first (BIG) commit

converters/converters.go

@@ -0,0 +1,273 @@
+// Package converters implements a solution for reading files from a request
+// and converting them to PDF.
+package converters
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"os/exec"
+	"text/template"
+
+	"github.com/gulien/gotenberg/config"
+	"github.com/gulien/gotenberg/helpers"
+
+	"github.com/satori/go.uuid"
+)
+
+type (
+	// Converter is the interface used in our convertHandler middleware.
+	// Indeed, we don't want to know in this middleware which converter is actually used.
+	Converter interface {
+		// Convert should returns the file path of the PDF created by the converter.
+		Convert() (string, error)
+		// Clear should removes all files used by the converter.
+		Clear() error
+	}
+
+	// DirectConverter allows us to convert a file to PDF.
+	DirectConverter struct {
+		// contentType is the content type of the file to convert.
+		contentType string
+		// filePath is the path of the file to convert.
+		filePath string
+		// resultFilePath is the path of the PDF created by
+		// the conversion.
+		resultFilePath string
+	}
+
+	// MultipartFormDataConverter contains an array of
+	// DirectConverter instances, each one having to convert a file to PDF.
+	MultipartFormDataConverter struct {
+		// converters contains all DirectConverter instances which will be used
+		// to convert files to PDF.
+		converters []*DirectConverter
+		// resultFilePath is the path of the PDF file created by the merge
+		// of all PDF files created by the DirectConverter instances.
+		resultFilePath string
+	}
+)
+
+// NewConverter instantiates a converter according to the content type of the request.
+func NewConverter(contentType string, r *http.Request) (Converter, error) {
+	switch contentType {
+	case "multipart/form-data":
+		return newMultipartFromDataConverter(contentType, r)
+	default:
+		return newDirectConverter(contentType, r.Body)
+	}
+}
+
+// ConverterUnprocessableEntityError is a custom error which is throwed when
+// a file's content type does not match with one of the allowed content types.
+type ConverterUnprocessableEntityError struct {
+	message string
+}
+
+// Error is the implementation of the function Error from the error interface.
+func (e *ConverterUnprocessableEntityError) Error() string {
+	return e.message
+}
+
+// filesExtensions associates all allowed content types with their file extension.
+var filesExtensions = map[string]string{
+	"application/pdf":          ".pdf",
+	"text/html":                ".html",
+	"application/octet-stream": ".doc",
+	"application/msword":       ".doc",
+	"application/zip":          ".docx",
+	"application/vnd.openxmlformats-officedocument.wordprocessingml.document": ".docx",
+}
+
+// newDirectConverter instantiates a DirectConverter.
+func newDirectConverter(contentType string, r io.Reader) (*DirectConverter, error) {
+	fileExtension, ok := filesExtensions[contentType]
+	if !ok {
+		return nil, &ConverterUnprocessableEntityError{message: "No file extension found"}
+	}
+
+	filePath := fmt.Sprintf("./%s%s", uuid.NewV4().String(), fileExtension)
+
+	file, err := os.Create(filePath)
+	if err != nil {
+		return nil, err
+	}
+
+	defer file.Close()
+
+	_, err = io.Copy(file, r)
+	if err != nil {
+		return nil, err
+	}
+	// resets the read pointer.
+	file.Seek(0, 0)
+
+	contentType, err = helpers.DetectFileContentType(file)
+	if err != nil {
+		return nil, &ConverterUnprocessableEntityError{message: fmt.Sprintf("An error occured while trying to detect the content type of a file: %s", err.Error())}
+	}
+
+	return &DirectConverter{contentType: contentType, filePath: filePath}, nil
+}
+
+// ConversionCommandData will be applied to the data-driven command's template
+// which will convert a file to PDF.
+type ConversionCommandData struct {
+	// FilePath is the path of the file to convert to PDF.
+	FilePath string
+	// The path of the PDF file created by the considered command.
+	ResultFilePath string
+}
+
+// Convert converts a file to PDF.
+func (c *DirectConverter) Convert() (string, error) {
+	var cmdTemplate *template.Template
+
+	switch c.contentType {
+	case "text/html":
+		cmdTemplate = config.AppConfig.Templates.HTMLtoPDF
+		break
+	case "application/octet-stream", "application/msword", "application/zip", "application/vnd.openxmlformats-officedocument.wordprocessingml.document":
+		cmdTemplate = config.AppConfig.Templates.WordToPDF
+		break
+	default:
+		// case "application/pdf".
