feat(pdfengines): inject Factur-X/ZUGFeRD XMP metadata

.bruno/Chromium/Convert/HTML to PDF.bru

@@ -53,6 +53,7 @@ body:multipart-form {
   ~embeds: @file(../test/integration/testdata/embed_1.xml)
   ~embeds: @file(../test/integration/testdata/embed_2.xml)
   ~embedsMetadata: {"embed_1.xml":{"mimeType":"text/xml","relationship":"Data"}, "embed_2.xml":{"mimeType":"text/xml","relationship":"Data"}}
+  ~facturx: {"conformanceLevel":"EN 16931","documentType":"INVOICE","documentFileName":"factur-x.xml","version":"1.0"}
   ~watermarkSource: text
   ~watermarkExpression: CONFIDENTIAL
   ~watermarkPages:

.bruno/Chromium/Convert/Markdown to PDF.bru

@@ -54,6 +54,7 @@ body:multipart-form {
   ~embeds: @file(../test/integration/testdata/embed_1.xml)
   ~embeds: @file(../test/integration/testdata/embed_2.xml)
   ~embedsMetadata: {"embed_1.xml":{"mimeType":"text/xml","relationship":"Data"}, "embed_2.xml":{"mimeType":"text/xml","relationship":"Data"}}
+  ~facturx: {"conformanceLevel":"EN 16931","documentType":"INVOICE","documentFileName":"factur-x.xml","version":"1.0"}
   ~watermarkSource: text
   ~watermarkExpression: CONFIDENTIAL
   ~watermarkPages:

.bruno/Chromium/Convert/URL to PDF.bru

@@ -53,6 +53,7 @@ body:multipart-form {
   ~embeds: @file(../test/integration/testdata/embed_1.xml)
   ~embeds: @file(../test/integration/testdata/embed_2.xml)
   ~embedsMetadata: {"embed_1.xml":{"mimeType":"text/xml","relationship":"Data"}, "embed_2.xml":{"mimeType":"text/xml","relationship":"Data"}}
+  ~facturx: {"conformanceLevel":"EN 16931","documentType":"INVOICE","documentFileName":"factur-x.xml","version":"1.0"}
   ~watermarkSource: text
   ~watermarkExpression: CONFIDENTIAL
   ~watermarkPages:

.bruno/LibreOffice/Convert to PDF.bru

@@ -70,6 +70,7 @@ body:multipart-form {
   ~embeds: @file(../test/integration/testdata/embed_1.xml)
   ~embeds: @file(../test/integration/testdata/embed_2.xml)
   ~embedsMetadata: {"embed_1.xml":{"mimeType":"text/xml","relationship":"Data"}, "embed_2.xml":{"mimeType":"text/xml","relationship":"Data"}}
+  ~facturx: {"conformanceLevel":"EN 16931","documentType":"INVOICE","documentFileName":"factur-x.xml","version":"1.0"}
   ~watermarkSource: text
   ~watermarkExpression: CONFIDENTIAL
   ~watermarkPages:

.bruno/PDF Engines/Embed/Embed Files.bru

@@ -15,6 +15,7 @@ body:multipart-form {
   embeds: @file(../test/integration/testdata/embed_1.xml)
   embeds: @file(../test/integration/testdata/embed_2.xml)
   embedsMetadata: {"embed_1.xml":{"mimeType":"text/xml","relationship":"Data"}, "embed_2.xml":{"mimeType":"text/xml","relationship":"Data"}}
+  ~facturx: {"conformanceLevel":"EN 16931","documentType":"INVOICE","documentFileName":"factur-x.xml","version":"1.0"}
   ~downloadFrom: [{"url":"https://example.com/attachment.xml","embedded":true}]
 }
 

.bruno/PDF Engines/Factur-X/Inject Factur-X XMP.bru

@@ -0,0 +1,26 @@
+meta {
+  name: Inject Factur-X XMP
+  type: http
+  seq: 1
+}
+
+post {
+  url: {{baseUrl}}/forms/pdfengines/factur-x
+  body: multipartForm
+  auth: none
+}
+
+body:multipart-form {
+  files: @file(../../test/integration/testdata/page_1.pdf)
+  facturx: {"conformanceLevel":"EN 16931","documentType":"INVOICE","documentFileName":"factur-x.xml","version":"1.0"}
+}
+
+headers {
+  ~Gotenberg-Output-Filename: factur-x
+  ~Gotenberg-Webhook-Url: http://localhost:8080/webhook
+  ~Gotenberg-Webhook-Error-Url: http://localhost:8080/webhook/error
+  ~Gotenberg-Webhook-Events-Url: http://localhost:8080/webhook/events
+  ~Gotenberg-Webhook-Method: POST
+  ~Gotenberg-Webhook-Error-Method: POST
+  ~Gotenberg-Webhook-Extra-Http-Headers: {"X-Custom":"value"}
+}

.bruno/PDF Engines/Merge/Merge PDFs.bru

@@ -31,6 +31,7 @@ body:multipart-form {
   ~stampOptions: {"scale":"0.5 abs","rot":"45"}
   ~rotateAngle: 90
   ~rotatePages:
+  ~facturx: {"conformanceLevel":"EN 16931","documentType":"INVOICE","documentFileName":"factur-x.xml","version":"1.0"}
 }
 
 headers {

.bruno/PDF Engines/Split/Split PDF.bru

@@ -31,6 +31,7 @@ body:multipart-form {
   ~stampOptions: {"scale":"0.5 abs","rot":"45"}
   ~rotateAngle: 90
   ~rotatePages:
+  ~facturx: {"conformanceLevel":"EN 16931","documentType":"INVOICE","documentFileName":"factur-x.xml","version":"1.0"}
 }
 
 headers {

Makefile

@@ -81,6 +81,7 @@ PDFENGINES_ENCRYPT_ENGINES=qpdf,pdfcpu,pdftk
 PDFENGINES_ROTATE_ENGINES=pdfcpu,pdftk
 PDFENGINES_EMBED_ENGINES=qpdf,pdfcpu
 PDFENGINES_EMBED_METADATA_ENGINES=qpdf
+PDFENGINES_FACTUR_X_ENGINES=qpdf
 PROMETHEUS_NAMESPACE=gotenberg
 PROMETHEUS_COLLECT_INTERVAL=1s
 PROMETHEUS_DISABLE_ROUTE_TELEMETRY=true
@@ -157,6 +158,7 @@ NO_CONCURRENCY=false
 # stamp
 # pdfengines-rotate
 # rotate
+# factur-x
 # pdfengines-bookmarks
 # bookmarks
 # prometheus-metrics

compose.yaml

@@ -81,6 +81,7 @@ services:
       - "--pdfengines-rotate-engines=${PDFENGINES_ROTATE_ENGINES}"
       - "--pdfengines-embed-engines=${PDFENGINES_EMBED_ENGINES}"
       - "--pdfengines-embed-metadata-engines=${PDFENGINES_EMBED_METADATA_ENGINES}"
+      - "--pdfengines-factur-x-engines=${PDFENGINES_FACTUR_X_ENGINES}"
       - "--pdfengines-disable-routes=${PDFENGINES_DISABLE_ROUTES}"
       - "--prometheus-namespace=${PROMETHEUS_NAMESPACE}"
       - "--prometheus-collect-interval=${PROMETHEUS_COLLECT_INTERVAL}"

pkg/gotenberg/mocks.go

@@ -60,6 +60,7 @@ type PdfEngineMock struct {
 	WatermarkMock          func(ctx context.Context, logger *slog.Logger, inputPath string, stamp Stamp) error
 	StampMock              func(ctx context.Context, logger *slog.Logger, inputPath string, stamp Stamp) error
 	RotateMock             func(ctx context.Context, logger *slog.Logger, inputPath string, angle int, pages string) error
+	InjectFacturXXMPMock   func(ctx context.Context, logger *slog.Logger, facturX FacturX, inputPath string) error
 }
 
 func (engine *PdfEngineMock) Merge(ctx context.Context, logger *slog.Logger, inputPaths []string, outputPath string) error {
@@ -122,6 +123,10 @@ func (engine *PdfEngineMock) Rotate(ctx context.Context, logger *slog.Logger, in
 	return engine.RotateMock(ctx, logger, inputPath, angle, pages)
 }
 
+func (engine *PdfEngineMock) InjectFacturXXMP(ctx context.Context, logger *slog.Logger, facturX FacturX, inputPath string) error {
+	return engine.InjectFacturXXMPMock(ctx, logger, facturX, inputPath)
+}
+
 // PdfEngineProviderMock is a mock for the [PdfEngineProvider] interface.
 type PdfEngineProviderMock struct {
 	PdfEngineMock func() (PdfEngine, error)

pkg/gotenberg/pdfengine.go

@@ -35,6 +35,10 @@ var (
 	// ErrPdfRotateAngleNotSupported is returned when the rotation angle is
 	// not supported.
 	ErrPdfRotateAngleNotSupported = errors.New("rotation angle not supported")
+
+	// ErrPdfFacturXValueNotSupported is returned when a Factur-X field value
+	// (e.g., an unknown conformance level or document type) is not supported.
+	ErrPdfFacturXValueNotSupported = errors.New("Factur-X value not supported")
 )
 
