using System.IdentityModel.Tokens.Jwt;
using System.Security.Claims;
using System.Security.Cryptography;
using Distribution.Features.User;
using Distribution.Infra.Authorization;
using Microsoft.AspNetCore.Mvc.Filters;
using Microsoft.IdentityModel.Tokens;

namespace Distribution.Infra.Authorization.Middleware;

/// <summary>
/// Ported from OSMCore's System/Authentication/JwtMiddleware.cs (action-filter attribute pattern,
/// applied per controller/action as [JwtMiddleware.CustomMiddleware]). Not applied anywhere in
/// this project — the standard AddJwtBearer handler (Program.cs) is this project's actual
/// validation path.
///
/// docs/authentication_flow.md explicitly calls out not running this alongside AuthMiddleware or
/// AddJwtBearer at the same time — all three independently re-validate the same RSA-signed token,
/// which is wasteful and error-prone (this is the same duplication OSMCore's own guide flags as a
/// Gotcha). Kept here, unregistered, only as a ported reference implementation.
///
/// Same two adaptations as AuthMiddleware: portable RSA parsing via
/// <see cref="RsaXmlKeyReader"/>, and local User/Role → role_id/role_level claim mapping after
/// validation (see AuthMiddleware's remarks for why this is required, not optional).
/// </summary>
public sealed class JwtMiddleware
{
    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method)]
    public sealed class CustomMiddlewareAttribute : Attribute, IAsyncActionFilter
    {
        public async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
        {
            var configuration = context.HttpContext.RequestServices.GetService<IConfiguration>();

            if (!TryGetToken(context.HttpContext, out var token))
            {
                await RejectAsync(context.HttpContext, "Authentication token is missing.");
                return;
            }

            try
            {
                if (configuration is null)
                {
                    throw new InvalidOperationException("Jwt configuration is missing.");
                }

                var principal = ValidateToken(token, configuration);

                var userRepo = context.HttpContext.RequestServices.GetRequiredService<IUserRepository>();
                if (!await TryAttachLocalRoleClaimsAsync(principal, userRepo))
                {
                    await RejectAsync(context.HttpContext, "User not found or inactive.");
                    return;
                }

                context.HttpContext.User = principal;
                PopulateContextItems(context.HttpContext, principal);

                await next();
            }
            catch (Exception ex) when (ex is SecurityTokenException or ArgumentException or CryptographicException or InvalidOperationException)
            {
                await RejectAsync(context.HttpContext, "Invalid or expired token.");
            }
        }

        private static ClaimsPrincipal ValidateToken(string token, IConfiguration configuration)
        {
            var xmlKey = configuration["Jwt:PublicKey"];

            if (string.IsNullOrWhiteSpace(xmlKey))
                throw new SecurityTokenException("JWT public key not configured.");

            using var rsa = RsaXmlKeyReader.ReadPublicKey(xmlKey);
            var rsaParameters = rsa.ExportParameters(false);

            var key = new RsaSecurityKey(rsaParameters)
            {
                KeyId = ComputeKeyId(rsaParameters)
            };

            var handler = new JwtSecurityTokenHandler();
            var parameters = new TokenValidationParameters
            {
                ValidateIssuer = true,
                ValidIssuer = configuration["Jwt:Issuer"],
                ValidateAudience = true,
                ValidAudience = configuration["Jwt:Audience"],
                ValidateIssuerSigningKey = true,
                IssuerSigningKey = key,
                ValidateLifetime = true,
                ClockSkew = TimeSpan.FromMinutes(1)
            };

            return handler.ValidateToken(token, parameters, out _);
        }

        /// <summary>Mirrors Program.cs's OnTokenValidated mapping — see class remarks.</summary>
        private static async Task<bool> TryAttachLocalRoleClaimsAsync(ClaimsPrincipal principal, IUserRepository userRepo)
        {
            var subClaim = principal.FindFirst("sub")?.Value ?? principal.FindFirst(ClaimTypes.NameIdentifier)?.Value;
            if (!Guid.TryParse(subClaim, out var userId))
                return false;

            var user = await userRepo.GetByIdAsync(userId);
            if (user is null || !user.IsActive)
                return false;

            var identity = (ClaimsIdentity)principal.Identity!;
            identity.AddClaim(new Claim("username", user.Username));
            identity.AddClaim(new Claim("role_id", user.FK_RoleId.ToString()));
            identity.AddClaim(new Claim("role_level", (user.Role?.Level ?? 0).ToString()));
            return true;
        }

        private static bool TryGetToken(HttpContext context, out string token)
        {
            token = string.Empty;

            if (TryGetBearerToken(context.Request.Headers.Authorization, out token))
            {
                return true;
            }

            var headerToken = context.Request.Headers["MobileAuthToken"].FirstOrDefault();
            if (TryGetBearerToken(headerToken, out token))
            {
                return true;
            }

            var cookieToken = context.Request.Cookies["access_token"];
            if (!string.IsNullOrWhiteSpace(cookieToken))
            {
                token = cookieToken.Trim();
                return true;
            }

            return false;
        }

        private static bool TryGetBearerToken(string? authorizationHeader, out string token)
        {
            token = string.Empty;

            if (string.IsNullOrWhiteSpace(authorizationHeader))
            {
                return false;
            }

            const string bearerPrefix = "Bearer ";
            if (!authorizationHeader.StartsWith(bearerPrefix, StringComparison.OrdinalIgnoreCase))
            {
                token = authorizationHeader.Trim();
                return !string.IsNullOrWhiteSpace(token);
            }

            token = authorizationHeader[bearerPrefix.Length..].Trim();
            return !string.IsNullOrWhiteSpace(token);
        }

        private static void PopulateContextItems(HttpContext context, ClaimsPrincipal principal)
        {
            context.Items["UserId"] = principal.FindFirst("sub")?.Value ?? principal.FindFirst(ClaimTypes.NameIdentifier)?.Value;
            context.Items["Username"] = principal.FindFirst("username")?.Value;
            context.Items["RoleId"] = principal.FindFirst("role_id")?.Value;
            context.Items["RoleLevel"] = principal.FindFirst("role_level")?.Value;
        }

        private static async Task RejectAsync(HttpContext context, string message)
        {
            context.Response.StatusCode = StatusCodes.Status401Unauthorized;
            await context.Response.WriteAsJsonAsync(new ApiResponse<object>
            {
                StatusCode = StatusCodes.Status401Unauthorized,
                Success = false,
                Message = message,
                Data = null
            });
        }

        private static string ComputeKeyId(RSAParameters publicParameters)
        {
            var modulus = publicParameters.Modulus ?? [];
            var exponent = publicParameters.Exponent ?? [];
            var payload = $"{Convert.ToBase64String(modulus)}.{Convert.ToBase64String(exponent)}";
            var hash = SHA256.HashData(System.Text.Encoding.UTF8.GetBytes(payload));
            return Base64UrlEncoder.Encode(hash);
        }
    }
}