'''
Created on 11.06.2015

@author: wn
'''

import MeterbusTypeConversion

class MeterbusLibException(Exception):
    pass

class InvalidFrameCodeException(MeterbusLibException):
    pass

class InvalidFrameException(MeterbusLibException):
    pass

class InvalidChecksumException(MeterbusLibException):
    pass

class InvalidStopCharException(MeterbusLibException):
    pass

class InvalidStartCharException(MeterbusLibException):
    pass

class InvalidLengthException(MeterbusLibException):
    pass

class InvalidSecondLengthException(MeterbusLibException):
    pass

class PayloadTooShortException(MeterbusLibException):
    pass

class Frame(object):
    def __init__(self, startCharacter, frameLength, firstPayload, telegram):
        self.telegram = telegram
        self.frameName = self.__class__.__name__
        self.frameLength = frameLength
        self.payloadLength = self.frameLength - 6
        self.frameStartCharacter = startCharacter
        self.firstPayload = firstPayload
        
    def parse(self):
        if self.telegram[0] != self.frameStartCharacter:
            raise InvalidStartCharException()
        if len(self.telegram) != self.frameLength:
            raise InvalidLengthException()
        self.verifyChecksumAndEnd()
        self.parse2()
        
    def verifyChecksumAndEnd(self):
        if (self.firstPayload != 0):
            checksum = sum(self.telegram[self.firstPayload:-2]) & 0xff
            if checksum != self.telegram[-2]:
                raise InvalidChecksumException()
            if self.telegram[-1] != 0x16:
                raise InvalidStopCharException()
        
    def parse2(self):
        raise NotImplementedError
    
    def getJSON(self):
        raise NotImplementedError
    

class SingleCharacter(Frame):
    def __init__(self, telegram):
        super(SingleCharacter, self).__init__(0xe5, 1, 0, telegram)
        
    def parse2(self):
        pass
        

class ShortFrame(Frame):
    def __init__(self, telegram):
        super(ShortFrame, self).__init__(0x10, 5, 1, telegram)

    def parse2(self):
        self.cField = self.telegram[1]
        self.address = self.telegram[2]
        

class ControlFrame(Frame):
    def __init__(self, telegram):
        super(ControlFrame, self).__init__(0x68, (telegram[1] + 6), 4, telegram)

    def parse2(self):
        if self.telegram[2] != self.payloadLength:
            raise InvalidSecondLengthException
        if self.payloadLength < 3:
            raise PayloadTooShortException("too short for c, a, ci fields")
        self.cField = self.telegram[4]
        self.address = self.telegram[5]
        self.ciField = self.telegram[6]


class LongFrame(ControlFrame):
    class FixedDataHeader(object):
        def __init__(self, data):
            self.data = data
            print("Fixed header length: %d" % len(self.data))
            
        def parse(self):
            self.identNr = MeterbusTypeConversion.bcd(self.data[:4])
            self.manufacturer = self.data[4:6]
            self.version = self.data[6]
            self.medium = self.data[7]
            self.accessNo = self.data[8]
            self.status = self.data[9]
            self.signature = self.data[10:]
            
    def parse2(self):
        super(LongFrame, self).parse2()
        if self.payloadLength < 3 + 12:
            raise PayloadTooShortException("too short for fixed data header")
        self.fixedDataHeader = LongFrame.FixedDataHeader(self.telegram[7:19])
        self.fixedDataHeader.parse()


class Telegram(object):
    def __init__(self):
        pass
    
    def fromHexString(self, hexString):
        self.hexString = hexString
        octetList = [int(o, 16) for o in self.hexString.split(' ')]
        self.telegram = bytearray(octetList)
        
        for i in self.telegram:
            print(int(i))
        
    def toHexString(self):
        return str([hex(b) for b in self.telegram])
    
    def parse(self):
        if self.telegram[0] == 0x68 and self.telegram[1] == 0x03:
            self.frame = ControlFrame(self.telegram)
        elif self.telegram[0] == 0x68:
            self.frame = LongFrame(self.telegram)
        elif self.telegram[0] == 0x10:
            self.frame = ShortFrame(self.telegram)
        elif self.telegram[0] == 0xe5:
            self.frame = SingleCharacter(self.telegram)
        else:
            raise InvalidStartCharException()
        
        self.frame.parse()
        
        print("Frame is %s" % self.frame)