chore(pdfengines): add stubs for common workflows

pkg/modules/chromium/routes.go

@@ -21,6 +21,7 @@ import (
 
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 	"github.com/gotenberg/gotenberg/v8/pkg/modules/api"
+	"github.com/gotenberg/gotenberg/v8/pkg/modules/pdfengines"
 )
 
 // FormDataChromiumOptions creates [Options] from the form data. Fallback to
@@ -316,39 +317,6 @@ func FormDataChromiumScreenshotOptions(ctx *api.Context) (*api.FormData, Screens
 	return form, screenshotOptions
 }
 
-// FormDataChromiumPdfFormats creates [gotenberg.PdfFormats] from the form
-// data. Fallback to default value if the considered key is not present.
-func FormDataChromiumPdfFormats(form *api.FormData) gotenberg.PdfFormats {
-	var (
-		pdfa  string
-		pdfua bool
-	)
-
-	form.
-		String("pdfa", &pdfa, "").
-		Bool("pdfua", &pdfua, false)
-
-	return gotenberg.PdfFormats{
-		PdfA:  pdfa,
-		PdfUa: pdfua,
-	}
-}
-
-// FormDataPdfMetadata creates metadata object from the form data.
-func FormDataPdfMetadata(form *api.FormData) map[string]interface{} {
-	var metadata map[string]interface{}
-	form.Custom("metadata", func(value string) error {
-		if len(value) > 0 {
-			err := json.Unmarshal([]byte(value), &metadata)
-			if err != nil {
-				return fmt.Errorf("unmarshal metadata: %w", err)
-			}
-		}
-		return nil
-	})
-	return metadata
-}
-
 // convertUrlRoute returns an [api.Route] which can convert a URL to PDF.
 func convertUrlRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 	return api.Route{
@@ -358,8 +326,8 @@ func convertUrlRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 		Handler: func(c echo.Context) error {
 			ctx := c.Get("context").(*api.Context)
 			form, options := FormDataChromiumPdfOptions(ctx)
-			pdfFormats := FormDataChromiumPdfFormats(form)
+			pdfFormats := pdfengines.FormDataPdfFormats(form)
-			metadata := FormDataPdfMetadata(form)
+			metadata := pdfengines.FormDataPdfMetadata(form)
 
 			var url string
 			err := form.
@@ -418,8 +386,8 @@ func convertHtmlRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 		Handler: func(c echo.Context) error {
 			ctx := c.Get("context").(*api.Context)
 			form, options := FormDataChromiumPdfOptions(ctx)
-			pdfFormats := FormDataChromiumPdfFormats(form)
+			pdfFormats := pdfengines.FormDataPdfFormats(form)
-			metadata := FormDataPdfMetadata(form)
+			metadata := pdfengines.FormDataPdfMetadata(form)
 
 			var inputPath string
 			err := form.
@@ -480,8 +448,8 @@ func convertMarkdownRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 		Handler: func(c echo.Context) error {
 			ctx := c.Get("context").(*api.Context)
 			form, options := FormDataChromiumPdfOptions(ctx)
-			pdfFormats := FormDataChromiumPdfFormats(form)
+			pdfFormats := pdfengines.FormDataPdfFormats(form)
-			metadata := FormDataPdfMetadata(form)
+			metadata := pdfengines.FormDataPdfMetadata(form)
 
 			var (
 				inputPath     string
@@ -664,34 +632,19 @@ func convertUrl(ctx *api.Context, chromium Api, engine gotenberg.PdfEngine, url
 		return fmt.Errorf("convert to PDF: %w", err)
 	}
 
-	// So far so good, the URL has been converted to PDF.
+	outputPaths, err := pdfengines.ConvertStub(ctx, engine, pdfFormats, []string{outputPath})
-	// Now, let's check if the client want to convert the resulting PDF
-	// to specific formats.
-	zeroValued := gotenberg.PdfFormats{}
-	if pdfFormats != zeroValued {
-		convertInputPath := outputPath
-		convertOutputPath := ctx.GeneratePath(".pdf")
-
-		err = engine.Convert(ctx, ctx.Log(), pdfFormats, convertInputPath, convertOutputPath)
 	if err != nil {
 		return fmt.Errorf("convert PDF: %w", err)
 	}
 
