using Microsoft.AspNetCore.Http;
using System.Buffers;

namespace YLErp.Web.App
{
    /// <summary>
    /// 异常处理中间件
    /// </summary>
    internal class ExceptionMiddleware
    {
        private readonly RequestDelegate _next;

        public ExceptionMiddleware(RequestDelegate next)
        {
            _next = next;
        }

        public async Task Invoke(HttpContext context)
        {
            try
            {
                await _next.Invoke(context);
            }
            catch (Exception ex)
            {
                await HandleExceptionMessageAsync(context, ex);
            }
        }

        private static async Task HandleExceptionMessageAsync(HttpContext context, Exception exception)
        {
            var message = string.Empty;

            var serviceExpcetion = exception as ServiceException;

            var request = context.Request;

            try
            {
                // 暴露完整异常（类型 + 所有内层 message + 堆栈），不再只取最内层 message，
                // 便于定位根因（如 SacInfo 序列化 TypeId 触发的 IsGenericParameter 反射异常）。
                message = exception.ToString();

                if (serviceExpcetion == null || serviceExpcetion.IsFaultError)
                {
                    var result = await request.BodyReader.ReadAsync();
                    var reqBody = ConvertBufferToString(result.Buffer);
                    LogFactory.GetLogger(context.Request.Path.Value).Error(serviceExpcetion ?? exception, $"[query]:{request.QueryString.Value};[body]:{reqBody}\r\n{message}");
                }
            }
            catch (Exception ex)
            {
                message += "\r\n\r\n" + ex.Message;
            }

            if (request.Path.StartsWithSegments("/m/api", StringComparison.OrdinalIgnoreCase) ||
                request.Headers["X-Requested-With"] == "XMLHttpRequest" && !request.Headers["Accept"].Contains("text/html"))
            {
                await context.Response.WriteAsJsonAsync(new
                {
                    code = -1,
                    success = false,
                    msg = message,
                    Data = serviceExpcetion?.Tag
                });
            }
            else
            {
                context.Response.ContentType = "text/html";
                var resultHtml = File.ReadAllText(Server.MapPath("Statics/html/ShowError.html"));
                resultHtml = resultHtml.Replace("{{ErrorMsg}}", message);
                await context.Response.WriteAsync(resultHtml);
            }
        }

        private static string ConvertBufferToString(in ReadOnlySequence<byte> readOnlySequence)
        {
            // Separate method because Span/ReadOnlySpan cannot be used in async methods
            ReadOnlySpan<byte> span = readOnlySequence.IsSingleSegment ? readOnlySequence.First.Span : readOnlySequence.ToArray().AsSpan();
            return System.Text.Encoding.UTF8.GetString(span);
        }
    }
}