package agent

import (
	"bytes"
	"os/exec"
	"runtime"
	"strconv"

	"golang.org/x/sys/unix"
)

// cpuPercent sums the per-process CPU shares ps reports. macOS exposes the
// host CPU ticks only through Mach calls, which need cgo.
func cpuPercent() (float64, error) {
	out, err := exec.Command("/bin/ps", "-A", "-o", "%cpu=").Output()
	if err != nil {
		return 0, err
	}
	var sum float64
	for _, f := range bytes.Fields(out) {
		// Some locales print a decimal comma.
		v, _ := strconv.ParseFloat(string(bytes.Replace(f, []byte(","), []byte("."), 1)), 64)
		sum += v
	}
	return clampPercent(sum / float64(runtime.NumCPU())), nil
}

// memUsage takes the kernel's own share of memory still available
// (kern.memorystatus_level, what `memory_pressure` prints).
func memUsage() (total, used uint64, err error) {
	total, err = unix.SysctlUint64("hw.memsize")
	if err != nil {
		return 0, 0, err
	}
	level, err := unix.SysctlUint32("kern.memorystatus_level")
	if err != nil {
		return 0, 0, err
	}
	if level > 100 {
		level = 100
	}
	return total, total / 100 * uint64(100-level), nil
}