-		// Important: the output path is now the converted file.
+	err = pdfengines.WriteMetadataStub(ctx, engine, metadata, outputPaths)
-		outputPath = convertOutputPath
-	}
-
-	// Writes and potentially overrides metadata entries, if any.
-	if len(metadata) > 0 {
-		err = engine.WriteMetadata(ctx, ctx.Log(), metadata, outputPath)
 	if err != nil {
 		return fmt.Errorf("write metadata: %w", err)
 	}
-	}
 
-	err = ctx.AddOutputPaths(outputPath)
+	err = ctx.AddOutputPaths(outputPaths...)
 	if err != nil {
-		return fmt.Errorf("add output path: %w", err)
+		return fmt.Errorf("add output paths: %w", err)
 	}
 
 	return nil

pkg/modules/chromium/routes_test.go

@@ -603,125 +603,6 @@ func TestFormDataChromiumScreenshotOptions(t *testing.T) {
 	}
 }
 
-func TestFormDataChromiumPdfFormats(t *testing.T) {
-	for _, tc := range []struct {
-		scenario              string
-		ctx                   *api.ContextMock
-		expectedPdfFormats    gotenberg.PdfFormats
-		expectValidationError bool
-	}{
-		{
-			scenario:              "no custom form fields",
-			ctx:                   &api.ContextMock{Context: new(api.Context)},
-			expectedPdfFormats:    gotenberg.PdfFormats{},
-			expectValidationError: false,
-		},
-		{
-			scenario: "pdfa and pdfua form fields",
-			ctx: func() *api.ContextMock {
-				ctx := &api.ContextMock{Context: new(api.Context)}
-				ctx.SetValues(map[string][]string{
-					"pdfa": {
-						"foo",
-					},
-					"pdfua": {
-						"true",
-					},
-				})
-				return ctx
-			}(),
-			expectedPdfFormats:    gotenberg.PdfFormats{PdfA: "foo", PdfUa: true},
-			expectValidationError: false,
-		},
-	} {
-		t.Run(tc.scenario, func(t *testing.T) {
-			tc.ctx.SetLogger(zap.NewNop())
-			form := tc.ctx.Context.FormData()
-			actual := FormDataChromiumPdfFormats(form)
-
-			if !reflect.DeepEqual(actual, tc.expectedPdfFormats) {
-				t.Fatalf("expected %+v but got: %+v", tc.expectedPdfFormats, actual)
-			}
-
-			err := form.Validate()
-
-			if tc.expectValidationError && err == nil {
-				t.Fatal("expected validation error but got none", err)
-			}
-
-			if !tc.expectValidationError && err != nil {
-				t.Fatalf("expected no validation error but got: %v", err)
-			}
-		})
-	}
-}
-
-func TestFormDataPdfMetadata(t *testing.T) {
-	for _, tc := range []struct {
-		scenario              string
-		ctx                   *api.ContextMock
-		expectedMetadata      map[string]interface{}
-		expectValidationError bool
-	}{
-		{
-			scenario:              "no metadata form field",
-			ctx:                   &api.ContextMock{Context: new(api.Context)},
-			expectedMetadata:      nil,
-			expectValidationError: false,
-		},
-		{
-			scenario: "invalid metadata form field",
-			ctx: func() *api.ContextMock {
-				ctx := &api.ContextMock{Context: new(api.Context)}
-				ctx.SetValues(map[string][]string{
-					"metadata": {
-						"foo",
-					},
-				})
-				return ctx
-			}(),
-			expectedMetadata:      nil,
-			expectValidationError: true,
-		},
-		{
-			scenario: "valid metadata form field",
-			ctx: func() *api.ContextMock {
-				ctx := &api.ContextMock{Context: new(api.Context)}
-				ctx.SetValues(map[string][]string{
-					"metadata": {
-						"{\"foo\":\"bar\"}",
-					},
-				})
-				return ctx
-			}(),
-			expectedMetadata: map[string]interface{}{
-				"foo": "bar",
-			},
-			expectValidationError: false,
-		},
-	} {
-		t.Run(tc.scenario, func(t *testing.T) {
-			tc.ctx.SetLogger(zap.NewNop())
-			form := tc.ctx.Context.FormData()
-			actual := FormDataPdfMetadata(form)
-
-			if !reflect.DeepEqual(actual, tc.expectedMetadata) {
-				t.Fatalf("expected %+v but got: %+v", tc.expectedMetadata, actual)
-			}
-
-			err := form.Validate()
-
-			if tc.expectValidationError && err == nil {
-				t.Fatal("expected validation error but got none", err)
-			}
-
-			if !tc.expectValidationError && err != nil {
-				t.Fatalf("expected no validation error but got: %v", err)
-			}
-		})
-	}
-}
-
 func TestConvertUrlRoute(t *testing.T) {
 	for _, tc := range []struct {
 		scenario               string