+		cmdTemplate = nil
+		c.resultFilePath = c.filePath
+
+		return c.resultFilePath, nil
+	}
+
+	c.resultFilePath = fmt.Sprintf("./%s.pdf", uuid.NewV4().String())
+
+	cmdData := &ConversionCommandData{
+		FilePath:       c.filePath,
+		ResultFilePath: c.resultFilePath,
+	}
+
+	var data bytes.Buffer
+	if err := cmdTemplate.Execute(&data, cmdData); err != nil {
+		return "", fmt.Errorf("An error occured while executing a template: %s", err)
+	}
+	cmd := data.String()
+
+	e := exec.Command("/bin/sh", "-c", cmd)
+	if err := e.Run(); err != nil {
+		return "", fmt.Errorf("An error occured while executing the command %s: %s", cmd, err)
+	}
+
+	return c.resultFilePath, nil
+}
+
+// Clear removes all files used by an instance of DirectConverter.
+func (c *DirectConverter) Clear() error {
+	if err := os.Remove(c.filePath); err != nil {
+		return err
+	}
+
+	// if "application/pdf" content type, the file path is the same
+	// as the result file path.
+	if c.contentType != "application/pdf" {
+		if err := os.Remove(c.resultFilePath); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// newMultipartFromDataConverter instantiates a MultipartFormDataConverter.
+func newMultipartFromDataConverter(contentType string, r *http.Request) (*MultipartFormDataConverter, error) {
+	err := r.ParseMultipartForm(32 << 20)
+	if err != nil {
+		return nil, err
+	}
+
+	formData := r.MultipartForm
+	files := formData.File["files"]
+	c := &MultipartFormDataConverter{}
+
+	for i := range files {
+		file, err := files[i].Open()
+		if err != nil {
+			return nil, err
+		}
+
+		defer file.Close()
+
+		contentType, err := helpers.DetectMultipartFileContentType(file)
+		if err != nil {
+			return nil, err
+		}
+
+		d, err := newDirectConverter(contentType, file)
+		if err != nil {
+			return nil, err
+		}
+
+		c.converters = append(c.converters, d)
+	}
+
+	return c, nil
+}
+
+// MergeCommandData will be applied to the data-driven command's template
+// which will merge PDF files.
+type MergeCommandData struct {
+	// FilesPaths are the paths of the PDF files to merge.
+	FilesPaths []string
+	// The path of the PDF file created by the considered command.
+	ResultFilePath string
+}
+
+// Convert converts all files from form data to PDF
+// and then merges those resulting PDF into one final PDF.
+func (c *MultipartFormDataConverter) Convert() (string, error) {
+	var filesPaths []string
+
+	for _, d := range c.converters {
+		filePath, err := d.Convert()
+		if err != nil {
+			return "", err
+		}
+
+		filesPaths = append(filesPaths, filePath)
+	}
+
+	c.resultFilePath = fmt.Sprintf("./%s.pdf", uuid.NewV4().String())
+	cmdTemplate := config.AppConfig.Templates.MergePDF
+	cmdData := &MergeCommandData{
+		FilesPaths:     filesPaths,
+		ResultFilePath: c.resultFilePath,
+	}
+
+	var data bytes.Buffer
+	if err := cmdTemplate.Execute(&data, cmdData); err != nil {
+		return "", fmt.Errorf("An error occured while executing a template: %s", err)
+	}
+	cmd := data.String()
+
+	e := exec.Command("/bin/sh", "-c", cmd)
+	if err := e.Run(); err != nil {
+		return "", fmt.Errorf("An error occured while executing the command %s: %s", cmd, err)
+	}
+
+	return c.resultFilePath, nil
+}
+
+// Clear removes all files used by an instance of MultipartFormDataConverter.
+func (c *MultipartFormDataConverter) Clear() error {
+	for _, d := range c.converters {
+		if err := d.Clear(); err != nil {
+			return err
+		}
+	}
+
+	if err := os.Remove(c.resultFilePath); err != nil {
+		return err
+	}
+
+	return nil
+}