/*
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 engine

import (
	"fmt"
	"math/rand"
	"sync"
	"time"

	"github.com/cgrates/cgrates/cache"
	"github.com/cgrates/cgrates/utils"
)

// NewStatService initializes a StatService
func NewStatService(dm *DataManager, storeInterval time.Duration) (ss *StatService, err error) {
	return &StatService{dm: dm, storeInterval: storeInterval,
		stopBackup: make(chan struct{})}, nil
}

// StatService builds stats for events
type StatService struct {
	dm               *DataManager
	storeInterval    time.Duration
	stopBackup       chan struct{}
	storedStatQueues utils.StringMap // keep a record of stats which need saving, map[statsTenantID]bool
	ssqMux           sync.RWMutex    // protects storedStatQueues
}

// ListenAndServe loops keeps the service alive
func (sS *StatService) ListenAndServe(exitChan chan bool) error {
	go sS.runBackup() // start backup loop
	e := <-exitChan
	exitChan <- e // put back for the others listening for shutdown request
	return nil
}

// Shutdown is called to shutdown the service
func (sS *StatService) Shutdown() error {
	utils.Logger.Info("<StatS> service shutdown initialized")
	close(sS.stopBackup)
	sS.storeStats()
	utils.Logger.Info("<StatS> service shutdown complete")
	return nil
}

// runBackup will regularly store resources changed to dataDB
func (sS *StatService) runBackup() {
	if sS.storeInterval <= 0 {
		return
	}
	for {
		select {
		case <-sS.stopBackup:
			return
		default:
		}
		sS.storeStats()
		time.Sleep(sS.storeInterval)
	}
}

// storeResources represents one task of complete backup
func (sS *StatService) storeStats() {
	var failedSqIDs []string
	for { // don't stop untill we store all dirty statQueues
		sS.ssqMux.Lock()
		sID := sS.storedStatQueues.GetOne()
		if sID != "" {
			delete(sS.storedStatQueues, sID)
		}
		sS.ssqMux.Unlock()
		if sID == "" {
			break // no more keys, backup completed
		}
		if sqIf, ok := cache.Get(utils.StatQueuePrefix + sID); !ok || sqIf == nil {
			utils.Logger.Warning(fmt.Sprintf("<StatS> failed retrieving from cache stat queue with ID: %s", sID))
		} else if err := sS.StoreStatQueue(sqIf.(*StatQueue)); err != nil {
			failedSqIDs = append(failedSqIDs, sID) // record failure so we can schedule it for next backup
		}
		// randomize the CPU load and give up thread control
		time.Sleep(time.Duration(rand.Intn(1000)) * time.Nanosecond)
	}
	if len(failedSqIDs) != 0 { // there were errors on save, schedule the keys for next backup
		sS.ssqMux.Lock()
		for _, sqID := range failedSqIDs {
			sS.storedStatQueues[sqID] = true
		}
		sS.ssqMux.Unlock()
	}
}

// StoreStatQueue stores the statQueue in DB and corrects dirty flag
func (sS *StatService) StoreStatQueue(sq *StatQueue) (err error) {
	if sq.dirty == nil || !*sq.dirty {
		return
	}
	if err = sS.dm.SetStatQueue(sq); err != nil {
		utils.Logger.Warning(
			fmt.Sprintf("<StatS> failed saving StatQueue with ID: %s, error: %s",
				sq.TenantID(), err.Error()))
	} else {
		*sq.dirty = false
	}
	return
}

/*
// setQueue adds or modifies a queue into cache
// sort will reorder the sS.queues
func (ss *StatService) loadQueue(qID string) (q *StatQueue, err error) {
	sq, err := sS.dataDB.GetStatsConfig(qID)
	if err != nil {
		return nil, err
	}
	return NewStatQueue(sS.evCache, sS.ms, sq, sqSM)
}

func (ss *StatService) setQueue(q *StatQueue) {
	sS.queuesCache[q.cfg.ID] = q
	sS.queues = append(sS.queues, q)
}

// remQueue will remove a queue based on it's ID
func (ss *StatService) remQueue(qID string) (si *StatQueue) {
	si = sS.queuesCache[qID]
	sS.queues.remWithID(qID)
	delete(sS.queuesCache, qID)
	return
}

// store stores the necessary storedMetrics to dataDB
func (ss *StatService) storeMetrics() {
	for _, si := range sS.queues {
		if !si.cfg.Store || !si.dirty { // no need to save
			continue
		}
		if siSM := si.GetStoredMetrics(); siSM != nil {
			if err := sS.dataDB.SetSQStoredMetrics(siSM); err != nil {
				utils.Logger.Warning(
					fmt.Sprintf("<StatService> failed saving StoredMetrics for QueueID: %s, error: %s",
						si.cfg.ID, err.Error()))
			}
		}
		// randomize the CPU load and give up thread control
		time.Sleep(time.Duration(rand.Intn(1000)) * time.Nanosecond)
	}
	return
}

