v3.0.0 (#18)

internal/pkg/notify/doc.go

@@ -0,0 +1,5 @@
+/*
+Package notify is used across the application
+to display nice outputs to the user.
+*/
+package notify

internal/pkg/notify/notify.go

@@ -0,0 +1,30 @@
+package notify
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/labstack/gommon/color"
+)
+
+var (
+	stdout *color.Color
+	stderr *color.Color
+)
+
+func init() {
+	stdout = color.New()
+	stdout.SetOutput(os.Stdout)
+	stderr = color.New()
+	stderr.SetOutput(os.Stderr)
+}
+
+// Println prints a message to stdout.
+func Println(message string) {
+	stdout.Printf("⇨ %s\n", message)
+}
+
+// ErrPrintln prints an error to stderr.
+func ErrPrintln(err error) {
+	stderr.Printf("%s\n", color.Red(fmt.Sprintf("⇨ error: %v", err)))
+}

internal/pkg/pm2/chrome.go

@@ -0,0 +1,70 @@
+package pm2
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/mafredri/cdp/devtool"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/notify"
+)
+
+// Chrome facilitates starting or shutting down
+// Chrome headless with PM2.
+type Chrome struct{}
+
+// Launch starts Chrome headless with PM2.
+func (c *Chrome) Launch() error {
+	return launch(c)
+}
+
+// Shutdown stops Chrome headless and
+// removes it from the list of PM2
+// processes.
+func (c *Chrome) Shutdown() error {
+	return shutdown(c)
+}
+
+func (c *Chrome) getArgs() []string {
+	return []string{
+		"--no-sandbox",
+		"--headless",
+		"--remote-debugging-port=9222",
+		"--disable-gpu",
+		"--disable-translate",
+		"--disable-extensions",
+		"--disable-background-networking",
+		"--safebrowsing-disable-auto-update",
+		"--disable-sync",
+		"--disable-default-apps",
+		"--hide-scrollbars",
+		"--metrics-recording-only",
+		"--mute-audio",
+		"--no-first-run",
+	}
+}
+
+func (c *Chrome) getName() string {
+	return "google-chrome-stable"
+}
+
+func (c *Chrome) getFullname() string {
+	return "Chrome headless"
+}
+
+func (c *Chrome) isViable() bool {
+	// check if Chrome is correctly running.
+	devt := devtool.New("http://127.0.0.1:9222")
+	_, err := devt.Create(context.TODO())
+	return err == nil
+}
+
+func (c *Chrome) warmup() {
+	notify.Println(fmt.Sprintf("warming-up %s", c.getFullname()))
+	time.Sleep(5 * time.Second)
+}
+
+// Compile-time checks to ensure type implements desired interfaces.
+var (
+	_ = Process(new(Chrome))
+)

internal/pkg/pm2/chrome_test.go

@@ -0,0 +1,19 @@
+package pm2
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestChromeLaunch(t *testing.T) {
+	p := &Chrome{}
+	err := p.Launch()
+	require.Nil(t, err)
+}
+
+func TestChromeShutdown(t *testing.T) {
+	p := &Chrome{}
+	err := p.Shutdown()
+	require.Nil(t, err)
+}

internal/pkg/pm2/doc.go

@@ -0,0 +1,12 @@
+/*
+Package pm2 facilitates starting external
+processes on which our API depends.
+
+For instance, it starts Chrome headless and
+unoconv listener with PM2.
+
+The PM2 process manager launch those processes and keep
+them running in the background. If for some reason they
+crash, it will also restart them.
+*/
+package pm2

