#!/usr/bin/env python

"""
See https://edx-wiki.atlassian.net/wiki/display/ENG/PO+File+workflow

This task merges and compiles the human-readable .po files on the
local filesystem into machine-readable .mo files. This is typically
necessary as part of the build process since these .mo files are
needed by Django when serving the web app.

The configuration file (in edx-platform/conf/locale/config) specifies which
languages to generate.

"""

import os, sys, logging
from polib import pofile

from config import BASE_DIR, CONFIGURATION
from execute import execute

LOG = logging.getLogger(__name__)


def merge(locale, target='django.po', fail_if_missing=True):
    """
    For the given locale, merge django-partial.po, messages.po, mako.po -> django.po
    target is the resulting filename

    If fail_if_missing is true, and the files to be merged are missing,
    throw an Exception, otherwise return silently.

    If fail_if_missing is false, and the files to be merged are missing,
    just return silently.

    """
    LOG.info('Merging locale={0}'.format(locale))
    locale_directory = CONFIGURATION.get_messages_dir(locale)
    files_to_merge = ('django-partial.po', 'messages.po', 'mako.po')
    try:
        validate_files(locale_directory, files_to_merge)
    except Exception, e:
        if not fail_if_missing:
            return
        raise e

    # merged file is merged.po
    merge_cmd = 'msgcat -o merged.po ' + ' '.join(files_to_merge)
    execute(merge_cmd, working_directory=locale_directory)

    # clean up redunancies in the metadata
    merged_filename = locale_directory.joinpath('merged.po')
    clean_metadata(merged_filename)

    # rename merged.po -> django.po (default)
    django_filename = locale_directory.joinpath(target)
    os.rename(merged_filename, django_filename) # can't overwrite file on Windows


def clean_metadata(file):
    """
    Clean up redundancies in the metadata caused by merging.
    """
    # Reading in the .po file and saving it again fixes redundancies.
    pomsgs = pofile(file)
    # The msgcat tool marks the metadata as fuzzy, but it's ok as it is.
    pomsgs.metadata_is_fuzzy = False
    pomsgs.save()


def validate_files(dir, files_to_merge):
    """
    Asserts that the given files exist.
    files_to_merge is a list of file names (no directories).
    dir is the directory (a path object from path.py) in which the files should appear.
    raises an Exception if any of the files are not in dir.
    """
    for path in files_to_merge:
        pathname = dir.joinpath(path)
        if not pathname.exists():
            raise Exception("I18N: Cannot generate because file not found: {0}".format(pathname))


def main():
    logging.basicConfig(stream=sys.stdout, level=logging.INFO)

    for locale in CONFIGURATION.locales:
        merge(locale)
    # Dummy text is not required. Don't raise exception if files are missing.
    merge(CONFIGURATION.dummy_locale, fail_if_missing=False)
    compile_cmd = 'django-admin.py compilemessages'
    execute(compile_cmd, working_directory=BASE_DIR)


if __name__ == '__main__':
    main()
