#!/usr/bin/env python3
# Copyright (c) 2017-present, Facebook, Inc.
# All rights reserved.
#
# This source code is licensed under the license found in the LICENSE file in
# the root directory of this source tree. An additional grant of patent rights
# can be found in the PATENTS file in the same directory.
"""
BLEU scoring of generated translations against reference translations.
"""

import argparse
import os
import sys

from fairseq import bleu, tokenizer
from fairseq.data import dictionary


def get_parser():
    parser = argparse.ArgumentParser(description='Command-line script for BLEU scoring.')
    parser.add_argument('-s', '--sys', default='-', help='system output')
    parser.add_argument('-r', '--ref', required=True, help='references')
    parser.add_argument('-o', '--order', default=4, metavar='N',
                        type=int, help='consider ngrams up to this order')
    parser.add_argument('--ignore-case', action='store_true',
                        help='case-insensitive scoring')
    return parser


def main():
    parser = get_parser()
    args = parser.parse_args()
    print(args)

    assert args.sys == '-' or os.path.exists(args.sys), \
        "System output file {} does not exist".format(args.sys)
    assert os.path.exists(args.ref), \
        "Reference file {} does not exist".format(args.ref)

    dict = dictionary.Dictionary()

    def readlines(fd):
        for line in fd.readlines():
            if args.ignore_case:
                yield line.lower()
            yield line

    def score(fdsys):
        with open(args.ref) as fdref:
            scorer = bleu.Scorer(dict.pad(), dict.eos(), dict.unk())
            for sys_tok, ref_tok in zip(readlines(fdsys), readlines(fdref)):
                sys_tok = tokenizer.Tokenizer.tokenize(sys_tok, dict)
                ref_tok = tokenizer.Tokenizer.tokenize(ref_tok, dict)
                scorer.add(ref_tok, sys_tok)
            print(scorer.result_string(args.order))

    if args.sys == '-':
        score(sys.stdin)
    else:
        with open(args.sys, 'r') as f:
            score(f)


if __name__ == '__main__':
    main()