 // PdfEngineInvalidArgsError represents an error returned by a PDF engine when
@@ -151,6 +155,55 @@ type Bookmark struct {
 	Children []Bookmark `json:"children,omitempty"`
 }
 
+const (
+	// FacturXConformanceMinimum represents the MINIMUM Factur-X conformance level.
+	FacturXConformanceMinimum string = "MINIMUM"
+
+	// FacturXConformanceBasicWL represents the BASIC WL Factur-X conformance level.
+	FacturXConformanceBasicWL string = "BASIC WL"
+
+	// FacturXConformanceBasic represents the BASIC Factur-X conformance level.
+	FacturXConformanceBasic string = "BASIC"
+
+	// FacturXConformanceEN16931 represents the EN 16931 Factur-X conformance level.
+	FacturXConformanceEN16931 string = "EN 16931"
+
+	// FacturXConformanceExtended represents the EXTENDED Factur-X conformance level.
+	FacturXConformanceExtended string = "EXTENDED"
+
+	// FacturXConformanceXRechnung represents the XRECHNUNG Factur-X conformance level.
+	FacturXConformanceXRechnung string = "XRECHNUNG"
+
+	// FacturXDocumentTypeInvoice represents the INVOICE Factur-X document type.
+	FacturXDocumentTypeInvoice string = "INVOICE"
+
+	// FacturXDocumentTypeOrder represents the ORDER Factur-X document type.
+	FacturXDocumentTypeOrder string = "ORDER"
+
+	// FacturXDocumentTypeOrderResponse represents the ORDER_RESPONSE Factur-X document type.
+	FacturXDocumentTypeOrderResponse string = "ORDER_RESPONSE"
+
+	// FacturXDocumentTypeOrderChange represents the ORDER_CHANGE Factur-X document type.
+	FacturXDocumentTypeOrderChange string = "ORDER_CHANGE"
+)
+
+// FacturX gathers the properties required by the Factur-X/ZUGFeRD standard for
+// the document-level XMP metadata packet of a PDF/A-3.
+type FacturX struct {
+	// ConformanceLevel is one of the FacturXConformance* values.
+	ConformanceLevel string
+
+	// DocumentType is one of the FacturXDocumentType* values.
+	DocumentType string
+
+	// DocumentFileName is the name of the embedded XML invoice (e.g.,
+	// "factur-x.xml").
+	DocumentFileName string
+
+	// Version is the Factur-X version (e.g., "1.0").
+	Version string
+}
+
 // PdfEngine provides an interface for operations on PDFs. Implementations
 // can use various tools like PDFtk, or implement functionality directly in
 // Go.
@@ -216,6 +269,12 @@ type PdfEngine interface {
 	// Rotate rotates pages of a PDF file by the given angle (90, 180, 270).
 	// If pages is empty, all pages are rotated.
 	Rotate(ctx context.Context, logger *slog.Logger, inputPath string, angle int, pages string) error
+
+	// InjectFacturXXMP injects Factur-X/ZUGFeRD XMP metadata into the
+	// document-level XMP packet (Catalog /Metadata stream) of a PDF/A-3. It
+	// registers the fx namespace, the four fx properties, and the matching
+	// PDF/A extension schema so the result stays PDF/A-valid.
+	InjectFacturXXMP(ctx context.Context, logger *slog.Logger, facturX FacturX, inputPath string) error
 }
 
 // PdfEngineProvider offers an interface to instantiate a [PdfEngine].

pkg/modules/api/formdata.go

@@ -424,6 +424,89 @@ func (form *FormData) EmbedsMetadata(target *map[string]map[string]string) *Form
 	return form
 }
 
+// FacturX parses the "facturx" form field (a JSON string) into a
+// [gotenberg.FacturX]. The "conformanceLevel" property is mandatory; the
+// "documentType", "version", and "documentFileName" properties default to
+// "INVOICE", "1.0", and "factur-x.xml" respectively. It leaves the target
+// untouched when the field is absent.
+//
+//	var facturX gotenberg.FacturX
+//
+//	ctx.FormData().FacturX(&facturX, false)
+func (form *FormData) FacturX(target *gotenberg.FacturX, mandatory bool) *FormData {
+	if form.errors != nil {
+		return form
+	}
+
+	val, ok := form.values["facturx"]
+	if !ok || len(val) == 0 || val[0] == "" {
+		if mandatory {
+			form.append(fmt.Errorf("form field '%s' is required", "facturx"))
+		}
+		return form
+	}
+
+	var parsed struct {
+		ConformanceLevel string `json:"conformanceLevel"`
+		DocumentType     string `json:"documentType"`
+		DocumentFileName string `json:"documentFileName"`
+		Version          string `json:"version"`
+	}
+
+	err := json.Unmarshal([]byte(val[0]), &parsed)
+	if err != nil {
+		form.append(fmt.Errorf("form field 'facturx' is invalid: %w", err))
+		return form
+	}
+
+	facturX := gotenberg.FacturX{
+		ConformanceLevel: parsed.ConformanceLevel,
+		DocumentType:     parsed.DocumentType,
+		DocumentFileName: parsed.DocumentFileName,
+		Version:          parsed.Version,
+	}
+
+	if facturX.DocumentType == "" {
+		facturX.DocumentType = gotenberg.FacturXDocumentTypeInvoice
+	}
+
+	if facturX.Version == "" {
+		facturX.Version = "1.0"
+	}
+
+	if facturX.DocumentFileName == "" {
+		facturX.DocumentFileName = "factur-x.xml"
+	}
+
+	switch facturX.ConformanceLevel {
+	case gotenberg.FacturXConformanceMinimum,
+		gotenberg.FacturXConformanceBasicWL,
+		gotenberg.FacturXConformanceBasic,
+		gotenberg.FacturXConformanceEN16931,
+		gotenberg.FacturXConformanceExtended,
+		gotenberg.FacturXConformanceXRechnung:
+	case "":
+		form.append(errors.New("form field 'facturx' is invalid: 'conformanceLevel' is required"))
+		return form
+	default:
+		form.append(fmt.Errorf("form field 'facturx' is invalid: unsupported 'conformanceLevel' '%s'", facturX.ConformanceLevel))
+		return form
+	}
+
+	switch facturX.DocumentType {
+	case gotenberg.FacturXDocumentTypeInvoice,
+		gotenberg.FacturXDocumentTypeOrder,
+		gotenberg.FacturXDocumentTypeOrderResponse,
+		gotenberg.FacturXDocumentTypeOrderChange:
+	default:
+		form.append(fmt.Errorf("form field 'facturx' is invalid: unsupported 'documentType' '%s'", facturX.DocumentType))
+		return form
+	}
+
+	*target = facturX
+	return form
+}
+
 // MandatoryPaths binds the absolute paths of form data files, according to a
 // list of file extensions, to a string slice variable. It populates an error
 // if there is no file for given file extensions.

pkg/modules/api/formdata_test.go

@@ -7,6 +7,8 @@ import (
 	"reflect"
 	"testing"
 	"time"
+
+	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 )
 
 func TestFormData_Validate(t *testing.T) {
@@ -1783,3 +1785,111 @@ func TestFormData_Embeds(t *testing.T) {
 		t.Errorf("expected %v but got %v", expected, actual)
 	}
 }
+
+func TestFormData_FacturX(t *testing.T) {
+	for _, tc := range []struct {
+		scenario  string
+		form      *FormData
+		mandatory bool
+		expect    gotenberg.FacturX
+		expectErr bool
+	}{
+		{
+			scenario:  "key does not exist, not mandatory",
+			form:      &FormData{},
+			mandatory: false,
+			expect:    gotenberg.FacturX{},
+		},
+		{
+			scenario:  "key does not exist, mandatory",
+			form:      &FormData{},
+			mandatory: true,
+			expectErr: true,
+		},
+		{
+			scenario: "all fields provided",
+			form: &FormData{
+				values: map[string][]string{
+					"facturx": {`{"conformanceLevel":"EXTENDED","documentType":"ORDER","documentFileName":"order.xml","version":"2.0"}`},
+				},
+			},
+			expect: gotenberg.FacturX{
+				ConformanceLevel: gotenberg.FacturXConformanceExtended,
+				DocumentType:     gotenberg.FacturXDocumentTypeOrder,
+				DocumentFileName: "order.xml",
+				Version:          "2.0",
+			},
+		},
+		{
+			scenario: "only conformance level, defaults applied",
+			form: &FormData{
+				values: map[string][]string{
+					"facturx": {`{"conformanceLevel":"EN 16931"}`},
+				},
+			},
+			expect: gotenberg.FacturX{
+				ConformanceLevel: gotenberg.FacturXConformanceEN16931,
+				DocumentType:     gotenberg.FacturXDocumentTypeInvoice,
+				DocumentFileName: "factur-x.xml",
+				Version:          "1.0",
+			},
+		},
+		{
+			scenario: "invalid JSON",
+			form: &FormData{
+				values: map[string][]string{
+					"facturx": {`{not json`},
+				},
+			},
+			expectErr: true,
+		},
+		{
+			scenario: "missing conformance level",
+			form: &FormData{
+				values: map[string][]string{
+					"facturx": {`{"documentType":"INVOICE"}`},
+				},
+			},
+			expectErr: true,
+		},
+		{
+			scenario: "unsupported conformance level",
+			form: &FormData{
+				values: map[string][]string{
+					"facturx": {`{"conformanceLevel":"FOO"}`},
+				},
+			},
+			expectErr: true,
+		},
+		{
+			scenario: "unsupported document type",
+			form: &FormData{
+				values: map[string][]string{
+					"facturx": {`{"conformanceLevel":"BASIC","documentType":"RECEIPT"}`},
+				},
+			},
+			expectErr: true,
+		},
+	} {
+		t.Run(tc.scenario, func(t *testing.T) {
+			var actual gotenberg.FacturX
+
+			tc.form.FacturX(&actual, tc.mandatory)
+
+			if tc.expectErr {
+				if tc.form.errors == nil {
+					t.Error("expected an error but got none")
+				}
+				return
+			}
+
+			if tc.form.errors != nil {
+				t.Errorf("expected no error but got: %v", tc.form.errors)
+			}
+
+			if !reflect.DeepEqual(actual, tc.expect) {
+				t.Errorf("expected %+v but got %+v", tc.expect, actual)
+			}
+		})
+	}
+}

