# 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('*'))

# function that is looking at the leading (first) character in the transmission
def StripLeadingSpaces(Transmission):
    # getting the length / amount of characters in the transmission
  TransmissionLength = len(Transmission)
  # if there is more than nothing in the transmission
  # checking to see if the first character is a space
  # if it is a space, the length is reduced by 1
  if TransmissionLength > 0:
    FirstSignal = Transmission[0]
    while FirstSignal == SPACE and TransmissionLength > 0:
      TransmissionLength -= 1
      Transmission = Transmission[1:]
      if TransmissionLength > 0:
        FirstSignal = Transmission[0]
  # if the transmission is 0
  # it displays an error message that there are no signals in the file
  if TransmissionLength == 0:
    ReportError("No signal received")
  return Transmission

# looking at the rest of the characters in the transmission
def StripTrailingSpaces(Transmission):
  LastChar = len(Transmission) - 1
  while Transmission[LastChar] == SPACE:
    LastChar -= 1
    Transmission = Transmission[:-1]
  return Transmission

# EDIT
# attempt at changing the GetTransmission Function
# now allows a direct transmission input rather than having to have a .txt file to read from
def GetTransmission():
    # asks the user if they would like to load a file or direct input for translation
  choice = input("Would you like to load a file? (Yes/No): ")
  if choice == "Yes":
      # if user wants to load file, code remains the same and user inputs the file name
      # the transmission in the loaded file will be then translated into english and morse code
    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:
        # if there is nothing in the file (len=0) then this message is dispalyed
      ReportError("No transmission found")
      Transmission = EMPTYSTRING
  else:
      # if the user decides to input a transmission directly, they will input 'No' instead
      # prompt message to get the user to input the transmission
      # note that only = and spaces are allowed
    Transmission = input("Enter your transmission String (Use '=' and spaces only ): ")
    Transmission = StripLeadingSpaces(Transmission)
    # if there is a transmission submitted correctly then it will translate it and return the translations
    if len(Transmission) > 0:
      Transmission = StripTrailingSpaces(Transmission)
      Transmission = Transmission + EOL
  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)

# when the user wants to send morse code
def SendMorseCode(MorseCode):
    # asks the user to enter a message using only uppercase and spaces
  PlainText = input("Enter your message (uppercase letters and spaces only): ")
  # calculating the amount of characters
  PlainTextLength = len(PlainText)
  MorseCodeString = EMPTYSTRING
  # for each character in the message submitted by the user
  # finds the morse code equivalent and adds them to the morse code string to make a morse code phrase or word
  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)

# this creates the menu layout
def DisplayMenu():
  print()
  print("Main Menu")
  print("=========")
  print("R - Receive Morse code")
  print("S - Send Morse code")
  print("X - Exit program")
  print()

# GetMenuOption function is used to ask the user what they would like to do with the program
def GetMenuOption():
  MenuOption = EMPTYSTRING
  # while the input is not 1
  # as the input only requires a single letter, the program will display the prompt when the box is empty
  while len(MenuOption) != 1:
    MenuOption = input("Enter your choice: ")
  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']

# storing the morse code for each letter in a MorseCode list
  MorseCode = [' ','.-','-...','-.-.','-..','.','..-.','--.','....','..','.---','-.-','.-..','--','-.','---','.--.','--.-','.-.','...','-','..-','...-','.--','-..-','-.--','--..']

# Deciding what each input will do
# when the code is run, programEnd = False as it is running
  ProgramEnd = False
  # while the program is running, display the menu for the user
  while not ProgramEnd:
    DisplayMenu()
    #calls the menu function to ask the user for their input
    MenuOption = GetMenuOption()
    # if the input is R, it calls the ReceiveMorseCode function
    if MenuOption == 'R':
      ReceiveMorseCode(Dash, Letter, Dot)
    # if the input is S, it calls the SendMorseCode function
    elif MenuOption == 'S':
      SendMorseCode(MorseCode)
    # If the input is X, then in will turn ProgramEnd to True, meaning that the menu will no longer appear and the program will stop running.
    elif MenuOption == 'X':
      ProgramEnd = True
    # Incase the input does not match up to the available options, then it will ask the user for another input and display the options again
    else:
        print("This is an invalid input, please try again: ")


if __name__ == "__main__":
  SendReceiveMessages()