#!/usr/local/bin/python

import sys, math

import optparse, fileinput
optparser = optparse.OptionParser(usage="%prog [options] INPUT_FILENAME*")
optparser.add_option('-m', '--model', dest='model_filename', type='str', default=None, help='language model file')
optparser.add_option('-o', '--output', dest='output_filename', type='str', default="-", help='output file')
(opts,args) = optparser.parse_args()

if opts.model_filename is None:
    sys.stderr.write("Error: must provide exactly one language model file\n")
    sys.exit(1)
model_file = file(opts.model_filename)

ngrams = {}
n = None
for line in model_file:
    (ngram,p) = line.split("\t")
    ngram = tuple(ngram.split())
    if n is None:
        n = len(ngram)
    ngrams[ngram] = float(p)

if opts.output_filename == "-":
    output_file = sys.stdout
else:
    output_file = file(opts.output_filename, "w")

for line in fileinput.input(args):
    words = line.split()
    words = ['<s>'] * (n-1) + words + ['</s>']

    p = 0.0
    try:
        for i in xrange(len(words)-n+1):
            p += math.log10(ngrams.get(tuple(words[i:i+n]), 0.0))
        output_file.write(line.strip() + "\t => exp(%f)\n" % p)
    except OverflowError:
        output_file.write(line.strip() + "\t => zero\n")
        
    
    output_file.write