pkg/modules/chromium/routes.go

@@ -454,6 +454,7 @@ func convertUrlRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 			stampFile := pdfengines.FormDataPdfStampFile(form)
 			rotateAngle, rotatePages := pdfengines.FormDataPdfRotate(form, false)
 			embedsMetadata := pdfengines.FormDataPdfEmbedsMetadata(form)
+			facturX := pdfengines.FormDataPdfFacturX(form, false)
 
 			var url string
 			err := form.
@@ -477,7 +478,7 @@ func convertUrlRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 				return fmt.Errorf("validate stamp: %w", err)
 			}
 
-			err = convertUrl(ctx, chromium, engine, url, options, mode, pdfFormats, metadata, userPassword, ownerPassword, embedPaths, embedsMetadata, watermark, stamp, rotateAngle, rotatePages)
+			err = convertUrl(ctx, chromium, engine, url, options, mode, pdfFormats, metadata, userPassword, ownerPassword, embedPaths, embedsMetadata, facturX, watermark, stamp, rotateAngle, rotatePages)
 			if err != nil {
 				return fmt.Errorf("convert URL to PDF: %w", err)
 			}
@@ -542,6 +543,7 @@ func convertHtmlRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 			stampFile := pdfengines.FormDataPdfStampFile(form)
 			rotateAngle, rotatePages := pdfengines.FormDataPdfRotate(form, false)
 			embedsMetadata := pdfengines.FormDataPdfEmbedsMetadata(form)
+			facturX := pdfengines.FormDataPdfFacturX(form, false)
 
 			var inputPath string
 			err := form.
@@ -562,7 +564,7 @@ func convertHtmlRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 
 			url := fmt.Sprintf("file://%s", inputPath)
 			options.AllowedFilePrefixes = []string{ctx.DirPath()}
-			err = convertUrl(ctx, chromium, engine, url, options, mode, pdfFormats, metadata, userPassword, ownerPassword, embedPaths, embedsMetadata, watermark, stamp, rotateAngle, rotatePages)
+			err = convertUrl(ctx, chromium, engine, url, options, mode, pdfFormats, metadata, userPassword, ownerPassword, embedPaths, embedsMetadata, facturX, watermark, stamp, rotateAngle, rotatePages)
 			if err != nil {
 				return fmt.Errorf("convert HTML to PDF: %w", err)
 			}
@@ -624,6 +626,7 @@ func convertMarkdownRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 			stampFile := pdfengines.FormDataPdfStampFile(form)
 			rotateAngle, rotatePages := pdfengines.FormDataPdfRotate(form, false)
 			embedsMetadata := pdfengines.FormDataPdfEmbedsMetadata(form)
+			facturX := pdfengines.FormDataPdfFacturX(form, false)
 
 			var (
 				inputPath     string
@@ -653,7 +656,7 @@ func convertMarkdownRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 			}
 
 			options.AllowedFilePrefixes = []string{ctx.DirPath()}
-			err = convertUrl(ctx, chromium, engine, url, options, mode, pdfFormats, metadata, userPassword, ownerPassword, embedPaths, embedsMetadata, watermark, stamp, rotateAngle, rotatePages)
+			err = convertUrl(ctx, chromium, engine, url, options, mode, pdfFormats, metadata, userPassword, ownerPassword, embedPaths, embedsMetadata, facturX, watermark, stamp, rotateAngle, rotatePages)
 			if err != nil {
 				return fmt.Errorf("convert markdown to PDF: %w", err)
 			}
@@ -778,7 +781,7 @@ func markdownToHtml(ctx *api.Context, inputPath string, markdownPaths []string)
 	return fmt.Sprintf("file://%s", inputPath), nil
 }
 
-func convertUrl(ctx *api.Context, chromium Api, engine gotenberg.PdfEngine, url string, options PdfOptions, mode gotenberg.SplitMode, pdfFormats gotenberg.PdfFormats, metadata map[string]any, userPassword, ownerPassword string, embedPaths []string, embedsMetadata map[string]map[string]string, watermark, stamp gotenberg.Stamp, rotateAngle int, rotatePages string) error {
+func convertUrl(ctx *api.Context, chromium Api, engine gotenberg.PdfEngine, url string, options PdfOptions, mode gotenberg.SplitMode, pdfFormats gotenberg.PdfFormats, metadata map[string]any, userPassword, ownerPassword string, embedPaths []string, embedsMetadata map[string]map[string]string, facturX gotenberg.FacturX, watermark, stamp gotenberg.Stamp, rotateAngle int, rotatePages string) error {
 	outputPath := ctx.GeneratePath(".pdf")
 	// See https://github.com/gotenberg/gotenberg/issues/1130.
 	filename := ctx.OutputFilename(outputPath)
@@ -887,6 +890,11 @@ func convertUrl(ctx *api.Context, chromium Api, engine gotenberg.PdfEngine, url
 		return fmt.Errorf("set embeds metadata: %w", err)
 	}
 
+	err = pdfengines.InjectFacturXXMPStub(ctx, engine, facturX, convertOutputPaths)
+	if err != nil {
+		return fmt.Errorf("inject Factur-X XMP: %w", err)
+	}
+
 	err = pdfengines.EncryptPdfStub(ctx, engine, userPassword, ownerPassword, convertOutputPaths)
 	if err != nil {
 		return fmt.Errorf("encrypt PDFs: %w", err)

pkg/modules/exiftool/exiftool.go

@@ -523,6 +523,11 @@ func (engine *ExifTool) EmbedFilesMetadata(ctx context.Context, logger *slog.Log
 	return fmt.Errorf("set embeds metadata with ExifTool: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
+// InjectFacturXXMP is not available in this implementation.
+func (engine *ExifTool) InjectFacturXXMP(ctx context.Context, logger *slog.Logger, facturX gotenberg.FacturX, inputPath string) error {
+	return fmt.Errorf("inject Factur-X XMP with ExifTool: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
 // Interface guards.
 var (
 	_ gotenberg.Module      = (*ExifTool)(nil)

pkg/modules/libreoffice/pdfengine/pdfengine.go

@@ -135,6 +135,11 @@ func (engine *LibreOfficePdfEngine) Rotate(ctx context.Context, logger *slog.Log
 	return fmt.Errorf("rotate PDF with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
+// InjectFacturXXMP is not available in this implementation.
+func (engine *LibreOfficePdfEngine) InjectFacturXXMP(ctx context.Context, logger *slog.Logger, facturX gotenberg.FacturX, inputPath string) error {
+	return fmt.Errorf("inject Factur-X XMP with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
 // Interface guards.
 var (
 	_ gotenberg.Module      = (*LibreOfficePdfEngine)(nil)

pkg/modules/libreoffice/routes.go

@@ -38,6 +38,7 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 			stampFile := pdfengines.FormDataPdfStampFile(form)
 			angle, rotatePages := pdfengines.FormDataPdfRotate(form, false)
 			embedsMetadata := pdfengines.FormDataPdfEmbedsMetadata(form)
+			facturX := pdfengines.FormDataPdfFacturX(form, false)
 
 			zeroValuedSplitMode := gotenberg.SplitMode{}
 
@@ -503,6 +504,11 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 				return fmt.Errorf("set embeds metadata: %w", err)
 			}
 