pkg/modules/libreoffice/routes.go

@@ -13,6 +13,7 @@ import (
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 	"github.com/gotenberg/gotenberg/v8/pkg/modules/api"
 	libreofficeapi "github.com/gotenberg/gotenberg/v8/pkg/modules/libreoffice/api"
+	"github.com/gotenberg/gotenberg/v8/pkg/modules/pdfengines"
 )
 
 // convertRoute returns an [api.Route] which can convert LibreOffice documents
@@ -26,7 +27,10 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 			ctx := c.Get("context").(*api.Context)
 			defaultOptions := libreofficeapi.DefaultOptions()
 
-			// Let's get the data from the form and validate them.
+			form := ctx.FormData()
+			pdfFormats := pdfengines.FormDataPdfFormats(form)
+			metadata := pdfengines.FormDataPdfMetadata(form)
+
 			var (
 				inputPaths                      []string
 				password                        string
@@ -51,14 +55,11 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 				quality                         int
 				reduceImageResolution           bool
 				maxImageResolution              int
-				pdfa                            string
-				pdfua                           bool
 				nativePdfFormats                bool
 				merge                           bool
-				metadata                        map[string]interface{}
 			)
 
-			err := ctx.FormData().
+			err := form.
 				MandatoryPaths(libreOffice.Extensions(), &inputPaths).
 				String("password", &password, defaultOptions.Password).
 				Bool("landscape", &landscape, defaultOptions.Landscape).
@@ -120,8 +121,6 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 					maxImageResolution = intValue
 					return nil
 				}).
-				String("pdfa", &pdfa, "").
-				Bool("pdfua", &pdfua, false).
 				Bool("nativePdfFormats", &nativePdfFormats, true).
 				Bool("merge", &merge, false).
 				Custom("metadata", func(value string) error {
@@ -138,12 +137,6 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 				return fmt.Errorf("validate form data: %w", err)
 			}
 
-			pdfFormats := gotenberg.PdfFormats{
-				PdfA:  pdfa,
-				PdfUa: pdfua,
-			}
-
-			// Alright, let's convert each document to PDF.
 			outputPaths := make([]string, len(inputPaths))
 			for i, inputPath := range inputPaths {
 				outputPaths[i] = ctx.GeneratePath(".pdf")
@@ -206,11 +199,8 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 				}
 			}
 
-			// So far so good, let's check if we have to merge the PDFs.
+			if merge {
-			if len(outputPaths) > 1 && merge {
+				outputPath, err := pdfengines.MergeStub(ctx, engine, outputPaths)
-				outputPath := ctx.GeneratePath(".pdf")
-
-				err = engine.Merge(ctx, ctx.Log(), outputPaths, outputPath)
 				if err != nil {
 					return fmt.Errorf("merge PDFs: %w", err)
 				}
@@ -219,35 +209,17 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 				outputPaths = []string{outputPath}
 			}
 
-			// Let's check if the client want to convert each PDF to a specific
+			if !nativePdfFormats {
-			// PDF format.
+				outputPaths, err = pdfengines.ConvertStub(ctx, engine, pdfFormats, outputPaths)
-			zeroValued := gotenberg.PdfFormats{}
-			if !nativePdfFormats && pdfFormats != zeroValued {
-				convertOutputPaths := make([]string, len(outputPaths))
-
-				for i, outputPath := range outputPaths {
-					convertInputPath := outputPath
-					convertOutputPaths[i] = ctx.GeneratePath(".pdf")
-
-					err = engine.Convert(ctx, ctx.Log(), pdfFormats, convertInputPath, convertOutputPaths[i])
 				if err != nil {
-						return fmt.Errorf("convert PDF: %w", err)
+					return fmt.Errorf("convert PDFs: %w", err)
 				}
 			}
 
