Make server middleware standalone functions.

Removing direct dependencies from the server configuration.

Signed-off-by: David Calavera <david.calavera@gmail.com>

api/server/middleware/version_test.go

@@ -0,0 +1,64 @@
+package middleware
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/docker/docker/api/server/httputils"
+	"github.com/docker/docker/pkg/version"
+	"golang.org/x/net/context"
+)
+
+func TestVersionMiddleware(t *testing.T) {
+	handler := func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
+		if httputils.VersionFromContext(ctx) == "" {
+			t.Fatalf("Expected version, got empty string")
+		}
+		return nil
+	}
+
+	defaultVersion := version.Version("1.10.0")
+	minVersion := version.Version("1.2.0")
+	m := NewVersionMiddleware(defaultVersion.String(), defaultVersion, minVersion)
+	h := m(handler)
+
+	req, _ := http.NewRequest("GET", "/containers/json", nil)
+	resp := httptest.NewRecorder()
+	ctx := context.Background()
+	if err := h(ctx, resp, req, map[string]string{}); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestVersionMiddlewareWithErrors(t *testing.T) {
+	handler := func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
+		if httputils.VersionFromContext(ctx) == "" {
+			t.Fatalf("Expected version, got empty string")
+		}
+		return nil
+	}
+
+	defaultVersion := version.Version("1.10.0")
+	minVersion := version.Version("1.2.0")
+	m := NewVersionMiddleware(defaultVersion.String(), defaultVersion, minVersion)
+	h := m(handler)
+
+	req, _ := http.NewRequest("GET", "/containers/json", nil)
+	resp := httptest.NewRecorder()
+	ctx := context.Background()
+
+	vars := map[string]string{"version": "0.1"}
+	err := h(ctx, resp, req, vars)
+
+	if !strings.Contains(err.Error(), "client version 0.1 is too old. Minimum supported API version is 1.2.0") {
+		t.Fatalf("Expected ErrorCodeOldClientVersion, got %v", err)
+	}
+
+	vars["version"] = "100000"
+	err = h(ctx, resp, req, vars)
+	if !strings.Contains(err.Error(), "client is newer than server") {
+		t.Fatalf("Expected ErrorCodeNewerClientVersion, got %v", err)
+	}
+}