+			err = pdfengines.InjectFacturXXMPStub(ctx, engine, facturX, outputPaths)
+			if err != nil {
+				return fmt.Errorf("inject Factur-X XMP: %w", err)
+			}
+
 			err = pdfengines.EncryptPdfStub(ctx, engine, userPassword, ownerPassword, outputPaths)
 			if err != nil {
 				return fmt.Errorf("encrypt PDFs: %w", err)

pkg/modules/pdfcpu/pdfcpu.go

@@ -452,6 +452,11 @@ func (engine *PdfCpu) EmbedFilesMetadata(ctx context.Context, logger *slog.Logge
 	return fmt.Errorf("set embeds metadata with pdfcpu: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
+// InjectFacturXXMP is not available in this implementation.
+func (engine *PdfCpu) InjectFacturXXMP(ctx context.Context, logger *slog.Logger, facturX gotenberg.FacturX, inputPath string) error {
+	return fmt.Errorf("inject Factur-X XMP with pdfcpu: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
 // EmbedFiles embeds files into a PDF. All files are embedded as file attachments
 // without modifying the main PDF content.
 func (engine *PdfCpu) EmbedFiles(ctx context.Context, logger *slog.Logger, filePaths []string, inputPath string) error {

pkg/modules/pdfengines/multi.go

@@ -28,6 +28,7 @@ type multiPdfEngines struct {
 	watermarkEngines      []gotenberg.PdfEngine
 	stampEngines          []gotenberg.PdfEngine
 	rotateEngines         []gotenberg.PdfEngine
+	facturXEngines        []gotenberg.PdfEngine
 }
 
 func newMultiPdfEngines(
@@ -44,7 +45,8 @@ func newMultiPdfEngines(
 	writeBookmarksEngines,
 	watermarkEngines,
 	stampEngines,
-	rotateEngines []gotenberg.PdfEngine,
+	rotateEngines,
+	facturXEngines []gotenberg.PdfEngine,
 ) *multiPdfEngines {
 	return &multiPdfEngines{
 		mergeEngines:          mergeEngines,
@@ -61,6 +63,7 @@ func newMultiPdfEngines(
 		watermarkEngines:      watermarkEngines,
 		stampEngines:          stampEngines,
 		rotateEngines:         rotateEngines,
+		facturXEngines:        facturXEngines,
 	}
 }
 
@@ -320,6 +323,17 @@ func (multi *multiPdfEngines) EmbedFilesMetadata(ctx context.Context, logger *sl
 	)
 }
 
+// InjectFacturXXMP injects Factur-X/ZUGFeRD XMP metadata using the first
+// available engine that supports it.
+func (multi *multiPdfEngines) InjectFacturXXMP(ctx context.Context, logger *slog.Logger, facturX gotenberg.FacturX, inputPath string) error {
+	return runWithFallbackVoid(ctx, "pdfengines.InjectFacturXXMP", multi.facturXEngines,
+		func(ctx context.Context, engine gotenberg.PdfEngine) error {
+			return engine.InjectFacturXXMP(ctx, logger, facturX, inputPath)
+		},
+		func(err error) error { return fmt.Errorf("inject Factur-X XMP with multi PDF engines: %w", err) },
+	)
+}
+
 // Interface guards.
 var (
 	_ gotenberg.PdfEngine = (*multiPdfEngines)(nil)

pkg/modules/pdfengines/pdfengines.go

@@ -42,6 +42,7 @@ type PdfEngines struct {
 	watermarkNames      []string
 	stampNames          []string
 	rotateNames         []string
+	facturXNames        []string
 	engines             []gotenberg.PdfEngine
 	disableRoutes       bool
 }
@@ -66,6 +67,7 @@ func (mod *PdfEngines) Descriptor() gotenberg.ModuleDescriptor {
 			fs.StringSlice("pdfengines-watermark-engines", []string{"pdfcpu", "pdftk"}, "Set the PDF engines and their order for the watermark feature - empty means all")
 			fs.StringSlice("pdfengines-stamp-engines", []string{"pdfcpu", "pdftk"}, "Set the PDF engines and their order for the stamp feature - empty means all")
 			fs.StringSlice("pdfengines-rotate-engines", []string{"pdfcpu", "pdftk"}, "Set the PDF engines and their order for the rotate feature - empty means all")
+			fs.StringSlice("pdfengines-factur-x-engines", []string{"qpdf"}, "Set the PDF engines and their order for the Factur-X XMP feature - empty means all")
 			fs.Bool("pdfengines-disable-routes", false, "Disable the routes")
 
 			// Deprecated flags.
@@ -99,6 +101,7 @@ func (mod *PdfEngines) Provision(ctx *gotenberg.Context) error {
 	watermarkNames := flags.MustStringSlice("pdfengines-watermark-engines")
 	stampNames := flags.MustStringSlice("pdfengines-stamp-engines")
 	rotateNames := flags.MustStringSlice("pdfengines-rotate-engines")
+	facturXNames := flags.MustStringSlice("pdfengines-factur-x-engines")
 	mod.disableRoutes = flags.MustBool("pdfengines-disable-routes")
 
 	engines, err := ctx.Modules(new(gotenberg.PdfEngine))
@@ -195,6 +198,11 @@ func (mod *PdfEngines) Provision(ctx *gotenberg.Context) error {
 		mod.rotateNames = rotateNames
 	}
 
+	mod.facturXNames = defaultNames
+	if len(facturXNames) > 0 {
+		mod.facturXNames = facturXNames
+	}
+
 	return nil
 }
 
@@ -250,6 +258,7 @@ func (mod *PdfEngines) Validate() error {
 	findNonExistingEngines(mod.watermarkNames)
 	findNonExistingEngines(mod.stampNames)
 	findNonExistingEngines(mod.rotateNames)
+	findNonExistingEngines(mod.facturXNames)
 
 	if len(nonExistingEngines) == 0 {
 		return nil
@@ -276,6 +285,7 @@ func (mod *PdfEngines) SystemMessages() []string {
 		fmt.Sprintf("watermark engines - %s", strings.Join(mod.watermarkNames, " ")),
 		fmt.Sprintf("stamp engines - %s", strings.Join(mod.stampNames, " ")),
 		fmt.Sprintf("rotate engines - %s", strings.Join(mod.rotateNames, " ")),
+		fmt.Sprintf("Factur-X engines - %s", strings.Join(mod.facturXNames, " ")),
 	}
 }
 
@@ -310,6 +320,7 @@ func (mod *PdfEngines) PdfEngine() (gotenberg.PdfEngine, error) {
 		engines(mod.watermarkNames),
 		engines(mod.stampNames),
 		engines(mod.rotateNames),
+		engines(mod.facturXNames),
 	), nil
 }
 
@@ -340,6 +351,7 @@ func (mod *PdfEngines) Routes() ([]api.Route, error) {
 		watermarkRoute(engine),
 		stampRoute(engine),
 		rotateRoute(engine),
+		facturXRoute(engine),
 	}, nil
 }
 

pkg/modules/pdfengines/routes.go

@@ -467,6 +467,31 @@ func EmbedFilesMetadataStub(ctx *api.Context, engine gotenberg.PdfEngine, metada
 	return nil
 }
 
+// FormDataPdfFacturX extracts Factur-X parameters from form data.
+// The "facturx" field is a JSON string with the four fx properties.
+func FormDataPdfFacturX(form *api.FormData, mandatory bool) gotenberg.FacturX {
+	var facturX gotenberg.FacturX
+	form.FacturX(&facturX, mandatory)
+	return facturX
+}
+
+// InjectFacturXXMPStub injects Factur-X XMP metadata into PDF files. If the
+// Factur-X data is not set, it does nothing.
+func InjectFacturXXMPStub(ctx *api.Context, engine gotenberg.PdfEngine, facturX gotenberg.FacturX, inputPaths []string) error {
+	if facturX.ConformanceLevel == "" {
+		return nil
+	}
+
+	for _, inputPath := range inputPaths {
+		err := engine.InjectFacturXXMP(ctx, ctx.Log(), facturX, inputPath)
+		if err != nil {
+			return fmt.Errorf("inject Factur-X XMP into PDF '%s': %w", inputPath, err)
+		}
+	}
+
+	return nil
+}
+
 // FormDataPdfEncrypt extracts encryption parameters from form data.
 func FormDataPdfEncrypt(form *api.FormData) (userPassword, ownerPassword string) {
 	form.String("userPassword", &userPassword, "")
@@ -707,6 +732,7 @@ func mergeRoute(engine gotenberg.PdfEngine) api.Route {
 			stampFile := FormDataPdfStampFile(form)
 			angle, rotatePages := FormDataPdfRotate(form, false)
 			embedsMetadata := FormDataPdfEmbedsMetadata(form)
+			facturX := FormDataPdfFacturX(form, false)
 
 			var inputPaths []string
 			var flatten bool
@@ -830,6 +856,11 @@ func mergeRoute(engine gotenberg.PdfEngine) api.Route {
 				return fmt.Errorf("set embeds metadata: %w", err)
 			}
 
