refactoring-1

introduced pipelines and abstracted download process.go in Downloader interface

server/internal/pipes/FileWriter.go

@@ -0,0 +1,45 @@
+package pipes
+
+import (
+	"io"
+	"log/slog"
+	"os"
+)
+
+type FileWriter struct {
+	Path    string
+	IsFinal bool
+}
+
+func (f *FileWriter) Name() string { return "file-writer" }
+
+func (f *FileWriter) Connect(r io.Reader) (io.Reader, error) {
+	file, err := os.Create(f.Path)
+	if err != nil {
+		return nil, err
+	}
+
+	if f.IsFinal {
+		go func() {
+			defer file.Close()
+			if _, err := io.Copy(file, r); err != nil {
+				slog.Error("FileWriter (final) error", slog.Any("err", err))
+			}
+		}()
+		return r, nil
+	}
+
+	pr, pw := io.Pipe()
+
+	go func() {
+		defer file.Close()
+		defer pw.Close()
+
+		writer := io.MultiWriter(file, pw)
+		if _, err := io.Copy(writer, r); err != nil {
+			slog.Error("FileWriter (pipeline) error", slog.Any("err", err))
+		}
+	}()
+
+	return pr, nil
+}

server/internal/pipes/Transcoder.go

@@ -0,0 +1,66 @@
+package pipes
+
+import (
+	"bufio"
+	"errors"
+	"io"
+	"log/slog"
+	"os/exec"
+	"strings"
+)
+
+type Transcoder struct {
+	Args []string
+}
+
+func (t *Transcoder) Name() string { return "ffmpeg-transcoder" }
+
+func (t *Transcoder) Connect(r io.Reader) (io.Reader, error) {
+	cmd := exec.Command("ffmpeg",
+		append([]string{"-i", "pipe:0"}, append(t.Args, "-f", "webm", "pipe:1")...)...,
+	)
+
+	stdin, err := cmd.StdinPipe()
+	if err != nil {
+		return nil, err
+	}
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		return nil, err
+	}
+	stderr, err := cmd.StderrPipe()
+	if err != nil {
+		return nil, err
+	}
+
+	go func() {
+		reader := bufio.NewReader(stderr)
+		var line string
+
+		for {
+			part, err := reader.ReadString('\r')
+			line += part
+			if err != nil {
+				break
+			}
+
+			line = strings.TrimRight(line, "\r\n")
+			slog.Info("ffmpeg transcoder", slog.String("log", line))
+			line = ""
+		}
+	}()
+
+	go func() {
+		defer stdin.Close()
+		_, err := io.Copy(stdin, r)
+		if err != nil && !errors.Is(err, io.EOF) {
+			slog.Error("transcoder stdin error", slog.Any("err", err))
+		}
+	}()
+
+	if err := cmd.Start(); err != nil {
+		return nil, err
+	}
+
+	return stdout, nil
+}

server/internal/pipes/pipe.go

@@ -0,0 +1,8 @@
+package pipes
+
+import "io"
+
+type Pipe interface {
+	Name() string
+	Connect(r io.Reader) (io.Reader, error)
+}