#!/usr/bin/python
# -*- coding: UTF-8 -*-
# Copyright (C) 2008 Terence Simpson <tsimpson@ubuntu.com>
# License:
#  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.
#
# This script simulates «dget»'s behaviour for files hosted at
# launchpadlibrarian.net.
#
# Detailed description:
# This script attempts to download the source package in the same
# way as dget does, but from launchpadlibrarian.net, which doesn't
# store all the files in the same directory. It (the script) assumes
# that the files are stored in sequential directories on Launchpad
# Librarian and attempts to download and then unpack them.
# This is a Python rewrite of the original bash script

import sys, os
from optparse import OptionParser
import urllib2
import hashlib 
import subprocess
import GnuPGInterface
from cStringIO import StringIO
from email import FeedParser

Usage = u"""Usage: %prog [-d|(-v|-q)] <Launchpad URL>

This scripts simulates «dget»'s behaviour for files hosted at
launchpadlibrarian.net.

If you specify the -d option then it won't do anything, except download the
.dsc file, but just print the commands it would run otherwise.

Example:
	%prog http://launchpadlibrarian.net/10348157/coreutils_5.97-5.4ubuntu1.dsc
"""

unpack_cmd = "dpkg-source -x "
base_url = "http://launchpadlibrarian.net/"

Debug = Verbose = Quiet = False

def Unsign(data):
    if data.splitlines()[0] != "-----BEGIN PGP SIGNED MESSAGE-----":
        return data
    oldstdout = sys.stdout
    oldstderr = sys.stderr
    sys.stdout = sys.__stdout__
    sys.stderr = sys.__stderr__
    gpg = GnuPGInterface.GnuPG()
    proc = gpg.run(["--decrypt"], create_fhs=['stdin', 'stdout'])
    proc.handles['stdin'].write(data)
    proc.handles['stdin'].close()
    plain = proc.handles['stdout'].read()
    proc.handles['stdout'].close()
    try:
        proc.wait()
    except:
        pass
    sys.stdout = oldstdout
    sys.stderr = oldstderr
    return plain

def getEntries(data):
    parser = FeedParser.FeedParser()
    parser.feed(data)
    return parser.close()

class DscParse(object):
    """Attempt to get the file list from the .dsc file"""
    def __init__(self, data):
        """
        __init__(data)
        Given the contents of a .dsc, parse it and extract it's content
        """
        self.entries = getEntries(Unsign(data))
        self.files = [x.strip().split() for x in self.entries['Files'].splitlines()]

    def verify_all(self):
        """
        verify_all()
        Verifies all the files, first checking the size, then the md5 sum.
        Currently not used in this utility.
        """
        assert self.files, "I have no files"
        ret = []
        for f in self.files:
            ret.append(self.verify(f))
        return ret

    def verify(self, name):
        """
        verify(name)
        Verify the file 'name', first checking the size, then the md5 sum.
        """
        assert self.files, "I have no files"
        f = None
        if isinstance(name, list):
            f = name
        else:
            for i in self.files:
                if i[2] == name:
                    f = i
        if not f:
            raise ValueError, "%s is not in the .dsc" % name
        (sum, size, name) = tuple(f)
        stat = os.stat(name)
        if str(stat.st_size) != size:
            return (False, name, "Expected a size of %s, got %s" % \
                (size, stat.st_size))
        return self.getsum(name, sum)

    def getsum(self, name, sum=None):
        """
        getsum(name[, sum])
        Read the file 'name' (in 1MB chunks) and generate an md5 sum,
        then compares that to the md5 sum in the .dsc file.
        """
        chunk_size = 1073741824
        fd = open(name, 'rb')
        res = hashlib.md5()
        if not sum:
            assert self.files, "I have no files"
            sum = [x[0] for x in self.files if x[2] == name][0]
        data = fd.read(chunk_size)
        while data:
            res.update(data)
            data = fd.read(chunk_size)
        if res.hexdigest() != sum:
            return (False, name, "Expected md5sum of %r, got %r" % \
                (sum, res.hexdigest()) )
        return (True, name, None)

    def isNative(self):
        """
        isNative()
        Returns True if this .dsc describes a native debian package;
        else false.
        """
        return len(self.files) == 1