internal/pkg/pm2/pm2.go

@@ -0,0 +1,71 @@
+package pm2
+
+import (
+	"fmt"
+	"os/exec"
+
+	"github.com/thecodingmachine/gotenberg/internal/pkg/notify"
+)
+
+// Process is a type that can launch or
+// shutdown a process with PM2.
+type Process interface {
+	Launch() error
+	Shutdown() error
+	getArgs() []string
+	getName() string
+	getFullname() string
+	isViable() bool
+	warmup()
+}
+
+const maxRestartAttempts int = 5
+
+var humanNames = map[string]string{
+	"start":   "started",
+	"restart": "restarted",
+	"stop":    "stopped",
+}
+
+func launch(p Process) error {
+	if err := run(p, "start"); err != nil {
+		return err
+	}
+	p.warmup()
+	if !p.isViable() {
+		attempts := 0
+		for attempts < maxRestartAttempts && !p.isViable() {
+			run(p, "restart")
+			p.warmup()
+			attempts++
+		}
+		if !p.isViable() {
+			return fmt.Errorf("failed to launch %s", p.getFullname())
+		}
+	}
+	return nil
+}
+
+func shutdown(p Process) error {
+	return run(p, "stop")
+}
+
+func run(p Process, cmdName string) error {
+	cmdArgs := []string{
+		cmdName,
+		p.getName(),
+	}
+	if cmdName == "start" {
+		cmdArgs = append(cmdArgs, "--interpreter none", "--")
+		cmdArgs = append(cmdArgs, p.getArgs()...)
+	}
+	cmd := exec.Command(
+		"pm2",
+		cmdArgs...,
+	)
+	if err := cmd.Start(); err != nil {
+		return fmt.Errorf("%s %s with PM2: %v", cmdName, p.getFullname(), err)
+	}
+	notify.Println(fmt.Sprintf("%s %s with PM2", p.getFullname(), humanNames[cmdName]))
+	return nil
+}

internal/pkg/pm2/unoconv.go

@@ -0,0 +1,47 @@
+package pm2
+
+// Unoconv facilitates starting or shutting down
+// unoconv listener with PM2.
+type Unoconv struct{}
+
+// Launch starts unoconv listener with PM2.
+func (u *Unoconv) Launch() error {
+	return launch(u)
+}
+
+// Shutdown stops unoconv listener and
+// removes it from the list of PM2
+// processes.
+func (u *Unoconv) Shutdown() error {
+	return shutdown(u)
+}
+
+func (u *Unoconv) getArgs() []string {
+	return []string{
+		"--listener",
+		"--verbose",
+	}
+}
+
+func (u *Unoconv) getName() string {
+	return "unoconv"
+}
+
+func (u *Unoconv) getFullname() string {
+	return "unoconv listener"
+}
+
+func (u *Unoconv) isViable() bool {
+	// TODO find a way to check if
+	// unoconv is correctly started?
+	return true
+}
+
+func (u *Unoconv) warmup() {
+	// let's do nothing.
+}
+
+// Compile-time checks to ensure type implements desired interfaces.
+var (
+	_ = Process(new(Unoconv))
+)

internal/pkg/pm2/unoconv_test.go

@@ -0,0 +1,19 @@
+package pm2
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestUnoconvLaunch(t *testing.T) {
+	p := &Unoconv{}
+	err := p.Launch()
+	require.Nil(t, err)
+}
+
+func TestUnoconvShutdown(t *testing.T) {
+	p := &Unoconv{}
+	err := p.Shutdown()
+	require.Nil(t, err)
+}

