#!/usr/bin/env python

# Subtracts map spreadsheet A1->C from A0->B to produce A->B.

# A0 entries that are empty and have no comment documenting why they are empty

# are subtracted as well if there is a matching entry in A1.

import csv

import os.path

import sys

sys.path.append(os.path.dirname(__file__)+"/../lib")

import maps

import opts

import util

def main():

    ignore = opts.env_flag('ignore')

    try: _prog_name, map_1_path = sys.argv[:2]

    except ValueError:

        raise SystemExit('Usage: env [ignore=1] '+sys.argv[0]+' <from_map '

            'subtract_map [compare_col_num...] [| '+sys.argv[0]

            +' subtract_map_2]... >difference_map')

    compare_col_nums = map(int, sys.argv[2:]) # 0-based

    if compare_col_nums == []:

        compare_col_nums = None # list_subset() value for all columns

    def compare_on(row): return tuple(util.list_subset(row, compare_col_nums))

    headers = [None]*2

    # Get map 1

    input_cols = set()

    compare_cols = set()

    stream = open(map_1_path, 'rb')

    reader = csv.reader(stream)

    headers[1] = reader.next()

    for row in reader:

        if row[0] != '':

            input_cols.add(row[0])

            compare_cols.add(compare_on(row))

    stream.close()

    # Open map 0

    reader = csv.reader(sys.stdin)

    headers[0] = reader.next()

    # Check col labels

    if not maps.combinable(*headers) and not ignore:

        raise SystemExit('Map error: '

        'Map 0 column 0 label doesn\'t contain map 1 column 0 label')

    # Subtract map 1 from map 0

    writer = csv.writer(sys.stdout)

    writer.writerow(headers[0])

    for row in reader:

        if not (maps.is_nonexplicit_empty_mapping(row) and row[0] in input_cols

            or compare_on(row) in compare_cols): # not in map 1

            writer.writerow(row)

main()