#cheat-check a murecursion program
import string

#does every character of a string belong to some character set?
#Usually, whitespace,letters,, etc.
def allin(s,charset):
    for c in s:
        if not (c in charset):
            return False
    return True

#remove whitespace from a string
def remove_whitespace(s):
    t=''
    for c in s:
        if not (c in string.whitespace):
            t+=c
    return t

#return a list of the lines of the program; ignore comments
def getLines(programName):
    f=open(programName,'r')
    u=[]
    for nextline in f:
        if nextline[0] != '#':
            if not allin(nextline,string.whitespace):#ignore all whitespace lines
                #strip whitespace from start of line and newline from end
                j=0
                while not nextline[j] in string.ascii_letters:
                    j+=1
                u.append(nextline[j:-1])
    return u

#Given a string, check if it is allowed in
#the sublanguage.
#Allowed lines start with a keyword def, for, while, return,
#or they are increment lines var +=1
#or they are zero lines var=0
#or they are assignment lines var= ..and string following must be just
#letters and parentheses

def checkLegalLine(s):
    m=len(s)
    #print s
    allowed=string.ascii_letters+'(),:_'
    if (m>=3) and (s[0:3]=='def'):
        v=s[3:]
        v=remove_whitespace(v)
        #now we can only have letters, parentheses,
        #commas, and :
        if not allin(v,allowed):
            return False
        return True
    elif (m>=3) and (s[0:3]=='for'):
        v=s[3:]
        follow=v.split()
        if not len(follow)>=3:
            return False
        if not allin(follow[0],string.ascii_letters):
            return False
        if follow[1]!='in':
            return False
        x=''.join(follow[2:])
        x=remove_whitespace(x)
        if len(x)<9:
            return False
        if x[:5]!='range':
            return False
        if x[5]!='(':
            return False
        if x[-1]!=':':
            return False
        if x[-2]!=')':
            return False
        if not allin(x[6:-2],string.ascii_letters):
            return False
        return True
    elif (m>=5) and (s[:5]=='while'):
        v=s[5:]
        follow=v.split()
        x=''.join(follow)
        x=remove_whitespace(x)
        if x[-4:]!='!=0:':
            return False
        if not allin(x[:-4],string.ascii_letters):
            return False
        return True
    elif (m>=6) and (s[:6]=='return'):
        v=s[6:]
        v=remove_whitespace(v)
        if allin(v,string.ascii_letters):
            return True
        else:
            return False
    elif (m>=4) and ('+=' in s):
        s=remove_whitespace(s)
        j=s.index('+=')
        if allin(s[:j],string.ascii_letters) and (s[j:]=='+=1'):
            return True
        else:
            return False
    elif (m>=3) and ('=' in s):
        s=remove_whitespace(s)
        j=s.index('=')
        #print 'I am here',s
        if allin(s[:j],string.ascii_letters) and ((allin(s[j+1:],allowed) or s[-1]=='0')):
            #print 'and here'
            return True
        else:
            return False
    return False

#given list of lines, check to see if each is a legal line.
#Return False and report the line if an illegal one is found.
def check_for_badlines(linelist):
    for line in linelist:
        if not checkLegalLine(line):
            print ('forbidden line:',line)
            return False
    return True

def cheat_check(filename):
    v=getLines(filename)
    u=check_for_badlines(v)
    if not u:
        print ('Fix forbidden lines and try again.')
    else:
        print ('ok to run program')