feat: sync GIFv and saved GIF support

internal/app/files/gif_transcoder.go

@@ -0,0 +1,177 @@
+package files
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"time"
+)
+
+const (
+	gifTranscodeTimeout        = 20 * time.Second
+	gifTranscodeMaxInputBytes  = 50 << 20
+	gifTranscodeMaxOutputBytes = 200 << 20
+	gifTranscodeMaxConcurrent  = 2
+)
+
+// GIFVideo 是服务端把真实 GIF 规范化为 Telegram GIFv 后的结果。
+type GIFVideo struct {
+	Data     []byte
+	Width    int
+	Height   int
+	Duration float64
+}
+
+// GIFTranscoder 必须输出无声、faststart 的 H.264 MP4，并返回可持久化的视频元数据。
+type GIFTranscoder interface {
+	Transcode(ctx context.Context, data []byte) (GIFVideo, error)
+}
+
+type FFmpegGIFTranscoder struct {
+	ffmpeg  string
+	ffprobe string
+	timeout time.Duration
+	slots   chan struct{}
+}
+
+func NewFFmpegGIFTranscoder() (*FFmpegGIFTranscoder, error) {
+	ffmpeg, err := exec.LookPath("ffmpeg")
+	if err != nil {
+		return nil, err
+	}
+	ffprobeName := "ffprobe"
+	if ext := filepath.Ext(ffmpeg); ext != "" {
+		ffprobeName += ext
+	}
+	ffprobe := filepath.Join(filepath.Dir(ffmpeg), ffprobeName)
+	if _, err := os.Stat(ffprobe); err != nil {
+		ffprobe, err = exec.LookPath("ffprobe")
+		if err != nil {
+			return nil, err
+		}
+	}
+	return &FFmpegGIFTranscoder{
+		ffmpeg: ffmpeg, ffprobe: ffprobe, timeout: gifTranscodeTimeout,
+		slots: make(chan struct{}, gifTranscodeMaxConcurrent),
+	}, nil
+}
+
+func (t *FFmpegGIFTranscoder) Transcode(ctx context.Context, data []byte) (GIFVideo, error) {
+	if t == nil || t.ffmpeg == "" || t.ffprobe == "" {
+		return GIFVideo{}, fmt.Errorf("gif transcoder unavailable")
+	}
+	if len(data) == 0 || len(data) > gifTranscodeMaxInputBytes {
+		return GIFVideo{}, fmt.Errorf("gif input size out of range: %d", len(data))
+	}
+	select {
+	case t.slots <- struct{}{}:
+		defer func() { <-t.slots }()
+	case <-ctx.Done():
+		return GIFVideo{}, ctx.Err()
+	}
+	runCtx, cancel := context.WithTimeout(ctx, t.timeout)
+	defer cancel()
+
+	input, err := os.CreateTemp("", "telesrv-gif-*.gif")
+	if err != nil {
+		return GIFVideo{}, fmt.Errorf("create gif input: %w", err)
+	}
+	inputPath := input.Name()
+	defer os.Remove(inputPath)
+	if _, err := input.Write(data); err != nil {
+		input.Close()
+		return GIFVideo{}, fmt.Errorf("write gif input: %w", err)
+	}
+	if err := input.Close(); err != nil {
+		return GIFVideo{}, fmt.Errorf("close gif input: %w", err)
+	}
+	output, err := os.CreateTemp("", "telesrv-gifv-*.mp4")
+	if err != nil {
+		return GIFVideo{}, fmt.Errorf("create gif output: %w", err)
+	}
+	outputPath := output.Name()
+	output.Close()
+	defer os.Remove(outputPath)
+
+	cmd := exec.CommandContext(runCtx, t.ffmpeg,
+		"-hide_banner", "-loglevel", "error", "-y",
+		"-i", inputPath, "-map", "0:v:0", "-an",
+		"-vf", "scale=ceil(iw/2)*2:ceil(ih/2)*2:flags=lanczos",
+		"-c:v", "libx264", "-preset", "veryfast", "-crf", "23",
+		"-pix_fmt", "yuv420p", "-movflags", "+faststart", outputPath)
+	stderr, err := cmd.CombinedOutput()
+	if runCtx.Err() != nil {
+		return GIFVideo{}, runCtx.Err()
+	}
+	if err != nil {
+		return GIFVideo{}, commandError("ffmpeg gif transcode", err, stderr)
+	}
+	info, err := os.Stat(outputPath)
+	if err != nil || info.Size() <= 0 || info.Size() > gifTranscodeMaxOutputBytes {
+		return GIFVideo{}, fmt.Errorf("gif output size invalid")
+	}
+	meta, err := t.probe(runCtx, outputPath)
+	if err != nil {
+		return GIFVideo{}, err
+	}
+	video, err := os.ReadFile(outputPath)
+	if err != nil {
+		return GIFVideo{}, fmt.Errorf("read gif output: %w", err)
+	}
+	meta.Data = video
+	return meta, nil
+}
+
+func (t *FFmpegGIFTranscoder) probe(ctx context.Context, path string) (GIFVideo, error) {
+	cmd := exec.CommandContext(ctx, t.ffprobe, "-v", "error", "-select_streams", "v:0",
+		"-show_entries", "stream=width,height,duration:format=duration", "-of", "json", path)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		return GIFVideo{}, commandError("ffprobe gif output", err, out)
+	}
+	var result struct {
+		Streams []struct {
+			Width, Height int
+			Duration      string
+		} `json:"streams"`
+		Format struct {
+			Duration string `json:"duration"`
+		} `json:"format"`
+	}
+	if err := json.Unmarshal(out, &result); err != nil || len(result.Streams) != 1 {
+		return GIFVideo{}, fmt.Errorf("invalid ffprobe gif metadata")
+	}
+	duration := parsePositiveFloat(result.Streams[0].Duration)
+	if duration == 0 {
+		duration = parsePositiveFloat(result.Format.Duration)
+	}
+	stream := result.Streams[0]
+	if stream.Width <= 0 || stream.Height <= 0 || duration <= 0 {
+		return GIFVideo{}, fmt.Errorf("incomplete gif video metadata")
+	}
+	return GIFVideo{Width: stream.Width, Height: stream.Height, Duration: duration}, nil
+}
+
+func parsePositiveFloat(value string) float64 {
+	v, err := strconv.ParseFloat(strings.TrimSpace(value), 64)
+	if err != nil || v <= 0 {
+		return 0
+	}
+	return v
+}
+
+func commandError(op string, err error, output []byte) error {
+	msg := strings.TrimSpace(string(output))
+	if len(msg) > 512 {
+		msg = msg[:512]
+	}
+	if msg == "" {
+		return fmt.Errorf("%s: %w", op, err)
+	}
+	return fmt.Errorf("%s: %w: %s", op, err, msg)
+}