-				// Important: the output paths are now the converted files.
+			err = pdfengines.WriteMetadataStub(ctx, engine, metadata, outputPaths)
-				outputPaths = convertOutputPaths
-			}
-
-			// Writes and potentially overrides metadata entries, if any.
-			if len(metadata) > 0 {
-				for _, outputPath := range outputPaths {
-					err = engine.WriteMetadata(ctx, ctx.Log(), metadata, outputPath)
 			if err != nil {
 				return fmt.Errorf("write metadata: %w", err)
 			}
-				}
-			}
 
 			if len(outputPaths) > 1 {
 				// If .zip archive, document.docx -> document.docx.pdf.
@@ -263,8 +235,6 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 				}
 			}
 
-			// Last but not least, add the output paths to the context so that
-			// the API is able to send them as a response to the client.
 			err = ctx.AddOutputPaths(outputPaths...)
 			if err != nil {
 				return fmt.Errorf("add output paths: %w", err)

pkg/modules/pdfengines/routes.go

@@ -13,6 +13,98 @@ import (
 	"github.com/gotenberg/gotenberg/v8/pkg/modules/api"
 )
 
+// FormDataPdfFormats creates [gotenberg.PdfFormats] from the form data.
+// Fallback to default value if the considered key is not present.
+func FormDataPdfFormats(form *api.FormData) gotenberg.PdfFormats {
+	var (
+		pdfa  string
+		pdfua bool
+	)
+
+	form.
+		String("pdfa", &pdfa, "").
+		Bool("pdfua", &pdfua, false)
+
+	return gotenberg.PdfFormats{
+		PdfA:  pdfa,
+		PdfUa: pdfua,
+	}
+}
+
+// FormDataPdfMetadata creates metadata object from the form data.
+func FormDataPdfMetadata(form *api.FormData) map[string]interface{} {
+	var metadata map[string]interface{}
+	form.Custom("metadata", func(value string) error {
+		if len(value) > 0 {
+			err := json.Unmarshal([]byte(value), &metadata)
+			if err != nil {
+				return fmt.Errorf("unmarshal metadata: %w", err)
+			}
+		}
+		return nil
+	})
+	return metadata
+}
+
+// MergeStub merges given PDFs. If only one input PDF, it does nothing and
+// returns the corresponding input path.
+func MergeStub(ctx *api.Context, engine gotenberg.PdfEngine, inputPaths []string) (string, error) {
+	if len(inputPaths) == 0 {
+		return "", errors.New("no input paths")
+	}
+
+	if len(inputPaths) == 1 {
+		return inputPaths[0], nil
+	}
+
+	outputPath := ctx.GeneratePath(".pdf")
+	err := engine.Merge(ctx, ctx.Log(), inputPaths, outputPath)
+	if err != nil {
+		return "", fmt.Errorf("merge %d PDFs: %w", len(inputPaths), err)
+	}
+
+	return outputPath, nil
+}
+
+// ConvertStub transforms a given PDF to the specified formats defined in
+// [gotenberg.PdfFormats]. If no format, it does nothing and returns the input
+// paths.
+func ConvertStub(ctx *api.Context, engine gotenberg.PdfEngine, formats gotenberg.PdfFormats, inputPaths []string) ([]string, error) {
+	zeroValued := gotenberg.PdfFormats{}
+	if formats == zeroValued {
+		return inputPaths, nil
+	}
+
+	outputPaths := make([]string, len(inputPaths))
+	for i, inputPath := range inputPaths {
+		outputPaths[i] = ctx.GeneratePath(".pdf")
+
+		err := engine.Convert(ctx, ctx.Log(), formats, inputPath, outputPaths[i])
+		if err != nil {
+			return nil, fmt.Errorf("convert '%s': %w", inputPath, err)
+		}
+	}
+
+	return outputPaths, nil
+}
+
+// WriteMetadataStub writes the metadata into PDF files. If no metadata, it
+// does nothing.
+func WriteMetadataStub(ctx *api.Context, engine gotenberg.PdfEngine, metadata map[string]interface{}, inputPaths []string) error {
+	if len(metadata) == 0 {
+		return nil
+	}
+
+	for _, inputPath := range inputPaths {
+		err := engine.WriteMetadata(ctx, ctx.Log(), metadata, inputPath)
+		if err != nil {
+			return fmt.Errorf("write metadata into '%s': %w", inputPath, err)
+		}
+	}
+
+	return nil
+}
+
 // mergeRoute returns an [api.Route] which can merge PDFs.
 func mergeRoute(engine gotenberg.PdfEngine) api.Route {
 	return api.Route{
@@ -22,75 +114,37 @@ func mergeRoute(engine gotenberg.PdfEngine) api.Route {
 		Handler: func(c echo.Context) error {
 			ctx := c.Get("context").(*api.Context)
 
