Add middleware slice (#37)

middleware.go

@@ -2,4 +2,26 @@ package logger
 
 // MiddlewareInterface is a function to decorate handler
 // See middleware implementations in the middleware package.
-type MiddlewareInterface func(handler HandlerInterface) HandlerInterface
+type MiddlewareInterface func(HandlerInterface) HandlerInterface
+
+// Middlewares was a collection of middleware
+// the slice order matter when middleware are compose with DecorateHandler
+type Middlewares []MiddlewareInterface
+
+// Decorate will return the handler after decorate with middlewares
+func (m Middlewares) Decorate(handler HandlerInterface) HandlerInterface {
+	return DecorateHandler(handler, m...)
+}
+
+// DecorateHandler will return the handler after decorate with middlewares
+func DecorateHandler(handler HandlerInterface, middlewares ...MiddlewareInterface) HandlerInterface {
+	for _, middleware := range middlewares {
+		handler = middleware(handler)
+	}
+	return handler
+}
+
+// MiddlewareStack helper return Middlewares slice from given middlewares
+func MiddlewareStack(middlewares ...MiddlewareInterface) Middlewares {
+	return middlewares
+}

middleware_test.go

@@ -0,0 +1,65 @@
+package logger_test
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/gol4ng/logger"
+)
+
+func TestMiddlewareInterfaceDecorate(t *testing.T) {
+	myEntry := logger.Entry{}
+
+	fakeHandler := func(e logger.Entry) error {
+		assert.Equal(t, myEntry, e)
+		return errors.New("my fake handler error")
+	}
+	fakeMiddleware := func(h logger.HandlerInterface) logger.HandlerInterface {
+		return func(e logger.Entry) error {
+			assert.Equal(t, myEntry, e)
+			err := h(e)
+			assert.Error(t, err)
+			return errors.New("middleware prepend " + err.Error())
+		}
+	}
+	middlewares := logger.MiddlewareStack(fakeMiddleware)
+	handler := middlewares.Decorate(fakeHandler)
+
+	err := handler(myEntry)
+	assert.Error(t, err)
+	assert.Equal(t, "middleware prepend my fake handler error", err.Error())
+}
+
+func TestDecorateHandler(t *testing.T) {
+	myEntry := logger.Entry{}
+
+	fakeHandler := func(e logger.Entry) error {
+		assert.Equal(t, myEntry, e)
+		return errors.New("my fake handler error")
+	}
+	fakeMiddleware := func(h logger.HandlerInterface) logger.HandlerInterface {
+		return func(e logger.Entry) error {
+			assert.Equal(t, myEntry, e)
+			err := h(e)
+			assert.Error(t, err)
+			return errors.New("middleware prepend " + err.Error())
+		}
+	}
+	handler := logger.DecorateHandler(fakeHandler, fakeMiddleware)
+
+	err := handler(myEntry)
+	assert.Error(t, err)
+	assert.Equal(t, "middleware prepend my fake handler error", err.Error())
+}
+
+func TestMiddlewareStack(t *testing.T) {
+	fakeMiddleware := func(logger.HandlerInterface) logger.HandlerInterface {
+		return func(entry logger.Entry) error {
+			return nil
+		}
+	}
+
+	assert.IsType(t, logger.Middlewares{}, logger.MiddlewareStack(fakeMiddleware))
+}