#!/usr/bin/env python

# Inner-joins two map spreadsheets A->B and B->C to A->C

import csv

import sys

def main():

    try: _prog_name, map_1_path = sys.argv

    except ValueError:

        raise SystemExit('Usage: '+sys.argv[0]+' map_1 <map_0 >joined_map')

    # Get map 1

    map_1 = {}

    stream = open(map_1_path, 'rb')

    reader = csv.reader(stream)

    map_1_in, map_1_out = reader.next()[:2]

    for row in reader:

        if row[1] != '': map_1[row[0]] = row[1]

    stream.close()

    # Join map 1 to map 0

    reader = csv.reader(sys.stdin)

    map_0_in, map_0_out = reader.next()[:2]

    if not map_0_out == map_1_in: raise SystemExit( 'Map error: '

        'Map 0 output column name doesn\'t match map 1 input column name')

    writer = csv.writer(sys.stdout)

    writer.writerow([map_0_in, map_1_out])

    for row in reader:

        if row[1] in map_1: writer.writerow([row[0], map_1[row[1]]])

main()