#!/usr/bin/env python

# Copyright (C) 2011 GRNET S.A.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301, USA.

"""
A tool that connects to the Pithos backend and returns the size and contents
of a pithos object.

Since the backend does not have a "root" account we use the account given in
the URL as the user when connecting to the backend.
"""

from optparse import OptionParser
from sys import exit, stdout, stderr

try:
    from pithos.backends.modular import ModularBackend
except ImportError:
    stderr.write("Pithos backend was not found.\n")
    exit(2)


parser = OptionParser(usage='%prog [options] <URL>')
parser.add_option('--db', dest='db', metavar='URI',
        help='SQLAlchemy URI of the database [REQUIRED]')
parser.add_option('--data', dest='data', metavar='DIR',
        help='path to the directory where data are stored [REQUIRED]')
parser.add_option('-s', action='store_true', dest='size', default=False,
        help='print file size and exit')


def urlsplit(url):
    """Returns (accout, container, object) from a location string"""
    
    assert url.startswith('pithos://'), "Invalid URL"
    t = url.split('/', 4)
    assert len(t) == 5, "Invalid URL"
    return t[2:5]


def print_size(backend, url):
    """Writes object's size to stdout."""
    
    account, container, object = urlsplit(url)
    meta = backend.get_object_meta(account, account, container, object, None)
    print meta['bytes']


def print_data(backend, url):
    """Writes object's size to stdout."""
    
    account, container, object = urlsplit(url)
    size, hashmap = backend.get_object_hashmap(account, account, container,
            object)
    for hash in hashmap:
        block = backend.get_block(hash)
        if len(block) > size:
            block = block[:size]
        stdout.write(block)
        size -= len(block)


def main():
    options, args = parser.parse_args()
    if len(args) != 1 or not options.db or not options.data:
        parser.print_help()
        exit(1)

    url = args[0]
    backend = ModularBackend(None, options.db, None, options.data)
    
    if options.size:
        print_size(backend, url)
    else:
        print_data(backend, url)

if __name__ == '__main__':
    main()