internal/pkg/printer/doc.go

@@ -0,0 +1,52 @@
+/*
+Package printer contains structs which convert
+a specific file type to PDF:
+
+ // converting HTML to PDF.
+ p := &printer.HTML{
+	 Context: context.Background(),
+	 PaperWidth: 8.27,
+	 PaperHeight: 11.7,
+	 Landscape: false,
+ }
+ p.WithLocalURL("index.html")
+ if err := p.Print("result.pdf"); err != nil {
+	 return err
+ }
+
+ // converting Markdown to PDF:
+ // it assumes here that our template "index.html"
+ // will call toHTML method to convert
+ // markdown files to HTML.
+ p := &printer.Markdown{
+	 Context: context.Background(),
+	 TemplatePath: "index.html",
+	 PaperWidth: 8.27,
+	 PaperHeight: 11.7,
+	 Landscape: false,
+ }
+ if err := p.Print("result.pdf"); err != nil {
+	 return err
+ }
+
+ // converting Office documents to PDF:
+ // it converts each files independently and
+ // then merge them.
+ //
+ // Also, as unoconv cannot perform
+ // concurrent conversions, a lock is applied.
+ p := &printer.Office{
+	 Context: ctx,
+	 FilePaths: []string{"document.docx", "presentation.pptx"}
+ }
+ if err := p.Print("result.pdf"); err != nil {
+	 return err
+ }
+
+It is also able to merge a list of PDF files:
+
+ if err := printer.Merge([]string{"foo.pdf", "bar.pdf"}, "result.pdf"); err != nil {
+	 return err
+ }
+*/
+package printer

