go-ipp/request.go

/*
	Copyright 2022 Dolysis Consulting Limited

	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.

	For changes see the git log
*/
package ipp

import (
	"bytes"
	"encoding/binary"
	"io"
)

// Request defines a ipp request
type Request struct {
	ProtocolVersionMajor int8
	ProtocolVersionMinor int8

	Operation int16
	RequestId int32

	OperationAttributes map[string]interface{}
	JobAttributes       map[string]interface{}
	PrinterAttributes   map[string]interface{}

	File     io.Reader
	FileSize int
}

// NewRequest creates a new ipp request
func NewRequest(op int16, reqID int32) *Request {
	return &Request{
		ProtocolVersionMajor: ProtocolVersionMajor,
		ProtocolVersionMinor: ProtocolVersionMinor,
		Operation:            op,
		RequestId:            reqID,
		OperationAttributes:  make(map[string]interface{}),
		JobAttributes:        make(map[string]interface{}),
		PrinterAttributes:    make(map[string]interface{}),
		File:                 nil,
		FileSize:             -1,
	}
}

// Encode encodes the request to a byte slice
func (r *Request) Encode() ([]byte, error) {
	buf := new(bytes.Buffer)
	enc := NewAttributeEncoder(buf)

	if err := binary.Write(buf, binary.BigEndian, r.ProtocolVersionMajor); err != nil {
		return nil, err
	}

	if err := binary.Write(buf, binary.BigEndian, r.ProtocolVersionMinor); err != nil {
		return nil, err
	}

	if err := binary.Write(buf, binary.BigEndian, r.Operation); err != nil {
		return nil, err
	}

	if err := binary.Write(buf, binary.BigEndian, r.RequestId); err != nil {
		return nil, err
	}

	if err := binary.Write(buf, binary.BigEndian, int8(TagOperation)); err != nil {
		return nil, err
	}

	if err := enc.Encode(AttributeCharset, Charset); err != nil {
		return nil, err
	}

	if err := enc.Encode(AttributeNaturalLanguage, CharsetLanguage); err != nil {
		return nil, err
	}

	if len(r.OperationAttributes) > 0 {
		for attr, value := range r.OperationAttributes {
			if err := enc.Encode(attr, value); err != nil {
				return nil, err
			}
		}
	}

	if len(r.JobAttributes) > 0 {
		if err := binary.Write(buf, binary.BigEndian, int8(TagJob)); err != nil {
			return nil, err
		}
		for attr, value := range r.JobAttributes {
			if err := enc.Encode(attr, value); err != nil {
				return nil, err
			}
		}
	}

	if len(r.PrinterAttributes) > 0 {
		if err := binary.Write(buf, binary.BigEndian, int8(TagPrinter)); err != nil {
			return nil, err
		}
		for attr, value := range r.PrinterAttributes {
			if err := enc.Encode(attr, value); err != nil {
				return nil, err
			}
		}
	}

	if err := binary.Write(buf, binary.BigEndian, int8(TagEnd)); err != nil {
		return nil, err
	}

	return buf.Bytes(), nil
}

// RequestDecoder reads and decodes a request from a stream
type RequestDecoder struct {
	reader io.Reader
}

// NewRequestDecoder returns a new decoder that reads from r
func NewRequestDecoder(r io.Reader) *RequestDecoder {
	return &RequestDecoder{
		reader: r,
	}
}

// Decode decodes a ipp request into a request  struct. additional data will be written to an io.Writer if data is not nil
func (d *RequestDecoder) Decode(data io.Writer) (*Request, error) {
	req := new(Request)

	if err := binary.Read(d.reader, binary.BigEndian, &req.ProtocolVersionMajor); err != nil {
		return nil, err
	}

	if err := binary.Read(d.reader, binary.BigEndian, &req.ProtocolVersionMinor); err != nil {
		return nil, err
	}

	if err := binary.Read(d.reader, binary.BigEndian, &req.Operation); err != nil {
		return nil, err
	}

	if err := binary.Read(d.reader, binary.BigEndian, &req.RequestId); err != nil {
		return nil, err
	}

	startByteSlice := make([]byte, 1)

	tag := TagCupsInvalid
	previousAttributeName := ""
	tagSet := false

	attribDecoder := NewAttributeDecoder(d.reader)

	// decode attribute buffer
	for {
		if _, err := d.reader.Read(startByteSlice); err != nil {
			// when we read from a stream, we may get an EOF if we want to read the end tag
			// all data should be read and we can ignore the error
			if err == io.EOF {
				break
			}
			return nil, err
		}

		startByte := int8(startByteSlice[0])

		// check if attributes are completed
		if startByte == TagEnd {
			break
		}

		if startByte == TagOperation {
			if req.OperationAttributes == nil {
				req.OperationAttributes = make(map[string]interface{})
			}

			tag = TagOperation
			tagSet = true

		}

		if startByte == TagJob {
			if req.JobAttributes == nil {
				req.JobAttributes = make(map[string]interface{})
			}
			tag = TagJob
			tagSet = true
		}

		if startByte == TagPrinter {
			if req.PrinterAttributes == nil {
				req.PrinterAttributes = make(map[string]interface{})
			}
			tag = TagPrinter
			tagSet = true
		}

		if tagSet {
			if _, err := d.reader.Read(startByteSlice); err != nil {
				return nil, err
			}
			startByte = int8(startByteSlice[0])
		}

		attrib, err := attribDecoder.Decode(startByte)
		if err != nil {
			return nil, err
		}

		if attrib.Name != "" {
			appendAttributeToRequest(req, tag, attrib.Name, attrib.Value)
			previousAttributeName = attrib.Name
		} else {
			appendAttributeToRequest(req, tag, previousAttributeName, attrib.Value)
		}

		tagSet = false
	}

	if data != nil {
		if _, err := io.Copy(data, d.reader); err != nil {
			return nil, err
		}
	}

	return req, nil
}

func appendAttributeToRequest(req *Request, tag int8, name string, value interface{}) {
	switch tag {
	case TagOperation:
		req.OperationAttributes[name] = value
	case TagPrinter:
		req.PrinterAttributes[name] = value
	case TagJob:
		req.JobAttributes[name] = value
	}
}