[Fleet] Add elastic-api-version support (#2677)

internal/pkg/api/apiVersion.go

@@ -0,0 +1,81 @@
+// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+// or more contributor license agreements. Licensed under the Elastic License;
+// you may not use this file except in compliance with the Elastic License.
+
+package api
+
+import (
+	"errors"
+	"fmt"
+	"net/http"
+	"regexp"
+	"strings"
+)
+
+var (
+	ErrInvalidAPIVersionFormat = errors.New("invalid version format")
+	ErrUnsupportedAPIVersion   = errors.New("version is not supported")
+)
+
+const (
+	ElasticAPIVersionHeader = "Elastic-Api-Version"
+	DefaultVersion          = "2023-06-01"
+)
+
+var SupportedVersions = []string{DefaultVersion}
+
+var isValidVersionRegex = regexp.MustCompile(`^[0-9]{4}-[0-9]{2}-[0-9]{2}$`)
+
+type apiVersion struct {
+	supportedVersions []string
+	defaultVersion    string
+}
+
+func NewAPIVersion() *apiVersion {
+	return &apiVersion{
+		supportedVersions: SupportedVersions,
+		defaultVersion:    DefaultVersion,
+	}
+}
+
+func (a *apiVersion) validateVersionFormat(version string) error {
+	if !isValidVersionRegex.MatchString(version) {
+		return fmt.Errorf("received \"%s\", expected a valid date string formatted as YYYY-MM-DD. %w", version, ErrInvalidAPIVersionFormat)
+	}
+
+	return nil
+}
+
+func (a *apiVersion) isVersionSupported(version string) bool {
+	for _, vers := range a.supportedVersions {
+		if vers == version {
+			return true
+		}
+	}
+	return false
+}
+
+func (a *apiVersion) middleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+
+		headerValue := r.Header.Get(ElasticAPIVersionHeader)
+		if headerValue != "" {
+			err := a.validateVersionFormat(headerValue)
+			if err != nil {
+				ErrorResp(w, r, err)
+				return
+			}
+
+			if !a.isVersionSupported(headerValue) {
+				w.Header().Add(ElasticAPIVersionHeader, a.defaultVersion)
+				ErrorResp(w, r, fmt.Errorf("received %q, is not supported. supported versions are: [%s] %w", headerValue, strings.Join(a.supportedVersions, ", "), ErrUnsupportedAPIVersion))
+				return
+			}
+			w.Header().Add(ElasticAPIVersionHeader, headerValue)
+		} else {
+			w.Header().Add(ElasticAPIVersionHeader, a.defaultVersion)
+		}
+
+		next.ServeHTTP(w, r)
+	})
+}

internal/pkg/api/apiVersion_test.go

@@ -0,0 +1,93 @@
+// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+// or more contributor license agreements. Licensed under the Elastic License;
+// you may not use this file except in compliance with the Elastic License.
+
+package api
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAPIVersion_middleware(t *testing.T) {
+	supportedVersions := []string{"2022-01-01", "2022-02-01", "2022-03-01"}
+	defaultVersion := "2022-03-01"
+
+	tests := []struct {
+		name                       string
+		requestAPIVersionHeader    string
+		expectRespStatus           string
+		expectRespAPIVersionHeader string
+		expectErr                  string
+	}{
+		{
+			name:                    "with a misformatted Elastic-Api-Version header",
+			requestAPIVersionHeader: "iamnotvalid",
+			expectRespStatus:        "400 Bad Request",
+			expectErr:               "ErrInvalidAPIVersionFormat",
+		},
+		{
+			name:                    "with an invalid Elastic-Api-Version header",
+			requestAPIVersionHeader: "1990-01-01",
+			expectRespStatus:        "400 Bad Request",
+			expectErr:               "ErrUnsupportedAPIVersion",
+		},
+		{
+			name:                       "with a valid Elastic-Api-Version header",
+			requestAPIVersionHeader:    "2022-02-01",
+			expectRespAPIVersionHeader: "2022-02-01",
+			expectRespStatus:           "200 OK",
+		},
+		{
+			name:                       "without Elastic-Api-Version header",
+			expectRespAPIVersionHeader: "2022-03-01",
+			expectRespStatus:           "200 OK",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+
+			apiVersion := apiVersion{
+				supportedVersions: supportedVersions,
+				defaultVersion:    defaultVersion,
+			}
+
+			resp := httptest.NewRecorder()
+
+			req := httptest.NewRequest("GET", "/api/test", nil)
+
+			nextHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {})
+
+			if tc.requestAPIVersionHeader != "" {
+				req.Header.Set(ElasticAPIVersionHeader, tc.requestAPIVersionHeader)
+			}
+
+			apiVersion.middleware(nextHandler).ServeHTTP(resp, req)
+
+			respResult := resp.Result()
+			defer respResult.Body.Close()
+
+			if tc.expectRespStatus != "" {
+				assert.Equal(t, tc.expectRespStatus, respResult.Status)
+			}
+
+			if tc.expectRespAPIVersionHeader != "" {
+				assert.Equal(t, tc.expectRespAPIVersionHeader, resp.Header().Get(ElasticAPIVersionHeader))
+			}
+
+			if tc.expectErr != "" {
+				errorResp := &Error{}
+				dec := json.NewDecoder(resp.Body)
+				err := dec.Decode(&errorResp)
+
+				assert.NoError(t, err)
+				assert.Equal(t, tc.expectErr, errorResp.Error)
+			}
+		})
+	}
+}

internal/pkg/api/error.go

@@ -388,6 +388,25 @@ func NewHTTPErrResp(err error) HTTPErrResp {
 				zerolog.InfoLevel,
 			},
 		},
+		// Version
+		{
+			ErrInvalidAPIVersionFormat,
+			HTTPErrResp{
+				http.StatusBadRequest,
+				"ErrInvalidAPIVersionFormat",
+				"",
+				zerolog.InfoLevel,
+			},
+		},
+		{
+			ErrUnsupportedAPIVersion,
+			HTTPErrResp{
+				http.StatusBadRequest,
+				"ErrUnsupportedAPIVersion",
+				"",
+				zerolog.InfoLevel,
+			},
+		},
 		// file
 		{
 			delivery.ErrNoFile,