// +build !noloadavg

package collector

import (
	"fmt"
	"io/ioutil"
	"strconv"
	"strings"

	"github.com/golang/glog"
	"github.com/prometheus/client_golang/prometheus"
)

const (
	procLoad = "/proc/loadavg"
)

var (
	load1 = prometheus.NewGauge()
)

type loadavgCollector struct {
	registry prometheus.Registry
	config   Config
}

func init() {
	Factories["loadavg"] = NewLoadavgCollector
}

// Takes a config struct and prometheus registry and returns a new Collector exposing
// load, seconds since last login and a list of tags as specified by config.
func NewLoadavgCollector(config Config, registry prometheus.Registry) (Collector, error) {
	c := loadavgCollector{
		config:   config,
		registry: registry,
	}

	registry.Register(
		"node_load1",
		"1m load average",
		prometheus.NilLabels,
		load1,
	)
	return &c, nil
}

func (c *loadavgCollector) Update() (updates int, err error) {
	load, err := getLoad1()
	if err != nil {
		return updates, fmt.Errorf("Couldn't get load: %s", err)
	}
	updates++
	glog.V(1).Infof("Set node_load: %f", load)
	load1.Set(nil, load)

	return updates, err
}

func getLoad1() (float64, error) {
	data, err := ioutil.ReadFile(procLoad)
	if err != nil {
		return 0, err
	}
	return parseLoad(string(data))
}

func parseLoad(data string) (float64, error) {
	parts := strings.Fields(data)
	load, err := strconv.ParseFloat(parts[0], 64)
	if err != nil {
		return 0, fmt.Errorf("Could not parse load '%s': %s", parts[0], err)
	}
	return load, nil
}