-			// Let's get the data from the form and validate them.
+			form := ctx.FormData()
-			var (
+			pdfFormats := FormDataPdfFormats(form)
-				inputPaths []string
+			metadata := FormDataPdfMetadata(form)
-				pdfa       string
-				pdfua      bool
-				metadata   map[string]interface{}
-			)
 
-			err := ctx.FormData().
+			var inputPaths []string
+			err := form.
 				MandatoryPaths([]string{".pdf"}, &inputPaths).
-				String("pdfa", &pdfa, "").
-				Bool("pdfua", &pdfua, false).
-				Custom("metadata", func(value string) error {
-					if len(value) > 0 {
-						err := json.Unmarshal([]byte(value), &metadata)
-						if err != nil {
-							return fmt.Errorf("unmarshal metadata: %w", err)
-						}
-					}
-					return nil
-				}).
 				Validate()
 			if err != nil {
 				return fmt.Errorf("validate form data: %w", err)
 			}
 
-			pdfFormats := gotenberg.PdfFormats{
-				PdfA:  pdfa,
-				PdfUa: pdfua,
-			}
-
-			// Alright, let's merge the PDFs.
 			outputPath := ctx.GeneratePath(".pdf")
-
 			err = engine.Merge(ctx, ctx.Log(), inputPaths, outputPath)
 			if err != nil {
 				return fmt.Errorf("merge PDFs: %w", err)
 			}
 
-			// So far so good, the PDFs are merged into one unique PDF.
+			outputPaths, err := ConvertStub(ctx, engine, pdfFormats, []string{outputPath})
-			// Now, let's check if the client want to convert this result PDF
-			// to specific PDF formats.
-			zeroValued := gotenberg.PdfFormats{}
-			if pdfFormats != zeroValued {
-				convertInputPath := outputPath
-				convertOutputPath := ctx.GeneratePath(".pdf")
-
-				err = engine.Convert(ctx, ctx.Log(), pdfFormats, convertInputPath, convertOutputPath)
 			if err != nil {
 				return fmt.Errorf("convert PDF: %w", err)
 			}
 
-				// Important: the output path is now the converted file.
+			err = WriteMetadataStub(ctx, engine, metadata, outputPaths)
-				outputPath = convertOutputPath
-			}
-
-			// Writes and potentially overrides metadata entries, if any.
-			if len(metadata) > 0 {
-				err = engine.WriteMetadata(ctx, ctx.Log(), metadata, outputPath)
 			if err != nil {
 				return fmt.Errorf("write metadata: %w", err)
 			}
-			}
 
-			// Last but not least, add the output path to the context so that
+			err = ctx.AddOutputPaths(outputPaths...)
-			// the API is able to send it as a response to the client.
-			err = ctx.AddOutputPaths(outputPath)
 			if err != nil {
-				return fmt.Errorf("add output path: %w", err)
+				return fmt.Errorf("add output paths: %w", err)
 			}
 
 			return nil
@@ -108,27 +162,17 @@ func convertRoute(engine gotenberg.PdfEngine) api.Route {
 		Handler: func(c echo.Context) error {
 			ctx := c.Get("context").(*api.Context)
 