internal/pkg/printer/html.go

@@ -0,0 +1,188 @@
+package printer
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"strings"
+
+	"github.com/mafredri/cdp"
+	"github.com/mafredri/cdp/devtool"
+	"github.com/mafredri/cdp/protocol/network"
+	"github.com/mafredri/cdp/protocol/page"
+	"github.com/mafredri/cdp/protocol/runtime"
+	"github.com/mafredri/cdp/protocol/target"
+	"github.com/mafredri/cdp/rpcc"
+)
+
+// HTML facilitates HTML to PDF conversion.
+type HTML struct {
+	Context      context.Context
+	URL          string
+	HeaderHTML   string
+	FooterHTML   string
+	PaperWidth   float64
+	PaperHeight  float64
+	MarginTop    float64
+	MarginBottom float64
+	MarginLeft   float64
+	MarginRight  float64
+	Landscape    bool
+}
+
+const defaultHeaderFooterHTML string = "<html><head></head><body></body></html>"
+
+// Print converts HTML to PDF.
+// Credits: https://medium.com/compass-true-north/go-service-to-convert-web-pages-to-pdf-using-headless-chrome-5fd9ffbae1af
+func (html *HTML) Print(destination string) error {
+	// use the DevTools HTTP/JSON API to manage targets (e.g. pages, webworkers).
+	devt := devtool.New("http://127.0.0.1:9222")
+	pt, err := devt.Create(html.Context)
+	if err != nil {
+		return fmt.Errorf("creating DevTools target: %v", err)
+	}
+	// open a new RPC connection to the Chrome Debugging Protocol target.
+	conn, err := rpcc.DialContext(html.Context, pt.WebSocketDebuggerURL)
+	if err != nil {
+		return fmt.Errorf("creating RPC connection: %v", err)
+	}
+	defer conn.Close()
+	// create new browser context.
+	baseBrowser := cdp.NewClient(conn)
+	newContextTarget, err := baseBrowser.Target.CreateBrowserContext(html.Context)
+	if err != nil {
+		return fmt.Errorf("creating new browser context: %v", err)
+	}
+	// create a new blank target with the new browser context.
+	newTargetArgs := target.NewCreateTargetArgs("about:blank").
+		SetBrowserContextID(newContextTarget.BrowserContextID)
+	newTarget, err := baseBrowser.Target.CreateTarget(html.Context, newTargetArgs)
+	if err != nil {
+		return fmt.Errorf("creating new blank target: %v", err)
+	}
+	// connect the client to the new target.
+	newTargetWsURL := fmt.Sprintf("ws://127.0.0.1:9222/devtools/page/%s", newTarget.TargetID)
+	newContextConn, err := rpcc.DialContext(html.Context, newTargetWsURL)
+	if err != nil {
+		return fmt.Errorf("connecting client to blank target: %v", err)
+	}
+	defer newContextConn.Close()
+	// close the target when done.
+	closeTargetArgs := target.NewCloseTargetArgs(newTarget.TargetID)
+	defer baseBrowser.Target.CloseTarget(html.Context, closeTargetArgs)
+	c := cdp.NewClient(newContextConn)
+	// enable the runtime.
+	if err := c.Runtime.Enable(html.Context); err != nil {
+		return fmt.Errorf("enabling runtime: %v", err)
+	}
+	// enable the network.
+	if err := c.Network.Enable(html.Context, network.NewEnableArgs()); err != nil {
+		return fmt.Errorf("enabling network: %v", err)
+	}
+	// enable events on the page domain.
+	if err := c.Page.Enable(html.Context); err != nil {
+		return fmt.Errorf("enabling events on page domain: %v", err)
+	}
+	// create a client to listen for the load event to be fired.
+	loadEventFiredClient, err := c.Page.LoadEventFired(html.Context)
+	if err != nil {
+		return fmt.Errorf("creating client listening for load event: %v", err)
+	}
+	defer loadEventFiredClient.Close()
+	// tell the page to navigate to the URL.
+	navArgs := page.NewNavigateArgs(html.URL)
+	_, err = c.Page.Navigate(html.Context, navArgs)
+	if err != nil {
+		return fmt.Errorf("%s: navigating to URL: %v", html.URL, err)
+	}
+	// wait for the page to finish loading.
+	_, err = loadEventFiredClient.Recv()
+	if err != nil {
+		return fmt.Errorf("waiting for page loading: %v", err)
+	}
+	// inject a script to make sure web fonts are loaded.
+	script := `new Promise((resolve, reject) => {
+		document.fonts.ready.then(function () {
+			resolve('fonts loaded');
+		});
+		setTimeout(resolve.bind(resolve, 'timeout'), %.0f);
+	});`
+	scriptArg := runtime.NewEvaluateArgs(script).SetAwaitPromise(true)
+	returnObj, _ := c.Runtime.Evaluate(html.Context, scriptArg)
+	loadFontsResult := string(returnObj.Result.Value)
+	if strings.Contains(loadFontsResult, "timeout") {
+		return errors.New("timed out loading fonts")
+	}
+	// if no header or footer, use the default template
+	// for avoiding displaying default Chrome templates.
+	if html.HeaderHTML == "" {
+		html.HeaderHTML = defaultHeaderFooterHTML
+	}
+	if html.FooterHTML == "" {
+		html.FooterHTML = defaultHeaderFooterHTML
+	}
+	print, err := c.Page.PrintToPDF(
+		html.Context,
+		page.NewPrintToPDFArgs().
+			SetPaperWidth(html.PaperWidth).
+			SetPaperHeight(html.PaperHeight).
+			SetMarginTop(html.MarginTop).
+			SetMarginBottom(html.MarginBottom).
+			SetMarginLeft(html.MarginLeft).
+			SetMarginRight(html.MarginRight).
+			SetLandscape(html.Landscape).
+			SetDisplayHeaderFooter(true).
+			SetHeaderTemplate(html.HeaderHTML).
+			SetFooterTemplate(html.FooterHTML).
+			SetPrintBackground(true),
+	)
+	if err != nil {
+		return fmt.Errorf("printing page to PDF: %v", err)
+	}
+	return writeBytesToFile(destination, print.Data)
+}
+
+// WithLocalURL sets a local URL from a file path.
+func (html *HTML) WithLocalURL(fpath string) {
+	html.URL = fmt.Sprintf("file://%s", fpath)
+}
+
+// WithHeaderFile sets header content from a file.
+func (html *HTML) WithHeaderFile(fpath string) error {
+	if fpath == "" {
+		return nil
+	}
+	contentHTML, err := fileContentToString(fpath)
+	if err != nil {
+		return err
+	}
+	html.HeaderHTML = contentHTML
+	return nil
+}
+
+// WithFooterFile sets footer content from a file.
+func (html *HTML) WithFooterFile(fpath string) error {
+	if fpath == "" {
+		return nil
+	}
+	contentHTML, err := fileContentToString(fpath)
+	if err != nil {
+		return err
+	}
+	html.FooterHTML = contentHTML
+	return nil
+}
+
+func fileContentToString(fpath string) (string, error) {
+	b, err := ioutil.ReadFile(fpath)
+	if err != nil {
+		return "", fmt.Errorf("%s: reading file: %v", fpath, err)
+	}
+	return string(b), nil
+}
+
+// Compile-time checks to ensure type implements desired interfaces.
+var (
+	_ = Printer(new(HTML))
+)