+			err = InjectFacturXXMPStub(ctx, engine, facturX, outputPaths)
+			if err != nil {
+				return fmt.Errorf("inject Factur-X XMP: %w", err)
+			}
+
 			err = EncryptPdfStub(ctx, engine, userPassword, ownerPassword, outputPaths)
 			if err != nil {
 				return fmt.Errorf("encrypt PDFs: %w", err)
@@ -866,6 +897,7 @@ func splitRoute(engine gotenberg.PdfEngine) api.Route {
 			stampFile := FormDataPdfStampFile(form)
 			angle, rotatePages := FormDataPdfRotate(form, false)
 			embedsMetadata := FormDataPdfEmbedsMetadata(form)
+			facturX := FormDataPdfFacturX(form, false)
 
 			var inputPaths []string
 			var flatten bool
@@ -940,6 +972,11 @@ func splitRoute(engine gotenberg.PdfEngine) api.Route {
 				return fmt.Errorf("set embeds metadata: %w", err)
 			}
 
+			err = InjectFacturXXMPStub(ctx, engine, facturX, convertOutputPaths)
+			if err != nil {
+				return fmt.Errorf("inject Factur-X XMP: %w", err)
+			}
+
 			err = EncryptPdfStub(ctx, engine, userPassword, ownerPassword, convertOutputPaths)
 			if err != nil {
 				return fmt.Errorf("encrypt PDFs: %w", err)
@@ -1265,6 +1302,7 @@ func embedRoute(engine gotenberg.PdfEngine) api.Route {
 			form := ctx.FormData()
 			embedPaths := FormDataPdfEmbeds(form)
 			embedsMetadata := FormDataPdfEmbedsMetadata(form)
+			facturX := FormDataPdfFacturX(form, false)
 
 			var inputPaths []string
 			err := form.
@@ -1283,6 +1321,11 @@ func embedRoute(engine gotenberg.PdfEngine) api.Route {
 				return fmt.Errorf("set embeds metadata: %w", err)
 			}
 
+			err = InjectFacturXXMPStub(ctx, engine, facturX, inputPaths)
+			if err != nil {
+				return fmt.Errorf("inject Factur-X XMP: %w", err)
+			}
+
 			err = ctx.AddOutputPaths(inputPaths...)
 			if err != nil {
 				return fmt.Errorf("add output paths: %w", err)
@@ -1413,3 +1456,39 @@ func rotateRoute(engine gotenberg.PdfEngine) api.Route {
 		},
 	}
 }
+
+// facturXRoute returns an [api.Route] which injects Factur-X/ZUGFeRD XMP
+// metadata into PDF/A-3 files.
+func facturXRoute(engine gotenberg.PdfEngine) api.Route {
+	return api.Route{
+		Method:      http.MethodPost,
+		Path:        "/forms/pdfengines/factur-x",
+		IsMultipart: true,
+		Handler: func(c echo.Context) error {
+			ctx := c.Get("context").(*api.Context)
+
+			form := ctx.FormData()
+			facturX := FormDataPdfFacturX(form, true)
+
+			var inputPaths []string
+			err := form.
+				MandatoryPaths([]string{".pdf"}, &inputPaths).
+				Validate()
+			if err != nil {
+				return fmt.Errorf("validate form data: %w", err)
+			}
+
+			err = InjectFacturXXMPStub(ctx, engine, facturX, inputPaths)
+			if err != nil {
+				return fmt.Errorf("inject Factur-X XMP into PDFs: %w", err)
+			}
+
+			err = ctx.AddOutputPaths(inputPaths...)
+			if err != nil {
+				return fmt.Errorf("add output paths: %w", err)
+			}
+
+			return nil
+		},
+	}
+}

pkg/modules/pdftk/pdftk.go

@@ -500,6 +500,11 @@ func (engine *PdfTk) EmbedFilesMetadata(ctx context.Context, logger *slog.Logger
 	return fmt.Errorf("set embeds metadata with PDFtk: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
+// InjectFacturXXMP is not available in this implementation.
+func (engine *PdfTk) InjectFacturXXMP(ctx context.Context, logger *slog.Logger, facturX gotenberg.FacturX, inputPath string) error {
+	return fmt.Errorf("inject Factur-X XMP with PDFtk: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
 // Interface guards.
 var (
 	_ gotenberg.Module      = (*PdfTk)(nil)

