/*
Real-time Charging System for Telecom & ISP environments
Copyright (C) 2012-2014 ITsysCOM GmbH

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>
*/

package sessionmanager

import (
	"bufio"
	"errors"
	"fmt"
	"log/syslog"
	"net"
	"time"

	"github.com/cgrates/cgrates/config"
	"github.com/cgrates/cgrates/engine"
	"github.com/cgrates/cgrates/utils"
	"github.com/cgrates/fsock"
)

var cfg *config.CGRConfig // Share the configuration with the rest of the package

// The freeswitch session manager type holding a buffer for the network connection
// and the active sessions
type FSSessionManager struct {
	conn        net.Conn
	buf         *bufio.Reader
	sessions    []*Session
	connector   engine.Connector
	debitPeriod time.Duration
	loggerDB    engine.LogStorage
}

func NewFSSessionManager(storage engine.LogStorage, connector engine.Connector, debitPeriod time.Duration) *FSSessionManager {
	return &FSSessionManager{loggerDB: storage, connector: connector, debitPeriod: debitPeriod}
}

// Connects to the freeswitch mod_event_socket server and starts
// listening for events.
func (sm *FSSessionManager) Connect(cgrCfg *config.CGRConfig) (err error) {
	cfg = cgrCfg // make config global
	eventFilters := map[string]string{"Call-Direction": "inbound"}
	if fsock.FS, err = fsock.NewFSock(cfg.FreeswitchServer, cfg.FreeswitchPass, cfg.FreeswitchReconnects, sm.createHandlers(), eventFilters, engine.Logger.(*syslog.Writer)); err != nil {
		return err
	} else if !fsock.FS.Connected() {
		return errors.New("Cannot connect to FreeSWITCH")
	}
	fsock.FS.ReadEvents()
	return errors.New("stopped reading events")
}

func (sm *FSSessionManager) createHandlers() (handlers map[string][]func(string)) {
	hb := func(body string) {
		ev := new(FSEvent).New(body)
		sm.OnHeartBeat(ev)
	}
	cp := func(body string) {
		ev := new(FSEvent).New(body)
		sm.OnChannelPark(ev)
	}
	ca := func(body string) {
		ev := new(FSEvent).New(body)
		sm.OnChannelAnswer(ev)
	}
	ch := func(body string) {
		ev := new(FSEvent).New(body)
		sm.OnChannelHangupComplete(ev)
	}
	return map[string][]func(string){
		"HEARTBEAT":               []func(string){hb},
		"CHANNEL_PARK":            []func(string){cp},
		"CHANNEL_ANSWER":          []func(string){ca},
		"CHANNEL_HANGUP_COMPLETE": []func(string){ch},
	}
}

// Searches and return the session with the specifed uuid
func (sm *FSSessionManager) GetSession(uuid string) *Session {
	for _, s := range sm.sessions {
		if s.uuid == uuid {
			return s
		}
	}
	return nil
}

// Disconnects a session by sending hangup command to freeswitch
func (sm *FSSessionManager) DisconnectSession(uuid string, notify string) {
	// engine.Logger.Debug(fmt.Sprintf("Session: %+v", s.uuid))
	_, err := fsock.FS.SendApiCmd(fmt.Sprintf("uuid_setvar %s cgr_notify %s\n\n", uuid, notify))
	if err != nil {
		engine.Logger.Err(fmt.Sprintf("could not send disconect api notification to freeswitch: %v", err))
	}
	err = fsock.FS.SendMsgCmd(uuid, map[string]string{"call-command": "hangup", "hangup-cause": "MANAGER_REQUEST"}) // without + sign
	if err != nil {
		engine.Logger.Err(fmt.Sprintf("could not send disconect msg to freeswitch: %v", err))
	}
	return
}

// Remove session from sessin list, removes all related in case of multiple runs
func (sm *FSSessionManager) RemoveSession(uuid string) {
	for i, ss := range sm.sessions {
		if ss.uuid == uuid {
			sm.sessions = append(sm.sessions[:i], sm.sessions[i+1:]...)
			return
		}
	}
}

// Sets the call timeout valid of starting of the call
func (sm *FSSessionManager) setMaxCallDuration(uuid string, maxDur time.Duration) error {
	_, err := fsock.FS.SendApiCmd(fmt.Sprintf("sched_hangup +%d %s\n\n", int(maxDur.Seconds()), uuid))
	if err != nil {
		engine.Logger.Err("could not send sched_hangup command to freeswitch")
		return err
	}
	return nil
}

