feat(ansi): cut

ansi/truncate.go

@@ -7,6 +7,17 @@ import (
 	"github.com/rivo/uniseg"
 )
 
+// Cut the string, without adding any prefix or tail strings.
+// This function is aware of ANSI escape codes and will not break them, and
+// accounts for wide-characters (such as East Asians and emojis).
+// Note that the [left] parameter is inclusive, while [right] isn't.
+func Cut(s string, left, right int) string {
+	if left == 0 {
+		return Truncate(s, right, "")
+	}
+	return TruncateLeft(Truncate(s, right, ""), left, "")
+}
+
 // Truncate truncates a string to a given length, adding a tail to the
 // end if the string is longer than the given length.
 // This function is aware of ANSI escape codes and will not break them, and

ansi/truncate_test.go

@@ -300,3 +300,29 @@ func TestTruncateLeft(t *testing.T) {
 		})
 	}
 }
+
+func TestCut(t *testing.T) {
+	t.Run("simple string", func(t *testing.T) {
+		got := Cut("This is a long string", 2, 6)
+		expect := "is i"
+		if got != expect {
+			t.Errorf("exptected %q, got %q", expect, got)
+		}
+	})
+
+	t.Run("with ansi", func(t *testing.T) {
+		got := Cut("I really \x1B[38;2;249;38;114mlove\x1B[0m Go!", 4, 25)
+		expect := "ally \x1b[38;2;249;38;114mlove\x1b[0m Go!"
+		if got != expect {
+			t.Errorf("exptected %q, got %q", expect, got)
+		}
+	})
+
+	t.Run("left is 0", func(t *testing.T) {
+		got := Cut("Foo \x1B[38;2;249;38;114mbar\x1B[0mbaz", 0, 5)
+		expect := "Foo \x1B[38;2;249;38;114mb\x1B[0m"
+		if got != expect {
+			t.Errorf("exptected %q, got %q", expect, got)
+		}
+	})
+}