/*
   Copyright 2014 CoreOS, Inc.

   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 stats

import (
	"encoding/json"
	"log"
	"sync"
	"time"

	"github.com/coreos/etcd/raft"
)

// ServerStats encapsulates various statistics about an EtcdServer and its
// communication with other members of the cluster
type ServerStats struct {
	Name string `json:"name"`
	// TODO(jonboulle): use ID instead of name?
	ID        string         `json:"id"`
	State     raft.StateType `json:"state"`
	StartTime time.Time      `json:"startTime"`

	LeaderInfo struct {
		Name      string    `json:"leader"`
		Uptime    string    `json:"uptime"`
		StartTime time.Time `json:"startTime"`
	} `json:"leaderInfo"`

	RecvAppendRequestCnt uint64  `json:"recvAppendRequestCnt,"`
	RecvingPkgRate       float64 `json:"recvPkgRate,omitempty"`
	RecvingBandwidthRate float64 `json:"recvBandwidthRate,omitempty"`

	SendAppendRequestCnt uint64  `json:"sendAppendRequestCnt"`
	SendingPkgRate       float64 `json:"sendPkgRate,omitempty"`
	SendingBandwidthRate float64 `json:"sendBandwidthRate,omitempty"`

	sendRateQueue *statsQueue
	recvRateQueue *statsQueue

	sync.Mutex
}

func (ss *ServerStats) JSON() []byte {
	ss.Lock()
	stats := *ss
	ss.Unlock()
	stats.LeaderInfo.Uptime = time.Now().Sub(stats.LeaderInfo.StartTime).String()
	stats.SendingPkgRate, stats.SendingBandwidthRate = stats.SendRates()
	stats.RecvingPkgRate, stats.RecvingBandwidthRate = stats.RecvRates()
	b, err := json.Marshal(stats)
	// TODO(jonboulle): appropriate error handling?
	if err != nil {
		log.Printf("stats: error marshalling server stats: %v", err)
	}
	return b
}

// Initialize clears the statistics of ServerStats and resets its start time
func (ss *ServerStats) Initialize() {
	if ss == nil {
		return
	}
	now := time.Now()
	ss.StartTime = now
	ss.LeaderInfo.StartTime = now
	ss.sendRateQueue = &statsQueue{
		back: -1,
	}
	ss.recvRateQueue = &statsQueue{
		back: -1,
	}
}

// RecvRates calculates and returns the rate of received append requests
func (ss *ServerStats) RecvRates() (float64, float64) {
	return ss.recvRateQueue.Rate()
}

// SendRates calculates and returns the rate of sent append requests
func (ss *ServerStats) SendRates() (float64, float64) {
	return ss.sendRateQueue.Rate()
}

// RecvAppendReq updates the ServerStats in response to an AppendRequest
// from the given leader being received
func (ss *ServerStats) RecvAppendReq(leader string, reqSize int) {
	ss.Lock()
	defer ss.Unlock()

	now := time.Now()

	ss.State = raft.StateFollower
	if leader != ss.LeaderInfo.Name {
		ss.LeaderInfo.Name = leader
		ss.LeaderInfo.StartTime = now
	}

	ss.recvRateQueue.Insert(
		&RequestStats{
			SendingTime: now,
			Size:        reqSize,
		},
	)
	ss.RecvAppendRequestCnt++
}

// SendAppendReq updates the ServerStats in response to an AppendRequest
// being sent by this server
func (ss *ServerStats) SendAppendReq(reqSize int) {
	ss.Lock()
	defer ss.Unlock()

	now := time.Now()

	if ss.State != raft.StateLeader {
		ss.State = raft.StateLeader
		ss.LeaderInfo.Name = ss.ID
		ss.LeaderInfo.StartTime = now
	}

	ss.sendRateQueue.Insert(
		&RequestStats{
			SendingTime: now,
			Size:        reqSize,
		},
	)

	ss.SendAppendRequestCnt++
}