Make run identities collision-resistant and outputs exclusive

internal/cli/run_id.go

@@ -0,0 +1,34 @@
+package cli
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"path/filepath"
+	"strings"
+	"time"
+)
+
+type RunIDGenerator func(time.Time) (string, error)
+
+func defaultRunIDGenerator(startedAt time.Time) (string, error) {
+	var suffix [16]byte
+	if _, err := io.ReadFull(rand.Reader, suffix[:]); err != nil {
+		return "", fmt.Errorf("read random run ID suffix: %w", err)
+	}
+	return fmt.Sprintf("run-%d-%s", startedAt.UnixNano(), hex.EncodeToString(suffix[:])), nil
+}
+
+func validateRunID(runID string) error {
+	if runID == "" {
+		return fmt.Errorf("run ID must not be empty")
+	}
+	if runID != strings.TrimSpace(runID) {
+		return fmt.Errorf("run ID %q must not have surrounding whitespace", runID)
+	}
+	if strings.ContainsAny(runID, `/\\`) || filepath.IsAbs(runID) || filepath.Clean(runID) != runID || runID == "." || runID == ".." {
+		return fmt.Errorf("run ID %q must be one safe path component", runID)
+	}
+	return nil
+}