Mono repo -> Master (#22553)

Combines the following repositories into one:

https://github.com/mattermost/mattermost-server
https://github.com/mattermost/mattermost-webapp
https://github.com/mattermost/focalboard
https://github.com/mattermost/mattermost-plugin-playbooks

server/platform/services/docextractor/mmpreview.go

@@ -0,0 +1,85 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package docextractor
+
+// MMPreview is a micro-service to convert from any libreoffice supported
+// format into a PDF file, and then we use the regular pdf extractor to convert
+// it into plain text.
+
+import (
+	"bytes"
+	"io"
+	"mime/multipart"
+	"net/http"
+	"path"
+	"strings"
+
+	"github.com/pkg/errors"
+)
+
+type mmPreviewExtractor struct {
+	url          string
+	secret       string
+	pdfExtractor pdfExtractor
+}
+
+var mmpreviewSupportedExtensions = map[string]bool{
+	"ppt":  true,
+	"odp":  true,
+	"xls":  true,
+	"xlsx": true,
+	"ods":  true,
+}
+
+func newMMPreviewExtractor(url string, secret string, pdfExtractor pdfExtractor) *mmPreviewExtractor {
+	return &mmPreviewExtractor{url: url, secret: secret, pdfExtractor: pdfExtractor}
+}
+
+func (mpe *mmPreviewExtractor) Match(filename string) bool {
+	extension := strings.TrimPrefix(path.Ext(filename), ".")
+	return mmpreviewSupportedExtensions[extension]
+}
+
+func (mpe *mmPreviewExtractor) Extract(filename string, file io.ReadSeeker) (string, error) {
+	b, w, err := createMultipartFormData("file", filename, file)
+	if err != nil {
+		return "", errors.Wrap(err, "Unable to generate file preview using mmpreview.")
+	}
+	req, err := http.NewRequest("POST", mpe.url+"/toPDF", &b)
+	if err != nil {
+		return "", errors.Wrap(err, "Unable to generate file preview using mmpreview.")
+	}
+	req.Header.Set("Content-Type", w.FormDataContentType())
+	if mpe.secret != "" {
+		req.Header.Add("Authentication", mpe.secret)
+	}
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return "", errors.Wrap(err, "Unable to generate file preview using mmpreview.")
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != 200 {
+		return "", errors.New("Unable to generate file preview using mmpreview (The server has replied with an error)")
+	}
+	data, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", errors.Wrap(err, "unable to read the response from mmpreview")
+	}
+	return mpe.pdfExtractor.Extract(filename, bytes.NewReader(data))
+}
+
+func createMultipartFormData(fieldName, fileName string, fileData io.ReadSeeker) (bytes.Buffer, *multipart.Writer, error) {
+	var b bytes.Buffer
+	var err error
+	w := multipart.NewWriter(&b)
+	var fw io.Writer
+	if fw, err = w.CreateFormFile(fieldName, fileName); err != nil {
+		return b, nil, err
+	}
+	if _, err = io.Copy(fw, fileData); err != nil {
+		return b, nil, err
+	}
+	w.Close()
+	return b, w, nil
+}