plc4go/internal/modbus/MessageCodec.go

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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
 *
 *   https://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 modbus

import (
	"context"
	"encoding/base64"

	"github.com/pkg/errors"
	"github.com/rs/zerolog"

	"github.com/apache/plc4x/plc4go/protocols/modbus/readwrite/model"
	"github.com/apache/plc4x/plc4go/spi"
	_default "github.com/apache/plc4x/plc4go/spi/default"
	"github.com/apache/plc4x/plc4go/spi/options"
	"github.com/apache/plc4x/plc4go/spi/transports"
)

//go:generate go tool plc4xGenerator -type=MessageCodec
type MessageCodec struct {
	_default.DefaultCodec

	expectationCounter int32

	passLogToModel bool

	log zerolog.Logger
}

var (
	_ spi.TransportInstanceExposer = (*MessageCodec)(nil)
)

func NewMessageCodec(transportInstance transports.TransportInstance, _options ...options.WithOption) *MessageCodec {
	passLoggerToModel, _ := options.ExtractPassLoggerToModel(_options...)
	customLogger := options.ExtractCustomLoggerOrDefaultToGlobal(_options...)
	codec := &MessageCodec{
		expectationCounter: 1,
		passLogToModel:     passLoggerToModel,
		log:                customLogger,
	}
	codec.DefaultCodec = _default.NewDefaultCodec(codec, transportInstance, _options...)
	return codec
}

func (m *MessageCodec) GetCodec() spi.MessageCodec {
	return m
}

func (m *MessageCodec) Send(ctx context.Context, interactionInfo string, message spi.Message) error {
	m.log.Trace().Str("interactionInfo", interactionInfo).Msg("Sending message")
	// Cast the message to the correct type of struct
	tcpAdu := message.(model.ModbusTcpADU)
	// Serialize the request
	theBytes, err := tcpAdu.Serialize()
	if err != nil {
		return errors.Wrap(err, "error serializing request")
	}

	// Send it to the PLC
	err = m.GetTransportInstance().Write(ctx, theBytes)
	if err != nil {
		return errors.Wrap(err, "error sending request")
	}
	return nil
}

func (m *MessageCodec) Receive(ctx context.Context) (spi.Message, error) {
	ti := m.GetTransportInstance()
	if !ti.IsConnected() {
		return nil, errors.New("Transport instance not connected")
	}

	if err := ti.FillBuffer(ctx, func(pos uint, currentByte byte, reader transports.ExtendedReader) bool {
		m.log.Trace().Uint("pos", pos).Uint8("currentByte", currentByte).Msg("filling")
		numBytesAvailable, err := ti.GetNumBytesAvailableInBuffer()
		if err != nil {
			m.log.Debug().Err(err).Msg("error getting available bytes")
			return false
		}
		m.log.Trace().Uint32("numBytesAvailable", numBytesAvailable).Msg("check available bytes < 6")
		return numBytesAvailable < 6
	}); err != nil {
		m.log.Debug().Err(err).Msg("error filling buffer")
	}

	// We need at least 6 bytes in order to know how big the packet is in total
	if num, err := ti.GetNumBytesAvailableInBuffer(); (err == nil) && (num >= 6) {
		m.log.Debug().Uint32("num", num).Msg("we got num readable bytes")
		data, err := ti.PeekReadableBytes(ctx, 6)
		if err != nil {
			m.log.Warn().Err(err).Msg("error peeking")
			// TODO: Possibly clean up ...
			return nil, nil
		}
		// Get the size of the entire packet
		packetSize := (uint32(data[4]) << 8) + uint32(data[5]) + 6
		if num < packetSize {
			m.log.Debug().
				Uint32("num", num).
				Uint32("packetSize", packetSize).Msg("Not enough bytes. Got: num Need: packetSize")
			return nil, nil
		}
		data, err = ti.Read(ctx, packetSize)
		if err != nil {
			// TODO: Possibly clean up ...
			return nil, nil
		}
		ctxForModel := options.GetLoggerContextForModel(ctx, m.log, options.WithPassLoggerToModel(m.passLogToModel))
		tcpAdu, err := model.ModbusADUParse[model.ModbusTcpADU](ctxForModel, data, model.DriverType_MODBUS_TCP, true)
		if err != nil {
			dataStr := base64.StdEncoding.EncodeToString(data)
			m.log.Warn().Err(err).
				Str("data", dataStr). // Max PDU size is 253 bytes, and catching parse errors for inspection is important
				Uint32("packetSize", packetSize).
				Msg("error parsing")
			// TODO: Possibly clean up ...
			return nil, nil
		}
		return tcpAdu, nil
	} else if err != nil {
		m.log.Warn().Err(err).Msg("Got error reading")
		return nil, nil
	}
	// TODO: maybe we return here a not enough error error
	return nil, nil
}