// Copyright 2017 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 !noqdisc

package collector

import (
	"encoding/json"
	"io/ioutil"
	"path/filepath"

	"github.com/ema/qdisc"
	"github.com/go-kit/kit/log"
	"github.com/prometheus/client_golang/prometheus"
	"gopkg.in/alecthomas/kingpin.v2"
)

type qdiscStatCollector struct {
	bytes      typedDesc
	packets    typedDesc
	drops      typedDesc
	requeues   typedDesc
	overlimits typedDesc
	qlength    typedDesc
	backlog    typedDesc
	logger     log.Logger
}

var (
	collectorQdisc = kingpin.Flag("collector.qdisc.fixtures", "test fixtures to use for qdisc collector end-to-end testing").Default("").String()
)

func init() {
	registerCollector("qdisc", defaultDisabled, NewQdiscStatCollector)
}

// NewQdiscStatCollector returns a new Collector exposing queuing discipline statistics.
func NewQdiscStatCollector(logger log.Logger) (Collector, error) {
	return &qdiscStatCollector{
		bytes: typedDesc{prometheus.NewDesc(
			prometheus.BuildFQName(namespace, "qdisc", "bytes_total"),
			"Number of bytes sent.",
			[]string{"device", "kind"}, nil,
		), prometheus.CounterValue},
		packets: typedDesc{prometheus.NewDesc(
			prometheus.BuildFQName(namespace, "qdisc", "packets_total"),
			"Number of packets sent.",
			[]string{"device", "kind"}, nil,
		), prometheus.CounterValue},
		drops: typedDesc{prometheus.NewDesc(
			prometheus.BuildFQName(namespace, "qdisc", "drops_total"),
			"Number of packets dropped.",
			[]string{"device", "kind"}, nil,
		), prometheus.CounterValue},
		requeues: typedDesc{prometheus.NewDesc(
			prometheus.BuildFQName(namespace, "qdisc", "requeues_total"),
			"Number of packets dequeued, not transmitted, and requeued.",
			[]string{"device", "kind"}, nil,
		), prometheus.CounterValue},
		overlimits: typedDesc{prometheus.NewDesc(
			prometheus.BuildFQName(namespace, "qdisc", "overlimits_total"),
			"Number of overlimit packets.",
			[]string{"device", "kind"}, nil,
		), prometheus.CounterValue},
		qlength: typedDesc{prometheus.NewDesc(
			prometheus.BuildFQName(namespace, "qdisc", "current_queue_length"),
			"Number of packets currently in queue to be sent.",
			[]string{"device", "kind"}, nil,
		), prometheus.GaugeValue},
		backlog: typedDesc{prometheus.NewDesc(
			prometheus.BuildFQName(namespace, "qdisc", "backlog"),
			"Number of bytes currently in queue to be sent.",
			[]string{"device", "kind"}, nil,
		), prometheus.GaugeValue},
		logger: logger,
	}, nil
}

func testQdiscGet(fixtures string) ([]qdisc.QdiscInfo, error) {
	var res []qdisc.QdiscInfo

	b, err := ioutil.ReadFile(filepath.Join(fixtures, "results.json"))
	if err != nil {
		return res, err
	}

	err = json.Unmarshal(b, &res)
	return res, err
}

func (c *qdiscStatCollector) Update(ch chan<- prometheus.Metric) error {
	var msgs []qdisc.QdiscInfo
	var err error

	fixtures := *collectorQdisc

	if fixtures == "" {
		msgs, err = qdisc.Get()
	} else {
		msgs, err = testQdiscGet(fixtures)
	}

	if err != nil {
		return err
	}

	for _, msg := range msgs {
		// Only report root qdisc information.
		if msg.Parent != 0 {
			continue
		}

		ch <- c.bytes.mustNewConstMetric(float64(msg.Bytes), msg.IfaceName, msg.Kind)
		ch <- c.packets.mustNewConstMetric(float64(msg.Packets), msg.IfaceName, msg.Kind)
		ch <- c.drops.mustNewConstMetric(float64(msg.Drops), msg.IfaceName, msg.Kind)
		ch <- c.requeues.mustNewConstMetric(float64(msg.Requeues), msg.IfaceName, msg.Kind)
		ch <- c.overlimits.mustNewConstMetric(float64(msg.Overlimits), msg.IfaceName, msg.Kind)
		ch <- c.qlength.mustNewConstMetric(float64(msg.Qlen), msg.IfaceName, msg.Kind)
		ch <- c.backlog.mustNewConstMetric(float64(msg.Backlog), msg.IfaceName, msg.Kind)
	}

	return nil
}