// Sends the transfer command to unpark the call to freeswitch
func (sm *FSSessionManager) unparkCall(uuid, call_dest_nb, notify string) {
	_, err := fsock.FS.SendApiCmd(fmt.Sprintf("uuid_setvar %s cgr_notify %s\n\n", uuid, notify))
	if err != nil {
		engine.Logger.Err("could not send unpark api notification to freeswitch")
	}
	_, err = fsock.FS.SendApiCmd(fmt.Sprintf("uuid_transfer %s %s\n\n", uuid, call_dest_nb))
	if err != nil {
		engine.Logger.Err("could not send unpark api call to freeswitch")
	}
}

func (sm *FSSessionManager) OnHeartBeat(ev Event) {
	engine.Logger.Info("freeswitch ♥")
}

func (sm *FSSessionManager) OnChannelPark(ev Event) {
	var maxCallDuration time.Duration // This will be the maximum duration this channel will be allowed to last
	var durInitialized bool
	attrsDC := utils.AttrDerivedChargers{Tenant: ev.GetTenant(utils.META_DEFAULT), Category: ev.GetCategory(utils.META_DEFAULT), Direction: ev.GetDirection(utils.META_DEFAULT),
		Account: ev.GetAccount(utils.META_DEFAULT), Subject: ev.GetSubject(utils.META_DEFAULT)}
	var dcs utils.DerivedChargers
	if err := sm.connector.GetDerivedChargers(attrsDC, &dcs); err != nil {
		engine.Logger.Err(fmt.Sprintf("Could not get derived charging for event %s: %s", ev.GetUUID(), err.Error()))
		sm.unparkCall(ev.GetUUID(), ev.GetCallDestNr(utils.META_DEFAULT), SYSTEM_ERROR) // We unpark on original destination
		return
	}
	dcs, _ = dcs.AppendDefaultRun()
	for _, dc := range dcs {
		startTime, err := ev.GetAnswerTime(PARK_TIME)
		if err != nil {
			engine.Logger.Err("Error parsing answer event start time, using time.Now!")
			startTime = time.Now()
		}
		// if there is no account configured leave the call alone
		if dc.RunId == utils.DEFAULT_RUNID && !utils.IsSliceMember([]string{utils.PREPAID, utils.PSEUDOPREPAID}, ev.GetReqType(utils.META_DEFAULT)) {
			return // we unpark only prepaid and pseudoprepaid calls
		}
		if ev.MissingParameter() {
			sm.unparkCall(ev.GetUUID(), ev.GetCallDestNr(dc.DestinationField), MISSING_PARAMETER)
			engine.Logger.Err(fmt.Sprintf("Missing parameter for %s", ev.GetUUID()))
			return
		}
		cd := engine.CallDescriptor{
			Direction:   ev.GetDirection(dc.DirectionField),
			Tenant:      ev.GetTenant(dc.TenantField),
			Category:    ev.GetCategory(dc.CategoryField),
			Subject:     ev.GetSubject(dc.SubjectField),
			Account:     ev.GetAccount(dc.AccountField),
			Destination: ev.GetDestination(dc.DestinationField),
			TimeStart:   startTime,
			TimeEnd:     startTime.Add(cfg.SMMaxCallDuration),
		}
		var remainingDurationFloat float64
		err = sm.connector.GetMaxSessionTime(cd, &remainingDurationFloat)
		if err != nil {
			engine.Logger.Err(fmt.Sprintf("Could not get max session time for %s: %v", ev.GetUUID(), err))
			sm.unparkCall(ev.GetUUID(), ev.GetCallDestNr(""), SYSTEM_ERROR) // We unpark on original destination
			return
		}
		remainingDuration := time.Duration(remainingDurationFloat)
		// Set maxCallDuration, smallest out of all forked sessions
		if !durInitialized { // first time we set it /not initialized yet
			maxCallDuration = remainingDuration
			durInitialized = true
		} else if maxCallDuration > remainingDuration {
			maxCallDuration = remainingDuration
		}
	}
	if maxCallDuration == 0 {
		//engine.Logger.Info(fmt.Sprintf("Not enough credit for trasferring the call %s for %s.", ev.GetUUID(), cd.GetKey(cd.Subject)))
		sm.unparkCall(ev.GetUUID(), ev.GetCallDestNr(utils.META_DEFAULT), INSUFFICIENT_FUNDS)
		return
	}
	sm.setMaxCallDuration(ev.GetUUID(), maxCallDuration)
	sm.unparkCall(ev.GetUUID(), ev.GetCallDestNr(utils.META_DEFAULT), AUTH_OK)
}

