feat(middleware): add chain middleware

Fixes: #12

Author: piraz

middleware/chain.go

@@ -0,0 +1,22 @@
+package middleware
+
+import (
+	"net/http"
+)
+
+// Middleware represents a function that can wrap a http.Handler with
+// additional functionality. It takes a http.Handler and returns a new
+// http.Handler that includes the middleware's behavior.
+type Middleware func(http.Handler) http.Handler
+
+// Chain creates a chain of HTTP middleware functions to wrap around a
+// http.Handler.
+// It applies each middleware in the order they are provided, allowing for
+// layered processing of HTTP requests and responses.
+func Chain(next http.Handler, ms ...Middleware) http.Handler {
+	for i := len(ms) - 1; i >= 0; i-- {
+		m := ms[i]
+		next = m(next)
+	}
+	return next
+}

middleware/chain_test.go

@@ -0,0 +1,89 @@
+package middleware
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/candango/httpok/testrunner"
+	"github.com/stretchr/testify/assert"
+)
+
+type PlainHandler struct {
+	http.Handler
+}
+
+func (h *PlainHandler) GetSomething(w http.ResponseWriter, r *http.Request) {
+	w.Write([]byte("Something"))
+}
+
+func (h *PlainHandler) GetSomethingElse(w http.ResponseWriter, r *http.Request) {
+	w.Write([]byte("Something else"))
+}
+
+func NewPlainServeMux() http.Handler {
+	plain := &PlainHandler{}
+	h := http.NewServeMux()
+	h.HandleFunc("/something", plain.GetSomething)
+	h.HandleFunc("/something_else", plain.GetSomethingElse)
+	return h
+}
+
+func TestChainMiddlewareServer(t *testing.T) {
+	plain := NewPlainServeMux()
+
+	runner := testrunner.NewHttpTestRunner(t).WithHandler(plain)
+
+	t.Run("Plain runner", func(t *testing.T) {
+		res, err := runner.WithPath("/something").Get()
+		if err != nil {
+			t.Error(err)
+		}
+		assert.Equal(t, "200 OK", res.Status)
+		assert.Equal(t, "Something", testrunner.BodyAsString(t, res))
+
+		res, err = runner.WithPath("/something_else").Get()
+		if err != nil {
+			t.Error(err)
+		}
+		assert.Equal(t, "200 OK", res.Status)
+		assert.Equal(t, "Something else", testrunner.BodyAsString(t, res))
+	})
+
+	changeSomething := func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			if r.URL.String() == "/something" {
+				w.Write([]byte("First Middleware with "))
+			}
+			next.ServeHTTP(w, r)
+		})
+	}
+
+	blockSomethingElse := func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			if r.URL.String() == "/something_else" {
+				http.Error(w, "Not allowed", http.StatusMethodNotAllowed)
+				return
+			}
+			next.ServeHTTP(w, r)
+		})
+	}
+
+	chain := Chain(plain, changeSomething, blockSomethingElse)
+	runner = testrunner.NewHttpTestRunner(t).WithHandler(chain)
+
+	t.Run("Chained runner", func(t *testing.T) {
+		res, err := runner.WithPath("/something").Get()
+		if err != nil {
+			t.Error(err)
+		}
+		assert.Equal(t, "200 OK", res.Status)
+		assert.Equal(t, "First Middleware with Something", testrunner.BodyAsString(t, res))
+
+		res, err = runner.WithPath("/something_else").Get()
+		if err != nil {
+			t.Error(err)
+		}
+		assert.Equal(t, "405 Method Not Allowed", res.Status)
+		assert.Equal(t, "Not allowed\n", testrunner.BodyAsString(t, res))
+	})
+}