pkg/modules/qpdf/facturx_test.go

@@ -0,0 +1,249 @@
+package qpdf
+
+import (
+	"errors"
+	"strings"
+	"testing"
+
+	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
+)
+
+func TestValidateFacturX(t *testing.T) {
+	valid := gotenberg.FacturX{
+		ConformanceLevel: gotenberg.FacturXConformanceEN16931,
+		DocumentType:     gotenberg.FacturXDocumentTypeInvoice,
+		DocumentFileName: "factur-x.xml",
+		Version:          "1.0",
+	}
+
+	tests := []struct {
+		name      string
+		mutate    func(f *gotenberg.FacturX)
+		wantError bool
+	}{
+		{name: "valid", mutate: func(*gotenberg.FacturX) {}},
+		{
+			name:   "valid BASIC WL conformance",
+			mutate: func(f *gotenberg.FacturX) { f.ConformanceLevel = gotenberg.FacturXConformanceBasicWL },
+		},
+		{
+			name:   "valid ORDER document type",
+			mutate: func(f *gotenberg.FacturX) { f.DocumentType = gotenberg.FacturXDocumentTypeOrder },
+		},
+		{
+			name:      "unsupported conformance level",
+			mutate:    func(f *gotenberg.FacturX) { f.ConformanceLevel = "FOO" },
+			wantError: true,
+		},
+		{
+			name:      "empty conformance level",
+			mutate:    func(f *gotenberg.FacturX) { f.ConformanceLevel = "" },
+			wantError: true,
+		},
+		{
+			name:      "unsupported document type",
+			mutate:    func(f *gotenberg.FacturX) { f.DocumentType = "RECEIPT" },
+			wantError: true,
+		},
+		{
+			name:      "empty document file name",
+			mutate:    func(f *gotenberg.FacturX) { f.DocumentFileName = "" },
+			wantError: true,
+		},
+		{
+			name:      "empty version",
+			mutate:    func(f *gotenberg.FacturX) { f.Version = "" },
+			wantError: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			facturX := valid
+			tt.mutate(&facturX)
+
+			err := validateFacturX(facturX)
+			if tt.wantError {
+				if err == nil {
+					t.Fatal("expected an error, got nil")
+				}
+				if !errors.Is(err, gotenberg.ErrPdfFacturXValueNotSupported) {
+					t.Errorf("expected ErrPdfFacturXValueNotSupported, got %v", err)
+				}
+				return
+			}
+
+			if err != nil {
+				t.Errorf("expected no error, got %v", err)
+			}
+		})
+	}
+}
+
+func TestFindMetadataStream(t *testing.T) {
+	tests := []struct {
+		name      string
+		input     string
+		wantKey   string
+		wantXMP   string
+		wantError bool
+	}{
+		{
+			name: "metadata stream found",
+			// "PFhtcD4=" is base64 for "<xmp>".
+			input:   `{"qpdf":[{},{"obj:1 0 R":{"value":{"/Type":"/Catalog","/Metadata":"4 0 R"}},"obj:4 0 R":{"stream":{"dict":{"/Type":"/Metadata","/Subtype":"/XML"},"data":"PHhtcD4="}}}]}`,
+			wantKey: "obj:4 0 R",
+			wantXMP: "<xmp>",
+		},
+		{
+			name:      "catalog without metadata reference",
+			input:     `{"qpdf":[{},{"obj:1 0 R":{"value":{"/Type":"/Catalog"}}}]}`,
+			wantError: true,
+		},
+		{
+			name:      "metadata object missing",
+			input:     `{"qpdf":[{},{"obj:1 0 R":{"value":{"/Type":"/Catalog","/Metadata":"4 0 R"}}}]}`,
+			wantError: true,
+		},
+		{
+			name:      "metadata object is not a stream",
+			input:     `{"qpdf":[{},{"obj:1 0 R":{"value":{"/Type":"/Catalog","/Metadata":"4 0 R"}},"obj:4 0 R":{"value":{"/Type":"/Metadata"}}}]}`,
+			wantError: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			objects, err := parsePdfObjects([]byte(tt.input))
+			if err != nil {
+				t.Fatalf("parse objects: %v", err)
+			}
+
+			key, dict, xmp, err := findMetadataStream(objects)
+			if tt.wantError {
+				if err == nil {
+					t.Fatal("expected an error, got nil")
+				}
+				return
+			}
+
+			if err != nil {
+				t.Fatalf("expected no error, got %v", err)
+			}
+			if key != tt.wantKey {
+				t.Errorf("key = %q, want %q", key, tt.wantKey)
+			}
+			if xmp != tt.wantXMP {
+				t.Errorf("xmp = %q, want %q", xmp, tt.wantXMP)
+			}
+			if dict == nil {
+				t.Error("expected a non-nil dict")
+			}
+		})
+	}
+}
+
+func TestInjectFacturXIntoXMP(t *testing.T) {
+	facturX := gotenberg.FacturX{
+		ConformanceLevel: gotenberg.FacturXConformanceEN16931,
+		DocumentType:     gotenberg.FacturXDocumentTypeInvoice,
+		DocumentFileName: "factur-x.xml",
+		Version:          "1.0",
+	}
+
+	// The packet a LibreOffice PDF/A-3b export produces: no pdfaExtension bag.
+	libreOfficeXMP := `<?xpacket begin="" id="W5M0MpCehiHzreSzNTczkc9d"?>
+<x:xmpmeta xmlns:x="adobe:ns:meta/">
+ <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+  <rdf:Description rdf:about="" xmlns:pdfaid="http://www.aiim.org/pdfa/ns/id/">
+   <pdfaid:part>3</pdfaid:part>
+   <pdfaid:conformance>B</pdfaid:conformance>
+  </rdf:Description>
+ </rdf:RDF>
+</x:xmpmeta>
+<?xpacket end="w"?>`
+
+	t.Run("creates extension schema when bag absent", func(t *testing.T) {
+		got, changed := injectFacturXIntoXMP(libreOfficeXMP, facturX)
+		if !changed {
+			t.Fatal("expected changed = true")
+		}
+		assertContains(t, got, facturXNamespaceURI)
+		assertContains(t, got, "<fx:ConformanceLevel>EN 16931</fx:ConformanceLevel>")
+		assertContains(t, got, "<fx:DocumentType>INVOICE</fx:DocumentType>")
+		assertContains(t, got, "<fx:DocumentFileName>factur-x.xml</fx:DocumentFileName>")
+		assertContains(t, got, "<fx:Version>1.0</fx:Version>")
+		assertContains(t, got, "pdfaExtension:schemas")
+		assertContains(t, got, "http://www.aiim.org/pdfa/ns/extension/")
+		// The fx blocks must land inside the RDF container.
+		if strings.Index(got, facturXNamespaceURI) > strings.LastIndex(got, "</rdf:RDF>") {
+			t.Error("fx content injected outside the rdf:RDF container")
+		}
+	})
+
+	t.Run("idempotent when fx already present", func(t *testing.T) {
+		once, _ := injectFacturXIntoXMP(libreOfficeXMP, facturX)
+		twice, changed := injectFacturXIntoXMP(once, facturX)
+		if changed {
+			t.Error("expected changed = false on a packet that already declares fx")
+		}
+		if twice != once {
+			t.Error("expected the packet to be left untouched")
+		}
+		if strings.Count(twice, "<pdfaExtension:schemas>") != 1 {
+			t.Error("expected exactly one pdfaExtension:schemas declaration")
+		}
+	})
+
+	t.Run("appends entry to an existing bag", func(t *testing.T) {
+		withBag := `<x:xmpmeta xmlns:x="adobe:ns:meta/">
+ <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+  <rdf:Description rdf:about="" xmlns:pdfaExtension="http://www.aiim.org/pdfa/ns/extension/" xmlns:pdfaSchema="http://www.aiim.org/pdfa/ns/schema#" xmlns:pdfaProperty="http://www.aiim.org/pdfa/ns/property#">
+   <pdfaExtension:schemas>
+    <rdf:Bag>
+     <rdf:li rdf:parseType="Resource"><pdfaSchema:prefix>other</pdfaSchema:prefix></rdf:li>
+    </rdf:Bag>
+   </pdfaExtension:schemas>
+  </rdf:Description>
+ </rdf:RDF>
+</x:xmpmeta>`
+		got, changed := injectFacturXIntoXMP(withBag, facturX)
+		if !changed {
+			t.Fatal("expected changed = true")
+		}
+		assertContains(t, got, facturXNamespaceURI)
+		if strings.Count(got, "<pdfaExtension:schemas>") != 1 {
+			t.Error("expected the existing pdfaExtension:schemas bag to be reused, not duplicated")
+		}
+		if strings.Count(got, "<pdfaSchema:prefix>") != 2 {
+			t.Error("expected both the existing and the fx schema entries")
+		}
+	})
+
+	t.Run("no rdf:RDF anchor leaves packet unchanged", func(t *testing.T) {
+		got, changed := injectFacturXIntoXMP("not an xmp packet", facturX)
+		if changed {
+			t.Error("expected changed = false")
+		}
+		if got != "not an xmp packet" {
+			t.Error("expected the packet to be left untouched")
+		}
+	})
+
+	t.Run("escapes runtime values", func(t *testing.T) {
+		escaped := facturX
+		escaped.DocumentFileName = "a&b<c>.xml"
+		got, _ := injectFacturXIntoXMP(libreOfficeXMP, escaped)
+		assertContains(t, got, "a&amp;b&lt;c&gt;.xml")
+		if strings.Contains(got, "<fx:DocumentFileName>a&b<c>.xml") {
+			t.Error("expected the document file name to be XML-escaped")
+		}
+	})
+}
+
+func assertContains(t *testing.T, haystack, needle string) {
+	t.Helper()
+	if !strings.Contains(haystack, needle) {
+		t.Errorf("expected output to contain %q", needle)
+	}
+}

pkg/modules/qpdf/qpdf.go

@@ -3,7 +3,9 @@ package qpdf
 import (
 	"bytes"
 	"context"
+	"encoding/base64"
 	"encoding/json"
+	"encoding/xml"
 	"errors"
 	"fmt"
 	"log/slog"
@@ -527,8 +529,10 @@ func patchCatalogAF(catalogRef string, catalogValue map[string]any, filespecRefs
 }
 
 // writeAndApplyUpdate marshals the update objects as QPDF JSON v2, writes
-// them to a temp file, and applies the update via --update-from-json.
+// them to a temp file, and applies the update via --update-from-json. extraArgs
-func (engine *QPdf) writeAndApplyUpdate(ctx context.Context, logger *slog.Logger, inputPath string, updateObjects map[string]any) error {
+// are appended to the QPDF command (e.g., --json-stream-data=inline when the
+// update replaces stream data).
+func (engine *QPdf) writeAndApplyUpdate(ctx context.Context, logger *slog.Logger, inputPath string, updateObjects map[string]any, extraArgs ...string) error {
 	updateJSON := map[string]any{
 		"qpdf": []any{
 			map[string]any{
@@ -560,9 +564,10 @@ func (engine *QPdf) writeAndApplyUpdate(ctx context.Context, logger *slog.Logger
 		return fmt.Errorf("close temp file: %w", err)
 	}
 
-	updateArgs := make([]string, 0, 5+len(engine.globalArgs))
+	updateArgs := make([]string, 0, 5+len(engine.globalArgs)+len(extraArgs))
 	updateArgs = append(updateArgs, inputPath)
 	updateArgs = append(updateArgs, engine.globalArgs...)
+	updateArgs = append(updateArgs, extraArgs...)
 	updateArgs = append(updateArgs, "--newline-before-endstream")
 	updateArgs = append(updateArgs, "--update-from-json="+tmpFile.Name())
 	updateArgs = append(updateArgs, "--replace-input")
@@ -635,6 +640,322 @@ func stripQpdfStringPrefix(s string) string {
 	return s
 }
 