func (sm *FSSessionManager) OnChannelAnswer(ev Event) {
	//engine.Logger.Info("<SessionManager> FreeSWITCH answer.")
	// Make sure cgr_type is enforced even if not set by FreeSWITCH
	if ev.MissingParameter() {
		sm.DisconnectSession(ev.GetUUID(), MISSING_PARAMETER)
	}
	if _, err := fsock.FS.SendApiCmd(fmt.Sprintf("uuid_setvar %s cgr_reqtype %s\n\n", ev.GetUUID(), ev.GetReqType(""))); err != nil {
		engine.Logger.Err(fmt.Sprintf("Error on attempting to overwrite cgr_type in chan variables: %v", err))
	}
	attrsDC := utils.AttrDerivedChargers{Tenant: ev.GetTenant(utils.META_DEFAULT), Category: ev.GetCategory(utils.META_DEFAULT),
		Direction: ev.GetDirection(utils.META_DEFAULT), Account: ev.GetAccount(utils.META_DEFAULT), Subject: ev.GetSubject(utils.META_DEFAULT)}
	var dcs utils.DerivedChargers
	if err := sm.connector.GetDerivedChargers(attrsDC, &dcs); err != nil {
		engine.Logger.Err(fmt.Sprintf("Could not get derived charging for event %s: %s", ev.GetUUID(), err.Error()))
		sm.unparkCall(ev.GetUUID(), ev.GetCallDestNr(utils.META_DEFAULT), SYSTEM_ERROR) // We unpark on original destination
		return
	}
	dcs, _ = dcs.AppendDefaultRun()
	s := NewSession(ev, sm, dcs)
	if s != nil {
		sm.sessions = append(sm.sessions, s)
	}
}

