/*
 * Copyright 2018-present Open Networking Foundation

 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at

 * http://www.apache.org/licenses/LICENSE-2.0

 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package omci

import (
	"encoding/binary"
	"encoding/hex"
	"errors"
	"fmt"
	"strconv"

	"github.com/google/gopacket"
	"github.com/opencord/omci-lib-go/v2"
	me "github.com/opencord/omci-lib-go/v2/generated"
	log "github.com/sirupsen/logrus"
)

var omciLogger = log.WithFields(log.Fields{
	"module": "OMCI",
})

// NOTE this is basically the same as https://github.com/opencord/voltha-openonu-adapter-go/blob/master/internal/pkg/onuadaptercore/omci_cc.go#L545-L564
// we should probably move it in "omci-lib-go"
func Serialize(msgType omci.MessageType, request gopacket.SerializableLayer, tid uint16) ([]byte, error) {
	omciLayer := &omci.OMCI{
		TransactionID: tid,
		MessageType:   msgType,
	}
	var options gopacket.SerializeOptions
	options.FixLengths = true

	buffer := gopacket.NewSerializeBuffer()
	err := gopacket.SerializeLayers(buffer, options, omciLayer, request)
	if err != nil {
		return nil, err
	}
	return buffer.Bytes(), nil
}

func SetTxIdInEncodedPacket(packet []byte, txId uint16) []byte {
	valid := packet[2:]

	b := make([]byte, 2)
	binary.BigEndian.PutUint16(b, txId)

	return append(b, valid...)
}

func CreateMibResetRequest(tid uint16) ([]byte, error) {

	request := &omci.MibResetRequest{
		MeBasePacket: omci.MeBasePacket{
			EntityClass: me.OnuDataClassID,
		},
	}
	pkt, err := Serialize(omci.MibResetRequestType, request, tid)
	if err != nil {
		omciLogger.WithFields(log.Fields{
			"Err": err,
		}).Fatalf("Cannot Serialize MibResetRequest")
		return nil, err
	}
	return HexEncode(pkt)
}

func CreateMibResetResponse(tid uint16) ([]byte, error) {

	request := &omci.MibResetResponse{
		MeBasePacket: omci.MeBasePacket{
			EntityClass: me.OnuDataClassID,
		},
		Result: me.Success,
	}
	pkt, err := Serialize(omci.MibResetResponseType, request, tid)
	if err != nil {
		omciLogger.WithFields(log.Fields{
			"Err": err,
		}).Error("Cannot Serialize MibResetResponse")
		return nil, err
	}
	return pkt, nil
}

func CreateMibUploadRequest(tid uint16) ([]byte, error) {
	request := &omci.MibUploadRequest{
		MeBasePacket: omci.MeBasePacket{
			EntityClass: me.OnuDataClassID,
			// Default Instance ID is 0
		},
	}
	pkt, err := Serialize(omci.MibUploadRequestType, request, tid)
	if err != nil {
		omciLogger.WithFields(log.Fields{
			"Err": err,
		}).Fatalf("Cannot Serialize MibUploadRequest")
		return nil, err
	}
	return HexEncode(pkt)
}

func CreateMibUploadResponse(omciMsg *omci.OMCI, mibDb *MibDb) ([]byte, error) {

	isExtended := false
	numberOfCommands := mibDb.NumberOfBaselineCommands
	if omciMsg.DeviceIdentifier == omci.ExtendedIdent {
		isExtended = true
		numberOfCommands = mibDb.NumberOfExtendedCommands
	}
	response := &omci.MibUploadResponse{
		MeBasePacket: omci.MeBasePacket{
			EntityClass: me.OnuDataClassID,
			Extended:    isExtended,
		},
		NumberOfCommands: numberOfCommands,
	}
	omciLogger.WithFields(log.Fields{
		"NumberOfCommands": numberOfCommands, "isExtended": isExtended}).Debug("mib-upload-response")

	omciLayer := &omci.OMCI{
		TransactionID:    omciMsg.TransactionID,
		MessageType:      omci.MibUploadResponseType,
		DeviceIdentifier: omciMsg.DeviceIdentifier,
	}
	var options gopacket.SerializeOptions
	options.FixLengths = true

	buffer := gopacket.NewSerializeBuffer()
	err := gopacket.SerializeLayers(buffer, options, omciLayer, response)
	if err != nil {
		omciLogger.WithFields(log.Fields{
			"Err":  err,
			"TxID": strconv.FormatInt(int64(omciMsg.TransactionID), 16),
		}).Error("cannot-Serialize-MibUploadResponse")
		return nil, err
	}
	pkt := buffer.Bytes()

	log.WithFields(log.Fields{
		"TxID": strconv.FormatInt(int64(omciMsg.TransactionID), 16),
		"pkt":  hex.EncodeToString(pkt),
	}).Trace("omci-mib-upload-response")

