From 8f3cc2e28e903ba9229f5ea80774e380d26bf5fe Mon Sep 17 00:00:00 2001
From: Tulir Asokan <tulir@maunium.net>
Date: Mon, 19 Jan 2026 19:53:31 +0200
Subject: [PATCH] media: fix lottie stickers not being decompressed

---
 pkg/connector/directdownload.go |  4 ++--
 pkg/connector/media/sticker.go  | 40 ++++++++++++++++++++++++++++++---
 pkg/connector/media/transfer.go |  4 ++--
 3 files changed, 41 insertions(+), 7 deletions(-)

diff --git a/pkg/connector/directdownload.go b/pkg/connector/directdownload.go
index 61783314..ea101ce3 100644
--- a/pkg/connector/directdownload.go
+++ b/pkg/connector/directdownload.go
@@ -161,7 +161,7 @@ func (tc *TelegramConnector) Download(ctx context.Context, mediaID networkid.Med
 			log.Debug().
 				Int64("document_id", msgMedia.Document.GetID()).
 				Bool("is_sticker", isSticker).
-				Msg("downloading photo")
+				Msg("downloading document")
 			readyTransferer = transferer.WithDocument(msgMedia.Document, info.Thumbnail)
 		case *tg.MessageMediaWebPage:
 			webpage, ok := msgMedia.Webpage.(*tg.WebPage)
@@ -172,7 +172,7 @@ func (tc *TelegramConnector) Download(ctx context.Context, mediaID networkid.Med
 			if pc, ok := webpage.GetPhoto(); ok && pc.TypeID() == tg.PhotoTypeID {
 				log.Debug().
 					Int64("photo_id", pc.GetID()).
-					Msg("downloading photo")
+					Msg("downloading webpage photo")
 				readyTransferer = transferer.WithPhoto(pc)
 			} else {
 				return nil, fmt.Errorf("not a photo: %T", pc.TypeName())
diff --git a/pkg/connector/media/sticker.go b/pkg/connector/media/sticker.go
index d678abc5..160df901 100644
--- a/pkg/connector/media/sticker.go
+++ b/pkg/connector/media/sticker.go
@@ -18,9 +18,12 @@ package media
 
 import (
 	"context"
+	"fmt"
+	"io"
 	"os"
 	"strconv"
 
+	"github.com/klauspost/compress/gzip"
 	"github.com/rs/zerolog"
 	"go.mau.fi/util/ffmpeg"
 	"go.mau.fi/util/lottie"
@@ -107,13 +110,44 @@ func (c *AnimatedStickerConfig) convertWebm(ctx context.Context, src *os.File) *
 	}
 }
 
-func (c *AnimatedStickerConfig) convert(ctx context.Context, src *os.File) *ConvertedSticker {
-	if c.Target == "disable" {
-		return nil
+func extractGZip(src *os.File) (*ConvertedSticker, error) {
+	reader, err := gzip.NewReader(src)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create gzip reader: %w", err)
 	}
+	defer func() {
+		_ = reader.Close()
+	}()
+	replFile, err := os.OpenFile(src.Name()+".json", os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create temp file: %w", err)
+	}
+	defer func() {
+		_ = replFile.Close()
+	}()
+	n, err := io.Copy(replFile, reader)
+	if err != nil {
+		return nil, fmt.Errorf("failed to extract lottie gzip: %w", err)
+	}
+	return &ConvertedSticker{
+		Success:  true,
+		NewPath:  replFile.Name(),
+		MIMEType: "video/lottie+json",
+		Size:     int(n),
+	}, nil
+}
 
+func (c *AnimatedStickerConfig) convert(ctx context.Context, src *os.File) *ConvertedSticker {
 	log := zerolog.Ctx(ctx).With().Str("animated_sticker_target", c.Target).Logger()
 
+	if c.Target == "disable" {
+		converted, err := extractGZip(src)
+		if err != nil {
+			log.Err(err).Msg("Failed to extract lottie sticker")
+		}
+		return converted
+	}
+
 	if !lottie.Supported() {
 		log.Warn().Msg("Not converting lottie sticker as lottieconverter is not installed")
 		return nil
diff --git a/pkg/connector/media/transfer.go b/pkg/connector/media/transfer.go
index 2ebc6cfa..9699c153 100644
--- a/pkg/connector/media/transfer.go
+++ b/pkg/connector/media/transfer.go
@@ -293,7 +293,7 @@ func (t *ReadyTransferer) Transfer(ctx context.Context, store *store.Container,
 			if t.inner.fileInfo.MimeType == "video/webm" {
 				converted = t.inner.animatedStickerConfig.convertWebm(ctx, osFile)
 			} else {
-				t.inner.fileInfo.MimeType = "video/lottie+json"
+				t.inner.fileInfo.MimeType = "application/x-tgsticker" // This is expected to get overridden by convert
 				converted = t.inner.animatedStickerConfig.convert(ctx, osFile)
 			}
 			if converted != nil {
@@ -407,7 +407,7 @@ func (t *ReadyTransferer) ToDirectMediaResponse(ctx context.Context) (mediaproxy
 				if t.inner.fileInfo.MimeType == "video/webm" {
 					converted = t.inner.animatedStickerConfig.convertWebm(ctx, w)
 				} else {
-					t.inner.fileInfo.MimeType = "video/lottie+json"
+					t.inner.fileInfo.MimeType = "application/x-tgsticker" // This is expected to get overridden by convert
 					converted = t.inner.animatedStickerConfig.convert(ctx, w)
 				}
 				if converted == nil {