package agent

import (
	"runtime"
	"sync"
	"syscall"

	"github.com/x-grk/longpolling-remote-access/internal/proto"
)

// statMu serializes samples: the CPU figure is a delta against the last one.
var statMu sync.Mutex

// sysStat samples the machine's load. It costs nothing while nobody asks: the
// panel requests it only for an open status page.
func sysStat() (proto.SysStatResult, error) {
	statMu.Lock()
	defer statMu.Unlock()
	res := proto.SysStatResult{NCPU: runtime.NumCPU()}
	cpu, err := cpuPercent()
	if err != nil {
		return res, err
	}
	res.CPU = cpu
	if res.MemTotal, res.MemUsed, err = memUsage(); err != nil {
		return res, err
	}
	var fs syscall.Statfs_t
	if err := syscall.Statfs("/", &fs); err != nil {
		return res, err
	}
	res.DiskTotal = uint64(fs.Blocks) * uint64(fs.Bsize)
	res.DiskFree = uint64(fs.Bavail) * uint64(fs.Bsize)
	return res, nil
}

func clampPercent(v float64) float64 {
	if v < 0 {
		return 0
	}
	if v > 100 {
		return 100
	}
	return v
}