Add strikethrough formatting

telegram/formatter/formatter.go

@@ -20,6 +20,8 @@ type InsertionStack []*Insertion
 var boldRunesMarkdown = []rune("**")
 var boldRunesXEP0393 = []rune("*")
 var italicRunes = []rune("_")
+var strikeRunesMarkdown = []rune("~~")
+var strikeRunesXEP0393 = []rune("~")
 var codeRunes = []rune("`")
 var preRuneStart = []rune("```\n")
 var preRuneEnd = []rune("\n```")
@@ -133,6 +135,8 @@ func EntityToMarkdown(entity *client.TextEntity) (*Insertion, *Insertion) {
 		return markupBraces(entity, boldRunesMarkdown, boldRunesMarkdown)
 	case client.TypeTextEntityTypeItalic:
 		return markupBraces(entity, italicRunes, italicRunes)
+	case client.TypeTextEntityTypeStrikethrough:
+		return markupBraces(entity, strikeRunesMarkdown, strikeRunesMarkdown)
 	case client.TypeTextEntityTypeCode:
 		return markupBraces(entity, codeRunes, codeRunes)
 	case client.TypeTextEntityTypePre:
@@ -159,6 +163,8 @@ func EntityToXEP0393(entity *client.TextEntity) (*Insertion, *Insertion) {
 		return markupBraces(entity, boldRunesXEP0393, boldRunesXEP0393)
 	case client.TypeTextEntityTypeItalic:
 		return markupBraces(entity, italicRunes, italicRunes)
+	case client.TypeTextEntityTypeStrikethrough:
+		return markupBraces(entity, strikeRunesXEP0393, strikeRunesXEP0393)
 	case client.TypeTextEntityTypeCode:
 		// inline code is non-standard
 		return markupBraces(entity, codeRunes, codeRunes)

telegram/formatter/formatter_test.go

@@ -366,3 +366,29 @@ func TestFormattingXEP0393InlineCode(t *testing.T) {
 		t.Errorf("Wrong intersecting formatting: %v", markup)
 	}
 }
+
+func TestFormattingMarkdownStrikethrough(t *testing.T) {
+	markup := Format("Everyone dislikes cake.", []*client.TextEntity{
+		&client.TextEntity{
+			Offset: 9,
+			Length: 3,
+			Type:   &client.TextEntityTypeStrikethrough{},
+		},
+	}, EntityToMarkdown)
+	if markup != "Everyone ~~dis~~likes cake." {
+		t.Errorf("Wrong strikethrough formatting: %v", markup)
+	}
+}
+
+func TestFormattingXEP0393Strikethrough(t *testing.T) {
+	markup := Format("Everyone dislikes cake.", []*client.TextEntity{
+		&client.TextEntity{
+			Offset: 9,
+			Length: 3,
+			Type:   &client.TextEntityTypeStrikethrough{},
+		},
+	}, EntityToXEP0393)
+	if markup != "Everyone ~dis~likes cake." {
+		t.Errorf("Wrong strikethrough formatting: %v", markup)
+	}
+}