package hostcollect

import (
	"fmt"
	"math"
	"strings"

	"github.com/itworx/pulse/internal/host"
)

// parseLoadAverage reads the three load figures from /proc/loadavg. The remaining
// fields (runnable/total tasks and last PID) are deliberately ignored: the domain has
// no place for them and a process count from a PID namespace would be misleading.
func parseLoadAverage(data []byte) (host.RawLoad, error) {
	fields := strings.Fields(string(data))
	if len(fields) < 3 {
		return host.RawLoad{}, errBadLoadAverage
	}
	values := [3]float64{}
	for index := 0; index < 3; index++ {
		value, ok := parseFloat(fields[index])
		if !ok || value < 0 || math.IsNaN(value) || math.IsInf(value, 0) {
			return host.RawLoad{}, errBadLoadAverage
		}
		values[index] = value
	}
	return host.RawLoad{One: values[0], Five: values[1], Fifteen: values[2]}, nil
}

func (c *Collector) loadAverage() (host.RawLoad, error) {
	data, err := readLimited(c.procPath("loadavg"), maxProcessFileBytes)
	if err != nil {
		return host.RawLoad{}, fmt.Errorf("hostcollect: read loadavg: %w", err)
	}
	return parseLoadAverage(data)
}