    # Access to fields in the .dsc via a dict-like interface
    def __getitem__(self, item):
        """
        x.__getitem(item) -> x[item]
        """
        return self.entries.__getitem__(item)

    def __contains__(self, item):
        """
        x.__contains__(item) -> item in x
        """
        return self.entries.__contains__(item)

    def __getattr__(self, attr):
        """
        x.__getattr__(attr) -> item.attr
        """
        return getattr(self.entries, attr)

def error(ret, msg, *args):
    """Prints an error message, unless quiet is set, and exits with ret"""
    if not Quiet:
        print >> sys.stderr, msg % args
    sys.exit(ret)

def debug(msg, *args):
    """If debugging is enabled, print a message"""
    if Debug:
        print >> sys.stderr, msg % args

def info(msg, *args):
    """If verbose is enabled, print a message"""
    if Verbose:
        print msg % tuple(args)

def status(msg, *args):
    """Prints a message, unless quiet is enabled"""
    if not Quiet:
        print msg % tuple(args)

def Download(dscinfo, number, filename, verify=True):
    """Download filename"""
    ftype = filename.endswith(".diff.gz") and "diff.gz" or \
        filename.endswith(".orig.tar.gz") and "orig.tar.gz" or \
        filename.endswith(".dsc") and "dsc" or "tar.gz"
    if verify and os.path.exists(filename):
        info('Verifying "%s"', filename)
        res = dscinfo.verify(filename)
        if not res[0]:
            error(104, "Verification of %s failed: %s", filename, res[2])
    status("Getting %s", filename)
    debug("%s%s/%s", base_url,number,filename)
    try:
        fd = urllib2.urlopen("%s%s/%s" % (base_url, number, filename))
        outfd = open(filename, 'wb')
        outfd.write(fd.read())
        fd.close()
        outfd.close()
    except urllib2.URLError, e:
        status("Failed to fetch «%s» file, aborting.", ftype)
        error(105, "Error: %s", e)
    except urllib2.HTTPError, e:
        status("Failed to fetch «%s» file, aborting.", ftype)
        error(106, "Error: (%d %s)", e.code, e.msg)
    except IOError, e:
        status('Could not create "%s"', filename)
        error(107, "Error: %s", e)

def unpack():
    out = open('/dev/null', 'w')
    err = open('/dev/null', 'w')
    ret = subprocess.call(unpack_cmd.split(), stdout=out, stderr=err)
    out.close()
    err.close()
    if ret:
        status("Failed to unpack source, aborting.")
        sys.exit(108)

def getHost(url):
    return urllib2.splithost(urllib2.splittype(url)[1])[0]

if __name__ == "__main__":
    parser = OptionParser(usage=Usage)
    parser.add_option("-d", "--debug", action="store_true", dest="debug",
        default=False, help="Enable debugging")
    parser.add_option("-v", "--verbose", action="store_true", dest="verbose",
        default=False, help="Enable verbose output")
    parser.add_option("-q", "--quiet", action="store_true", dest="quiet",
        default=False, help="Never print any output")

    (options, args) = parser.parse_args()
    if len(args) != 1:
        parser.error("Missing URL")
    Debug = options.debug
    Verbose = options.verbose
    Quiet = options.quiet
    if Verbose and Quiet:
        error(4, "Specifying both --verbose and --quiet does not make sense")
    if Quiet:
        sys.stderr = StringIO()
        sys.stdout = StringIO()

    url = args[0]

    if url.startswith("https://"):
        url = url.replace("https://", "http://", 1)

    if not url.startswith("http://"):
        url = "http://" + url

    if getHost(url).startswith("www."):
        url = url.replace("www.", "", 1)

    if getHost(url) != getHost(base_url):
        error(1, "Error: This utility only works for files on %s.\nMaybe you want to try dget?", base_url)

    (number, filename) = url.split('/')[3:]

    if not filename.endswith('.dsc'):
        error(2, "You have to provide the URL for the .dsc file.")

    try:
        number = int(number)
    except:
        error(3, "Bad URL format")

    unpack_cmd += filename

    if os.path.exists(filename):
        os.remove(filename)

    Download(None, number, filename, False)
    try:
        fd = open(filename)
        dsc_data = fd.read()
        fd.close()
    except Exception, e:
        status("Error: Please report this bug, providing the URL and attach"\
               " the following backtrace")
        raise

    dscinfo = DscParse(dsc_data)

# launchpadlibrarian.net seems to store in this order:
# For native packages:
# <number>/.changes
# <number>+1/.tar.gz
# <number>+2/.dsc
# For non-native packages:
# <number>/.changes
# <number>+1/.orig.tar.gz
# <number>+2/.diff.gz
# <number>+3/.dsc
##
# *Assuming* this does not change, we can figure out where the files are on
# launchpadlibrarian.net relative to the .dsc file we're given.

# Only one file listed in the .dsc means it's native package
    if len(dscinfo.files) == 1:
        Download(dscinfo, number-1, dscinfo.files[0][-1]) # .tar.gz
    else:
        Download(dscinfo, number-1, dscinfo.files[1][-1]) # .diff.gz
        Download(dscinfo, number-2, dscinfo.files[0][-1]) # .orig.tar.gz

    status("Unpacking")
    unpack()