/*
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 Affero 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 Affero General Public License for more details.

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

package ers

import (
	"encoding/json"
	"fmt"
	"io"
	"os"
	"path"
	"strings"
	"sync"
	"time"

	"github.com/cgrates/cgrates/agents"
	"github.com/cgrates/cgrates/utils"

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

func NewJSONFileER(cfg *config.CGRConfig, cfgIdx int,
	rdrEvents, partialEvents 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,
		sourceDir:     srcPath,
		rdrEvents:     rdrEvents,
		partialEvents: partialEvents,
		rdrError:      rdrErr,
		rdrExit:       rdrExit,
		conReqs:       make(chan struct{}, cfg.ERsCfg().Readers[cfgIdx].ConcurrentReqs),
	}

	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
	sourceDir     string        // path to the directory monitored by the reader for new events
	rdrEvents     chan *erEvent // channel to dispatch the events created to
	partialEvents chan *erEvent // channel to dispatch the partial 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) serveDefault() {
	if rdr.Config().StartDelay > 0 {
		select {
		case <-time.After(rdr.Config().StartDelay):
		case <-rdr.rdrExit:
			utils.Logger.Info(
				fmt.Sprintf("<%s> stop monitoring path <%s>",
					utils.ERs, rdr.sourceDir))
			return
		}
	}
	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.sourceDir))
			return
		case <-tm.C:
		}
		processReaderDir(rdr.sourceDir, utils.JSNSuffix, rdr.processFile)
		tm.Reset(rdr.Config().RunDelay)
	}
}

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):
		go func() {
			time.Sleep(rdr.Config().StartDelay)

			// Ensure that files already existing in the source path are processed
			// before the reader starts listening for filesystem change events.
			processReaderDir(rdr.sourceDir, utils.JSNSuffix, rdr.processFile)

			if err := utils.WatchDir(rdr.sourceDir, rdr.processFile,
				utils.ERs, rdr.rdrExit); err != nil {
				rdr.rdrError <- err
			}
		}()
	default:
		go rdr.serveDefault()
	}
	return
}

// processFile is called for each file in a directory and dispatches erEvents from it
func (rdr *JSONFileER) processFile(fName string) (err error) {
	if cap(rdr.conReqs) != 0 { // 0 goes for no limit
		rdr.conReqs <- struct{}{} // Queue here for maxOpenFiles
		defer func() { <-rdr.conReqs }()
	}
	absPath := path.Join(rdr.sourceDir, 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]any
	if err = json.Unmarshal(byteValue, &data); err != nil {
		return
	}

	evsPosted := 0
	reqVars := &utils.DataNode{Type: utils.NMMapType, Map: map[string]*utils.DataNode{utils.MetaFileName: utils.NewLeafNode(fName), utils.MetaReaderID: utils.NewLeafNode(rdr.cgrCfg.ERsCfg().Readers[rdr.cfgIdx].ID)}}

	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) // create an AgentRequest
	if pass, err := rdr.fltrS.Pass(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)
	rdrEv := rdr.rdrEvents
	if _, isPartial := cgrEv.APIOpts[utils.PartialOpt]; isPartial {
		rdrEv = rdr.partialEvents
	}
	rdrEv <- &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.Since(timeStart)))
	return
}