"""
Author  : flo aka freemanbach
date    : 2019.02.16
Purpose :  Need a file checksum software for all kinds of reasons, YODAHEIM.
        :  There is a Java version too, but its alpha/beta stage
	:  Java skillz is lacking in hobbit power !
Comments: need to implement a ton more before this is truly effective
        :  May add Adler and CRC32 algorithm soon
example : python chksum.py -v
example : python chksum.py -h
"""

import os
import sys
import hashlib  # main hashing libs 
import hmac     # message algorithm
import zlib     # adler and crc32

try:
    import getopt   # parameter package lib
except ImportError as err:
    print("Missing GetOpt Library, install it Yodaheim !")
    sys.exit(1)


def md5(fname):
    # https://stackoverflow.com/questions/1131220/get-md5-hash-of-big-files-in-python
    # i agreed with the Author of this code, this is the fastest approach in reading 
    # from a file and hashing its contents
    # reading in 4k block at a time should be sufficient, others will use 1024 or 2048
    hash_md5 = hashlib.md5()
    with open(fname, "rb") as f:
        for chunk in iter(lambda: f.read(4096), b""):
            hash_md5.update(chunk)
    return hash_md5.hexdigest()

def sha1(fname):
    hash_sha1 = hashlib.sha1()
    with open(fname, "rb") as f:
        for chunk in iter(lambda: f.read(4096), b""):
            hash_sha1.update(chunk)
    return hash_sha1.hexdigest()

def sha224(fname):
    hash_sha224 = hashlib.sha224()
    with open(fname, "rb") as f:
        for chunk in iter(lambda: f.read(4096), b""):
            hash_sha224.update(chunk)
    return hash_sha224.hexdigest()

def sha256(fname):
    hash_sha256 = hashlib.sha256()
    with open(fname, "rb") as f:
        for chunk in iter(lambda: f.read(4096), b""):
            hash_sha256.update(chunk)
    return hash_sha256.hexdigest()

def sha384(fname):
    hash_sha384 = hashlib.sha384()
    with open(fname, "rb") as f:
        for chunk in iter(lambda: f.read(4096), b""):
            hash_sha384.update(chunk)
    return hash_sha384.hexdigest()

def sha512(fname):
    hash_sha512 = hashlib.sha512()
    with open(fname, "rb") as f:
        for chunk in iter(lambda: f.read(4096), b""):
            hash_sha512.update(chunk)
    return hash_sha512.hexdigest()

"""
There are no such thing as sha1024 in the python hashlib arsenal.
I would need to write my own sha 1024 algorithm
def sha1024(fname):
    hash_sha1024 = hashlib.sha1024()
    with open(fname, "rb") as f:
        for chunk in iter(lambda: f.read(4096), b""):
            hash_sha1024.update(chunk)
    return hash_sha1024.hexdigest()

"""


def version():

    print "version 0.0.3"


def chksumtypes():

    print "\nAvailable Algorithms: "
    print "\t\t\t" + str(hashlib.algorithms)


def getCheckSum(tp, fp):

    if tp == "md5":
        chksum = md5(fp)
        print str(chksum) + "\t" + "*" + str(fp)
    elif tp == "sha1":
        chksum = sha1(fp)
        print str(chksum) + "\t" + "*" + str(fp)
    elif tp == "sha224":
        chksum = sha224(fp)
        print str(chksum) + "\t" + "*" + str(fp)
    elif tp == "sha256":
        chksum = sha256(fp)
        print str(chksum) + "\t" + "*" + str(fp)
    elif tp == "sha384":
        chksum = sha384(fp)
        print str(chksum) + "\t" + "*" + str(fp)
    elif tp == "sha512":
        chksum = sha512(fp)
        print str(chksum) + "\t" + "*" + str(fp)
    else:
        print "There is no other option, home!"
        sys.exit(1)


def failed():

    print "Danger, Danger, Will Robinson !             "
    print "File and Software checksum did not MATCHed !"
    print "Quiting....................................."
    sys.exit(1)


def verifyCheckSum(tp, fp, cksumf):

    with open(cksumf, "r+") as f:
        a = f.read()
    cs = a.split()[0]

