using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Security.Claims;
using System.Text.Json;
using System.Text.Json.Serialization;
using System.IdentityModel.Tokens.Jwt;
using line_gestao_api.Dtos;
using line_gestao_api.Models;
using Microsoft.AspNetCore.Http;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.ChangeTracking;

namespace line_gestao_api.Services;

public class AuditLogBuilder : IAuditLogBuilder
{
    private static readonly Dictionary<string, string> PageByEntity = new(StringComparer.OrdinalIgnoreCase)
    {
        { nameof(MobileLine), "Geral" },
        { nameof(MuregLine), "Mureg" },
        { nameof(BillingClient), "Faturamento" },
        { nameof(ParcelamentoLine), "Parcelamentos" },
        { nameof(ParcelamentoMonthValue), "Parcelamentos" },
        { nameof(UserData), "Dados e Usuários" },
        { nameof(ApplicationUser), "Dados e Usuários" },
        { nameof(VigenciaLine), "Vigência" },
        { nameof(ChipVirgemLine), "Chips Virgens e Recebidos" },
        { nameof(ControleRecebidoLine), "Chips Virgens e Recebidos" },
        { nameof(TrocaNumeroLine), "Troca de número" }
    };

    private static readonly HashSet<string> IgnoredProperties = new(StringComparer.OrdinalIgnoreCase)
    {
        "TenantId",
        "CreatedAt",
        "UpdatedAt",
        "PasswordHash",
        "SecurityStamp",
        "ConcurrencyStamp",
        "NormalizedEmail",
        "NormalizedUserName",
        "LockoutEnd",
        "AccessFailedCount",
        "LockoutEnabled",
        "EmailConfirmed",
        "PhoneNumberConfirmed",
        "TwoFactorEnabled"
    };

    private static readonly JsonSerializerOptions JsonOptions = new()
    {
        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull
    };

    private readonly IHttpContextAccessor _httpContextAccessor;
    private readonly ITenantProvider _tenantProvider;

    public AuditLogBuilder(IHttpContextAccessor httpContextAccessor, ITenantProvider tenantProvider)
    {
        _httpContextAccessor = httpContextAccessor;
        _tenantProvider = tenantProvider;
    }

    public List<AuditLog> BuildAuditLogs(ChangeTracker changeTracker)
    {
        var tenantId = _tenantProvider.TenantId;
        if (tenantId == null)
        {
            return new List<AuditLog>();
        }

        changeTracker.DetectChanges();

        var httpContext = _httpContextAccessor.HttpContext;
        var userInfo = ResolveUserInfo(httpContext?.User);
        var request = httpContext?.Request;
        var requestPath = request?.Path.Value;
        var requestMethod = request?.Method;
        var ipAddress = httpContext?.Connection?.RemoteIpAddress?.ToString();

        var logs = new List<AuditLog>();

        foreach (var entry in changeTracker.Entries())
        {
            if (entry.State == EntityState.Detached || entry.State == EntityState.Unchanged)
                continue;

            if (entry.Entity is AuditLog)
                continue;

            var entityName = entry.Metadata.ClrType.Name;
            if (!PageByEntity.TryGetValue(entityName, out var page))
                continue;

            var changes = BuildChanges(entry);
            if (changes.Count == 0)
                continue;

            logs.Add(new AuditLog
            {
                TenantId = tenantId.Value,
                OccurredAtUtc = DateTime.UtcNow,
                UserId = userInfo.UserId,
                UserName = userInfo.UserName,
                UserEmail = userInfo.UserEmail,
                Action = ResolveAction(entry.State),
                Page = page,
                EntityName = entityName,
                EntityId = BuildEntityId(entry),
                EntityLabel = BuildEntityLabel(entry),
                ChangesJson = JsonSerializer.Serialize(changes, JsonOptions),
                RequestPath = requestPath,
                RequestMethod = requestMethod,
                IpAddress = ipAddress
            });
        }

        return logs;
    }

    private static string ResolveAction(EntityState state)
        => state switch
        {
            EntityState.Added => "CREATE",
            EntityState.Modified => "UPDATE",
            EntityState.Deleted => "DELETE",
            _ => "UNKNOWN"
        };

    private static List<AuditFieldChangeDto> BuildChanges(EntityEntry entry)
    {
        var changes = new List<AuditFieldChangeDto>();

        foreach (var property in entry.Properties)
        {
            if (IgnoredProperties.Contains(property.Metadata.Name))
                continue;

            if (entry.State == EntityState.Added)
            {
                var newValue = FormatValue(property.CurrentValue);
                if (newValue == null)
                    continue;

                changes.Add(new AuditFieldChangeDto
                {
                    Field = property.Metadata.Name,
                    ChangeType = "added",
                    NewValue = newValue
                });
            }
            else if (entry.State == EntityState.Deleted)
            {
                var oldValue = FormatValue(property.OriginalValue);
                if (oldValue == null)
                    continue;