-			// Let's get the data from the form and validate them.
+			form := ctx.FormData()
-			var (
+			pdfFormats := FormDataPdfFormats(form)
-				inputPaths []string
-				pdfa       string
-				pdfua      bool
-			)
 
-			err := ctx.FormData().
+			var inputPaths []string
+			err := form.
 				MandatoryPaths([]string{".pdf"}, &inputPaths).
-				String("pdfa", &pdfa, "").
-				Bool("pdfua", &pdfua, false).
 				Validate()
 			if err != nil {
 				return fmt.Errorf("validate form data: %w", err)
 			}
 
-			pdfFormats := gotenberg.PdfFormats{
-				PdfA:  pdfa,
-				PdfUa: pdfua,
-			}
-
 			zeroValued := gotenberg.PdfFormats{}
 			if pdfFormats == zeroValued {
 				return api.WrapError(
@@ -140,18 +184,14 @@ func convertRoute(engine gotenberg.PdfEngine) api.Route {
 				)
 			}
 
-			// Alright, let's convert the PDFs.
+			outputPaths, err := ConvertStub(ctx, engine, pdfFormats, inputPaths)
-			outputPaths := make([]string, len(inputPaths))
-			for i, inputPath := range inputPaths {
-				outputPaths[i] = ctx.GeneratePath(".pdf")
-
-				err = engine.Convert(ctx, ctx.Log(), pdfFormats, inputPath, outputPaths[i])
 			if err != nil {
-					return fmt.Errorf("convert PDF: %w", err)
+				return fmt.Errorf("convert PDFs: %w", err)
 			}
 
 			if len(outputPaths) > 1 {
 				// If .zip archive, keep the original filename.
+				for i, inputPath := range inputPaths {
 					err = ctx.Rename(outputPaths[i], inputPath)
 					if err != nil {
 						return fmt.Errorf("rename output path: %w", err)
@@ -161,8 +201,6 @@ func convertRoute(engine gotenberg.PdfEngine) api.Route {
 				}
 			}
 
-			// Last but not least, add the output paths to the context so that
-			// the API is able to send them as a response to the client.
 			err = ctx.AddOutputPaths(outputPaths...)
 			if err != nil {
 				return fmt.Errorf("add output paths: %w", err)
@@ -182,9 +220,7 @@ func readMetadataRoute(engine gotenberg.PdfEngine) api.Route {
 		Handler: func(c echo.Context) error {
 			ctx := c.Get("context").(*api.Context)
 
-			// Let's get the data from the form and validate them.
 			var inputPaths []string
-
 			err := ctx.FormData().
 				MandatoryPaths([]string{".pdf"}, &inputPaths).
 				Validate()
@@ -192,7 +228,6 @@ func readMetadataRoute(engine gotenberg.PdfEngine) api.Route {
 				return fmt.Errorf("validate form data: %w", err)
 			}
 
-			// Alright, let's read the metadata.
 			res := make(map[string]map[string]interface{}, len(inputPaths))
 			for _, inputPath := range inputPaths {
 				metadata, err := engine.ReadMetadata(ctx, ctx.Log(), inputPath)
@@ -223,7 +258,6 @@ func writeMetadataRoute(engine gotenberg.PdfEngine) api.Route {
 		Handler: func(c echo.Context) error {
 			ctx := c.Get("context").(*api.Context)
 
-			// Let's get the data from the form and validate them.
 			var (
 				inputPaths []string
 				metadata   map[string]interface{}
@@ -248,16 +282,11 @@ func writeMetadataRoute(engine gotenberg.PdfEngine) api.Route {
 				return fmt.Errorf("validate form data: %w", err)
 			}
 
-			// Alright, let's convert the PDFs.
+			err = WriteMetadataStub(ctx, engine, metadata, inputPaths)
-			for _, inputPath := range inputPaths {
-				err = engine.WriteMetadata(ctx, ctx.Log(), metadata, inputPath)
 			if err != nil {
 				return fmt.Errorf("write metadata: %w", err)
 			}
-			}
 
