feat: style ranges

ranges.go

@@ -6,6 +6,20 @@
 	"github.com/charmbracelet/x/ansi"
 )
 
+// StyleRanges allows to, given a string, style a range of it differently.
+// The function will take into account existing styles.
+// See [StyleRanges] to style multipe ranges in the same string.
+func StyleRange(s string, start, end int, style Style) string {
+	if end == 0 {
+		return s
+	}
+	return StyleRanges(s, []Range{{
+		start,
+		end,
+		style,
+	}})
+}
+
 // StyleRanges allows to, given a string, style ranges of it differently.
 // The function will take into account existing styles.
 // Ranges should not overlap.

ranges_test.go

@@ -6,6 +6,80 @@ import (
 	"github.com/muesli/termenv"
 )
 
+func TestStyleRange(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		rng      Range
+		expected string
+	}{
+		{
+			name:     "empty ranges",
+			input:    "hello world",
+			rng:      Range{},
+			expected: "hello world",
+		},
+		{
+			name:     "single range in middle",
+			input:    "hello world",
+			rng:      NewRange(6, 11, NewStyle().Bold(true)),
+			expected: "hello \x1b[1mworld\x1b[0m",
+		},
+		{
+			name:     "multiple ranges",
+			input:    "hello world",
+			rng:      NewRange(0, 5, NewStyle().Bold(true)),
+			expected: "\x1b[1mhello\x1b[0m world",
+		},
+		{
+			name:     "overlapping with existing ANSI",
+			input:    "hello \x1b[32mworld\x1b[0m",
+			rng:      NewRange(0, 5, NewStyle().Bold(true)),
+			expected: "\x1b[1mhello\x1b[0m \x1b[32mworld\x1b[0m",
+		},
+		{
+			name:     "style at start",
+			input:    "hello world",
+			rng:      NewRange(0, 5, NewStyle().Bold(true)),
+			expected: "\x1b[1mhello\x1b[0m world",
+		},
+		{
+			name:     "style at end",
+			input:    "hello world",
+			rng:      NewRange(6, 11, NewStyle().Bold(true)),
+			expected: "hello \x1b[1mworld\x1b[0m",
+		},
+		{
+			name:     "multiple styles with gap",
+			input:    "hello beautiful world",
+			rng:      NewRange(0, 5, NewStyle().Bold(true)),
+			expected: "\x1b[1mhello\x1b[0m beautiful world",
+		},
+		{
+			name:     "adjacent ranges",
+			input:    "hello world",
+			rng:      NewRange(6, 11, NewStyle().Italic(true)),
+			expected: "hello \x1b[3mworld\x1b[0m",
+		},
+		{
+			name:     "wide-width characters",
+			input:    "Hello 你好 世界",
+			rng:      NewRange(11, 50, NewStyle().Bold(true)), // "世界"
+			expected: "Hello 你好 \x1b[1m世界\x1b[0m",
+		},
+	}
+
+	for _, tt := range tests {
+		renderer.SetColorProfile(termenv.ANSI)
+		t.Run(tt.name, func(t *testing.T) {
+			result := StyleRange(tt.input, tt.rng.Start, tt.rng.End, tt.rng.Style)
+			if result != tt.expected {
+				t.Errorf("StyleRanges()\n got = %q\nwant = %q\n", result, tt.expected)
+			}
+		})
+	}
+}
+
 func TestStyleRanges(t *testing.T) {
 	tests := []struct {
 		name     string