package hostcollect

import (
	"fmt"
	"math"
	"strings"
)

// maxUptimeSeconds is the bound internal/host enforces (100 years). Rejecting here
// keeps an implausible reading from failing normalization later, where the cause is
// harder to see.
const maxUptimeSeconds = 100 * 365 * 24 * 60 * 60

// parseUptime reads the first field of /proc/uptime, the seconds since boot. The
// second field (idle time summed over cores) is intentionally unused.
func parseUptime(data []byte) (float64, error) {
	fields := strings.Fields(string(data))
	if len(fields) == 0 {
		return 0, errBadUptime
	}
	seconds, ok := parseFloat(fields[0])
	if !ok || seconds < 0 || seconds > maxUptimeSeconds || math.IsNaN(seconds) || math.IsInf(seconds, 0) {
		return 0, errBadUptime
	}
	return seconds, nil
}

func (c *Collector) uptimeSeconds() (float64, error) {
	data, err := readLimited(c.procPath("uptime"), maxProcessFileBytes)
	if err != nil {
		return 0, fmt.Errorf("hostcollect: read uptime: %w", err)
	}
	return parseUptime(data)
}