package communication

const (
	SLIP_END         = 0xC0
	SLIP_ESC         = 0xDB
	SLIP_ESC_END     = 0xDC
	SLIP_ESC_ESC     = 0xDD
	SLIP_MAX_PAYLOAD = 1500
)

type dataLink struct {
	rx chan []byte
}

func newDataLink() dataLink {
	dl := dataLink{}

	dl.rx = make(chan []byte)

	return dl
}

func (dl *dataLink) start(source chan byte) {
	go dl.receive(source)
}

func (dl *dataLink) receive(source chan byte) {
	for {
		frame := unslip(source)
		dl.rx <- frame
	}
}

func unslip(source chan byte) []byte {
	escaped := false
	buffer := make([]byte, 0)

	for {
		octet := <-source
		if escaped {
			switch octet {
			case SLIP_ESC_END:
				buffer = append(buffer, SLIP_END)
			case SLIP_ESC_ESC:
				buffer = append(buffer, SLIP_ESC)
			}
		} else {
			switch octet {
			case SLIP_END:
				break
			case SLIP_ESC:
				escaped = true
				continue
			default:
				buffer = append(buffer, octet)
				continue
			}
			break
		}
	}

	return buffer
}