/*
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"
	"os"
	"path"
	"strings"
	"sync"
	"time"

	"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"
)

func NewJSONFileER(cfg *config.CGRConfig, cfgIdx int,
	rdrEvents chan *erEvent, rdrErr chan error,
	fltrS *engine.FilterS, rdrExit chan struct{}) (er EventReader, err error) {
	srcPath := cfg.ERsCfg().Readers[cfgIdx].SourcePath
	if strings.HasSuffix(srcPath, utils.Slash) {
		srcPath = srcPath[:len(srcPath)-1]
	}
	jsonEr := &JSONFileER{
		cgrCfg:    cfg,
		cfgIdx:    cfgIdx,
		fltrS:     fltrS,
		rdrDir:    srcPath,
		rdrEvents: rdrEvents,
		rdrError:  rdrErr,
		rdrExit:   rdrExit,
		conReqs:   make(chan struct{}, cfg.ERsCfg().Readers[cfgIdx].ConcurrentReqs)}
	var processFile struct{}
	for i := 0; i < cfg.ERsCfg().Readers[cfgIdx].ConcurrentReqs; i++ {
		jsonEr.conReqs <- processFile // Empty initiate so we do not need to wait later when we pop
	}
	return jsonEr, nil
}

// JSONFileER implements EventReader interface for .json files
type JSONFileER struct {
	sync.RWMutex
	cgrCfg    *config.CGRConfig
	cfgIdx    int // index of config instance within ERsCfg.Readers
	fltrS     *engine.FilterS
	rdrDir    string
	rdrEvents chan *erEvent // channel to dispatch the events created to
	rdrError  chan error
	rdrExit   chan struct{}
	conReqs   chan struct{} // limit number of opened files
}

func (rdr *JSONFileER) Config() *config.EventReaderCfg {
	return rdr.cgrCfg.ERsCfg().Readers[rdr.cfgIdx]
}

func (rdr *JSONFileER) Serve() (err error) {
	switch rdr.Config().RunDelay {
	case time.Duration(0): // 0 disables the automatic read, maybe done per API
		return
	case time.Duration(-1):
		return utils.WatchDir(rdr.rdrDir, rdr.processFile,
			utils.ERs, rdr.rdrExit)
	default:
		go func() {
			tm := time.NewTimer(0)
			for {
				// Not automated, process and sleep approach
				select {
				case <-rdr.rdrExit:
					tm.Stop()
					utils.Logger.Info(
						fmt.Sprintf("<%s> stop monitoring path <%s>",
							utils.ERs, rdr.rdrDir))
					return
				case <-tm.C:
				}
				filesInDir, _ := os.ReadDir(rdr.rdrDir)
				for _, file := range filesInDir {
					if !strings.HasSuffix(file.Name(), utils.JSONSuffix) { // hardcoded file extension for json event reader
						continue // used in order to filter the files from directory
					}
					go func(fileName string) {
						if err := rdr.processFile(rdr.rdrDir, fileName); err != nil {
							utils.Logger.Warning(
								fmt.Sprintf("<%s> processing file %s, error: %s",
									utils.ERs, fileName, err.Error()))
						}
					}(file.Name())
				}
				tm.Reset(rdr.Config().RunDelay)
			}
		}()
	}
	return
}

// processFile is called for each file in a directory and dispatches erEvents from it
func (rdr *JSONFileER) processFile(fPath, fName string) (err error) {
	if cap(rdr.conReqs) != 0 { // 0 goes for no limit
		processFile := <-rdr.conReqs // Queue here for maxOpenFiles
		defer func() { rdr.conReqs <- processFile }()
	}
	absPath := path.Join(fPath, fName)
	utils.Logger.Info(
		fmt.Sprintf("<%s> parsing <%s>", utils.ERs, absPath))
	var file *os.File
	if file, err = os.Open(absPath); err != nil {
		return
	}
	defer file.Close()
	timeStart := time.Now()
	var byteValue []byte
	if byteValue, err = io.ReadAll(file); err != nil {
		return
	}

	var data map[string]interface{}
	if err = json.Unmarshal(byteValue, &data); err != nil {
		return
	}

	evsPosted := 0
	reqVars := &utils.DataNode{Type: utils.NMMapType, Map: map[string]*utils.DataNode{utils.FileName: utils.NewLeafNode(fName)}}

	agReq := agents.NewAgentRequest(
		utils.MapStorage(data), reqVars,
		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
	if pass, err := rdr.fltrS.Pass(context.TODO(), agReq.Tenant, rdr.Config().Filters,
		agReq); err != nil {
		utils.Logger.Warning(
			fmt.Sprintf("<%s> reading file: <%s>  ignoring due to filter error: <%s>",
				utils.ERs, absPath, err.Error()))
		return err
	} else if !pass {
		return nil
	}
	if err = agReq.SetFields(rdr.Config().Fields); err != nil {
		utils.Logger.Warning(
			fmt.Sprintf("<%s> reading file: <%s>  ignoring due to error: <%s>",
				utils.ERs, absPath, err.Error()))
		return
	}
	cgrEv := utils.NMAsCGREvent(agReq.CGRRequest, agReq.Tenant, utils.NestingSep, agReq.Opts)
	rdr.rdrEvents <- &erEvent{
		cgrEvent: cgrEv,
		rdrCfg:   rdr.Config(),
	}
	evsPosted++

	if rdr.Config().ProcessedPath != "" {
		// Finished with file, move it to processed folder
		outPath := path.Join(rdr.Config().ProcessedPath, fName)
		if err = os.Rename(absPath, outPath); err != nil {
			return
		}
	}

	utils.Logger.Info(
		fmt.Sprintf("%s finished processing file <%s>. Events posted: %d, run duration: %s",
			utils.ERs, absPath, evsPosted, time.Now().Sub(timeStart)))
	return
}
