########################################################################
#
# Functions for downloading the Europarl data-set from the internet
# and loading it into memory. This data-set is used for translation
# between English and most European languages.
#
# http://www.statmt.org/europarl/
#
# Implemented in Python 3.6
#
# Usage:
# 1) Set the variable data_dir with the desired storage directory.
# 2) Determine the language-code to use e.g. "da" for Danish.
# 3) Call maybe_download_and_extract() to download the data-set
#    if it is not already located in the given data_dir.
# 4) Call load_data(english=True) and load_data(english=False)
#    to load the two data-files.
# 5) Use the returned data in your own program.
#
# Format:
# The Europarl data-set contains millions of text-pairs between English
# and most European languages. The data is stored in two text-files.
# The data is returned as lists of strings by the load_data() function.
#
# The list of currently supported languages and their codes are as follows:
#
# bg - Bulgarian
# cs - Czech
# da - Danish
# de - German
# el - Greek
# es - Spanish
# et - Estonian
# fi - Finnish
# fr - French
# hu - Hungarian
# it - Italian
# lt - Lithuanian
# lv - Latvian
# nl - Dutch
# pl - Polish
# pt - Portuguese
# ro - Romanian
# sk - Slovak
# sl - Slovene
# sv - Swedish
#
########################################################################
#
# This file is part of the TensorFlow Tutorials available at:
#
# https://github.com/Hvass-Labs/TensorFlow-Tutorials
#
# Published under the MIT License. See the file LICENSE for details.
#
# Copyright 2018 by Magnus Erik Hvass Pedersen
#
########################################################################

import os
import download

########################################################################

# Directory where you want to download and save the data-set.
# Set this before you start calling any of the functions below.
data_dir = "data/europarl/"

# Base-URL for the data-sets on the internet.
data_url = "http://www.statmt.org/europarl/v7/"


########################################################################
# Public functions that you may call to download the data-set from
# the internet and load the data into memory.


def maybe_download_and_extract(language_code="da"):
    """
    Download and extract the Europarl data-set if the data-file doesn't
    already exist in data_dir. The data-set is for translating between
    English and the given language-code (e.g. 'da' for Danish, see the
    list of available language-codes above).
    """

    # Create the full URL for the file with this data-set.
    url = data_url + language_code + "-en.tgz"

    download.maybe_download_and_extract(url=url, download_dir=data_dir)


def load_data(english=True, language_code="da", start="", end=""):
    """
    Load the data-file for either the English-language texts or
    for the other language (e.g. "da" for Danish).

    All lines of the data-file are returned as a list of strings.

    :param english:
      Boolean whether to load the data-file for
      English (True) or the other language (False).

    :param language_code:
      Two-char code for the other language e.g. "da" for Danish.
      See list of available codes above.

    :param start:
      Prepend each line with this text e.g. "ssss " to indicate start of line.

    :param end:
      Append each line with this text e.g. " eeee" to indicate end of line.

    :return:
      List of strings with all the lines of the data-file.
    """

    if english:
        # Load the English data.
        filename = "europarl-v7.{0}-en.en".format(language_code)
    else:
        # Load the other language.
        filename = "europarl-v7.{0}-en.{0}".format(language_code)

    # Full path for the data-file.
    path = os.path.join(data_dir, filename)

    # Open and read all the contents of the data-file.
    with open(path, encoding="utf-8") as file:
        # Read the line from file, strip leading and trailing whitespace,
        # prepend the start-text and append the end-text.
        texts = [start + line.strip() + end for line in file]

    return texts


########################################################################