Don't lie about the preview mimetype

For legacy reasons we stored all the previews with a png extention.
However we did not put png data in them all the time.

This caused the preview endpoints to always report that a preview is a
png file. Which was a lie.

Since we abstract away from the storage etc in the previewmanager. There
is no need anymore to store them as .png files and instead we can use
the actual file extention.

Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>

4 files changed, 61 insertions, 7 deletions

diff --git a/lib/private/Preview/Generator.php b/lib/private/Preview/Generator.php
index 402732ecda9..91173d41afa 100644
--- a/lib/private/Preview/Generator.php
+++ b/lib/private/Preview/Generator.php
@@ -128,7 +128,7 @@ class Generator {
 
 		// Try to get a cached preview. Else generate (and store) one
 		try {
-			$file = $this->getCachedPreview($previewFolder, $width, $height, $crop);
+			$file = $this->getCachedPreview($previewFolder, $width, $height, $crop, $maxPreview->getMimeType());
 		} catch (NotFoundException $e) {
 			$file = $this->generatePreview($previewFolder, $maxPreview, $width, $height, $crop, $maxWidth, $maxHeight);
 		}
@@ -173,7 +173,8 @@ class Generator {
 					continue;
 				}
 
-				$path = (string)$preview->width() . '-' . (string)$preview->height() . '-max.png';
+				$ext = $this->getExtention($preview->dataMimeType());
+				$path = (string)$preview->width() . '-' . (string)$preview->height() . '-max.' . $ext;
 				try {
 					$file = $previewFolder->newFile($path);
 					$file->putContent($preview->data());
@@ -201,14 +202,17 @@ class Generator {
 	 * @param int $width
 	 * @param int $height
 	 * @param bool $crop
+	 * @param string $mimeType
 	 * @return string
 	 */
-	private function generatePath($width, $height, $crop) {
+	private function generatePath($width, $height, $crop, $mimeType) {
 		$path = (string)$width . '-' . (string)$height;
 		if ($crop) {
 			$path .= '-crop';
 		}
-		$path .= '.png';
+
+		$ext = $this->getExtention($mimeType);
+		$path .= '.' . $ext;
 		return $path;
 	}
 
@@ -340,7 +344,7 @@ class Generator {
 		}
 
 
-		$path = $this->generatePath($width, $height, $crop);
+		$path = $this->generatePath($width, $height, $crop, $preview->dataMimeType());
 		try {
 			$file = $previewFolder->newFile($path);
 			$file->putContent($preview->data());
@@ -356,12 +360,13 @@ class Generator {
 	 * @param int $width
 	 * @param int $height
 	 * @param bool $crop
+	 * @param string $mimeType
 	 * @return ISimpleFile
 	 *
 	 * @throws NotFoundException
 	 */
-	private function getCachedPreview(ISimpleFolder $previewFolder, $width, $height, $crop) {
-		$path = $this->generatePath($width, $height, $crop);
+	private function getCachedPreview(ISimpleFolder $previewFolder, $width, $height, $crop, $mimeType) {
+		$path = $this->generatePath($width, $height, $crop, $mimeType);
 
 		return $previewFolder->getFile($path);
 	}
@@ -381,4 +386,21 @@ class Generator {
 
 		return $folder;
 	}
+
+	/**
+	 * @param string $mimeType
+	 * @return null|string
+	 */
+	private function getExtention($mimeType) {
+		switch ($mimeType) {
+			case 'image/png':
+				return 'png';
+			case 'image/jpeg':
+				return 'jpg';
+			case 'image/gif':
+				return 'gif';
+			default:
+				return null;
+		}
+	}
 }
diff --git a/lib/private/legacy/image.php b/lib/private/legacy/image.php
index a7d702ac032..925548ef26d 100644
--- a/lib/private/legacy/image.php
+++ b/lib/private/legacy/image.php
@@ -305,6 +305,24 @@ class OC_Image implements \OCP\IImage {
 	}
 
 	/**
+	 * @return null|string Returns the mimetype of the data
+	 */
+	public function dataMimeType() {
+		if (!$this->valid()) {
+			return null;
+		}
+
+		switch ($this->mimeType) {
+			case 'image/png':
+			case 'image/jpeg':
+			case 'image/gif':
+				return $this->mimeType;
+			default:
+				return 'image/png';
+		}
+	}
+
+	/**
 	 * @return null|string Returns the raw image data.
 	 */
 	public function data() {
diff --git a/lib/public/IImage.php b/lib/public/IImage.php
index f63a1b8ca60..70e8b3cff75 100644
--- a/lib/public/IImage.php
+++ b/lib/public/IImage.php
@@ -103,6 +103,12 @@ interface IImage {
 	public function resource();
 
 	/**
+	 * @return string Returns the raw data mimetype
+	 * @since 13.0.0
+	 */
+	public function dataMimeType();
+
+	/**
 	 * @return string Returns the raw image data.
 	 * @since 8.1.0
 	 */
diff --git a/tests/lib/Preview/GeneratorTest.php b/tests/lib/Preview/GeneratorTest.php
index f1383b0691b..130cccdf09e 100644
--- a/tests/lib/Preview/GeneratorTest.php
+++ b/tests/lib/Preview/GeneratorTest.php
@@ -93,6 +93,8 @@ class GeneratorTest extends \Test\TestCase {
 		$maxPreview = $this->createMock(ISimpleFile::class);
 		$maxPreview->method('getName')
 			->willReturn('1000-1000-max.png');
+		$maxPreview->method('getMimeType')
+			->willReturn('image/png');
 
 		$previewFolder->method('getDirectoryListing')
 			->willReturn([$maxPreview]);
@@ -170,6 +172,7 @@ class GeneratorTest extends \Test\TestCase {
 		$image->method('width')->willReturn(2048);
 		$image->method('height')->willReturn(2048);
 		$image->method('valid')->willReturn(true);
+		$image->method('dataMimeType')->willReturn('image/png');
 
 		$this->helper->method('getThumbnail')
 			->will($this->returnCallback(function ($provider, $file, $x, $y) use ($invalidProvider, $validProvider, $image) {
@@ -185,6 +188,7 @@ class GeneratorTest extends \Test\TestCase {
 
 		$maxPreview = $this->createMock(ISimpleFile::class);
 		$maxPreview->method('getName')->willReturn('2048-2048-max.png');
+		$maxPreview->method('getMimeType')->willReturn('image/png');
 
 		$previewFile = $this->createMock(ISimpleFile::class);
 
@@ -219,6 +223,7 @@ class GeneratorTest extends \Test\TestCase {
 		$image->method('data')
 			->willReturn('my resized data');
 		$image->method('valid')->willReturn(true);
+		$image->method('dataMimeType')->willReturn('image/png');
 
 		$previewFile->expects($this->once())
 			->method('putContent')
@@ -362,6 +367,8 @@ class GeneratorTest extends \Test\TestCase {
 		$maxPreview = $this->createMock(ISimpleFile::class);
 		$maxPreview->method('getName')
 			->willReturn($maxX . '-' . $maxY . '-max.png');
+		$maxPreview->method('getMimeType')
+			->willReturn('image/png');
 
 		$previewFolder->method('getDirectoryListing')
 			->willReturn([$maxPreview]);
@@ -382,6 +389,7 @@ class GeneratorTest extends \Test\TestCase {
 		$image->method('height')->willReturn($maxY);
 		$image->method('width')->willReturn($maxX);
 		$image->method('valid')->willReturn(true);
+		$image->method('dataMimeType')->willReturn('image/png');
 
 		$preview = $this->createMock(ISimpleFile::class);
 		$previewFolder->method('newFile')