package main

import (
	"strings"
	"sync"
	"time"
)

const batteryCacheSeconds = 15

type BatteryProbe func() (bool, error)

type batteryWatch struct {
	mu      sync.Mutex
	probe   BatteryProbe
	now     func() time.Time
	debugf  func(format string, args ...any)
	checked time.Time
	value   bool
	warned  bool
}

func newBatteryWatch(probe BatteryProbe, now func() time.Time) *batteryWatch {
	return &batteryWatch{probe: probe, now: now}
}

func (w *batteryWatch) OnBattery() bool {
	w.mu.Lock()
	defer w.mu.Unlock()
	moment := w.now()
	if !w.checked.IsZero() && moment.Sub(w.checked) < time.Duration(batteryCacheSeconds)*time.Second {
		return w.value
	}
	w.checked = moment
	value, err := w.probe()
	if err != nil {
		value = false
		if !w.warned && w.debugf != nil {
			w.debugf("battery state unknown, treating as mains power: %v", err)
		}
		w.warned = true
	}
	w.value = value
	return value
}

func parsePmset(text string) bool {
	return strings.Contains(text, "Now drawing from 'Battery Power'")
}

func windowsOnBattery(acLine, batteryFlag byte) bool {
	return acLine == 0 && batteryFlag != 128 && batteryFlag != 255
}