[feature] Add `avif` file support (#4331)

# Description

> If this is a code change, please include a summary of what you've coded, and link to the issue(s) it closes/implements.
>
> If this is a documentation change, please briefly describe what you've changed and why.

This pull request implements support for reading avif images properly.

closes https://codeberg.org/superseriousbusiness/gotosocial/issues/4330

## Checklist

Please put an x inside each checkbox to indicate that you've read and followed it: `[ ]` -> `[x]`

If this is a documentation change, only the first checkbox must be filled (you can delete the others if you want).

- [x] I/we have read the [GoToSocial contribution guidelines](https://codeberg.org/superseriousbusiness/gotosocial/src/branch/main/CONTRIBUTING.md).
- [x] I/we have discussed the proposed changes already, either in an issue on the repository, or in the Matrix chat.
- [x] I/we have not leveraged AI to create the proposed changes.
- [x] I/we have performed a self-review of added code.
- [x] I/we have written code that is legible and maintainable by others.
- [x] I/we have commented the added code, particularly in hard-to-understand areas.
- [x] I/we have made any necessary changes to documentation.
- [x] I/we have added tests that cover new code.
- [x] I/we have run tests and they pass locally with the changes.
- [x] I/we have run `go fmt ./...` and `golangci-lint run`.

Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4331
Co-authored-by: tobi <tobi.smethurst@protonmail.com>
Co-committed-by: tobi <tobi.smethurst@protonmail.com>

8 files changed, 75 insertions, 5 deletions

diff --git a/internal/api/client/instance/instancepatch_test.go b/internal/api/client/instance/instancepatch_test.go
index dc3eb84b1..f23a44dc8 100644
--- a/internal/api/client/instance/instancepatch_test.go
+++ b/internal/api/client/instance/instancepatch_test.go
@@ -112,6 +112,7 @@ func (suite *InstancePatchTestSuite) TestInstancePatch1() {
         "image/jpeg",
         "image/gif",
         "image/webp",
+        "image/avif",
         "audio/mp2",
         "audio/mp3",
         "audio/mpeg",
@@ -255,6 +256,7 @@ func (suite *InstancePatchTestSuite) TestInstancePatch2() {
         "image/jpeg",
         "image/gif",
         "image/webp",
+        "image/avif",
         "audio/mp2",
         "audio/mp3",
         "audio/mpeg",
@@ -398,6 +400,7 @@ func (suite *InstancePatchTestSuite) TestInstancePatch3() {
         "image/jpeg",
         "image/gif",
         "image/webp",
+        "image/avif",
         "audio/mp2",
         "audio/mp3",
         "audio/mpeg",
@@ -592,6 +595,7 @@ func (suite *InstancePatchTestSuite) TestInstancePatch6() {
         "image/jpeg",
         "image/gif",
         "image/webp",
+        "image/avif",
         "audio/mp2",
         "audio/mp3",
         "audio/mpeg",
@@ -757,6 +761,7 @@ func (suite *InstancePatchTestSuite) TestInstancePatch8() {
         "image/jpeg",
         "image/gif",
         "image/webp",
+        "image/avif",
         "audio/mp2",
         "audio/mp3",
         "audio/mpeg",
@@ -941,6 +946,7 @@ func (suite *InstancePatchTestSuite) TestInstancePatch9() {
         "image/jpeg",
         "image/gif",
         "image/webp",
+        "image/avif",
         "audio/mp2",
         "audio/mp3",
         "audio/mpeg",
diff --git a/internal/media/ffmpeg.go b/internal/media/ffmpeg.go
index 676eba9be..05e8c69a6 100644
--- a/internal/media/ffmpeg.go
+++ b/internal/media/ffmpeg.go
@@ -342,16 +342,21 @@ func (res *result) GetFileType() (gtsmodel.FileType, string, string) {
 	case "mov,mp4,m4a,3gp,3g2,mj2":
 		switch {
 		case len(res.video) > 0:
-			if len(res.audio) == 0 &&
-				res.duration <= 30 {
+			switch {
+			case res.video[0].framerate == 0 && res.video[0].stream.codec == "av1":
+				// Looks like an avif image.
+				return gtsmodel.FileTypeImage,
+					"image/avif", "avif"
+			case len(res.audio) == 0 && res.duration <= 30:
 				// Short, soundless
 				// video file aka gifv.
 				return gtsmodel.FileTypeGifv,
 					"video/mp4", "mp4"
+			default:
+				// Video file (with or without audio).
+				return gtsmodel.FileTypeVideo,
+					"video/mp4", "mp4"
 			}
-			// Video file (with or without audio).
-			return gtsmodel.FileTypeVideo,
-				"video/mp4", "mp4"
 		case len(res.audio) > 0 &&
 			res.audio[0].codec == "aac":
 			// m4a only supports [aac] audio.
diff --git a/internal/media/manager.go b/internal/media/manager.go
index a7bd8948b..2ec222f3c 100644
--- a/internal/media/manager.go
+++ b/internal/media/manager.go
@@ -38,6 +38,7 @@ var SupportedMIMETypes = []string{
 	"image/jpeg", // .jpeg
 	"image/gif",  // .gif
 	"image/webp", // .webp
+	"image/avif", // .avif
 
