#SBTX QWRXLVQVE v0.1
#Python 2.7.X
#May 14th 2021
#
#Operates on text files
#Currently does not have robust error-detection
#Also not particularly fast or efficient
#It doesn't handle special characters well either
#Nor does it play nice with multiple encodings
#Overwriting files is out too

def alphabetsoup(imp): #Derive a string holding our translation pattern
    alphalist="ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    alphalist2=[]
    for letter in imp:
        if letter in alphalist or letter in alphalist2:
            continue
        else:
            alphalist2.append(letter)
    alphalist2.sort()
    alphalist=alphalist+"".join(alphalist2)
    return alphalist

def spacefinder(imp): #Find where all the spaces are, then reverse their locations
    spacelist=[]
    for i in range(len(imp)):
        if imp[i]==" ":
            i=(i*(-1))
            spacelist.append(i)
    return spacelist

def encode(imp):
    spacelist=spacefinder(imp)
    newimp=list(imp.replace(" ","").upper())
    alphalist=alphabetsoup(newimp)
    for i in range(len(newimp)):
        if i%2==0:#Spaghetti code to translate up or down based on the characters position in the string
            newimp[i]=alphalist[(alphalist.index(newimp[i])+(i))%(len(alphalist))]
        else:
            newimp[i]=alphalist[(alphalist.index(newimp[i])-(i))%(len(alphalist))]
    for item in spacelist:
        newimp.insert(item," ")
    return "".join(newimp)

def decode(imp):
    spacelist=spacefinder(imp)
    newimp=list(imp.replace(" ","").upper())
    alphalist=alphabetsoup(newimp)
    for i in range(len(newimp)):
        if i%2==0:
            newimp[i]=alphalist[(alphalist.index(newimp[i])-(i))%(len(alphalist))]
        else:
            newimp[i]=alphalist[(alphalist.index(newimp[i])+(i))%(len(alphalist))]
    for item in spacelist:
        newimp.insert(item," ")
    return "".join(newimp)

#Accept work inputs
teckstfile=raw_input("Which file would you like to access?\n")
opcoderino=raw_input("Encode (E) or Decode (D)?\n")

#Develop openvars
tf_open=open(teckstfile)
tf_work=(teckstfile.split("."))
tf_work.insert(-1,"_d.")
tf_work=open("".join(tf_work),"w")
#Actually do something
for line in tf_open:
    if opcoderino=="E":
        line=line.strip()
        tf_work.write(encode(line)+"\n")
    if opcoderino=="D":
        line=line.strip()
        tf_work.write(decode(line)+"\n")
        

tf_open.close()
tf_work.close()