// Copyright 2015 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// +build !nomeminfo
// +build !windows,!netbsd

package collector

import (
	"fmt"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/common/log"
)

const (
	memInfoSubsystem = "memory"
)

type meminfoCollector struct{}

func init() {
	Factories["meminfo"] = NewMeminfoCollector
}

// NewMeminfoCollector returns a new Collector exposing memory stats.
func NewMeminfoCollector() (Collector, error) {
	return &meminfoCollector{}, nil
}

// Update calls (*meminfoCollector).getMemInfo to get the platform specific
// memory metrics.
func (c *meminfoCollector) Update(ch chan<- prometheus.Metric) error {
	memInfo, err := c.getMemInfo()
	if err != nil {
		return fmt.Errorf("couldn't get meminfo: %s", err)
	}
	log.Debugf("Set node_mem: %#v", memInfo)
	for k, v := range memInfo {
		ch <- prometheus.MustNewConstMetric(
			prometheus.NewDesc(
				prometheus.BuildFQName(Namespace, memInfoSubsystem, k),
				fmt.Sprintf("Memory information field %s.", k),
				nil, nil,
			),
			prometheus.GaugeValue, v,
		)
	}
	return nil
}