feat: implement pure-go RIFF EXIF injector

helper/exif.go

@@ -1,15 +1,11 @@
 package helper
 
 import (
+	"bytes"
+	"encoding/binary"
 	"encoding/json"
 	"fmt"
-	"log"
 	"math/big"
-	"os"
-	"path/filepath"
-	"strings"
-
-	"github.com/google/uuid"
 )
 
 type StickerMetadata struct {
@@ -19,7 +15,6 @@ type StickerMetadata struct {
 	Emojis    []string `json:"emojis,omitempty"`
 }
 
-// Added matching writeUIntLE from F-BOT_GO reference
 func writeUIntLE(buffer []byte, value, offset, byteLength int64) {
 	slice := make([]byte, byteLength)
 	val := new(big.Int)
@@ -36,7 +31,7 @@ func writeUIntLE(buffer []byte, value, offset, byteLength int64) {
 
 func createMetadataBytes(packName, publisher string) []byte {
 	exifObj := StickerMetadata{
-		PackId:    "com.wa.bot.sticker", // or generic ID
+		PackId:    "com.wa.bot.sticker",
 		Name:      packName,
 		Publisher: publisher,
 		Emojis:    []string{"😀"},
@@ -44,83 +39,143 @@ func createMetadataBytes(packName, publisher string) []byte {
 
 	exifJson, err := json.Marshal(exifObj)
 	if err != nil {
-		log.Printf("Failed to marshal EXIF: %v", err)
 		return nil
 	}
 
-	// WebP EXIF JSON string representation inside the file
 	bit := []byte{0x49, 0x49, 0x2A, 0x00, 0x08, 0x00, 0x00, 0x00, 0x01, 0x00, 0x41, 0x57, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x16, 0x00, 0x00, 0x00}
 	bit = append(bit, exifJson...)
-
-	// Crucial fix: Inject JSON string length at offset 14 (4 bytes)
 	writeUIntLE(bit, int64(len(exifJson)), 14, 4)
 
 	return bit
 }
 
-func getOrCreateDefaultExif() string {
+// InjectExif takes raw WebP bytes and constructs a new WebP RIFF byte slice containing the EXIF metadata
-	defaultExifPath := "temp/default.exif"
+func InjectExif(webpData []byte, packName, publisher string) ([]byte, error) {
-
+	if len(webpData) < 12 || string(webpData[0:4]) != "RIFF" || string(webpData[8:12]) != "WEBP" {
-	if err := os.MkdirAll("temp", 0755); err != nil {
+		return nil, fmt.Errorf("not a valid WEBP file")
-		log.Printf("Failed to create temp directory: %v", err)
-		return ""
 	}
 
-	// ALWAYS recreate temp/default.exif just in case previous boots were corrupted
+	var width, height uint32
-	// This corrects broken instances locally instantly
+	hasVP8X := false
-	packName := os.Getenv("STICKER_NAME")
+	var vp8xFlags byte
-	if packName == "" {
+	var vp8xBytes []byte
-		packName = "Bot"
+
+	var chunks [][]byte
+
+	// Default defaults for VP8X canvas sizes
+	width = 512
+	height = 512
+
+	offset := 12
+	for offset < len(webpData) {
+		if offset+8 > len(webpData) {
+			break
+		}
+		chunkID := string(webpData[offset : offset+4])
+		chunkSize := binary.LittleEndian.Uint32(webpData[offset+4 : offset+8])
+
+		paddedSize := chunkSize
+		if paddedSize%2 != 0 {
+			paddedSize++
+		}
+
+		if offset+8+int(paddedSize) > len(webpData) {
+			break
+		}
+
+		chunkData := webpData[offset+8 : offset+8+int(paddedSize)]
+
+		switch chunkID {
+		case "VP8X":
+			hasVP8X = true
+			vp8xFlags = chunkData[0]
+			vp8xBytes = chunkData
+			// extract dimensions
+			wBytes := []byte{chunkData[4], chunkData[5], chunkData[6], 0}
+			hBytes := []byte{chunkData[7], chunkData[8], chunkData[9], 0}
+			width = binary.LittleEndian.Uint32(wBytes) + 1
+			height = binary.LittleEndian.Uint32(hBytes) + 1
+		case "VP8 ":
+			if !hasVP8X {
+				// extract 14 bit scale block
+				w := uint32(chunkData[6]) | (uint32(chunkData[7]) << 8)
+				width = w & 0x3FFF
+				h := uint32(chunkData[8]) | (uint32(chunkData[9]) << 8)
+				height = h & 0x3FFF
+			}
+			chunks = append(chunks, webpData[offset:offset+8+int(paddedSize)])
+		case "VP8L":
+			if !hasVP8X {
+				// Parse bits 1-28 for w/h
+				b0 := uint32(chunkData[1])
+				b1 := uint32(chunkData[2])
+				b2 := uint32(chunkData[3])
+				b3 := uint32(chunkData[4])
+				width = 1 + (((b1 & 0x3F) << 8) | b0)
+				height = 1 + (((b3 & 0xF) << 10) | (b2 << 2) | ((b1 & 0xC0) >> 6))
+			}
+			chunks = append(chunks, webpData[offset:offset+8+int(paddedSize)])
+		default:
+			if chunkID != "EXIF" {
+				chunks = append(chunks, webpData[offset:offset+8+int(paddedSize)])
+			}
+		}
+		offset += 8 + int(paddedSize)
 	}
 