-			// Last but not least, add the output paths to the context so that
-			// the API is able to send them as a response to the client.
 			err = ctx.AddOutputPaths(inputPaths...)
 			if err != nil {
 				return fmt.Errorf("add output paths: %w", err)

pkg/modules/pdfengines/routes_test.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"net/http"
 	"net/http/httptest"
+	"reflect"
 	"slices"
 	"strings"
 	"testing"
@@ -16,6 +17,287 @@ import (
 	"github.com/gotenberg/gotenberg/v8/pkg/modules/api"
 )
 
+func TestFormDataPdfFormats(t *testing.T) {
+	for _, tc := range []struct {
+		scenario              string
+		ctx                   *api.ContextMock
+		expectedPdfFormats    gotenberg.PdfFormats
+		expectValidationError bool
+	}{
+		{
+			scenario:              "no custom form fields",
+			ctx:                   &api.ContextMock{Context: new(api.Context)},
+			expectedPdfFormats:    gotenberg.PdfFormats{},
+			expectValidationError: false,
+		},
+		{
+			scenario: "pdfa and pdfua form fields",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetValues(map[string][]string{
+					"pdfa": {
+						"foo",
+					},
+					"pdfua": {
+						"true",
+					},
+				})
+				return ctx
+			}(),
+			expectedPdfFormats:    gotenberg.PdfFormats{PdfA: "foo", PdfUa: true},
+			expectValidationError: false,
+		},
+	} {
+		t.Run(tc.scenario, func(t *testing.T) {
+			tc.ctx.SetLogger(zap.NewNop())
+			form := tc.ctx.Context.FormData()
+			actual := FormDataPdfFormats(form)
+
+			if !reflect.DeepEqual(actual, tc.expectedPdfFormats) {
+				t.Fatalf("expected %+v but got: %+v", tc.expectedPdfFormats, actual)
+			}
+
+			err := form.Validate()
+
+			if tc.expectValidationError && err == nil {
+				t.Fatal("expected validation error but got none", err)
+			}
+
+			if !tc.expectValidationError && err != nil {
+				t.Fatalf("expected no validation error but got: %v", err)
+			}
+		})
+	}
+}
+
+func TestFormDataPdfMetadata(t *testing.T) {
+	for _, tc := range []struct {
+		scenario              string
+		ctx                   *api.ContextMock
+		expectedMetadata      map[string]interface{}
+		expectValidationError bool
+	}{
+		{
+			scenario:              "no metadata form field",
+			ctx:                   &api.ContextMock{Context: new(api.Context)},
+			expectedMetadata:      nil,
+			expectValidationError: false,
+		},
+		{
+			scenario: "invalid metadata form field",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetValues(map[string][]string{
+					"metadata": {
+						"foo",
+					},
+				})
+				return ctx
+			}(),
+			expectedMetadata:      nil,
+			expectValidationError: true,
+		},
+		{
+			scenario: "valid metadata form field",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetValues(map[string][]string{
+					"metadata": {
+						"{\"foo\":\"bar\"}",
+					},
+				})
+				return ctx
+			}(),
+			expectedMetadata: map[string]interface{}{
+				"foo": "bar",
+			},
+			expectValidationError: false,
+		},
+	} {
+		t.Run(tc.scenario, func(t *testing.T) {
+			tc.ctx.SetLogger(zap.NewNop())
+			form := tc.ctx.Context.FormData()
+			actual := FormDataPdfMetadata(form)
+
+			if !reflect.DeepEqual(actual, tc.expectedMetadata) {
+				t.Fatalf("expected %+v but got: %+v", tc.expectedMetadata, actual)
+			}
+
+			err := form.Validate()
+
+			if tc.expectValidationError && err == nil {
+				t.Fatal("expected validation error but got none", err)
+			}
+
+			if !tc.expectValidationError && err != nil {
+				t.Fatalf("expected no validation error but got: %v", err)
+			}
+		})
+	}
+}
+
+func TestMergeStub(t *testing.T) {
+	for _, tc := range []struct {
+		scenario    string
+		engine      gotenberg.PdfEngine
+		inputPaths  []string
+		expectError bool
+	}{
+		{
+			scenario:    "no input path (nil)",
+			inputPaths:  nil,
+			expectError: true,