	return pkt, nil
}

func CreateMibUploadNextRequest(tid uint16, seqNumber uint16) ([]byte, error) {

	request := &omci.MibUploadNextRequest{
		MeBasePacket: omci.MeBasePacket{
			EntityClass: me.OnuDataClassID,
			// Default Instance ID is 0
		},
		CommandSequenceNumber: seqNumber,
	}
	pkt, err := Serialize(omci.MibUploadNextRequestType, request, tid)

	if err != nil {
		omciLogger.WithFields(log.Fields{
			"Err": err,
		}).Fatalf("Cannot Serialize MibUploadNextRequest")
		return nil, err
	}
	return HexEncode(pkt)
}

func ParseMibUploadNextRequest(omciPkt gopacket.Packet) (*omci.MibUploadNextRequest, error) {
	msgLayer := omciPkt.Layer(omci.LayerTypeMibUploadNextRequest)
	if msgLayer == nil {
		err := "omci Msg layer could not be detected for LayerTypeMibUploadNextRequest"
		omciLogger.Error(err)
		return nil, errors.New(err)
	}
	msgObj, msgOk := msgLayer.(*omci.MibUploadNextRequest)
	if !msgOk {
		err := "omci Msg layer could not be assigned for MibUploadNextRequest"
		omciLogger.Error(err)
		return nil, errors.New(err)
	}
	return msgObj, nil
}

func CreateMibUploadNextResponse(omciPkt gopacket.Packet, omciMsg *omci.OMCI, mibDb *MibDb) ([]byte, error) {

	msgObj, err := ParseMibUploadNextRequest(omciPkt)
	if err != nil {
		err := "omci Msg layer could not be assigned for LayerTypeGetRequest"
		omciLogger.Error(err)
		return nil, errors.New(err)
	}

	omciLogger.WithFields(log.Fields{
		"EntityClass":           msgObj.EntityClass,
		"EntityInstance":        msgObj.EntityInstance,
		"CommandSequenceNumber": msgObj.CommandSequenceNumber,
	}).Trace("received-omci-mibUploadNext-request")

	isExtended := false
	numberOfCommands := mibDb.NumberOfBaselineCommands
	if omciMsg.DeviceIdentifier == omci.ExtendedIdent {
		isExtended = true
		numberOfCommands = mibDb.NumberOfExtendedCommands
	}
	if msgObj.CommandSequenceNumber > numberOfCommands {
		omciLogger.WithFields(log.Fields{
			"CommandSequenceNumber": msgObj.CommandSequenceNumber,
			"MibDbNumberOfCommands": numberOfCommands,
		}).Error("mibdb-does-not-contain-item")
		return nil, fmt.Errorf("mibdb-does-not-contain-item")
	}
	if isExtended {
		pkt := SetTxIdInEncodedPacket(mibDb.extendedResponses[int(msgObj.CommandSequenceNumber)], omciMsg.TransactionID)
		return pkt, nil
	} else {
		currentEntry := mibDb.baselineItems[int(msgObj.CommandSequenceNumber)]

		// if packet is set then we don't need to serialize the packet, it's already done
		if currentEntry.packet != nil {
			omciLogger.WithFields(log.Fields{
				"CommandSequenceNumber": msgObj.CommandSequenceNumber,
				"MibDbNumberOfCommands": numberOfCommands,
				"packet":                currentEntry.packet,
				"request-txid":          omciMsg.TransactionID,
			}).Info("sending-custom-packet")

			// NOTE we need to replace the first two bytes of the packet with the correct transactionId
			pkt := SetTxIdInEncodedPacket(currentEntry.packet, omciMsg.TransactionID)

			return pkt, nil
		}
		reportedMe, meErr := me.LoadManagedEntityDefinition(currentEntry.classId, me.ParamData{
			EntityID:   currentEntry.entityId.ToUint16(),
			Attributes: currentEntry.params,
		})

		if meErr.GetError() != nil {
			omciLogger.Errorf("Error while generating %s: %v", currentEntry.classId.String(), meErr.Error())
		}
		response := &omci.MibUploadNextResponse{
			MeBasePacket: omci.MeBasePacket{
				EntityClass: me.OnuDataClassID,
			},
			ReportedME: *reportedMe,
		}

		omciLogger.WithFields(log.Fields{
			"reportedMe": reportedMe,
		}).Trace("created-omci-mibUploadNext-response")

		pkt, err := Serialize(omci.MibUploadNextResponseType, response, omciMsg.TransactionID)

		if err != nil {
			omciLogger.WithFields(log.Fields{
				"Err": err,
			}).Fatalf("Cannot Serialize MibUploadNextRequest")
			return nil, err
		}

		return pkt, nil
	}
}