// dumpStoredMetrics regularly dumps metrics to dataDB
func (ss *StatService) dumpStoredMetrics() {
	for {
		select {
		case <-sS.stopStoring:
			return
		}
		sS.storeMetrics()
		time.Sleep(sS.storeInterval)
	}
}

// processEvent processes a StatsEvent through the queues and caches it when needed
func (ss *StatService) processEvent(ev StatsEvent) (err error) {
	evStatsID := ev.ID()
	if evStatsID == "" { // ID is mandatory
		return errors.New("missing ID field")
	}
	for _, stInst := range sS.queues {
		if err := stInst.ProcessEvent(ev); err != nil {
			utils.Logger.Warning(
				fmt.Sprintf("<StatService> QueueID: %s, ignoring event with ID: %s, error: %s",
					stInst.cfg.ID, evStatsID, err.Error()))
		}
		if stInst.cfg.Blocker {
			break
		}
	}
	return
}

// V1ProcessEvent implements StatV1 method for processing an Event
func (ss *StatService) V1ProcessEvent(ev StatsEvent, reply *string) (err error) {
	if err = sS.processEvent(ev); err == nil {
		*reply = utils.OK
	}
	return
}

// V1GetQueueIDs returns list of queue IDs configured in the service
func (ss *StatService) V1GetQueueIDs(ignored struct{}, reply *[]string) (err error) {
	if len(sS.queuesCache) == 0 {
		return utils.ErrNotFound
	}
	for k := range sS.queuesCache {
		*reply = append(*reply, k)
	}
	return
}

// V1GetStringMetrics returns the metrics as string values
func (ss *StatService) V1GetStringMetrics(queueID string, reply *map[string]string) (err error) {
	sq, has := sS.queuesCache[queueID]
	if !has {
		return utils.ErrNotFound
	}
	metrics := make(map[string]string, len(sq.sqMetrics))
	for metricID, metric := range sq.sqMetrics {
		metrics[metricID] = metric.GetStringValue("")
	}
	*reply = metrics
	return
}

// V1GetFloatMetrics returns the metrics as float64 values
func (ss *StatService) V1GetFloatMetrics(queueID string, reply *map[string]float64) (err error) {
	sq, has := sS.queuesCache[queueID]
	if !has {
		return utils.ErrNotFound
	}
	metrics := make(map[string]float64, len(sq.sqMetrics))
	for metricID, metric := range sq.sqMetrics {
		metrics[metricID] = metric.GetFloat64Value()
	}
	*reply = metrics
	return
}

// ArgsLoadQueues are the arguments passed to V1LoadQueues
type ArgsLoadQueues struct {
	QueueIDs *[]string
}

// V1LoadQueues loads the queues specified by qIDs into the service
// loads all if args.QueueIDs is nil
func (ss *StatService) V1LoadQueues(args ArgsLoadQueues, reply *string) (err error) {
	qIDs := args.QueueIDs
	if qIDs == nil {
		sqPrfxs, err := sS.dataDB.GetKeysForPrefix(utils.StatsConfigPrefix)
		if err != nil {
			return err
		}
		queueIDs := make([]string, len(sqPrfxs))
		for i, prfx := range sqPrfxs {
			queueIDs[i] = prfx[len(utils.StatsConfigPrefix):]
		}
		if len(queueIDs) != 0 {
			qIDs = &queueIDs
		}
	}
	if qIDs == nil || len(*qIDs) == 0 {
		return utils.ErrNotFound
	}
	var sQs []*StatQueue // cache here so we lock only later when data available
	for _, qID := range *qIDs {
		if _, hasPrev := sS.queuesCache[qID]; hasPrev {
			continue // don't overwrite previous, could be extended in the future by carefully checking cached events
		}
		if q, err := sS.loadQueue(qID); err != nil {
			utils.Logger.Err(fmt.Sprintf("<StatS> failed loading quueue with id: <%s>, err: <%s>",
				q.cfg.ID, err.Error()))
			continue
		} else {
			sQs = append(sQs, q)
		}
	}
	sS.Lock()
	for _, q := range sQs {
		sS.setQueue(q)
	}
	sS.queues.Sort()
	sS.Unlock()
	*reply = utils.OK
	return
}

// Call implements rpcclient.RpcClientConnection interface for internal RPC
// here for testing purposes
func (ss *StatService) Call(serviceMethod string, args interface{}, reply interface{}) error {
	methodSplit := strings.Split(serviceMethod, ".")
	if len(methodSplit) != 2 {
		return rpcclient.ErrUnsupporteServiceMethod
	}
	method := reflect.ValueOf(ss).MethodByName(methodSplit[0][len(methodSplit[0])-2:] + methodSplit[1])
	if !method.IsValid() {
		return rpcclient.ErrUnsupporteServiceMethod
	}
	params := []reflect.Value{reflect.ValueOf(args), reflect.ValueOf(reply)}
	ret := method.Call(params)
	if len(ret) != 1 {
		return utils.ErrServerError
	}
	if ret[0].Interface() == nil {
		return nil
	}
	err, ok := ret[0].Interface().(error)
	if !ok {
		return utils.ErrServerError
	}
	return err
}

*/