-	publisher := os.Getenv("STICKER_PUBLISHER")
+	exifMeta := createMetadataBytes(packName, publisher)
-	if publisher == "" {
+	if exifMeta == nil {
-		publisher = "Bot"
+		return nil, fmt.Errorf("failed to create exif byte payload")
 	}
 
-	exifContent := createMetadataBytes(packName, publisher)
+	// Turn on EXIF flag (bit 3) in VP8X
-	if exifContent == nil {
+	if !hasVP8X {
-		return ""
+		vp8xBytes = make([]byte, 10)
+		vp8xFlags = 0x08 // EXIF flag is bit 3
+		vp8xBytes[0] = vp8xFlags
+		w := width - 1
+		h := height - 1
+		vp8xBytes[4] = byte(w)
+		vp8xBytes[5] = byte(w >> 8)
+		vp8xBytes[6] = byte(w >> 16)
+		vp8xBytes[7] = byte(h)
+		vp8xBytes[8] = byte(h >> 8)
+		vp8xBytes[9] = byte(h >> 16)
+	} else {
+		vp8xBytes[0] = vp8xFlags | 0x08
 	}
 
-	if err := os.WriteFile(defaultExifPath, exifContent, 0644); err != nil {
+	var buf bytes.Buffer
-		log.Printf("Failed to write default EXIF: %v", err)
+	buf.WriteString("RIFF")
-		return ""
+	buf.Write([]byte{0, 0, 0, 0}) // Total size placeholder
+	buf.WriteString("WEBP")
+
+	// Write VP8X
+	buf.WriteString("VP8X")
+	vp8xSize := make([]byte, 4)
+	binary.LittleEndian.PutUint32(vp8xSize, 10)
+	buf.Write(vp8xSize)
+	buf.Write(vp8xBytes)
+
+	// Write existing chunks
+	for _, chunk := range chunks {
+		buf.Write(chunk)
 	}
 
-	return defaultExifPath
+	// Write EXIF
-}
+	buf.WriteString("EXIF")
-
+	exifSize := uint32(len(exifMeta))
-func ResolveExif(args []string) (string, bool) {
+	exifSizeSlice := make([]byte, 4)
-	if len(args) == 0 {
+	binary.LittleEndian.PutUint32(exifSizeSlice, exifSize)
-		return getOrCreateDefaultExif(), false
+	buf.Write(exifSizeSlice)
-	}
+	buf.Write(exifMeta)
-
+	if exifSize%2 != 0 {
-	argStr := strings.Join(args, " ")
+		buf.WriteByte(0)
-	parts := strings.Split(argStr, "|")
-
-	packName := strings.TrimSpace(parts[0])
-	publisher := "Bot"
-	if len(parts) > 1 {
-		publisher = strings.TrimSpace(parts[1])
-	}
-
-	if packName == "" && publisher == "Bot" {
-		return getOrCreateDefaultExif(), false
-	}
-
-	exifContent := createMetadataBytes(packName, publisher)
-	if exifContent == nil {
-		return getOrCreateDefaultExif(), false
 	}
 
-	id := uuid.New().String()
+	result := buf.Bytes()
-	tempPath := filepath.Join("temp", fmt.Sprintf("%s.exif", id))
+	totalSize := uint32(len(result) - 8)
-
+	binary.LittleEndian.PutUint32(result[4:8], totalSize)
-	if err := os.WriteFile(tempPath, exifContent, 0644); err != nil {
-		log.Printf("Failed to write dynamic EXIF: %v", err)
-		return getOrCreateDefaultExif(), false
-	}
 
-	return tempPath, true
+	return result, nil
 }