//go:build linux

package beach

import (
	"os"
	"runtime"
	"sync"
	"syscall"
	"time"
)

var (
	cpuMu   sync.Mutex
	lastCPU cpuTimes
	lastAt  time.Time
	lastPct float64
)

func readFile(p string) string { b, _ := os.ReadFile(p); return string(b) }

// CollectHost reads /proc. CPU use is the change since the previous call; the
// first call takes a short sample of its own.
func CollectHost() Host {
	h := Host{Supported: true, CPUs: runtime.NumCPU(), Disks: []Filesystem{}}
	h.Hostname, _ = os.Hostname()
	h.Uptime = parseUptime(readFile("/proc/uptime"))
	h.Load = parseLoad(readFile("/proc/loadavg"))
	h.MemTotal, h.MemUsed, h.SwapTotal, h.SwapUsed = parseMeminfo(readFile("/proc/meminfo"))
	cpuMu.Lock()
	if now, err := parseCPU(readFile("/proc/stat")); err == nil {
		if lastAt.IsZero() {
			time.Sleep(250 * time.Millisecond)
			if n2, err := parseCPU(readFile("/proc/stat")); err == nil {
				lastPct, now = cpuPct(now, n2), n2
			}
			lastCPU, lastAt = now, time.Now()
		} else if time.Since(lastAt) > 500*time.Millisecond {
			lastPct = cpuPct(lastCPU, now)
			lastCPU, lastAt = now, time.Now()
		}
	}
	h.CPUPct = lastPct
	cpuMu.Unlock()
	for _, m := range realMounts(readFile("/proc/mounts")) {
		var st syscall.Statfs_t
		if syscall.Statfs(m, &st) == nil && st.Blocks > 0 {
			bs := uint64(st.Bsize)
			h.Disks = append(h.Disks, Filesystem{Mount: m, Total: st.Blocks * bs, Used: (st.Blocks - st.Bfree) * bs})
		}
	}
	return h
}