"""Xiaomi packet transport"""
from struct import pack, unpack
from .base import checksum, BaseTransport as BT
from .packet import BasePacket


class XiaomiTransport(BT):
	MASTER2ESC = 0x20
	ESC2MASTER = 0x23

	MASTER2BLE = 0x21
	BLE2MASTER = 0x24

	MASTER2BMS = 0x22
	BMS2MASTER = 0x25

	MOTOR	 = 0x01
	DEVFF	 = 0xFF

	_SaDa2Addr = { 	BT.HOST : { BT.MOTOR : MOTOR, BT.ESC  : MASTER2ESC, BT.BLE : MASTER2BLE, BT.BMS : MASTER2BMS },
					BT.ESC	: { BT.HOST : ESC2MASTER, BT.BLE : MASTER2BLE, BT.BMS : MASTER2BMS, BT.MOTOR : MOTOR },
					BT.BMS  : { BT.HOST : BMS2MASTER, BT.ESC : BMS2MASTER, BT.MOTOR : MOTOR },
					BT.MOTOR : {BT.HOST : MOTOR, BT.ESC : MOTOR, BT.BMS : MOTOR } }

	# TBC
	_BleAddr2SaDa = { 	MASTER2ESC : (BT.HOST, BT.ESC), 
						ESC2MASTER : (BT.ESC, BT.HOST),
						MASTER2BMS : (BT.HOST, BT.BMS),
						BMS2MASTER : (BT.BMS, BT.HOST),
						MASTER2BLE : (BT.HOST, BT.BLE),
						BLE2MASTER : (BT.BLE, BT.HOST),
						MOTOR	 : (BT.MOTOR, BT.HOST) }

	_BmsAddr2SaDa = { 	MASTER2ESC : (BT.BMS, BT.ESC), 
						ESC2MASTER : (BT.ESC, BT.BMS),
						MASTER2BMS : (BT.ESC, BT.BMS),
						BMS2MASTER : (BT.BMS, BT.ESC),
						MASTER2BLE : (BT.BMS, BT.BLE),
						BLE2MASTER : (BT.BLE, BT.BMS),
						MOTOR	 : (BT.MOTOR, BT.BMS) }


	def __init__(self, link, device=BT.HOST):
		super(XiaomiTransport, self).__init__(link)
		self.device = device


	def _make_addr(self, src, dst):
		return XiaomiTransport._SaDa2Addr[src][dst]

			
	def _split_addr(self, addr):
		if self.device==BT.BMS:
			return XiaomiTransport._BmsAddr2SaDa[addr]
		else:
			return XiaomiTransport._BleAddr2SaDa[addr]


	def _wait_pre(self):
		while True:
			while True:
				c = self.link.read(1)
				if c=="\x55":
					break
			while True:
				c = self.link.read(1)
				if c=="\xAA":
					return True 
				if c!="\x55":
					break # start waiting 55 again, else - this is 55, so wait for AA


	def recv(self):
		self._wait_pre()
		pkt = self.link.read(1)
		l = ord(pkt)+3
		for i in range(l):
			pkt += self.link.read(1)
		ck_calc = checksum(pkt[0:-2])
		ck_pkt = unpack("<H", pkt[-2:])[0]
		if ck_pkt!=ck_calc:
			print("Checksum mismatch !")
			return None
		sa, da = self._split_addr(ord(pkt[1]))
		return BasePacket(sa, da, ord(pkt[2]), ord(pkt[3]), pkt[4:-2]) # sa, da, cmd, arg, data

	
	def send(self, packet):
		dev = self._make_addr(packet.src, packet.dst)
		pkt = pack("<BBBB", len(packet.data)+2, dev, packet.cmd, packet.arg)+packet.data
		pkt = "\x55\xAA" + pkt + pack("<H", checksum(pkt))
		self.link.write(pkt)


__all__ = ["XiaomiTransport"]