+		},
+		{
+			scenario:    "no input path (empty)",
+			inputPaths:  make([]string, 0),
+			expectError: true,
+		},
+		{
+			scenario:    "only one input path",
+			inputPaths:  []string{"my.pdf"},
+			expectError: false,
+		},
+		{
+			scenario: "merge error",
+			engine: &gotenberg.PdfEngineMock{
+				MergeMock: func(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
+					return errors.New("foo")
+				},
+			},
+			inputPaths:  []string{"my.pdf", "my2.pdf"},
+			expectError: true,
+		},
+		{
+			scenario: "merge success",
+			engine: &gotenberg.PdfEngineMock{
+				MergeMock: func(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
+					return nil
+				},
+			},
+			inputPaths:  []string{"my.pdf", "my2.pdf"},
+			expectError: false,
+		},
+	} {
+		t.Run(tc.scenario, func(t *testing.T) {
+			_, err := MergeStub(new(api.Context), tc.engine, tc.inputPaths)
+
+			if tc.expectError && err == nil {
+				t.Fatal("expected error but got none", err)
+			}
+
+			if !tc.expectError && err != nil {
+				t.Fatalf("expected no error but got: %v", err)
+			}
+		})
+	}
+}
+
+func TestConvertStub(t *testing.T) {
+	for _, tc := range []struct {
+		scenario    string
+		engine      gotenberg.PdfEngine
+		pdfFormats  gotenberg.PdfFormats
+		expectError bool
+	}{
+		{
+			scenario:    "no PDF formats",
+			pdfFormats:  gotenberg.PdfFormats{},
+			expectError: false,
+		},
+		{
+			scenario: "convert error",
+			engine: &gotenberg.PdfEngineMock{
+				ConvertMock: func(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
+					return errors.New("foo")
+				},
+			},
+			pdfFormats: gotenberg.PdfFormats{
+				PdfA:  gotenberg.PdfA3b,
+				PdfUa: true,
+			},
+			expectError: true,
+		},
+		{
+			scenario: "convert success",
+			engine: &gotenberg.PdfEngineMock{
+				ConvertMock: func(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
+					return nil
+				},
+			},
+			pdfFormats: gotenberg.PdfFormats{
+				PdfA:  gotenberg.PdfA3b,
+				PdfUa: true,
+			},
+			expectError: false,
+		},
+	} {
+		t.Run(tc.scenario, func(t *testing.T) {
+			_, err := ConvertStub(new(api.Context), tc.engine, tc.pdfFormats, []string{"my.pdf", "my2.pdf"})
+
+			if tc.expectError && err == nil {
+				t.Fatal("expected error but got none", err)
+			}
+
+			if !tc.expectError && err != nil {
+				t.Fatalf("expected no error but got: %v", err)
+			}
+		})
+	}
+}
+
+func TestWriteMetadataStub(t *testing.T) {
+	for _, tc := range []struct {
+		scenario    string
+		engine      gotenberg.PdfEngine
+		metadata    map[string]interface{}
+		expectError bool
+	}{
+		{
+			scenario:    "no metadata (nil)",
+			metadata:    nil,
+			expectError: false,
+		},
+		{
+			scenario:    "no metadata (empty)",
+			metadata:    make(map[string]interface{}, 0),
+			expectError: false,
+		},
+		{
+			scenario: "write metadata error",
+			engine: &gotenberg.PdfEngineMock{
+				WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+					return errors.New("foo")
+				},
+			},
+			metadata:    map[string]interface{}{"foo": "bar"},
+			expectError: true,
+		},
+		{
+			scenario: "write metadata success",
+			engine: &gotenberg.PdfEngineMock{
+				WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+					return nil
+				},
+			},
+			metadata:    map[string]interface{}{"foo": "bar"},
+			expectError: false,
+		},
+	} {
+		t.Run(tc.scenario, func(t *testing.T) {
+			err := WriteMetadataStub(new(api.Context), tc.engine, tc.metadata, []string{"my.pdf", "my2.pdf"})
+
+			if tc.expectError && err == nil {
+				t.Fatal("expected error but got none", err)
+			}
+
+			if !tc.expectError && err != nil {
+				t.Fatalf("expected no error but got: %v", err)
+			}
+		})
+	}
+}
+
 func TestMergeHandler(t *testing.T) {
 	for _, tc := range []struct {
 		scenario               string