#!/usr/bin/env python

"""
Read two lists of intervals (with chromosomes) and count the number of entries
in the second set that intersect any entry in the first set.

TODO: This could use bitsets rather than the intervals package, would it be
      faster?

usage: %prog bed1 bed2 > out
"""

import sys

from bx import intervals
from bx import misc


def main():

    intersecters = {}

    # Read ranges

    for chr, start, end in read_intervals(misc.open_compressed(sys.argv[1])):
        if chr not in intersecters:
            intersecters[chr] = intervals.Intersecter()
        intersecters[chr].add_interval(intervals.Interval(start, end))

    # Count intersection

    total = 0

    for chr, start, end in read_intervals(misc.open_compressed(sys.argv[2])):
        if chr in intersecters:
            intersection = intersecters[chr].find(start, end)
            if intersection:
                total += 1

    print(total)


def read_intervals(input):
    for line in input:
        fields = line.split()
        yield fields[0], int(fields[1]), int(fields[2])


main()
