/*
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 ers

import (
	"encoding/json"
	"fmt"
	"io"
	"time"

	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/credentials"
	"github.com/aws/aws-sdk-go/aws/session"
	"github.com/aws/aws-sdk-go/service/s3"
	"github.com/cgrates/birpc/context"
	"github.com/cgrates/cgrates/agents"
	"github.com/cgrates/cgrates/config"
	"github.com/cgrates/cgrates/engine"
	"github.com/cgrates/cgrates/utils"
)

// NewS3ER return a new s3 event reader
func NewS3ER(cfg *config.CGRConfig, cfgIdx int,
	rdrEvents chan *erEvent, rdrErr chan error,
	fltrS *engine.FilterS, rdrExit chan struct{}) (er EventReader, err error) {

	rdr := &S3ER{
		cgrCfg:    cfg,
		cfgIdx:    cfgIdx,
		fltrS:     fltrS,
		rdrEvents: rdrEvents,
		rdrExit:   rdrExit,
		rdrErr:    rdrErr,
	}
	if concReq := rdr.Config().ConcurrentReqs; concReq != -1 {
		rdr.cap = make(chan struct{}, concReq)
		for i := 0; i < concReq; i++ {
			rdr.cap <- struct{}{}
		}
	}
	rdr.parseOpts(rdr.Config().Opts)
	return rdr, nil
}

// S3ER implements EventReader interface for s3 message
type S3ER struct {
	// sync.RWMutex
	cgrCfg *config.CGRConfig
	cfgIdx int // index of config instance within ERsCfg.Readers
	fltrS  *engine.FilterS

	rdrEvents chan *erEvent // channel to dispatch the events created to
	rdrExit   chan struct{}
	rdrErr    chan error
	cap       chan struct{}

	awsRegion string
	awsID     string
	awsKey    string
	awsToken  string
	queueID   string
	session   *session.Session

	poster engine.Poster
}

// Config returns the curent configuration
func (rdr *S3ER) Config() *config.EventReaderCfg {
	return rdr.cgrCfg.ERsCfg().Readers[rdr.cfgIdx]
}

// Serve will start the gorutines needed to watch the s3 topic
func (rdr *S3ER) Serve() (err error) {
	var sess *session.Session
	cfg := aws.Config{Endpoint: aws.String(rdr.Config().SourcePath)}
	if len(rdr.awsRegion) != 0 {
		cfg.Region = aws.String(rdr.awsRegion)
	}
	if len(rdr.awsID) != 0 &&
		len(rdr.awsKey) != 0 {
		cfg.Credentials = credentials.NewStaticCredentials(rdr.awsID, rdr.awsKey, rdr.awsToken)
	}
	if sess, err = session.NewSessionWithOptions(session.Options{Config: cfg}); err != nil {
		return
	}
	rdr.session = sess

	if rdr.Config().RunDelay == time.Duration(0) { // 0 disables the automatic read, maybe done per API
		return
	}

	go rdr.readLoop() // read until the connection is closed
	return
}

func (rdr *S3ER) processMessage(body []byte) (err error) {
	var decodedMessage map[string]interface{}
	if err = json.Unmarshal(body, &decodedMessage); err != nil {
		return
	}

	agReq := agents.NewAgentRequest(
		utils.MapStorage(decodedMessage), nil,
		nil, nil, nil, rdr.Config().Tenant,
		rdr.cgrCfg.GeneralCfg().DefaultTenant,
		utils.FirstNonEmpty(rdr.Config().Timezone,
			rdr.cgrCfg.GeneralCfg().DefaultTimezone),
		rdr.fltrS, nil, nil) // create an AgentRequest
	var pass bool
	if pass, err = rdr.fltrS.Pass(context.TODO(), agReq.Tenant, rdr.Config().Filters,
		agReq); err != nil || !pass {
		return
	}
	if err = agReq.SetFields(rdr.Config().Fields); err != nil {
		return
	}
	cgrEv := utils.NMAsCGREvent(agReq.CGRRequest, agReq.Tenant, utils.NestingSep, agReq.Opts)
	rdr.rdrEvents <- &erEvent{
		cgrEvent: cgrEv,
		rdrCfg:   rdr.Config(),
	}
	return
}

