Implemented a liquidsoap process launcher.

internal/radio/liquidsoap/liquidsoap.go

@@ -0,0 +1,63 @@
+package liquidsoap
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"syscall"
+	"time"
+
+	"github.com/pkg/errors"
+)
+
+var ErrNotRunning = errors.New("liquidsoap is not running")
+
+type Liquidsoap struct {
+	command *exec.Cmd
+}
+
+func NewLiquidsoap(liquidsoapPath, scriptPath string) (*Liquidsoap, error) {
+	cmd := exec.Command(liquidsoapPath, scriptPath)
+
+	if err := cmd.Start(); err != nil {
+		return nil, err
+	}
+
+	// If there are errors in a script this time will be sufficient to wait
+	// for them to occure.
+	time.Sleep(4 * time.Second)
+
+	if _, err := os.FindProcess(cmd.Process.Pid); err != nil {
+		stderr, _ := cmd.StderrPipe()
+		var stderr_content string
+		fmt.Fscanln(stderr, &stderr_content)
+
+		if err_wait := cmd.Wait(); err != nil {
+			return nil, errors.Wrapf(err_wait, "%s: %s", err.Error(), stderr_content)
+		}
+		return nil, errors.Wrapf(err, "%s: %s", err.Error(), stderr_content)
+	}
+
+	return &Liquidsoap{
+		command: cmd}, nil
+}
+
+func (l *Liquidsoap) Stop() error {
+	if !l.IsRunning() {
+		return ErrNotRunning
+	}
+
+	if err := l.command.Process.Signal(syscall.SIGINT); err != nil {
+		return err
+	}
+
+	if err := l.command.Wait(); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (l *Liquidsoap) IsRunning() bool {
+	return l.command.Process != nil && l.command.ProcessState == nil
+}