                changes.Add(new AuditFieldChangeDto
                {
                    Field = property.Metadata.Name,
                    ChangeType = "removed",
                    OldValue = oldValue
                });
            }
            else if (entry.State == EntityState.Modified)
            {
                if (!property.IsModified)
                    continue;

                var oldValue = FormatValue(property.OriginalValue);
                var newValue = FormatValue(property.CurrentValue);
                if (string.Equals(oldValue, newValue, StringComparison.Ordinal))
                    continue;

                changes.Add(new AuditFieldChangeDto
                {
                    Field = property.Metadata.Name,
                    ChangeType = "modified",
                    OldValue = oldValue,
                    NewValue = newValue
                });
            }
        }

        return changes;
    }

    private static string? BuildEntityId(EntityEntry entry)
    {
        var key = entry.Metadata.FindPrimaryKey();
        if (key == null)
            return null;

        var parts = new List<string>();
        foreach (var keyProperty in key.Properties)
        {
            var property = entry.Property(keyProperty.Name);
            var value = FormatValue(property.CurrentValue ?? property.OriginalValue);
            if (value == null)
                continue;
            parts.Add($"{keyProperty.Name}={value}");
        }

        return parts.Count == 0 ? null : string.Join(";", parts);
    }

    private static string? BuildEntityLabel(EntityEntry entry)
    {
        var entityName = entry.Metadata.ClrType.Name;
        return entityName switch
        {
            nameof(MobileLine) => GetValue(entry, "Linha") ?? GetValue(entry, "Item"),
            nameof(MuregLine) => GetValue(entry, "LinhaAntiga") ?? GetValue(entry, "LinhaNova") ?? GetValue(entry, "Item"),
            nameof(TrocaNumeroLine) => GetValue(entry, "LinhaAntiga") ?? GetValue(entry, "LinhaNova") ?? GetValue(entry, "Item"),
            nameof(ChipVirgemLine) => GetValue(entry, "NumeroDoChip") ?? GetValue(entry, "Item"),
            nameof(ControleRecebidoLine) => GetValue(entry, "NotaFiscal") ?? GetValue(entry, "Serial") ?? GetValue(entry, "Item"),
            nameof(BillingClient) => GetValue(entry, "Cliente") ?? GetValue(entry, "Item"),
            nameof(ParcelamentoLine) => GetValue(entry, "Linha") ?? GetValue(entry, "Cliente") ?? GetValue(entry, "Item"),
            nameof(ParcelamentoMonthValue) => GetValue(entry, "Competencia") ?? GetValue(entry, "ParcelamentoLineId"),
            nameof(UserData) => GetValue(entry, "Linha") ?? GetValue(entry, "Cliente") ?? GetValue(entry, "Item"),
            nameof(VigenciaLine) => GetValue(entry, "Linha") ?? GetValue(entry, "Cliente") ?? GetValue(entry, "Item"),
            nameof(ApplicationUser) => GetValue(entry, "Email") ?? GetValue(entry, "Name") ?? GetValue(entry, "Id"),
            _ => null
        };
    }

    private static string? GetValue(EntityEntry entry, string propertyName)
    {
        var property = entry.Properties.FirstOrDefault(p => p.Metadata.Name == propertyName);
        return property == null ? null : FormatValue(property.CurrentValue ?? property.OriginalValue);
    }

    private static string? FormatValue(object? value)
    {
        if (value == null)
            return null;

        switch (value)
        {
            case DateTime dt:
                var normalized = dt.Kind == DateTimeKind.Utc
                    ? dt
                    : (dt.Kind == DateTimeKind.Local ? dt.ToUniversalTime() : DateTime.SpecifyKind(dt, DateTimeKind.Utc));
                return normalized.ToString("O", CultureInfo.InvariantCulture);
            case DateTimeOffset dto:
                return dto.ToUniversalTime().ToString("O", CultureInfo.InvariantCulture);
            case IFormattable formattable:
                return formattable.ToString(null, CultureInfo.InvariantCulture);
            default:
                return value.ToString();
        }
    }

    private static (Guid? UserId, string? UserName, string? UserEmail) ResolveUserInfo(ClaimsPrincipal? user)
    {
        if (user?.Identity?.IsAuthenticated != true)
        {
            return (null, "SYSTEM", null);
        }

        var idValue = user.FindFirstValue(ClaimTypes.NameIdentifier)
            ?? user.FindFirstValue(JwtRegisteredClaimNames.Sub)
            ?? user.FindFirstValue("sub");

        var name = user.FindFirstValue("name")
            ?? user.FindFirstValue(ClaimTypes.Name)
            ?? user.Identity?.Name;

        var email = user.FindFirstValue(ClaimTypes.Email)
            ?? user.FindFirstValue(JwtRegisteredClaimNames.Email)
            ?? user.FindFirstValue("email");

        var userId = Guid.TryParse(idValue, out var parsed) ? parsed : (Guid?)null;
        var userName = string.IsNullOrWhiteSpace(name) ? email : name;

        return (userId, userName, email);
    }
}