func (rdr *S3ER) parseOpts(opts map[string]interface{}) {
	rdr.queueID = utils.DefaultQueueID
	if val, has := opts[utils.QueueID]; has {
		rdr.queueID = utils.IfaceAsString(val)
	}
	if val, has := opts[utils.AWSRegion]; has {
		rdr.awsRegion = utils.IfaceAsString(val)
	}
	if val, has := opts[utils.AWSKey]; has {
		rdr.awsID = utils.IfaceAsString(val)
	}
	if val, has := opts[utils.AWSSecret]; has {
		rdr.awsKey = utils.IfaceAsString(val)
	}
	if val, has := opts[utils.AWSToken]; has {
		rdr.awsToken = utils.IfaceAsString(val)
	}
}

func (rdr *S3ER) readLoop() (err error) {
	scv := s3.New(rdr.session)
	var keys []string
	if err = scv.ListObjectsV2Pages(&s3.ListObjectsV2Input{Bucket: aws.String(rdr.queueID)},
		func(lovo *s3.ListObjectsV2Output, b bool) bool {
			for _, objMeta := range lovo.Contents {
				if objMeta.Key != nil {
					keys = append(keys, *objMeta.Key)
				}
			}
			return !rdr.isClosed()
		}); err != nil {
		rdr.rdrErr <- err
		return
	}
	if rdr.isClosed() {
		return
	}
	for _, key := range keys {
		go rdr.readMsg(scv, key)
	}
	return
}

func (rdr *S3ER) createPoster() {
	processedOpt := getProcessOptions(rdr.Config().Opts)
	if len(processedOpt) == 0 &&
		len(rdr.Config().ProcessedPath) == 0 {
		return
	}
	rdr.poster = engine.NewS3Poster(utils.FirstNonEmpty(rdr.Config().ProcessedPath, rdr.Config().SourcePath),
		rdr.cgrCfg.GeneralCfg().PosterAttempts, processedOpt)
}

func (rdr *S3ER) isClosed() bool {
	select {
	case <-rdr.rdrExit:
		return true
	default:
		return false
	}
}

func (rdr *S3ER) readMsg(scv *s3.S3, key string) (err error) {
	if rdr.Config().ConcurrentReqs != -1 {
		<-rdr.cap // do not try to read if the limit is reached
		defer func() { rdr.cap <- struct{}{} }()
	}
	if rdr.isClosed() {
		return
	}

	obj, err := scv.GetObject(&s3.GetObjectInput{Bucket: &rdr.queueID, Key: &key})
	if err != nil {
		rdr.rdrErr <- err
		return
	}
	var msg []byte
	if msg, err = io.ReadAll(obj.Body); err != nil {
		utils.Logger.Warning(
			fmt.Sprintf("<%s> decoding message %s error: %s",
				utils.ERs, key, err.Error()))
		return
	}
	obj.Body.Close()
	if err = rdr.processMessage(msg); err != nil {
		utils.Logger.Warning(
			fmt.Sprintf("<%s> processing message %s error: %s",
				utils.ERs, key, err.Error()))
		return
	}
	if _, err = scv.DeleteObject(&s3.DeleteObjectInput{Bucket: &rdr.queueID, Key: &key}); err != nil {
		rdr.rdrErr <- err
		return
	}

	if rdr.poster != nil { // post it
		if err = rdr.poster.Post(msg, key); err != nil {
			utils.Logger.Warning(
				fmt.Sprintf("<%s> writing message %s error: %s",
					utils.ERs, key, err.Error()))
			return
		}
	}
	return
}
