# Skeleton Program for the AQA AS Summer 2018 examination
# this code should be used in conjunction with the Preliminary Material
# written by the AQA AS Programmer Team
# developed in a Python 3 environment


# Version Number : 1.6

SPACE = ' '
EOL = '#'
EMPTYSTRING = ''

def ReportError(s):
  print('{0:<5}'.format('*'),s,'{0:>5}'.format('*'))

def StripLeadingSpaces(Transmission):
  TransmissionLength = len(Transmission)
  if TransmissionLength > 0:
    FirstSignal = Transmission[0]
    while FirstSignal == SPACE and TransmissionLength > 0:
      TransmissionLength -= 1
      Transmission = Transmission[1:]
      if TransmissionLength > 0:
        FirstSignal = Transmission[0]
  if TransmissionLength == 0:
    ReportError("No signal received")
  return Transmission

def StripTrailingSpaces(Transmission):
  LastChar = len(Transmission) - 1
  while Transmission[LastChar] == SPACE:
    LastChar -= 1
    Transmission = Transmission[:-1]
  return Transmission

def GetTransmission():
  FileName = input("Enter file name: ")
  try:
    FileHandle = open(FileName, 'r')
    Transmission = FileHandle.readline()
    FileHandle.close()
    Transmission = StripLeadingSpaces(Transmission)
    if len(Transmission) > 0:
      Transmission = StripTrailingSpaces(Transmission)
      Transmission = Transmission + EOL
  except:
    ReportError("No transmission found")
    Transmission = EMPTYSTRING
  return Transmission

def GetNextSymbol(i, Transmission):
  if Transmission[i] == EOL:
    print()
    print("End of transmission")
    Symbol = EMPTYSTRING
  else:
    SymbolLength = 0
    Signal = Transmission[i]
    while Signal != SPACE and Signal != EOL:
      i += 1
      Signal = Transmission[i]
      SymbolLength += 1
    if SymbolLength == 1:
      Symbol = '.'
    elif SymbolLength == 3:
      Symbol = '-'
    elif SymbolLength == 0:
      Symbol = SPACE
    else:
      ReportError("Non-standard symbol received")
      Symbol = EMPTYSTRING
  return i, Symbol

def GetNextLetter(i, Transmission):
  SymbolString = EMPTYSTRING
  LetterEnd = False
  while not LetterEnd:
    i, Symbol = GetNextSymbol(i, Transmission)
    if Symbol == SPACE:
      LetterEnd = True
      i += 4
    elif Transmission[i] == EOL:
      LetterEnd = True
    elif Transmission[i + 1] == SPACE and Transmission[i + 2] == SPACE:
      LetterEnd = True
      i += 3
    else:
      i += 1
    SymbolString = SymbolString + Symbol
  return i, SymbolString

def Decode(CodedLetter, Dash, Letter, Dot):
  CodedLetterLength = len(CodedLetter)
  Pointer = 0
  for i in range(CodedLetterLength):
    Symbol = CodedLetter[i]
    if Symbol == SPACE:
      return SPACE
    elif Symbol == '-':
      Pointer = Dash[Pointer]
    else:
      Pointer = Dot[Pointer]
  return Letter[Pointer]

def ReceiveMorseCode(Dash, Letter, Dot):
  PlainText = EMPTYSTRING
  MorseCodeString = EMPTYSTRING
  Transmission = GetTransmission()
  LastChar = len(Transmission) - 1
  i = 0
  while i < LastChar:
    i, CodedLetter = GetNextLetter(i, Transmission)
    MorseCodeString = MorseCodeString + SPACE + CodedLetter
    PlainTextLetter = Decode(CodedLetter, Dash, Letter, Dot)
    PlainText = PlainText + PlainTextLetter
  print(MorseCodeString)
  print(PlainText)

def SendMorseCode(MorseCode):
  PlainText = input("Enter your message (uppercase letters and spaces only): ")
  PlainTextLength = len(PlainText)
  MorseCodeString = EMPTYSTRING
  for i in range(PlainTextLength):
    PlainTextLetter = PlainText[i]
    if PlainTextLetter == SPACE:
      Index = 0
    else:
      Index = ord(PlainTextLetter) - ord('A') + 1
    CodedLetter = MorseCode[Index]
    MorseCodeString = MorseCodeString + CodedLetter + SPACE
  print(MorseCodeString)

def DisplayMenu():
  print()
  print("Main Menu")
  print("=========")
  print("R - Receive Morse code")
  print("S - Send Morse code")
  print("X - Exit program")
  print()

def GetMenuOption():
  MenuOption = input("Enter your choice: ").upper()
  while MenuOption not in ['R', 'S', 'X']:
    MenuOption = input("Invalid choice, please choose a letter from the menu: ").upper()
  return MenuOption

def SendReceiveMessages():
  Dash = [20,23,0,0,24,1,0,17,0,21,0,25,0,15,11,0,0,0,0,22,13,0,0,10,0,0,0]
  Dot = [5,18,0,0,2,9,0,26,0,19,0,3,0,7,4,0,0,0,12,8,14,6,0,16,0,0,0]
  Letter = [' ','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z']

  MorseCode = [' ','.-','-...','-.-.','-..','.','..-.','--.','....','..','.---','-.-','.-..','--','-.','---','.--.','--.-','.-.','...','-','..-','...-','.--','-..-','-.--','--..']

  ProgramEnd = False
  while not ProgramEnd:
    DisplayMenu()
    MenuOption = GetMenuOption()
    if MenuOption == 'R':
      ReceiveMorseCode(Dash, Letter, Dot)
    elif MenuOption == 'S':
      SendMorseCode(MorseCode)
    elif MenuOption == 'X':
      ProgramEnd = True


if __name__ == "__main__":
  SendReceiveMessages()