellationToken = default)
    {
        var tenantId = _tenantProvider.TenantId;
        if (!tenantId.HasValue || tenantId.Value == Guid.Empty)
        {
            return;
        }

        await SyncTenantAsync(tenantId.Value, cancellationToken);
    }

    public async Task SyncTenantAsync(Guid tenantId, CancellationToken cancellationToken = default)
    {
        if (tenantId == Guid.Empty)
        {
            return;
        }

        var previousTenant = _tenantProvider.TenantId;

        try
        {
            _tenantProvider.SetTenantId(tenantId);
            await ProcessTenantAsync(tenantId, cancellationToken);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Falha ao sincronizar notificações de vigência para tenant {TenantId}.", tenantId);
        }
        finally
        {
            _tenantProvider.SetTenantId(previousTenant);
        }
    }

    private async Task ProcessTenantAsync(Guid tenantId, CancellationToken cancellationToken)
    {
        var today = DateTime.SpecifyKind(DateTime.UtcNow.Date, DateTimeKind.Utc);
        var notifyAllFutureDates = _options.NotifyAllFutureDates;
        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(cancellationToken);

        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(cancellationToken);

        await CleanupOutdatedNotificationsAsync(vigencias, notifyAllFutureDates, reminderDays, today, cancellationToken);

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

            var endDate = DateTime.SpecifyKind(vigencia.DtTerminoFidelizacao.Value.Date, DateTimeKind.Utc);
            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)
            {
                candidates.Add(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,
                    tenantId: tenantId));
                continue;
            }

            var daysUntil = (endDate - today).Days;
            if (!notifyAllFutureDates && !reminderDays.Contains(daysUntil))
            {
                continue;
            }

            candidates.Add(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,
                tenantId: tenantId));
        }

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

        var candidateTipos = candidates.Select(c => c.Tipo).Distinct().ToList();
        var candidateDates = candidates
            .Where(c => c.ReferenciaData.HasValue)
            .Select(c => DateTime.SpecifyKind(c.ReferenciaData!.Value.Date, DateTimeKind.Utc))
            .Distinct()
            .ToList();

        List<Notification> existingNotifications = new();
        if (candidateDates.Count > 0)
        {
            var minCandidateUtc = candidateDates.Min();
            var maxCandidateUtcExclusive = candidateDates.Max().AddDays(1);
            var candidateDateKeys = candidateDates
                .Select(d => d.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture))
                .ToHashSet();

            existingNotifications = await _db.Notifications.AsNoTracking()
                .Where(n => n.TenantId == tenantId)
                .Where(n => candidateTipos.Contains(n.Tipo))
                .Where(n => n.ReferenciaData != null &&
                            n.ReferenciaData.Value >= minCandidateUtc &&
                            n.ReferenciaData.Value < maxCandidateUtcExclusive)
                .ToListAsync(cancellationToken);

            existingNotifications = existingNotifications
                .Where(n => n.ReferenciaData != null &&
                            candidateDateKeys.Contains(n.ReferenciaData.Value.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture)))
                .ToList();
        }

        var existingSet = new HashSet<string>(existingNotifications.Select(n =>
            BuildDedupKey(
                n.Tipo,
                n.ReferenciaData!.Value,
                n.DiasParaVencer ?? 0,
                n.Usuario,
                n.Cliente,
                n.Linha)));
        var toInsert = candidates
            .Where(c => !existingSet.Contains(c.DedupKey))
            .ToList();

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

        await _db.Notifications.AddRangeAsync(toInsert, cancellationToken);
        await _db.SaveChangesAsync(cancellationToken);
    }

    private async Task CleanupOutdatedNotificationsAsync(
        IReadOnlyCollection<VigenciaLine> vigencias,
        bool notifyAllFutureDates,
        IReadOnlyCollection<int> reminderDays,
        DateTime today,
        CancellationToken cancellationToken)
    {
        var vigenciasById = vigencias.ToDictionary(v => v.Id, v => v);
        var vigenciasByLinha = vigencias
            .Where(v => !string.IsNullOrWhiteSpace(v.Linha))
            .GroupBy(v => v.Linha!)
            .Select(g => g.OrderByDescending(v => v.UpdatedAt).First())
            .ToDictionary(v => v.Linha!, v => v);

        var existingNotifications = await _db.Notifications.AsNoTracking()
            .Where(n => n.Tipo == "Vencido" || n.Tipo == "AVencer")
            .ToListAsync(cancellationToken);

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

        var idsToDelete = new List<Guid>();
        foreach (var notification in existingNotifications)
        {
            var vigencia = ResolveVigencia(notification, vigenciasById, vigenciasByLinha);
            if (vigencia?.DtTerminoFidelizacao is null)
            {
                idsToDelete.Add(notification.Id);
                continue;
            }

            var endDate = DateTime.SpecifyKind(vigencia.DtTerminoFidelizacao.Value.Date, DateTimeKind.Utc);
            if (endDate < today)
            {
                if (notification.Tipo != "Vencido")
                {
                    idsToDelete.Add(notification.Id);
                }

                continue;
            }

            var daysUntil = (endDate - today).Days;
            if (notification.Tipo == "Vencido")
            {
                idsToDelete.Add(notification.Id);
                continue;
            }

            if (notification.DiasParaVencer != daysUntil)
            {
                idsToDelete.Add(notification.Id);
                continue;
            }

            if (!notifyAllFutureDates && !reminderDays.Contains(daysUntil))
            {
                idsToDelete.Add(notification.Id);
            }
        }

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

        await _db.Notifications
            .Where(n => idsToDelete.Contains(n.Id))
            .ExecuteDeleteAsync(cancellationToken);
    }

    private static VigenciaLine? ResolveVigencia(
        Notification notification,
        IReadOnlyDictionary<Guid, VigenciaLine> vigenciasById,
        IReadOnlyDictionary<string, VigenciaLine> vigenciasByLinha)
    {
        if (notification.VigenciaLineId.HasValue
            && vigenciasById.TryGetValue(notification.VigenciaLineId.Value, out var byId))
        {
            return byId;
        }

        if (!string.IsNullOrWhiteSpace(notification.Linha)
            && vigenciasByLinha.TryGetValue(notification.Linha, out var byLinha))
        {
            return byLinha;
        }

        return null;
    }

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

    private static string BuildDedupKey(
        string tipo,
        DateTime referenciaData,
        int diasParaVencer,
        string? usuario,
        string? cliente,
        string? linha)
    {
        var parts = new[]
        {
            tipo.Trim().ToLowerInvariant(),
            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}";
    }
}