+// facturXNamespaceURI is the Factur-X/ZUGFeRD XMP namespace required by strict
+// validators.
+const facturXNamespaceURI = "urn:factur-x:pdfa:CrossIndustryDocument:invoice:1p0#"
+
+// InjectFacturXXMP injects Factur-X/ZUGFeRD XMP metadata into the document-level
+// XMP packet (Catalog /Metadata stream) of a PDF/A-3 using QPDF's JSON
+// manipulation. It reads the existing XMP packet, splices in the fx
+// rdf:Description plus the PDF/A extension-schema declaration, and writes the
+// stream back uncompressed so the document stays PDF/A-valid.
+//
+// It assumes the input already carries a Catalog /Metadata stream (always true
+// for a LibreOffice PDF/A export). The injection is idempotent: a packet that
+// already declares the fx namespace is left untouched.
+func (engine *QPdf) InjectFacturXXMP(ctx context.Context, logger *slog.Logger, facturX gotenberg.FacturX, inputPath string) error {
+	ctx, span := gotenberg.Tracer().Start(ctx, "qpdf.InjectFacturXXMP",
+		trace.WithSpanKind(trace.SpanKindClient),
+		trace.WithAttributes(semconv.ServerAddress(engine.binPath)),
+	)
+	defer span.End()
+
+	err := validateFacturX(facturX)
+	if err != nil {
+		span.RecordError(err)
+		span.SetStatus(codes.Error, err.Error())
+		return err
+	}
+
+	logger.DebugContext(ctx, fmt.Sprintf("injecting Factur-X XMP into %s with QPDF", inputPath))
+
+	args := append([]string{inputPath}, engine.globalArgs...)
+	args = append(args, "--newline-before-endstream", "--json-output", "--json-stream-data=inline")
+
+	output, err := engine.execCaptureOutput(ctx, args...)
+	if err != nil {
+		err = fmt.Errorf("get PDF JSON with QPDF: %w", err)
+		span.RecordError(err)
+		span.SetStatus(codes.Error, err.Error())
+		return err
+	}
+
+	objects, err := parsePdfObjects(output)
+	if err != nil {
+		span.RecordError(err)
+		span.SetStatus(codes.Error, err.Error())
+		return err
+	}
+
+	metaKey, metaDict, xmp, err := findMetadataStream(objects)
+	if err != nil {
+		err = fmt.Errorf("locate XMP metadata stream: %w", err)
+		span.RecordError(err)
+		span.SetStatus(codes.Error, err.Error())
+		return err
+	}
+
+	newXmp, changed := injectFacturXIntoXMP(xmp, facturX)
+	if !changed {
+		logger.DebugContext(ctx, "Factur-X XMP already present, skipping injection")
+		span.SetStatus(codes.Ok, "")
+		return nil
+	}
+
+	// PDF/A requires the metadata stream to be uncompressed and unfiltered. We
+	// provide the decoded XMP as the new stream data, so any existing filter
+	// must be dropped and the length left for QPDF to recompute.
+	delete(metaDict, "/Filter")
+	delete(metaDict, "/DecodeParms")
+	delete(metaDict, "/Length")
+
+	updateObjects := map[string]any{
+		metaKey: map[string]any{
+			"stream": map[string]any{
+				"dict": metaDict,
+				"data": base64.StdEncoding.EncodeToString([]byte(newXmp)),
+			},
+		},
+	}
+
+	err = engine.writeAndApplyUpdate(ctx, logger, inputPath, updateObjects, "--json-stream-data=inline")
+	if err != nil {
+		span.RecordError(err)
+		span.SetStatus(codes.Error, err.Error())
+		return err
+	}
+
+	span.SetStatus(codes.Ok, "")
+	return nil
+}
+
+// validateFacturX checks the Factur-X fields against the supported values.
+func validateFacturX(facturX gotenberg.FacturX) error {
+	switch facturX.ConformanceLevel {
+	case gotenberg.FacturXConformanceMinimum,
+		gotenberg.FacturXConformanceBasicWL,
+		gotenberg.FacturXConformanceBasic,
+		gotenberg.FacturXConformanceEN16931,
+		gotenberg.FacturXConformanceExtended,
+		gotenberg.FacturXConformanceXRechnung:
+	default:
+		return fmt.Errorf("conformance level '%s': %w", facturX.ConformanceLevel, gotenberg.ErrPdfFacturXValueNotSupported)
+	}
+
+	switch facturX.DocumentType {
+	case gotenberg.FacturXDocumentTypeInvoice,
+		gotenberg.FacturXDocumentTypeOrder,
+		gotenberg.FacturXDocumentTypeOrderResponse,
+		gotenberg.FacturXDocumentTypeOrderChange:
+	default:
+		return fmt.Errorf("document type '%s': %w", facturX.DocumentType, gotenberg.ErrPdfFacturXValueNotSupported)
+	}
+
+	if facturX.DocumentFileName == "" {
+		return fmt.Errorf("document file name is empty: %w", gotenberg.ErrPdfFacturXValueNotSupported)
+	}
+
+	if facturX.Version == "" {
+		return fmt.Errorf("version is empty: %w", gotenberg.ErrPdfFacturXValueNotSupported)
+	}
+
+	return nil
+}
+
+// findMetadataStream locates the document-level XMP metadata stream referenced
+// by the Catalog /Metadata entry. It returns the object key (e.g. "obj:4 0 R"),
+// the stream dict, and the decoded XMP packet.
+func findMetadataStream(objects map[string]json.RawMessage) (string, map[string]any, string, error) {
+	var metadataRef string
+	for _, raw := range objects {
+		var obj map[string]json.RawMessage
+		if err := json.Unmarshal(raw, &obj); err != nil {
+			continue
+		}
+
+		valueRaw, ok := obj["value"]
+		if !ok {
+			continue
+		}
+
+		var value map[string]any
+		if err := json.Unmarshal(valueRaw, &value); err != nil {
+			continue
+		}
+
+		if typeVal, _ := value["/Type"].(string); typeVal == "/Catalog" {
+			metadataRef, _ = value["/Metadata"].(string)
+			break
+		}
+	}
+
+	if metadataRef == "" {
+		return "", nil, "", errors.New("no /Metadata reference in the catalog")
+	}
+
+	// References in values use the "4 0 R" form; object keys use "obj:4 0 R".
+	objKey := "obj:" + metadataRef
+	raw, ok := objects[objKey]
+	if !ok {
+		return "", nil, "", fmt.Errorf("metadata object '%s' not found", objKey)
+	}
+
+	var obj map[string]json.RawMessage
+	if err := json.Unmarshal(raw, &obj); err != nil {
+		return "", nil, "", fmt.Errorf("unmarshal metadata object: %w", err)
+	}
+
+	streamRaw, ok := obj["stream"]
+	if !ok {
+		return "", nil, "", errors.New("metadata object is not a stream")
+	}
+
+	var stream struct {
+		Dict map[string]any `json:"dict"`
+		Data string         `json:"data"`
+	}
+	if err := json.Unmarshal(streamRaw, &stream); err != nil {
+		return "", nil, "", fmt.Errorf("unmarshal metadata stream: %w", err)
+	}
+
+	decoded, err := base64.StdEncoding.DecodeString(stream.Data)
+	if err != nil {
+		return "", nil, "", fmt.Errorf("decode metadata stream data: %w", err)
+	}
+
+	dict := stream.Dict
+	if dict == nil {
+		dict = make(map[string]any)
+	}
+
+	return objKey, dict, string(decoded), nil
+}
+
+// injectFacturXIntoXMP splices the fx rdf:Description and the PDF/A
+// extension-schema declaration into an XMP packet. It returns the new packet and
+// whether a change was made (false when the fx namespace is already present).
+func injectFacturXIntoXMP(xmp string, facturX gotenberg.FacturX) (string, bool) {
+	if strings.Contains(xmp, facturXNamespaceURI) {
+		return xmp, false
+	}
+
+	anchor := strings.LastIndex(xmp, "</rdf:RDF>")
+	if anchor == -1 {
+		return xmp, false
+	}
+
+	insert := facturXDescription(facturX)
+
+	if strings.Contains(xmp, "pdfaExtension:schemas") {
+		// An extension-schema bag already exists (e.g. emitted by another tool):
+		// splice the fx Description, then append the fx schema entry into the bag.
+		spliced := xmp[:anchor] + insert + xmp[anchor:]
+		return injectSchemaIntoExistingBag(spliced), true
+	}
+
+	// No extension-schema bag yet (the LibreOffice PDF/A case): create the whole
+	// container alongside the fx Description.
+	insert += facturXExtensionSchema()
+	return xmp[:anchor] + insert + xmp[anchor:], true
+}
+
+// injectSchemaIntoExistingBag appends the fx schema entry into an existing
+// pdfaExtension:schemas bag.
+func injectSchemaIntoExistingBag(xmp string) string {
+	mi := strings.Index(xmp, "pdfaExtension:schemas")
+	if mi == -1 {
+		return xmp
+	}
+
+	bag := strings.Index(xmp[mi:], "<rdf:Bag")
+	if bag == -1 {
+		return xmp
+	}
+
+	gt := strings.Index(xmp[mi+bag:], ">")
+	if gt == -1 {
+		return xmp
+	}
+
+	pos := mi + bag + gt + 1
+	return xmp[:pos] + "\n" + facturXSchemaLi() + xmp[pos:]
+}
+
+// facturXDescription builds the fx rdf:Description carrying the runtime values.
+func facturXDescription(facturX gotenberg.FacturX) string {
+	return fmt.Sprintf(`  <rdf:Description rdf:about="" xmlns:fx="%s">
+   <fx:DocumentType>%s</fx:DocumentType>
+   <fx:DocumentFileName>%s</fx:DocumentFileName>
+   <fx:Version>%s</fx:Version>
+   <fx:ConformanceLevel>%s</fx:ConformanceLevel>
+  </rdf:Description>
+`,
+		facturXNamespaceURI,
+		xmlEscape(facturX.DocumentType),
+		xmlEscape(facturX.DocumentFileName),
+		xmlEscape(facturX.Version),
+		xmlEscape(facturX.ConformanceLevel),
+	)
+}
+
+// facturXExtensionSchema builds the rdf:Description that declares the PDF/A
+// extension schema for the fx namespace, including the namespace declarations.
+func facturXExtensionSchema() string {
+	return fmt.Sprintf(`  <rdf:Description rdf:about="" xmlns:pdfaExtension="http://www.aiim.org/pdfa/ns/extension/" xmlns:pdfaSchema="http://www.aiim.org/pdfa/ns/schema#" xmlns:pdfaProperty="http://www.aiim.org/pdfa/ns/property#">
+   <pdfaExtension:schemas>
+    <rdf:Bag>
+%s
+    </rdf:Bag>
+   </pdfaExtension:schemas>
+  </rdf:Description>
+`, facturXSchemaLi())
+}
+
+// facturXSchemaLi builds the rdf:li describing the fx schema and its four
+// properties. These are fixed schema definitions, not runtime invoice values.
+func facturXSchemaLi() string {
+	return fmt.Sprintf(`     <rdf:li rdf:parseType="Resource">
+      <pdfaSchema:schema>Factur-X PDFA Extension Schema</pdfaSchema:schema>
+      <pdfaSchema:namespaceURI>%s</pdfaSchema:namespaceURI>
+      <pdfaSchema:prefix>fx</pdfaSchema:prefix>
+      <pdfaSchema:property>
+       <rdf:Seq>
+        <rdf:li rdf:parseType="Resource">
+         <pdfaProperty:name>DocumentFileName</pdfaProperty:name>
+         <pdfaProperty:valueType>Text</pdfaProperty:valueType>
+         <pdfaProperty:category>external</pdfaProperty:category>
+         <pdfaProperty:description>name of the embedded XML invoice file</pdfaProperty:description>
+        </rdf:li>
+        <rdf:li rdf:parseType="Resource">
+         <pdfaProperty:name>DocumentType</pdfaProperty:name>
+         <pdfaProperty:valueType>Text</pdfaProperty:valueType>
+         <pdfaProperty:category>external</pdfaProperty:category>
+         <pdfaProperty:description>INVOICE</pdfaProperty:description>
+        </rdf:li>
+        <rdf:li rdf:parseType="Resource">
+         <pdfaProperty:name>Version</pdfaProperty:name>
+         <pdfaProperty:valueType>Text</pdfaProperty:valueType>
+         <pdfaProperty:category>external</pdfaProperty:category>
+         <pdfaProperty:description>The actual version of the Factur-X XML schema</pdfaProperty:description>
+        </rdf:li>
+        <rdf:li rdf:parseType="Resource">
+         <pdfaProperty:name>ConformanceLevel</pdfaProperty:name>
+         <pdfaProperty:valueType>Text</pdfaProperty:valueType>
+         <pdfaProperty:category>external</pdfaProperty:category>
+         <pdfaProperty:description>The conformance level of the embedded Factur-X data</pdfaProperty:description>
+        </rdf:li>
+       </rdf:Seq>
+      </pdfaSchema:property>
+     </rdf:li>`, facturXNamespaceURI)
+}
+
+// xmlEscape escapes a string for safe inclusion in XML character data.
+func xmlEscape(s string) string {
+	var buf bytes.Buffer
+	_ = xml.EscapeText(&buf, []byte(s))
+	return buf.String()
+}
+
 // Watermark is not available in this implementation.
 func (engine *QPdf) Watermark(ctx context.Context, logger *slog.Logger, inputPath string, stamp gotenberg.Stamp) error {
 	_, span := gotenberg.Tracer().Start(ctx, "qpdf.Watermark",

