codename-sendaround/internal/messages.go

package internal

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
)

type messageOuter struct {
	Type string
}

type Message struct {
	FileOfferMessage           *FileOfferMessage
	FileUnofferMessage         *FileUnofferMessage
	FileTransferRequestMessage *FileTransferRequestMessage
	SessionInitializedMessage  *SessionInitializedMessage
}

func (m *Message) UnmarshalJSON(b []byte) (err error) {
	typeObj := new(messageOuter)
	if err = json.NewDecoder(bytes.NewReader(b)).Decode(typeObj); err != nil {
		return
	}

	switch typeObj.Type {
	case "fileOffer":
		v := new(struct {
			Data *FileOfferMessage
		})
		if err = json.NewDecoder(bytes.NewReader(b)).Decode(v); err != nil {
			return
		}
		m.FileOfferMessage = v.Data
	case "fileUnoffer":
		v := new(struct {
			Data *FileUnofferMessage
		})
		if err = json.NewDecoder(bytes.NewReader(b)).Decode(v); err != nil {
			return
		}
		m.FileUnofferMessage = v.Data
	case "fileTransferRequest":
		v := new(struct {
			Data *FileTransferRequestMessage
		})
		if err = json.NewDecoder(bytes.NewReader(b)).Decode(v); err != nil {
			return
		}
		m.FileTransferRequestMessage = v.Data
	case "sessionInitialized":
		v := new(struct {
			Data *SessionInitializedMessage
		})
		if err = json.NewDecoder(bytes.NewReader(b)).Decode(v); err != nil {
			return
		}
		m.SessionInitializedMessage = v.Data
	default:
		err = fmt.Errorf("Invalid message type: %s", typeObj.Type)
	}

	return
}

func (m *Message) MarshalJSON() (b []byte, err error) {
	var typeName = ""
	var data interface{}
	switch {
	case m.FileOfferMessage != nil:
		typeName = "fileOffer"
		data = m.FileOfferMessage
	case m.FileUnofferMessage != nil:
		typeName = "fileUnoffer"
		data = m.FileUnofferMessage
	case m.FileTransferRequestMessage != nil:
		typeName = "fileTransferRequest"
		data = m.FileTransferRequestMessage
	case m.SessionInitializedMessage != nil:
		typeName = "sessionInitialized"
		data = m.SessionInitializedMessage
	default:
		err = errors.New("can not encode msg due to unknown message type")
		return
	}
	buf := new(bytes.Buffer)
	err = json.NewEncoder(buf).Encode(map[string]interface{}{
		"type": typeName,
		"data": data,
	})
	if err != nil {
		return
	}
	b = buf.Bytes()
	return
}

type FileOfferMessage struct {
	FileName string `json:"fileName"`
	Length   uint64 `json:"length"`
	MimeType string `json:"mimeType"`
}

type FileTransferRequestMessage struct {
	FileName string `json:"fileName"`
}

type FileUnofferMessage struct {
	FileName string `json:"fileName"`
}

type SessionInitializedMessage struct {
}