Add additional helper method to init Google Client from specified fil…

…e path (#79)

* Add additional helper method to init Google Client from specified filepath

* Fix lint comments by shortening line

api/pkg/auth/google_auth.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/http"
+	"os"
 
 	"golang.org/x/oauth2"
 	"golang.org/x/oauth2/google"
@@ -48,7 +49,7 @@ func (s *idTokenSource) Token() (*oauth2.Token, error) {
 }
 
 // InitGoogleClient is a helper method to be used by CaraML components to initialise a Google Client that appends ID
-// tokens to the headers of all outgoing requests with ID tokens, regardless of the type of credentials used
+// tokens to the headers of all outgoing requests, regardless of the type of credentials used
 func InitGoogleClient(ctx context.Context) (*http.Client, error) {
 	cred, err := google.FindDefaultCredentials(ctx)
 	if err != nil {
@@ -64,11 +65,45 @@ func InitGoogleClient(ctx context.Context) (*http.Client, error) {
 		return idtoken.NewClient(ctx, defaultCaraMLAudience)
 	}
 
+	return getGoogleClientFromNonServiceAccountCredentials(ctx, cred)
+}
+
+// InitGoogleClientFromCredentialsFile is a helper method to be used by CaraML components to initialise a Google Client
+// that appends ID tokens to the headers of all outgoing requests, regardless of the type of credentials that are
+// located at the location of the given filepath
+func InitGoogleClientFromCredentialsFile(ctx context.Context, filepath string) (*http.Client, error) {
+	data, err := os.ReadFile(filepath)
+	if err != nil {
+		return nil, err
+	}
+	cred, err := google.CredentialsFromJSON(context.Background(), data)
+	if err != nil {
+		return nil, err
+	}
+
+	var f credentialsFile
+	if err := json.Unmarshal(cred.JSON, &f); err != nil {
+		return nil, err
+	}
+
+	if f.Type == serviceAccountKey {
+		return idtoken.NewClient(ctx, defaultCaraMLAudience, idtoken.WithCredentialsFile(filepath))
+	}
+
+	return getGoogleClientFromNonServiceAccountCredentials(ctx, cred)
+}
+
+// getGoogleClientFromNonServiceAccountCredentials is a helper method to wrap the given non-service account credentials
+// in a Google HTTP client that appends ID tokens to the headers of all outgoing requests
+func getGoogleClientFromNonServiceAccountCredentials(
+	context context.Context,
+	cred *google.Credentials,
+) (*http.Client, error) {
 	tokenSource := oauth2.ReuseTokenSource(nil, &idTokenSource{TokenSource: cred.TokenSource})
 
 	var opts []idtoken.ClientOption
 	opts = append(opts, option.WithTokenSource(tokenSource))
-	t, err := htransport.NewTransport(ctx, http.DefaultTransport, opts...)
+	t, err := htransport.NewTransport(context, http.DefaultTransport, opts...)
 	if err != nil {
 		return nil, err
 	}

api/pkg/auth/google_auth_test.go

@@ -15,7 +15,7 @@ import (
 // the service account credentials in any environment.
 //
 // At the end of the test, the returned function can be called to perform cleanup.
-func testSetupDummyGoogleCredentials(t *testing.T, dummyCredentials []byte) (reset func()) {
+func testSetupDummyGoogleCredentials(t *testing.T, dummyCredentials []byte) (fileName string, reset func()) {
 	file, err := os.CreateTemp("", "dummy-credentials")
 	if err != nil {
 		t.Fatal(err)
@@ -31,7 +31,7 @@ func testSetupDummyGoogleCredentials(t *testing.T, dummyCredentials []byte) (res
 		t.Fatal(err)
 	}
 
-	return func() {
+	return file.Name(), func() {
 		err := os.Unsetenv("GOOGLE_APPLICATION_CREDENTIALS")
 		if err != nil {
 			t.Log("Cleanup failed", err)
@@ -104,7 +104,7 @@ func TestTestInitGoogleClient(t *testing.T) {
 	for name, data := range tests {
 		t.Run(name, func(t *testing.T) {
 			if data.dummyCredential != "" {
-				reset := testSetupDummyGoogleCredentials(t, []byte(data.dummyCredential))
+				_, reset := testSetupDummyGoogleCredentials(t, []byte(data.dummyCredential))
 				defer reset()
 			}
 
@@ -119,3 +119,78 @@ func TestTestInitGoogleClient(t *testing.T) {
 		})
 	}
 }
+
+func TestInitGoogleClientFromCredentialsFile(t *testing.T) {
+	// Define tests
+	tests := map[string]struct {
+		dummyCredential string
+		err             string
+	}{
+		"failure | invalid file path": {
+			err: "open : no such file or directory",
+		},
+		"failure | invalid json file": {
+			dummyCredential: `{`,
+			err:             "unexpected end of JSON input",
+		},
+		"failure | json file with invalid credentials": {
+			dummyCredential: `{}`,
+			err:             "missing 'type' field in credentials",
+		},
+		"failure | service account not found": {
+			//nolint:lll // the private key is in a string literal and cannot contain arbitrary line breaks
+			dummyCredential: `{
+			    "type": "service_account",
+			    "project_id": "example-project",
+			    "private_key_id": "1",
+			    "private_key": "-----BEGIN RSA PRIVATE KEY-----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\nBeF5CT/JuNYk3bEBF0H/Q3VGO1/ggVS+YezdFbLWIRoMnLj6XCFEGg==\n-----END RSA PRIVATE KEY-----\n",
+			    "client_email": "service-account@example.com",
+			    "client_id": "1234",
+			    "auth_uri": "https://accounts.google.com/o/oauth2/auth",
+			    "token_uri": "https://accounts.google.com/o/oauth2/token"
+			}`,
+			err: "oauth2: cannot fetch token: 400 Bad Request\nResponse: " +
+				"{\"error\":\"invalid_grant\",\"error_description\":\"Invalid grant: account not found\"}",
+		},
+		"failure | invalid credentials": {
+			dummyCredential: `{
+			    "client_id": "dummyclientid.apps.googleusercontent.com",
+			    "client_secret": "dummy-secret",
+			    "quota_project_id": "test-project",
+			    "refresh_token": "dummy-token",
+			    "type": "unauthorized_user"
+			}`,
+			err: "unknown credential type: \"unauthorized_user\"",
+		},
+		"success | user account": {
+			dummyCredential: `{
+			    "client_id": "dummyclientid.apps.googleusercontent.com",
+			    "client_secret": "dummy-secret",
+			    "quota_project_id": "test-project",
+			    "refresh_token": "dummy-token",
+			    "type": "authorized_user"
+			}`,
+		},
+	}
+
+	// Run tests
+	for name, data := range tests {
+		t.Run(name, func(t *testing.T) {
+			var fileName string
+			if data.dummyCredential != "" {
+				var reset func()
+				fileName, reset = testSetupDummyGoogleCredentials(t, []byte(data.dummyCredential))
+				defer reset()
+			}
+
+			client, err := InitGoogleClientFromCredentialsFile(context.Background(), fileName)
+			if data.err != "" {
+				assert.EqualError(t, err, data.err)
+				assert.Nil(t, client)
+			} else {
+				assert.NoError(t, err)
+				assert.NotNil(t, client)
+			}
+		})
+	}
+}