First run at basic structure

internal/status/status.go

@@ -0,0 +1,79 @@
+package status
+
+import (
+	"fmt"
+	"image/color"
+)
+
+// HUD resource entry.
+type Meter struct {
+	Label string
+	Base  float64
+	Level float64
+	Color color.NRGBA
+}
+
+// Meter template values.
+type Config struct {
+	Label string
+	Base  float64
+	Color color.NRGBA
+}
+
+// Collection of meters.
+type Manager struct {
+	meters []Meter
+}
+
+// Builds meters from configs.
+func NewManager(cfgs []Config) *Manager {
+	meters := make([]Meter, len(cfgs))
+	for i, cfg := range cfgs {
+		meters[i] = Meter{
+			Label: safeLabel(cfg.Label, i),
+			Base:  clamp(cfg.Base, 0, 100),
+			Level: clamp(cfg.Base, 0, 100),
+			Color: nonTransparent(cfg.Color),
+		}
+	}
+
+	return &Manager{meters: meters}
+}
+
+// Resets levels to base.
+func (m *Manager) Update() {
+	for i := range m.meters {
+		m.meters[i].Level = m.meters[i].Base
+	}
+}
+
+// Meters exposes a copy of the internal slice to prevent mutation.
+func (m *Manager) Meters() []Meter {
+	out := make([]Meter, len(m.meters))
+	copy(out, m.meters)
+	return out
+}
+
+func clamp(value, min, max float64) float64 {
+	if value < min {
+		return min
+	}
+	if value > max {
+		return max
+	}
+	return value
+}
+
+func safeLabel(label string, fallback int) string {
+	if label == "" {
+		return fmt.Sprintf("Meter %d", fallback+1)
+	}
+	return label
+}
+
+func nonTransparent(c color.NRGBA) color.NRGBA {
+	if c.A == 0 {
+		c.A = 255
+	}
+	return c
+}