package middleware

import (
	"errors"
	"fmt"
	"log/slog"
	"net"
	"net/http"
	"os"
	"runtime/debug"
	"strings"

	"github.com/gin-gonic/gin"
)

// Recovery 替代 gin.Recovery()：panic 恢复语义保持一致（客户端断开类 panic 仅记录并中止，
// 其余 panic 返回 500 Internal Server Error），但 panic 与堆栈统一走 slog 结构化输出，
// 与全站 JSON 日志（含 request_id / trace_id）对齐，避免默认实现写 stderr 非结构化日志。
func Recovery() gin.HandlerFunc {
	return func(c *gin.Context) {
		defer func() {
			if r := recover(); r != nil {
				ctx := c.Request.Context()
				if isBrokenPipe(r) {
					// 连接已断开，无法再写响应：仅记录并中止。
					slog.ErrorContext(ctx, "GIN_PANIC_BROKEN_PIPE",
						"method", c.Request.Method, "path", c.Request.URL.Path, "recover", fmt.Sprint(r))
					c.Abort()
					return
				}
				slog.ErrorContext(ctx, "GIN_PANIC",
					"method", c.Request.Method, "path", c.Request.URL.Path, "ip", c.ClientIP(),
					"recover", fmt.Sprint(r), "stack", string(debug.Stack()))
				c.AbortWithStatus(http.StatusInternalServerError)
			}
		}()
		c.Next()
	}
}

// isBrokenPipe 判定 panic 是否源于客户端断开（broken pipe / connection reset），与 gin.Recovery 判定一致。
func isBrokenPipe(r any) bool {
	ne, ok := r.(*net.OpError)
	if !ok {
		return false
	}
	var se *os.SyscallError
	if !errors.As(ne, &se) {
		return false
	}
	seStr := strings.ToLower(se.Error())
	return strings.Contains(seStr, "broken pipe") || strings.Contains(seStr, "connection reset by peer")
}