refactor: 自定义业务错误 (#33)

* refactor: 自定义业务错误

* refactor: 隐藏服务器错误与统一 panic 响应

backend/internal/middleware/recovery.go

@@ -0,0 +1,64 @@
+package middleware
+
+import (
+	"errors"
+	"net"
+	"net/http"
+	"os"
+	"strings"
+
+	infraerrors "github.com/Wei-Shaw/sub2api/internal/infrastructure/errors"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/response"
+	"github.com/gin-gonic/gin"
+)
+
+// Recovery converts panics into the project's standard JSON error envelope.
+//
+// It preserves Gin's broken-pipe handling by not attempting to write a response
+// when the client connection is already gone.
+func Recovery() gin.HandlerFunc {
+	return gin.CustomRecoveryWithWriter(gin.DefaultErrorWriter, func(c *gin.Context, recovered any) {
+		recoveredErr, _ := recovered.(error)
+
+		if isBrokenPipe(recoveredErr) {
+			if recoveredErr != nil {
+				_ = c.Error(recoveredErr)
+			}
+			c.Abort()
+			return
+		}
+
+		if c.Writer.Written() {
+			c.Abort()
+			return
+		}
+
+		response.ErrorWithDetails(
+			c,
+			http.StatusInternalServerError,
+			infraerrors.UnknownMessage,
+			infraerrors.UnknownReason,
+			nil,
+		)
+		c.Abort()
+	})
+}
+
+func isBrokenPipe(err error) bool {
+	if err == nil {
+		return false
+	}
+
+	var opErr *net.OpError
+	if !errors.As(err, &opErr) {
+		return false
+	}
+
+	var syscallErr *os.SyscallError
+	if !errors.As(opErr.Err, &syscallErr) {
+		return false
+	}
+
+	msg := strings.ToLower(syscallErr.Error())
+	return strings.Contains(msg, "broken pipe") || strings.Contains(msg, "connection reset by peer")
+}