feat: add shimmer text rendering (#2027)

1 files changed, 143 insertions, 0 deletions

diff --git a/packages/tui/internal/util/shimmer.go b/packages/tui/internal/util/shimmer.go
new file mode 100644
index 000000000..88654ff07
--- /dev/null
+++ b/packages/tui/internal/util/shimmer.go
@@ -0,0 +1,143 @@
+package util
+
+import (
+	"math"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/charmbracelet/lipgloss/v2"
+	"github.com/charmbracelet/lipgloss/v2/compat"
+	"github.com/sst/opencode/internal/styles"
+)
+
+var shimmerStart = time.Now()
+
+// Shimmer renders text with a moving foreground highlight.
+// bg is the background color, dim is the base text color, bright is the highlight color.
+func Shimmer(s string, bg compat.AdaptiveColor, _ compat.AdaptiveColor, _ compat.AdaptiveColor) string {
+	if s == "" {
+		return ""
+	}
+
+	runes := []rune(s)
+	n := len(runes)
+	if n == 0 {
+		return s
+	}
+
+	pad := 10
+	period := float64(n + pad*2)
+	sweep := 2.5
+	elapsed := time.Since(shimmerStart).Seconds()
+	pos := (math.Mod(elapsed, sweep) / sweep) * period
+
+	half := 4.0
+
+	type seg struct {
+		useHex bool
+		hex    string
+		bold   bool
+		faint  bool
+		text   string
+	}
+	var segs []seg
+
+	useHex := hasTrueColor()
+	for i, r := range runes {
+		ip := float64(i + pad)
+		dist := math.Abs(ip - pos)
+		t := 0.0
+		if dist <= half {
+			x := math.Pi * (dist / half)
+			t = 0.5 * (1.0 + math.Cos(x))
+		}
+		// Cosine brightness: base + amp*t (quantized for grouping)
+		base := 0.55
+		amp := 0.45
+		brightness := base
+		if t > 0 {
+			brightness = base + amp*t
+		}
+		lvl := int(math.Round(brightness * 255.0))
+		if !useHex {
+			step := 24 // ~11 steps across range for non-truecolor
+			lvl = int(math.Round(float64(lvl)/float64(step))) * step
+		}
+
+		bold := lvl >= 208
+		faint := lvl <= 128
+
+		// truecolor if possible; else fallback to modifiers only
+		hex := ""
+		if useHex {
+			if lvl < 0 {
+				lvl = 0
+			}
+			if lvl > 255 {
+				lvl = 255
+			}
+			hex = rgbHex(lvl, lvl, lvl)
+		}
+
+		if len(segs) == 0 {
+			segs = append(segs, seg{useHex: useHex, hex: hex, bold: bold, faint: faint, text: string(r)})
+		} else {
+			last := &segs[len(segs)-1]
+			if last.useHex == useHex && last.hex == hex && last.bold == bold && last.faint == faint {
+				last.text += string(r)
+			} else {
+				segs = append(segs, seg{useHex: useHex, hex: hex, bold: bold, faint: faint, text: string(r)})
+			}
+		}
+	}
+
+	var b strings.Builder
+	for _, g := range segs {
+		st := styles.NewStyle().Background(bg)
+		if g.useHex && g.hex != "" {
+			c := compat.AdaptiveColor{Dark: lipgloss.Color(g.hex), Light: lipgloss.Color(g.hex)}
+			st = st.Foreground(c)
+		}
+		if g.bold {
+			st = st.Bold(true)
+		}
+		if g.faint {
+			st = st.Faint(true)
+		}
+		b.WriteString(st.Render(g.text))
+	}
+	return b.String()
+}
+
+func hasTrueColor() bool {
+	c := strings.ToLower(os.Getenv("COLORTERM"))
+	return strings.Contains(c, "truecolor") || strings.Contains(c, "24bit")
+}
+
+func rgbHex(r, g, b int) string {
+	if r < 0 {
+		r = 0
+	}
+	if r > 255 {
+		r = 255
+	}
+	if g < 0 {
+		g = 0
+	}
+	if g > 255 {
+		g = 255
+	}
+	if b < 0 {
+		b = 0
+	}
+	if b > 255 {
+		b = 255
+	}
+	return "#" + hex2(r) + hex2(g) + hex2(b)
+}
+
+func hex2(v int) string {
+	const digits = "0123456789abcdef"
+	return string([]byte{digits[(v>>4)&0xF], digits[v&0xF]})
+}