func (sm *FSSessionManager) OnChannelHangupComplete(ev Event) {
	s := sm.GetSession(ev.GetUUID())
	if s == nil { // Not handled by us
		return
	} else {
		sm.RemoveSession(s.uuid) // Unreference it early so we avoid concurrency
	}
	defer s.Close(ev)                            // Stop loop and save the costs deducted so far to database
	attrsDC := utils.AttrDerivedChargers{Tenant: ev.GetTenant(utils.META_DEFAULT), Category: ev.GetCategory(utils.META_DEFAULT), Direction: ev.GetDirection(utils.META_DEFAULT),
		Account: ev.GetAccount(utils.META_DEFAULT), Subject: ev.GetSubject(utils.META_DEFAULT)}
	var dcs utils.DerivedChargers
	if err := sm.connector.GetDerivedChargers(attrsDC, &dcs); err != nil {
		engine.Logger.Err(fmt.Sprintf("Could not get derived charging for event %s: %s", ev.GetUUID(), err.Error()))
		sm.unparkCall(ev.GetUUID(), ev.GetCallDestNr(utils.META_DEFAULT), SYSTEM_ERROR) // We unpark on original destination
		return
	}
	dcs, _ = dcs.AppendDefaultRun()
	for idx, dc := range dcs {
		if ev.GetReqType(dc.ReqTypeField) == utils.POSTPAID {
			startTime, err := ev.GetAnswerTime(dc.AnswerTimeField)
			if err != nil {
				engine.Logger.Crit("Error parsing postpaid call start time from event")
				return
			}
			duration, err := ev.GetDuration(dc.DurationField)
			if err != nil {
				engine.Logger.Crit(fmt.Sprintf("Error parsing call duration from event %s", err.Error()))
				return
			}
			cd := engine.CallDescriptor{
				Direction:     ev.GetDirection(dc.DirectionField),
				Tenant:        ev.GetTenant(dc.TenantField),
				Category:      ev.GetCategory(dc.CategoryField),
				Subject:       ev.GetSubject(dc.SubjectField),
				Account:       ev.GetAccount(dc.AccountField),
				LoopIndex:     0,
				DurationIndex: duration,
				Destination:   ev.GetDestination(dc.DestinationField),
				TimeStart:     startTime,
				TimeEnd:       startTime.Add(duration),
			}
			cc := &engine.CallCost{}
			err = sm.connector.Debit(cd, cc)
			if err != nil {
				engine.Logger.Err(fmt.Sprintf("Error making the general debit for postpaid call: %v", ev.GetUUID()))
				return
			}
			s.sessionRuns[idx].callCosts = append(s.sessionRuns[idx].callCosts, cc)
		} else if ev.GetReqType(dc.ReqTypeField) == utils.PREPAID { // Prepaid calls
			if len(s.sessionRuns[idx].callCosts) == 0 {
				continue // why would we have 0 callcosts
			}
			lastCC := s.sessionRuns[idx].callCosts[len(s.sessionRuns[idx].callCosts)-1]
			lastCC.Timespans.Decompress()
			// put credit back
			startTime, err := ev.GetAnswerTime(dc.AnswerTimeField)
			if err != nil {
				engine.Logger.Crit("Error parsing prepaid call start time from event")
				return
			}
			duration, err := ev.GetDuration(dc.DurationField)
			if err != nil {
				engine.Logger.Crit(fmt.Sprintf("Error parsing call duration from event %s", err.Error()))
				return
			}
			hangupTime := startTime.Add(duration)
			end := lastCC.Timespans[len(lastCC.Timespans)-1].TimeEnd
			refundDuration := end.Sub(hangupTime)
			var refundIncrements engine.Increments
			for i := len(lastCC.Timespans) - 1; i >= 0; i-- {
				ts := lastCC.Timespans[i]
				tsDuration := ts.GetDuration()
				if refundDuration <= tsDuration {
					lastRefundedIncrementIndex := 0
					for j := len(ts.Increments) - 1; j >= 0; j-- {
						increment := ts.Increments[j]
						if increment.Duration <= refundDuration {
							refundIncrements = append(refundIncrements, increment)
							refundDuration -= increment.Duration
							lastRefundedIncrementIndex = j
						}
					}
					ts.SplitByIncrement(lastRefundedIncrementIndex)
					break // do not go to other timespans
				} else {
					refundIncrements = append(refundIncrements, ts.Increments...)
					// remove the timespan entirely
					lastCC.Timespans[i] = nil
					lastCC.Timespans = lastCC.Timespans[:i]
					// continue to the next timespan with what is left to refund
					refundDuration -= tsDuration
				}
			}
			// show only what was actualy refunded (stopped in timespan)
			// engine.Logger.Info(fmt.Sprintf("Refund duration: %v", initialRefundDuration-refundDuration))
			if len(refundIncrements) > 0 {
				cd := &engine.CallDescriptor{
					Direction:   lastCC.Direction,
					Tenant:      lastCC.Tenant,
					Category:    lastCC.Category,
					Subject:     lastCC.Subject,
					Account:     lastCC.Account,
					Destination: lastCC.Destination,
					Increments:  refundIncrements,
				}
				var response float64
				err := sm.connector.RefundIncrements(*cd, &response)
				if err != nil {
					engine.Logger.Err(fmt.Sprintf("Debit cents failed: %v", err))
				}
			}
			cost := refundIncrements.GetTotalCost()
			lastCC.Cost -= cost
			lastCC.Timespans.Compress()
			// engine.Logger.Info(fmt.Sprintf("Rambursed %v cents", cost))
		}
	}

}

func (sm *FSSessionManager) GetDebitPeriod() time.Duration {
	return sm.debitPeriod
}

func (sm *FSSessionManager) MaxDebit(cd *engine.CallDescriptor, cc *engine.CallCost) error {
	return sm.connector.MaxDebit(*cd, cc)
}

func (sm *FSSessionManager) GetDbLogger() engine.LogStorage {
	return sm.loggerDB
}

func (sm *FSSessionManager) Shutdown() (err error) {
	if fsock.FS == nil || !fsock.FS.Connected() {
		return errors.New("Cannot shutdown sessions, fsock not connected")
	}
	engine.Logger.Info("Shutting down all sessions...")
	cmdKillPrepaid := "hupall MANAGER_REQUEST cgr_reqtype prepaid"
	cmdKillPostpaid := "hupall MANAGER_REQUEST cgr_reqtype postpaid"
	for _, cmd := range []string{cmdKillPrepaid, cmdKillPostpaid} {
		if _, err = fsock.FS.SendApiCmd(cmd); err != nil {
			engine.Logger.Err(fmt.Sprintf("Error on calls shutdown: %s", err))
		}
	}
	for guard := 0; len(sm.sessions) > 0 && guard < 20; guard++ {
		time.Sleep(100 * time.Millisecond) // wait for the hungup event to be fired
		engine.Logger.Info(fmt.Sprintf("<SessionManager> Shutdown waiting on sessions: %v", sm.sessions))
	}
	return
}