/*
Real-time Online/Offline Charging System (OCS) for Telecom & ISP environments
Copyright (C) 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 services

import (
	"fmt"
	"sync"

	"github.com/cgrates/birpc"
	"github.com/cgrates/birpc/context"
	"github.com/cgrates/cgrates/agents"
	"github.com/cgrates/cgrates/config"
	"github.com/cgrates/cgrates/engine"
	"github.com/cgrates/cgrates/servmanager"
	"github.com/cgrates/cgrates/utils"
)

// NewDiameterAgent returns the Diameter Agent
func NewDiameterAgent(cfg *config.CGRConfig, filterSChan chan *engine.FilterS,
	connMgr *engine.ConnManager, caps *engine.Caps,
	srvDep map[string]*sync.WaitGroup,
	srvIndexer *servmanager.ServiceIndexer) servmanager.Service {
	return &DiameterAgent{
		cfg:         cfg,
		filterSChan: filterSChan,
		connMgr:     connMgr,
		caps:        caps,
		srvDep:      srvDep,
		srvIndexer:  srvIndexer,
		stateDeps:   NewStateDependencies([]string{utils.StateServiceUP}),
	}
}

// DiameterAgent implements Agent interface
type DiameterAgent struct {
	sync.RWMutex
	cfg         *config.CGRConfig
	filterSChan chan *engine.FilterS
	stopChan    chan struct{}

	da      *agents.DiameterAgent
	connMgr *engine.ConnManager
	caps    *engine.Caps

	lnet  string
	laddr string

	srvDep map[string]*sync.WaitGroup

	intRPCconn birpc.ClientConnector       // expose API methods over internal connection
	srvIndexer *servmanager.ServiceIndexer // access directly services from here
	stateDeps  *StateDependencies          // channel subscriptions for state changes
}

// Start should handle the sercive start
func (da *DiameterAgent) Start(ctx *context.Context, shtDwn context.CancelFunc) error {
	if da.IsRunning() {
		return utils.ErrServiceAlreadyRunning
	}

	filterS, err := waitForFilterS(ctx, da.filterSChan)
	if err != nil {
		return err
	}
	da.Lock()
	defer da.Unlock()
	return da.start(filterS, shtDwn, da.caps)
}

func (da *DiameterAgent) start(filterS *engine.FilterS, shtDwn context.CancelFunc, caps *engine.Caps) error {
	var err error
	da.da, err = agents.NewDiameterAgent(da.cfg, filterS, da.connMgr, caps)
	if err != nil {
		utils.Logger.Err(fmt.Sprintf("<%s> failed to initialize agent: %v",
			utils.DiameterAgent, err))
		return err
	}
	da.lnet = da.cfg.DiameterAgentCfg().ListenNet
	da.laddr = da.cfg.DiameterAgentCfg().Listen
	da.stopChan = make(chan struct{})
	go func(d *agents.DiameterAgent) {
		if err := d.ListenAndServe(da.stopChan); err != nil {
			utils.Logger.Err(fmt.Sprintf("<%s> error: %s!",
				utils.DiameterAgent, err))
			shtDwn()
		}
	}(da.da)
	close(da.stateDeps.StateChan(utils.StateServiceUP))
	return nil
}

// Reload handles the change of config
func (da *DiameterAgent) Reload(ctx *context.Context, shtDwn context.CancelFunc) (err error) {
	da.Lock()
	defer da.Unlock()
	if da.lnet == da.cfg.DiameterAgentCfg().ListenNet &&
		da.laddr == da.cfg.DiameterAgentCfg().Listen {
		return
	}
	close(da.stopChan)
	var filterS *engine.FilterS
	if filterS, err = waitForFilterS(ctx, da.filterSChan); err != nil {
		return
	}
	return da.start(filterS, shtDwn, da.caps)
}

// Shutdown stops the service
func (da *DiameterAgent) Shutdown() (err error) {
	da.Lock()
	close(da.stopChan)
	da.da = nil
	da.Unlock()
	return // no shutdown for the momment
}

// IsRunning returns if the service is running
func (da *DiameterAgent) IsRunning() bool {
	da.RLock()
	defer da.RUnlock()
	return da.da != nil
}

// ServiceName returns the service name
func (da *DiameterAgent) ServiceName() string {
	return utils.DiameterAgent
}

// ShouldRun returns if the service should be running
func (da *DiameterAgent) ShouldRun() bool {
	return da.cfg.DiameterAgentCfg().Enabled
}

// StateChan returns signaling channel of specific state
func (da *DiameterAgent) StateChan(stateID string) chan struct{} {
	return da.stateDeps.StateChan(stateID)
}

// IntRPCConn returns the internal connection used by RPCClient
func (da *DiameterAgent) IntRPCConn() birpc.ClientConnector {
	return da.intRPCconn
}