1 files changed, 149 insertions, 0 deletions
diff --git a/internal/media/types.go b/internal/media/types.go
new file mode 100644
index 000000000..f1608f880
--- /dev/null
+++ b/internal/media/types.go
@@ -0,0 +1,149 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package media
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+
+	"github.com/h2non/filetype"
+)
+
+// mime consts
+const (
+	mimeImage = "image"
+
+	mimeJpeg      = "jpeg"
+	mimeImageJpeg = mimeImage + "/" + mimeJpeg
+
+	mimeGif      = "gif"
+	mimeImageGif = mimeImage + "/" + mimeGif
+
+	mimePng      = "png"
+	mimeImagePng = mimeImage + "/" + mimePng
+)
+
+
+// EmojiMaxBytes is the maximum permitted bytes of an emoji upload (50kb)
+// const EmojiMaxBytes = 51200
+
+// maxFileHeaderBytes represents the maximum amount of bytes we want
+// to examine from the beginning of a file to determine its type.
+//
+// See: https://en.wikipedia.org/wiki/File_format#File_header
+// and https://github.com/h2non/filetype
+const maxFileHeaderBytes = 262
+
+type Size string
+
+const (
+	SizeSmall    Size = "small"    // SizeSmall is the key for small/thumbnail versions of media
+	SizeOriginal Size = "original" // SizeOriginal is the key for original/fullsize versions of media and emoji
+	SizeStatic   Size = "static"   // SizeStatic is the key for static (non-animated) versions of emoji
+)
+
+type Type string
+
+const (
+	TypeAttachment Type = "attachment" // TypeAttachment is the key for media attachments
+	TypeHeader     Type = "header"     // TypeHeader is the key for profile header requests
+	TypeAvatar     Type = "avatar"     // TypeAvatar is the key for profile avatar requests
+	TypeEmoji      Type = "emoji"      // TypeEmoji is the key for emoji type requests
+)
+
+// parseContentType parses the MIME content type from a file, returning it as a string in the form (eg., "image/jpeg").
+// Returns an error if the content type is not something we can process.
+func parseContentType(content []byte) (string, error) {
+
+	// read in the first bytes of the file
+	fileHeader := make([]byte, maxFileHeaderBytes)
+	if _, err := bytes.NewReader(content).Read(fileHeader); err != nil {
+		return "", fmt.Errorf("could not read first magic bytes of file: %s", err)
+	}
+
+	kind, err := filetype.Match(fileHeader)
+	if err != nil {
+		return "", err
+	}
+
+	if kind == filetype.Unknown {
+		return "", errors.New("filetype unknown")
+	}
+
+	return kind.MIME.Value, nil
+}
+
+// supportedImage checks mime type of an image against a slice of accepted types,
+// and returns True if the mime type is accepted.
+func supportedImage(mimeType string) bool {
+	acceptedImageTypes := []string{
+		mimeImageJpeg,
+		mimeImageGif,
+		mimeImagePng,
+	}
+	for _, accepted := range acceptedImageTypes {
+		if mimeType == accepted {
+			return true
+		}
+	}
+	return false
+}
+
+// supportedEmoji checks that the content type is image/png -- the only type supported for emoji.
+func supportedEmoji(mimeType string) bool {
+	acceptedEmojiTypes := []string{
+		mimeImageGif,
+		mimeImagePng,
+	}
+	for _, accepted := range acceptedEmojiTypes {
+		if mimeType == accepted {
+			return true
+		}
+	}
+	return false
+}
+
+// ParseMediaType converts s to a recognized MediaType, or returns an error if unrecognized
+func ParseMediaType(s string) (Type, error) {
+	switch s {
+	case string(TypeAttachment):
+		return TypeAttachment, nil
+	case string(TypeHeader):
+		return TypeHeader, nil
+	case string(TypeAvatar):
+		return TypeAvatar, nil
+	case string(TypeEmoji):
+		return TypeEmoji, nil
+	}
+	return "", fmt.Errorf("%s not a recognized MediaType", s)
+}
+
+// ParseMediaSize converts s to a recognized MediaSize, or returns an error if unrecognized
+func ParseMediaSize(s string) (Size, error) {
+	switch s {
+	case string(SizeSmall):
+		return SizeSmall, nil
+	case string(SizeOriginal):
+		return SizeOriginal, nil
+	case string(SizeStatic):
+		return SizeStatic, nil
+	}
+	return "", fmt.Errorf("%s not a recognized MediaSize", s)
+}