Initial QSfera import

Server/vendor/github.com/crewjam/httperr/middleware.go

@@ -0,0 +1,62 @@
+package httperr
+
+import (
+	"context"
+	"net/http"
+)
+
+type onErrorIndexType int
+
+const onErrorIndex onErrorIndexType = iota
+
+// Middleware wraps the provided handler with middleware that captures errors which
+// are returned from HandlerFunc, or reported via ReportError, and invokes the provided
+// callback to render them. If the handler returns a status code >= 400, the response is
+// captured and passed to OnError as a Response.
+//
+type Middleware struct {
+	// OnError is a function that is called then a request fails with an error. If this function
+	// returns nil, then the error is assumed to be handled. If it returns a non-nil error, then
+	// that error is written to the client with Write()
+	OnError func(w http.ResponseWriter, r *http.Request, err error) error
+
+	// Handler is the next handler
+	Handler http.Handler
+}
+
+func (m Middleware) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	var unwrappedWriter = w
+	var wrappedWriter *basicWriter
+	if m.OnError != nil {
+		wrappedWriter, w = wrapWriter(w)
+	}
+
+	var didCallOnError bool
+	r = r.WithContext(context.WithValue(r.Context(), onErrorIndex, func(err error) {
+		if m.OnError != nil {
+			didCallOnError = true
+			handlerErr := m.OnError(unwrappedWriter, r, err)
+			if handlerErr != nil {
+				Write(unwrappedWriter, r, handlerErr)
+			}
+		}
+	}))
+
+	m.Handler.ServeHTTP(w, r)
+
+	if wrappedWriter != nil && wrappedWriter.statusCode >= 400 && !didCallOnError {
+		err := Response(*wrappedWriter.copy)
+		handlerErr := m.OnError(unwrappedWriter, r, err)
+		if handlerErr != nil {
+			Write(unwrappedWriter, r, handlerErr)
+		}
+	}
+}
+
+// ReportError reports the error to the function given in
+// OnError.
+func ReportError(r *http.Request, err error) {
+	if v := r.Context().Value(onErrorIndex); v != nil {
+		v.(func(error))(err)
+	}
+}