#! /usr/bin/env python3
# encoding: utf-8

import glob
import re
import sys

def grep(exp, filename):
	with open(filename) as f:
		matches = re.findall(exp, f.read())
	
	return matches

def find_reverse_deps(deps):
	all_dep_files = glob.glob("/var/db/pkg/*/*/*DEPEND")
	
	regexp = "(%s)[^:]*:[^/]+/[^=]+=" %("|".join(deps))
	matching_files = set(f for f in all_dep_files if grep(regexp, f))
	atoms = set("=" + f[12:].rsplit("/", 1)[0] for f in matching_files)
	
	return atoms


if __name__ == "__main__":
	if len(sys.argv) > 1:
		atoms = find_reverse_deps(sys.argv[1:])
		print(" ".join(sorted(atoms)))
	else:
		print("Usage: %s DEPENDENCY [more DEPENDENCIES...]" %(sys.argv[0]))
		print("Finds all reverse deps of DEPENDENCY")
		
		sys.exit(1)