#235: rename Language column to Type; attachment pastes show file extension

- history/mine table column 'Language' -> 'Type' (data-sort key 'type')
- /api/public and /api/mine rows gain a 'type' field: file extension for
  attachment pastes, stored language otherwise (default 'text')
- paste page stats label 'Language' -> 'Type'; summary line uses the same
  label; get-paste JSON gains 'type'
- store list queries LEFT JOIN attachments to expose the filename
- table.js sorting accepts the 'type' key

internal/api/issue235_type_test.go

@@ -0,0 +1,40 @@
+package api
+
+import "testing"
+
+// #235: Type column. Text pastes show the language, attachment pastes show
+// the file extension (lowercase, no dot).
+func TestDisplayType(t *testing.T) {
+	lang := "python"
+	cases := []struct {
+		lang *string
+		att  string
+		want string
+	}{
+		{nil, "", "text"},
+		{&lang, "", "python"},
+		{&lang, "report.pdf", "pdf"},
+		{nil, "photo.PNG", "png"},
+		{&lang, "archive.tar.gz", "gz"},
+		{&lang, "noext", "python"},     // no extension: fall back to language
+		{&lang, ".hidden", "python"},   // dotfile: no extension
+		{&lang, "dir/name.txt", "txt"}, // path component only
+	}
+	for _, c := range cases {
+		if got := displayType(c.lang, c.att); got != c.want {
+			t.Errorf("displayType(%v, %q) = %q, want %q", c.lang, c.att, got, c.want)
+		}
+	}
+}
+
+func TestAttachmentExtName(t *testing.T) {
+	cases := map[string]string{
+		"a.txt": "txt", "A.PNG": "png", "noext": "", ".hidden": "",
+		"x.": "", "dir/b.md": "md", "": "",
+	}
+	for in, want := range cases {
+		if got := attachmentExtName(in); got != want {
+			t.Errorf("attachmentExtName(%q) = %q, want %q", in, got, want)
+		}
+	}
+}

internal/api/server.go

@@ -315,11 +315,26 @@ func (a *apiServer) handleGetPaste(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, 200, map[string]any{
 		"id": row.ID, "content": row.Content, "content_type": row.ContentType,
 		"language": store.NullStrPtr(row.Language), "title": store.NullStrPtr(row.Title), "created_at": row.CreatedAt,
+		"type":     a.pasteTypeLabel(row),
 		"view_count": row.ViewCount, "visibility": row.Visibility,
 		"reads_remaining": rem,
 	})
 }
 
+// pasteTypeLabel computes the Type value for a single paste (#235): file
+// extension for attachment pastes, else the stored language, else "text".
+func (a *apiServer) pasteTypeLabel(row *store.PasteRow) string {
+	if att, err := a.store.GetAttachmentForPaste(row.ID); err == nil && att != nil {
+		if ext := attachmentExtName(att.Filename); ext != "" {
+			return ext
+		}
+	}
+	if !row.Language.Valid || row.Language.String == "" {
+		return "text"
+	}
+	return row.Language.String
+}
+
 func (a *apiServer) handleDeletePaste(w http.ResponseWriter, r *http.Request) {
 	id := chi.URLParam(r, "id")
 	row, err := a.store.GetPaste(id)
@@ -376,6 +391,33 @@ func (a *apiServer) deletionAuthorized(r *http.Request, row *store.PasteRow) boo
 		row.ViewerID.String != "" && row.ViewerID.String == vid
 }
 
+// displayType returns the Type-column value for a list row (#235): the file
+// extension for attachment pastes, otherwise the detected language (default
+// "text").
+func displayType(lang *string, attFilename string) string {
+	if ext := attachmentExtName(attFilename); ext != "" {
+		return ext
+	}
+	if lang == nil || *lang == "" {
+		return "text"
+	}
+	return *lang
+}
+
+// attachmentExtName returns the lowercase extension (without dot) of a
+// filename, or "" when there is none.
+func attachmentExtName(filename string) string {
+	name := filename
+	if i := strings.LastIndexByte(name, '/'); i >= 0 {
+		name = name[i+1:]
+	}
+	i := strings.LastIndexByte(name, '.')
+	if i <= 0 || i == len(name)-1 {
+		return ""
+	}
+	return strings.ToLower(name[i+1:])
+}
+
 // handleListMine serves /api/mine: pastes created from this browser (#37).
 func (a *apiServer) handleListMine(w http.ResponseWriter, r *http.Request) {
 	vid := currentViewerID(r)
@@ -394,7 +436,7 @@ func (a *apiServer) handleListMine(w http.ResponseWriter, r *http.Request) {
 	for _, row := range rows {
 		lang, title := store.NullStrPtr(row.Language), store.NullStrPtr(row.Title)
 		items = append(items, map[string]any{
-			"id": row.ID, "title": title, "language": lang,
+			"id": row.ID, "title": title, "language": lang, "type": displayType(lang, row.AttFilename),
 			"created_at": row.CreatedAt, "view_count": row.ViewCount, "size": row.Size,
 			"custom_slug": store.NullStrPtr(row.CustomSlug), "visibility": row.Visibility,
 			"is_can": row.IsCan,
@@ -415,7 +457,7 @@ func (a *apiServer) handleListPublic(w http.ResponseWriter, r *http.Request) {
 	for _, row := range rows {
 		lang, title := store.NullStrPtr(row.Language), store.NullStrPtr(row.Title)
 		items = append(items, map[string]any{
-			"id": row.ID, "title": title, "language": lang,
+			"id": row.ID, "title": title, "language": lang, "type": displayType(lang, row.AttFilename),
 			"created_at": row.CreatedAt, "view_count": row.ViewCount, "size": row.Size,
 			"custom_slug": store.NullStrPtr(row.CustomSlug),
 			"is_can":      row.IsCan,