test/integration/features/libreoffice_convert.feature

@@ -695,6 +695,43 @@ Feature: /forms/libreoffice/convert
     Then the response PDF(s) should have the "embed_1.xml" file embedded
     Then the response PDF(s) should have the "embed_2.xml" file embedded
 
+  @convert
+  @embed
+  @factur-x
+  Scenario: POST /forms/libreoffice/convert (Factur-X / ZUGFeRD)
+    Given I have a default Gotenberg container
+    When I make a "POST" request to Gotenberg at the "/forms/libreoffice/convert" endpoint with the following form data and header(s):
+      | files                     | testdata/page_1.docx                                                 | file   |
+      | pdfa                      | PDF/A-3b                                                             | field  |
+      | embeds                    | testdata/embed_1.xml                                                 | file   |
+      | embedsMetadata            | {"embed_1.xml":{"mimeType":"text/xml","relationship":"Alternative"}} | field  |
+      | facturx                   | {"conformanceLevel":"EN 16931"}                                      | field  |
+      | Gotenberg-Output-Filename | foo                                                                  | header |
+    Then the response status code should be 200
+    Then the response header "Content-Type" should be "application/pdf"
+    Then there should be 1 PDF(s) in the response
+    Then the response PDF(s) should be valid "PDF/A-3b" with a tolerance of 0 failed rule(s)
+    Then the response PDF(s) should have the "embed_1.xml" file embedded with relationship "Alternative"
+    Then the response PDF(s) should declare Factur-X XMP with conformance level "EN 16931"
+
+  @factur-x
+  Scenario: POST /forms/pdfengines/factur-x (Standalone)
+    Given I have a default Gotenberg container
+    When I make a "POST" request to Gotenberg at the "/forms/libreoffice/convert" endpoint with the following form data and header(s):
+      | files                     | testdata/page_1.docx | file   |
+      | pdfa                      | PDF/A-3b             | field  |
+      | Gotenberg-Output-Filename | base                 | header |
+    Then the response status code should be 200
+    When I make a "POST" request to Gotenberg at the "/forms/pdfengines/factur-x" endpoint with the following form data and header(s):
+      | files                     | teststore/base.pdf                                  | file   |
+      | facturx                   | {"conformanceLevel":"BASIC","documentType":"ORDER"} | field  |
+      | Gotenberg-Output-Filename | foo                                                 | header |
+    Then the response status code should be 200
+    Then the response header "Content-Type" should be "application/pdf"
+    Then there should be 1 PDF(s) in the response
+    Then the response PDF(s) should be valid "PDF/A-3b" with a tolerance of 0 failed rule(s)
+    Then the response PDF(s) should declare Factur-X XMP with conformance level "BASIC"
+
   # FIXME: once decrypt is done, add encrypt and check after the content of the PDF.
   @convert
   @metadata

test/integration/scenario/scenario.go

@@ -1349,6 +1349,57 @@ func (s *scenario) thePdfsShouldHaveEmbeddedFileWithRelationship(ctx context.Con
 	return nil
 }
 
+func (s *scenario) thePdfsShouldDeclareFacturXConformanceLevel(ctx context.Context, kind, conformanceLevel string) error {
+	dirPath := s.teststoreDir
+
+	_, err := os.Stat(dirPath)
+	if os.IsNotExist(err) {
+		return fmt.Errorf("directory %q does not exist", dirPath)
+	}
+
+	var paths []string
+	err = filepath.Walk(dirPath, func(path string, info os.FileInfo, pathErr error) error {
+		if pathErr != nil {
+			return pathErr
+		}
+		if strings.EqualFold(filepath.Ext(info.Name()), ".pdf") {
+			paths = append(paths, path)
+		}
+		return nil
+	})
+	if err != nil {
+		return fmt.Errorf("walk %q: %w", dirPath, err)
+	}
+
+	for _, path := range paths {
+		cmd := []string{
+			"pdfinfo",
+			"-meta",
+			filepath.Base(path),
+		}
+
+		output, err := execCommandInIntegrationToolsContainer(ctx, cmd, path)
+		if err != nil {
+			return fmt.Errorf("exec %q: %w", cmd, err)
+		}
+
+		if !strings.Contains(output, "urn:factur-x:pdfa:CrossIndustryDocument:invoice:1p0#") {
+			return errors.New("missing Factur-X namespace in XMP")
+		}
+
+		if !strings.Contains(output, "pdfaExtension:schemas") {
+			return errors.New("missing PDF/A extension schema in XMP")
+		}
+
+		conformanceTag := fmt.Sprintf("<fx:ConformanceLevel>%s</fx:ConformanceLevel>", conformanceLevel)
+		if !strings.Contains(output, conformanceTag) {
+			return fmt.Errorf("missing fx:ConformanceLevel %q in XMP", conformanceLevel)
+		}
+	}
+
+	return nil
+}
+
 func InitializeScenario(ctx *godog.ScenarioContext) {
 	s := &scenario{}
 	ctx.Before(func(ctx context.Context, sc *godog.Scenario) (context.Context, error) {
@@ -1389,6 +1440,7 @@ func InitializeScenario(ctx *godog.ScenarioContext) {
 	ctx.Then(`^the (response|webhook request) PDF\(s\) (should|should NOT) be encrypted`, s.thePdfsShouldBeEncrypted)
 	ctx.Then(`^the (response|webhook request) PDF\(s\) (should|should NOT) have the "([^"]*)" file embedded$`, s.thePdfsShouldHaveEmbeddedFile)
 	ctx.Then(`^the (response|webhook request) PDF\(s\) should have the "([^"]*)" file embedded with relationship "([^"]*)"$`, s.thePdfsShouldHaveEmbeddedFileWithRelationship)
+	ctx.Then(`^the (response|webhook request) PDF\(s\) should declare Factur-X XMP with conformance level "([^"]*)"$`, s.thePdfsShouldDeclareFacturXConformanceLevel)
 	ctx.Then(`^the "([^"]*)" PDF should have (\d+) page\(s\)$`, s.thePdfShouldHavePages)
 	ctx.Then(`^the "([^"]*)" PDF (should|should NOT) be set to landscape orientation$`, s.thePdfShouldBeSetToLandscapeOrientation)
 	ctx.Then(`^the "([^"]*)" PDF (should|should NOT) have the following content at page (\d+):$`, s.thePdfShouldHaveTheFollowingContentAtPage)