internal/pkg/printer/html_test.go

@@ -0,0 +1,39 @@
+package printer
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/thecodingmachine/gotenberg/test"
+)
+
+func TestHTML(t *testing.T) {
+	dirPath := test.HTMLTestDirPath(t)
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+	html := &HTML{
+		Context:      ctx,
+		PaperWidth:   8.27,
+		PaperHeight:  11.7,
+		MarginTop:    1,
+		MarginBottom: 1,
+		MarginLeft:   1,
+		MarginRight:  1,
+	}
+	html.WithLocalURL(fmt.Sprintf("%s/%s", dirPath, "index.html"))
+	err := html.WithHeaderFile(fmt.Sprintf("%s/%s", dirPath, "header.html"))
+	require.Nil(t, err)
+	err = html.WithFooterFile(fmt.Sprintf("%s/%s", dirPath, "footer.html"))
+	require.Nil(t, err)
+	dst := fmt.Sprintf("%s/%s", dirPath, "foo.pdf")
+	err = html.Print(dst)
+	require.Nil(t, err)
+	require.FileExists(t, dst)
+	err = os.RemoveAll(dirPath)
+	assert.Nil(t, err)
+}

internal/pkg/printer/markdown.go

@@ -0,0 +1,111 @@
+package printer
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"html/template"
+	"io/ioutil"
+	"path/filepath"
+
+	"github.com/microcosm-cc/bluemonday"
+	"github.com/russross/blackfriday/v2"
+	"github.com/thecodingmachine/gotenberg/internal/pkg/rand"
+)
+
+// Markdown facilitates Markdown to PDF conversion.
+type Markdown struct {
+	Context      context.Context
+	TemplatePath string
+	HeaderHTML   string
+	FooterHTML   string
+	PaperWidth   float64
+	PaperHeight  float64
+	MarginTop    float64
+	MarginBottom float64
+	MarginLeft   float64
+	MarginRight  float64
+	Landscape    bool
+
+	html *HTML
+}
+
+type templateData struct {
+	DirPath string
+}
+
+// Print converts markdown to PDF.
+func (md *Markdown) Print(destination string) error {
+	if md.html == nil {
+		md.html = &HTML{Context: md.Context}
+	}
+	if md.HeaderHTML != "" {
+		md.html.HeaderHTML = md.HeaderHTML
+	}
+	if md.FooterHTML != "" {
+		md.html.FooterHTML = md.FooterHTML
+	}
+	md.html.PaperWidth = md.PaperWidth
+	md.html.PaperHeight = md.PaperHeight
+	md.html.MarginTop = md.MarginTop
+	md.html.MarginBottom = md.MarginBottom
+	md.html.MarginLeft = md.MarginLeft
+	md.html.MarginRight = md.MarginRight
+	md.html.Landscape = md.Landscape
+	tmpl, err := template.
+		New(filepath.Base(md.TemplatePath)).
+		Funcs(template.FuncMap{"toHTML": toHTML}).
+		ParseFiles(md.TemplatePath)
+	if err != nil {
+		return fmt.Errorf("%s: parsing template: %v", md.TemplatePath, err)
+	}
+	dirPath := filepath.Dir(md.TemplatePath)
+	data := &templateData{DirPath: dirPath}
+	var buffer bytes.Buffer
+	if err := tmpl.Execute(&buffer, data); err != nil {
+		return fmt.Errorf("%s: executing template: %v", md.TemplatePath, err)
+	}
+	baseFilename, err := rand.Get()
+	if err != nil {
+		return err
+	}
+
+	dst := fmt.Sprintf("%s/%s.html", dirPath, baseFilename)
+	if err := writeBytesToFile(dst, buffer.Bytes()); err != nil {
+		return err
+	}
+	md.html.WithLocalURL(dst)
+	return md.html.Print(destination)
+}
+
+func toHTML(dirPath, filename string) (template.HTML, error) {
+	fpath := fmt.Sprintf("%s/%s", dirPath, filename)
+	b, err := ioutil.ReadFile(fpath)
+	if err != nil {
+		return "", fmt.Errorf("%s: reading file: %v", fpath, err)
+	}
+	unsafe := blackfriday.Run(b)
+	contentHTML := bluemonday.UGCPolicy().SanitizeBytes(unsafe)
+	return template.HTML(contentHTML), nil
+}
+
+// WithHeaderFile sets header content from a file.
+func (md *Markdown) WithHeaderFile(fpath string) error {
+	if md.html == nil {
+		md.html = &HTML{Context: md.Context}
+	}
+	return md.html.WithHeaderFile(fpath)
+}
+
+// WithFooterFile sets footer content from a file.
+func (md *Markdown) WithFooterFile(fpath string) error {
+	if md.html == nil {
+		md.html = &HTML{Context: md.Context}
+	}
+	return md.html.WithFooterFile(fpath)
+}
+
+// Compile-time checks to ensure type implements desired interfaces.
+var (
+	_ = Printer(new(Markdown))
+)

