#!/usr/bin/python3

"""
Pass through blocks from a maf file until a certain number of columns
have been passed.

usage: %prog -c cols < maf > maf
"""

import sys
from optparse import OptionParser

from bx.align import maf


def __main__():
    parser = OptionParser()
    parser.add_option("-c", "--cols", action="store")

    (options, args) = parser.parse_args()

    maf_reader = maf.Reader(sys.stdin, parse_e_rows=True)
    maf_writer = maf.Writer(sys.stdout)

    if not options.cols:
        raise Exception("Cols argument is required")
    cols = int(options.cols)

    count = 0

    for m in maf_reader:
        maf_writer.write(m)

        count += m.text_size

        if count >= cols:
            return


if __name__ == "__main__":
    __main__()