# ftp.py - handle urls with a ftp scheme
#
# Copyright (C) 1998, 1999 Albert Hopkins (marduk)
# Copyright (C) 2002 Mike W. Meyer
# Copyright (C) 2005 Arthur de Jong
#
# 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 St, Fifth Floor, Boston, MA  02110-1301 USA

"""This module defines the functions needed for creating Link objects for urls
using the ftp scheme."""

import urllib
import mimetypes
import ftplib
import urlparse
import string
import debugio

# FIXME: honor ftp proxy settings

# TODO: figure out a nicer way to close the connections with something like:
#try:
#    debugio.debug("FTP: "+ftp.quit())
#except:
#    debugio.debug("FTP: "+ftp.close())

# a map of netlocs to ftp connections
_ftpconnections = {}

def _getconnection(netloc):
    """Return a FTP connection object to the specified server."""
    # NOTE: this method is not thread safe
    if _ftpconnections.has_key(netloc):
        return _ftpconnections[netloc]
    # split url into useful parts
    (userpass, host) = urllib.splituser(netloc)
    if userpass is not None:
        (user, passwd) = urllib.splitpasswd(userpass)
    else:
        (user, passwd) = ('anonymous', '')
    (host, port) = urllib.splitnport(host,ftplib.FTP_PORT)
    # initialize a new connection
    ftp = ftplib.FTP()
    debugio.debug('schemes.ftp._getconnection(): CONNECT: '+ftp.connect(host, port))
    debugio.debug('schemes.ftp._getconnection(): LOGIN: '+ftp.login(user, passwd))
    _ftpconnections[netloc] = ftp
    return ftp

def _cwd(ftp, path):
    """Go down the path on the ftp server returning the part that cannot be
    changed into."""
    # split the path into directories
    dirs = path.split('/')
    try:
        # decend down the tree
        while len(dirs) > 0:
            d = dirs[0]
            if d != '':
                debugio.debug('schemes.ftp._cwd(): CWD '+d+': '+ftp.cwd(d))
            dirs.pop(0)
        return None
    except ftplib.error_perm, e:
        debugio.debug('schemes.ftp._cwd(): CWD '+d+' : '+str(e))
        return string.join(dirs,'/')

def fetch(link, acceptedtypes):
    """Fetch the specified link."""
    # try to fetch the document
    content = None
    try:
        ftp = _getconnection(link.netloc)
        debugio.debug('schemes.ftp.fetch(): FTP: CWD / : '+ftp.cwd('/'))
        # descend down the directory tree as far as we can go
        path=urllib.unquote(link.path)
        path=_cwd(ftp, path)
        # check if we are dealing with an (exising) directory
        if path is None:
            # check that the url ends with a slash
            if link.path[-1:] != '/':
                debugio.debug('schemes.ftp.fetch(): directory referenced without trailing slash')
                link.redirectdepth = 1
                link.add_child(urlparse.urljoin(link.url,link.path+'/'))
            else:
                # add children
                debugio.debug('schemes.ftp.fetch(): add files as children of this page')
                link.ispage = True
                debugio.debug('schemes.ftp.fetch(): TYPE A: '+ftp.voidcmd('TYPE A'))
                # FIXME: this raises an exception for empty directories
                for f in ftp.nlst():
                    link.add_child(urlparse.urljoin(link.url,urllib.quote(f)))
        else:
            # figure out the size of the document
            link.size = ftp.size(path)
            debugio.debug('schemes.ftp.fetch(): size='+str(link.size))
            # guess the mimetype of the document
            if link.mimetype is None:
                link.mimetype = mimetypes.guess_type(path)[0]
            # try to fetch file
            if link.mimetype in acceptedtypes:
                debugio.debug('schemes.ftp.fetch(): TYPE I: '+ftp.voidcmd('TYPE I'))
                (conn, size) = ftp.ntransfercmd('RETR ' + path)
                if size:
                   content = conn.makefile().read(size)
                else:
                   content = conn.makefile().read()
                debugio.debug('schemes.ftp.fetch(): fetched, size=%d' % len(content))
    except ftplib.all_errors, e:
        debugio.debug('schemes.ftp.fetch(): CAUGHT '+str(e))
        link.add_problem(str(e))
    # we're done
    return content