internal/pkg/printer/markdown_test.go

@@ -0,0 +1,39 @@
+package printer
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/thecodingmachine/gotenberg/test"
+)
+
+func TestMarkdown(t *testing.T) {
+	dirPath := test.MarkdownTestDirPath(t)
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+	markdown := &Markdown{
+		Context:      ctx,
+		TemplatePath: fmt.Sprintf("%s/%s", dirPath, "index.html"),
+		PaperWidth:   8.27,
+		PaperHeight:  11.7,
+		MarginTop:    1,
+		MarginBottom: 1,
+		MarginLeft:   1,
+		MarginRight:  1,
+	}
+	err := markdown.WithHeaderFile(fmt.Sprintf("%s/%s", dirPath, "header.html"))
+	require.Nil(t, err)
+	err = markdown.WithFooterFile(fmt.Sprintf("%s/%s", dirPath, "footer.html"))
+	require.Nil(t, err)
+	dst := fmt.Sprintf("%s/%s", dirPath, "foo.pdf")
+	err = markdown.Print(dst)
+	require.Nil(t, err)
+	require.FileExists(t, dst)
+	err = os.RemoveAll(dirPath)
+	assert.Nil(t, err)
+}

internal/pkg/printer/office.go

@@ -0,0 +1,62 @@
+package printer
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"sync"
+
+	"github.com/thecodingmachine/gotenberg/internal/pkg/rand"
+)
+
+var mu sync.Mutex
+
+// Office facilitates Office documents to PDF conversion.
+type Office struct {
+	Context   context.Context
+	FilePaths []string
+}
+
+// Print converts Office documents to PDF.
+func (o *Office) Print(destination string) error {
+	mu.Lock()
+	defer mu.Unlock()
+	fpaths := make([]string, len(o.FilePaths))
+	dirPath := filepath.Dir(destination)
+	for i, fpath := range o.FilePaths {
+		baseFilename, err := rand.Get()
+		if err != nil {
+			return err
+		}
+		tmpDest := fmt.Sprintf("%s/%s.pdf", dirPath, baseFilename)
+		cmd := exec.CommandContext(
+			o.Context,
+			"unoconv",
+			"--format",
+			"pdf",
+			"--output",
+			tmpDest,
+			fpath,
+		)
+		_, err = cmd.Output()
+		if o.Context.Err() == context.DeadlineExceeded {
+			return errors.New("unoconv: command timed out")
+		}
+		if err != nil {
+			return fmt.Errorf("unoconv: non-zero exit code: %v", err)
+		}
+		fpaths[i] = tmpDest
+	}
+	if len(fpaths) == 1 {
+		return os.Rename(fpaths[0], destination)
+	}
+	return Merge(fpaths, destination)
+}
+
+// Compile-time checks to ensure type implements desired interfaces.
+var (
+	_ = Printer(new(Office))
+)

