Added a primitive battery charge monitor.

webgui/charge_tracker.go

@@ -0,0 +1,35 @@
+package webgui
+
+import (
+	"time"
+)
+
+type ChargeTracker struct {
+	fullLevel    float64
+	currentLevel float64
+	lastUpdate   time.Time
+}
+
+// Creates a new charge tracker. fullLevel is in A h.
+func NewChargeTracker(fullLevel float64) *ChargeTracker {
+	return &ChargeTracker{
+		fullLevel:    fullLevel,
+		currentLevel: fullLevel, // Have to start somewhere.
+		lastUpdate:   time.Now(),
+	}
+}
+
+func (c *ChargeTracker) Update(amp float64) {
+	newNow := time.Now()
+	elapsed := newNow.Sub(c.lastUpdate).Hours()
+	c.lastUpdate = newNow
+	c.currentLevel -= elapsed * amp
+}
+
+func (c *ChargeTracker) CurrentLevel() float64 {
+	return c.currentLevel
+}
+
+func (c *ChargeTracker) Reset() {
+	c.currentLevel = c.fullLevel
+}