#Text encryption program.
#Written by Asa S. and Ben A.
#----------------------------------

import binascii, string

#This function converts an integer to hexadecimal
def iToHex(a):
    div=a/16
    rem=a%16
    if rem==10: rem="a"
    if rem==11: rem="b"
    if rem==12: rem="c"
    if rem==13: rem="d"
    if rem==14: rem="e"
    if rem==15: rem="f"
    if div > 0:
        return (str(iToHex(div)) + str(rem))
    else:
        return (str(rem))

#This funciton converts an ascii character to an integer
def aTob(as):
    bs=binascii.b2a_hex(as)
    return (int(bs,16))

#This function converts an integer to an ascii character   
def bToa(sb):
    e=iToHex(sb)
    if len(e)%2:
        e="0"+e
    return (binascii.a2b_hex(e))

# Scramble file function
#--------------------------------------------
def scrambleFile (srcName, destName):
    #Open src
    f=open(srcName, "r")
    #Read its contents
    s=f.read()
   
    #Close src
    f.close()

    #Open dest
    f=open(destName, "w")
    #Write the contents
    for x in s:
        if x<>"":
            #Convert our unencrypted text to a number
            num=aTob(x)
            #Shift that character over by 15 and wrap it
            num=num+10       
            if num>255:
                num=num-256
            #Convert the new encrypted number back to a character
            ascii=bToa(num)
            #Write that character into the file
            f.write(ascii)
       
    #Close dest
    f.close()
#--------------------------------------------
   
#Unscramble file function
#--------------------------------------------
def unscrambleFile (srcName, destName):
    #Open src
    f=open(srcName, "r")
    #Read its contents
    s=f.read()

    #Close src
    f.close()

    #Open dest
    f=open(destName, "w")
    #Write the contents
    for x in s:
        #If "x" isn't blank:
        if x!="":
            #Convert our encyrpted text into a number
            num=aTob(x)
            #Shift that character over by 15 and wrap it
            num=num-10
            if num<0:
                num=num+256
            #Convert the new unencrypted number back to a character
            ascii=bToa(num)
            #Write that character back into the file
            f.write(ascii)

    #Close dest
    f.close
#---------------------------------------
#Call functions in an infinite loop
while True:
    #Ask what the user wants to do
    function=input("Enter 1 to encrypt; enter 2 to decrypt; enter 3 to quit. >>> ")
    #See if the user wants to encrypt a file
    if function==1:
        x=raw_input("Enter the name of the file you wish to encrypt. >>> ")
        print ("Encrypting file...")
        scrambleFile(x, x)
        print ("Encryption successful.")
        see=input("Press 1 to read " + x + "; press 2 to continue to the main menu. >>> ")
        #Ask if they want to read the file
        if see==1:
            openx=open (x, "r")
            readx=openx.read()
            print (readx)
        if see==2:
            pass
    #See if the user wants to decrypt a file
    if function==2:
        x=raw_input("Enter the name of the file you wish to decrypt. >>> ")
        print ("Decrypting file...")
        unscrambleFile(x, x)
        print ("Decryption successful.")
        see=input("Press 1 to read " + x + "; press 2 to continue to the main menu. >>> ")
        #Ask if they want to read the file
        if see==1:
            openx=open (x, "r")
            readx=openx.read()
            print (readx)
        if see==2:
            pass
    #See if they want to quit; if they do, then break the loop
    if function==3:
        break

#Shift that character over by a number and wrap it
            num=num-x
            if num<0:
                num=num+256