 	"audio/mp2",  // .mp2
 	"audio/mp3",  // .mp3
diff --git a/internal/media/manager_test.go b/internal/media/manager_test.go
index 6182babbb..f6914acf0 100644
--- a/internal/media/manager_test.go
+++ b/internal/media/manager_test.go
@@ -789,6 +789,62 @@ func (suite *ManagerTestSuite) TestPngAlphaChannelProcess() {
 	equalFiles(suite.T(), suite.state.Storage, dbAttachment.Thumbnail.Path, "./test/test-png-alphachannel-thumbnail.jpeg")
 }
 
+func (suite *ManagerTestSuite) TestAvifProcess() {
+	ctx := suite.T().Context()
+
+	data := func(_ context.Context) (io.ReadCloser, error) {
+		// load bytes from a test image
+		b, err := os.ReadFile("./test/gotosocial.avif")
+		if err != nil {
+			panic(err)
+		}
+		return io.NopCloser(bytes.NewBuffer(b)), nil
+	}
+
+	accountID := "01FS1X72SK9ZPW0J1QQ68BD264"
+
+	// process the media with no additional info provided
+	processing, err := suite.manager.CreateMedia(ctx,
+		accountID,
+		data,
+		media.AdditionalMediaInfo{},
+	)
+	suite.NoError(err)
+	suite.NotNil(processing)
+
+	// do a blocking call to fetch the attachment
+	attachment, err := processing.Load(ctx)
+	suite.NoError(err)
+	suite.NotNil(attachment)
+
+	// make sure it's got the stuff set on it that we expect
+	// the attachment ID and accountID we expect
+	suite.Equal(processing.ID(), attachment.ID)
+	suite.Equal(accountID, attachment.AccountID)
+
+	// file meta should be correctly derived from the image
+	suite.EqualValues(gtsmodel.Original{
+		Width: 1038, Height: 980, Size: 1017240, Aspect: 1.0591837,
+	}, attachment.FileMeta.Original)
+	suite.EqualValues(gtsmodel.Small{
+		Width: 512, Height: 483, Size: 247296, Aspect: 1.0591837,
+	}, attachment.FileMeta.Small)
+	suite.Equal("image/avif", attachment.File.ContentType)
+	suite.Equal("image/webp", attachment.Thumbnail.ContentType)
+	suite.Equal(3815, attachment.File.FileSize)
+	suite.Equal(4198, attachment.Thumbnail.FileSize)
+	suite.Equal("LNQJQ7%M?w-;-pj[bbj[?^ofDiWB", attachment.Blurhash)
+
+	// now make sure the attachment is in the database
+	dbAttachment, err := suite.db.GetAttachmentByID(ctx, attachment.ID)
+	suite.NoError(err)
+	suite.NotNil(dbAttachment)
+
+	// ensure the files contain the expected data.
+	equalFiles(suite.T(), suite.state.Storage, dbAttachment.File.Path, "./test/gotosocial-processed.avif")
+	equalFiles(suite.T(), suite.state.Storage, dbAttachment.Thumbnail.Path, "./test/gotosocial-thumbnail.webp")
+}
+
 func (suite *ManagerTestSuite) TestSimpleJpegProcessWithCallback() {
 	ctx := suite.T().Context()
 
diff --git a/internal/media/test/gotosocial-processed.avif b/internal/media/test/gotosocial-processed.avif
new file mode 100644
index 000000000..f0433b70b
--- /dev/null
+++ b/internal/media/test/gotosocial-processed.avif
diff --git a/internal/media/test/gotosocial-thumbnail.webp b/internal/media/test/gotosocial-thumbnail.webp
new file mode 100644
index 000000000..370ca9d0b
--- /dev/null
+++ b/internal/media/test/gotosocial-thumbnail.webp
diff --git a/internal/media/test/gotosocial.avif b/internal/media/test/gotosocial.avif
new file mode 100644
index 000000000..f0433b70b
--- /dev/null
+++ b/internal/media/test/gotosocial.avif
diff --git a/internal/typeutils/internaltofrontend_test.go b/internal/typeutils/internaltofrontend_test.go
index a26ff114e..47ad284e6 100644
--- a/internal/typeutils/internaltofrontend_test.go
+++ b/internal/typeutils/internaltofrontend_test.go
@@ -1773,6 +1773,7 @@ func (suite *InternalToFrontendTestSuite) TestInstanceV1ToFrontend() {
         "image/jpeg",
         "image/gif",
         "image/webp",
+        "image/avif",
         "audio/mp2",
         "audio/mp3",
         "audio/mpeg",
@@ -1930,6 +1931,7 @@ func (suite *InternalToFrontendTestSuite) TestInstanceV2ToFrontend() {
         "image/jpeg",
         "image/gif",
         "image/webp",
+        "image/avif",
         "audio/mp2",
         "audio/mp3",
         "audio/mpeg",