// Copyright 2018 Open Networking Foundation
//
// 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.

package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"log"
	"net/http"
	"os"
	"os/signal"

	"github.com/Shopify/sarama"
	"github.com/prometheus/client_golang/prometheus"
)

var (
	broker = flag.String("broker", "voltha-kafka.default.svc.cluster.local:9092", "The Kafka broker")
	topic  = flag.String("topic", "voltha.kpis", "The Kafka topic")
)

var brokers []string

func kafkaInit(brokers []string) {
	config := sarama.NewConfig()
	config.Consumer.Return.Errors = true

	master, err := sarama.NewConsumer(brokers, config)
	if err != nil {
		panic(err)
	}
	defer func() {
		if err := master.Close(); err != nil {
			panic(err)
		}
	}()
	consumer, err := master.ConsumePartition(*topic, 0, sarama.OffsetOldest)
	if err != nil {
		panic(err)
	}
	signals := make(chan os.Signal, 1)
	signal.Notify(signals, os.Interrupt)
	doneCh := make(chan struct{})
	go func() {
		for {
			select {
			case err := <-consumer.Errors():
				fmt.Println(err)
			case msg := <-consumer.Messages():
				// fmt.Println(string(msg.Value))

				kpi := KPI{}

				err := json.Unmarshal(msg.Value, &kpi)

				if err != nil {
					log.Fatal(err)
				}

				export(kpi)

			case <-signals:
				fmt.Println("Interrupt is detected")
				doneCh <- struct{}{}
			}
		}
	}()
	<-doneCh
}

func runServer() {
	fmt.Println("Starting Server")
	http.Handle("/metrics", prometheus.Handler())
	http.ListenAndServe(":8080", nil)
}

func init() {

	// read config from cli flags
	flag.Parse()
	brokers = make([]string, 0)
	brokers = []string{*broker}
	fmt.Println("Connecting to broker: ", brokers)
	fmt.Println("Listening to topic: ", *topic)

	// register metrics within Prometheus
	prometheus.MustRegister(txBytesTotal)
	prometheus.MustRegister(rxBytesTotal)
	prometheus.MustRegister(txPacketsTotal)
	prometheus.MustRegister(rxPacketsTotal)
}

func main() {
	go kafkaInit(brokers)
	runServer()
}