using System;
using System.Linq;
using System.Net.Http;
using System.Security.Cryptography;
using System.Text;
using System.Web.Http;
using System.Web.Http.Controllers;
using System.Web.Http.Filters;
using WebAPI;
using WebAPI.Service;

namespace project.Filter
{
    public class SignatureVerifyAttribute : AuthorizationFilterAttribute
    {
        private const string SecretKey = "MES_2026_SecretKey_XYZ!@#";

        public override async System.Threading.Tasks.Task OnAuthorizationAsync(
            HttpActionContext actionContext,
            System.Threading.CancellationToken cancellationToken)
        {
            var hasAttr = actionContext.ActionDescriptor.GetCustomAttributes<RequireSignatureAttribute>(true).Any()
                       || actionContext.ControllerContext.ControllerDescriptor.GetCustomAttributes<RequireSignatureAttribute>(true).Any();

            if (!hasAttr)
            {
                return; 
            }

            var headers = actionContext.Request.Headers;
            string timestamp = null, nonce = null, clientSign = null;

            if (headers.Contains("X-Timestamp"))
                timestamp = headers.GetValues("X-Timestamp").FirstOrDefault();
            if (headers.Contains("X-Nonce"))
                nonce = headers.GetValues("X-Nonce").FirstOrDefault();
            if (headers.Contains("X-Sign"))
                clientSign = headers.GetValues("X-Sign").FirstOrDefault();

            if (string.IsNullOrEmpty(timestamp) || string.IsNullOrEmpty(nonce) || string.IsNullOrEmpty(clientSign))
            {
                actionContext.Response = actionContext.Request.CreateResponse(System.Net.HttpStatusCode.BadRequest,
                    new { success = false, msg = "缺少签名参数（X-Timestamp/X-Nonce/X-Sign）" });
                return;
            }


            double ts;
            if (!double.TryParse(timestamp, out ts))
            {
                actionContext.Response = actionContext.Request.CreateResponse(System.Net.HttpStatusCode.BadRequest,
                    new { success = false, msg = "时间戳格式错误" });
                return;
            }
            var currentTs = (DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).TotalSeconds;
            var diff = Math.Abs(currentTs - ts);
            if (diff > 300) // 300秒 = 5分钟
            {
                actionContext.Response = actionContext.Request.CreateResponse(System.Net.HttpStatusCode.BadRequest,
                    new { success = false, msg = "请求已过期" });
                return;
            }

            string rawData = "";

            if (actionContext.Request.Method == HttpMethod.Get)
            {
                var query = actionContext.Request.RequestUri.Query;
                if (!string.IsNullOrEmpty(query) && query.StartsWith("?"))
                {
                    rawData = query.Substring(1); 
                }
            }
            else
            {
                var bodyBytes = await actionContext.Request.Content.ReadAsByteArrayAsync();
                rawData = Encoding.UTF8.GetString(bodyBytes);

                actionContext.Request.Content = new ByteArrayContent(bodyBytes);
                if (actionContext.Request.Content.Headers.ContentType != null)
                {
                    actionContext.Request.Content.Headers.ContentType =
                        new System.Net.Http.Headers.MediaTypeHeaderValue(
                            actionContext.Request.Content.Headers.ContentType.MediaType);
                }
            }
            var signStr = rawData + "&timestamp=" + timestamp + "&nonce=" + nonce + "&key=" + SecretKey;
            var serverSign = ComputeHmacSha256(signStr, SecretKey);

            
            if (serverSign != clientSign.ToUpper())
            {
                actionContext.Response = actionContext.Request.CreateResponse(System.Net.HttpStatusCode.Unauthorized,
                    new { success = false, msg = "签名验证失败" });
                return;
            }
        }

        private string ComputeHmacSha256(string data, string key)
        {
            var keyBytes = Encoding.UTF8.GetBytes(key);
            var dataBytes = Encoding.UTF8.GetBytes(data);

            using (var hmac = new HMACSHA256(keyBytes))
            {
                var hashBytes = hmac.ComputeHash(dataBytes);
                return BitConverter.ToString(hashBytes).Replace("-", "").ToUpper();
            }
        }
    }
}