    if tp == "md5":
        chksum = md5(fp)
        if chksum == cs:
            print "The file\'s checksum and checksumming this file here MATCHed !"
            print "File checksum    : " + "\t" + str(cs)
            print "software checksum: " + "\t" + str(chksum)
        else:
            failed()
    elif tp == "sha1":
        chksum = sha1(fp)
        if chksum == cs:
            print "The file\'s checksum and checksumming this file here MATCHed !"
            print "File checksum    : " + "\t" + str(cs)
            print "software checksum: " + "\t" + str(chksum)
        else:
            failed()
    elif tp == "sha224":
        chksum = sha224(fp)
        if chksum == cs:
            print "The file\'s checksum and checksumming this file here MATCHed !"
            print "File checksum    : " + "\t" + str(cs)
            print "software checksum: " + "\t" + str(chksum)
        else:
            failed()
    elif tp == "sha256":
        chksum = sha256(fp)
        if chksum == cs:
            print "The file\'s checksum and checksumming this file here MATCHed !"
            print "File checksum    : " + "\t" + str(cs)
            print "software checksum: " + "\t" + str(chksum)
        else:
            failed()
    elif tp == "sha384":
        chksum = sha384(fp)
        if chksum == cs:
            print "The file\'s checksum and checksumming this file here MATCHed !"
            print "File checksum    : " + "\t" + str(cs)
            print "software checksum: " + "\t" + str(chksum)
        else:
            failed()
    elif tp == "sha512":
        chksum = sha512(fp)
        if chksum == cs:
            print "The file\'s checksum and checksumming this file here MATCHed !"
            print "File checksum    : " + "\t" + str(cs)
            print "software checksum: " + "\t" + str(chksum)
        else:
            failed()
    else:
        print "There is no other option, Yodaheim !"
        sys.exit(1)


def usage():

    # Help info
    usage = """
            usage: python chksum.py [-t,--tp = checksum_algorithm] [-g,--gp = filename] 
                                     [-c,--cs = filename.{md5:sha1:sha224:sha256:sha384:sha512}  ] [-h] [-v]
			
            examples:
            python chksum.py
            python chksum.py -t sha1 -g linux.iso 
            python chksum.py -t sha1 -g linux.iso -c filename.{md5:sha1:sha224:sha256:sha384:sha512}

            python chksum.py -v
            python chksum.py -h

            options :
            -t, --tp=value, --tp value  Collision Algorithms {md5:sha1:sha224:sha256:sha384:sha512}
            -g, --gp=value, --gp value  file to check to get checksum
            -c, --cs=value, --cs value  supply this value, this software will verify the 
			                            checksum against the downloaded file
            -v                          show program's version number and exit
            -h                          show this help message and exit
            """

    print usage


# Feel the main 
def main():

    # default values
    type, filename, csumf = "", "", ""

    # using getopt function for giggles only
    try:
        opts, args = getopt.getopt(sys.argv[1:], 't:g:c:vh', ['tp=', 'gp=', 'cs='])
    except getopt.GetoptError as err:
        # print something and exit
        print str(err)
        usage()
        sys.exit(2)

    # pull data from getopt
    for o, a in opts:
        if o in ('-t', '--tp'):
            if a.strip().lower() == "md5":
                type = a.strip().lower()
            elif a.strip().lower() == "sha1":
                type = a.strip().lower()
            elif a.strip().lower() == "sha224":
                type = a.strip().lower()
            elif a.strip().lower() == "sha256":
                type = a.strip().lower()
            elif a.strip().lower() == "sha384":
                type = a.strip().lower()
            elif a.strip().lower() == "sha512":
                type = a.strip().lower()
            else:
                print "Please enter the limited correct type of file Collision Algorithm available to you. "
                chksumtypes()
                sys.exit(2)
        elif o in ('-g', '--gp'):
            if os.path.isfile(a.strip().lower()):
                filename = a.strip().lower()
            else:
                print "Please enter in your source file. "
                sys.exit(2)
        elif o in ('-c', '--cs'):
            if os.path.isfile(a.strip().lower()):
                csumf = a.strip().lower()
            else:
                print "Please enter in your checksum file."
                sys.exit(2)
        elif o in ('-v', '--version'):
            version()
            sys.exit()
        elif o in ('-h', '--help'):
            usage()
            sys.exit()
        elif o in ('', ''):
            usage()
            sys.exit()
        else:
            assert False, "unhandled option"
            sys.exit(1)

    # the brain of the operation, yodaheim
    # 
    if len(sys.argv) == 7:
        verifyCheckSum(type,filename,csumf)
    elif len(sys.argv) == 5:
        getCheckSum(type,filename)
    else:
        usage()
        sys.exit()
	

# Feel the main, now !
if __name__ == "__main__":
    main()