internal/pkg/printer/office_test.go

@@ -0,0 +1,31 @@
+package printer
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/thecodingmachine/gotenberg/test"
+)
+
+func TestOffice(t *testing.T) {
+	dirPath := test.OfficeTestDirPath(t)
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+	office := &Office{
+		Context: ctx,
+		FilePaths: []string{
+			fmt.Sprintf("%s/%s", dirPath, "document.docx"),
+		},
+	}
+	dst := fmt.Sprintf("%s/%s", dirPath, "foo.pdf")
+	err := office.Print(dst)
+	require.Nil(t, err)
+	require.FileExists(t, dst)
+	err = os.RemoveAll(dirPath)
+	assert.Nil(t, err)
+}

internal/pkg/printer/printer.go

@@ -0,0 +1,29 @@
+package printer
+
+import (
+	"fmt"
+	"io/ioutil"
+
+	pdfcpuAPI "github.com/hhrutter/pdfcpu/pkg/api"
+	pdfcpuConfig "github.com/hhrutter/pdfcpu/pkg/pdfcpu"
+)
+
+// Printer is a type that can create a PDF file from a source.
+// The source is defined in the underlying implementation.
+type Printer interface {
+	Print(destination string) error
+}
+
+// Merge merges PDF files.
+func Merge(fpaths []string, destination string) error {
+	cmd := pdfcpuAPI.MergeCommand(fpaths, destination, pdfcpuConfig.NewDefaultConfiguration())
+	_, err := pdfcpuAPI.Merge(cmd)
+	return err
+}
+
+func writeBytesToFile(dst string, b []byte) error {
+	if err := ioutil.WriteFile(dst, b, 0644); err != nil {
+		return fmt.Errorf("%s: writting file: %v", dst, err)
+	}
+	return nil
+}

internal/pkg/printer/printer_test.go

@@ -0,0 +1,27 @@
+package printer
+
+import (
+	"fmt"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/thecodingmachine/gotenberg/test"
+)
+
+func TestMerge(t *testing.T) {
+	dirPath := test.PDFTestDirPath(t)
+	dst := fmt.Sprintf("%s/%s", dirPath, "foo.pdf")
+	err := Merge(
+		[]string{
+			fmt.Sprintf("%s/%s", dirPath, "gotenberg.pdf"),
+			fmt.Sprintf("%s/%s", dirPath, "gotenberg.pdf"),
+		},
+		dst,
+	)
+	require.Nil(t, err)
+	require.FileExists(t, dst)
+	err = os.RemoveAll(dirPath)
+	assert.Nil(t, err)
+}

internal/pkg/rand/doc.go

@@ -0,0 +1,7 @@
+/*
+Package rand helps generating a random string.
+
+It should be used for creating directory and
+file names in order to avoid collision.
+*/
+package rand

internal/pkg/rand/rand.go

@@ -0,0 +1,17 @@
+package rand
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"fmt"
+)
+
+// Get returns a random string.
+func Get() (string, error) {
+	randBytes := make([]byte, 16)
+	_, err := rand.Read(randBytes)
+	if err != nil {
+		return "", fmt.Errorf("creating random string: %v", err)
+	}
+	return hex.EncodeToString(randBytes), nil
+}

internal/pkg/rand/rand_test.go

@@ -0,0 +1,16 @@
+package rand
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestGet(t *testing.T) {
+	rand1, err := Get()
+	require.Nil(t, err)
+	rand2, err := Get()
+	require.Nil(t, err)
+	assert.NotEqual(t, rand1, rand2)
+}