#!/usr/bin/python

from contextlib import contextmanager
import os, subprocess, exceptions
import debian.changelog, debian.deb822
from shutil import copy



packages = [
    'shibboleth/xmltooling',
    "shibboleth/opensaml2"]
distribution = "sid"
build_place = os.path.join(os.getcwd(), 'debian_build')

class CommandError(exceptions.StandardError):
    pass

@contextmanager
def current_directory(dir):
    "Change the current directory as a context manager; when the context exits, return."
    cwd = os.getcwd()
    os.chdir(dir)
    yield
    os.chdir(cwd)

def run_cmd(args, **kwords):
    rcode =  subprocess.call( args, **kwords)
    if rcode <> 0:
        raise CommandError(args)

def command_output(args) :
    p = subprocess.Popen(args, stdout=subprocess.PIPE)
    output = p.communicate()
    output = output[0]
    if p.returncode != 0:
        raise CommandError(args)
    return output

def dsc_files(dsc) :
    '''Describe all the files included in dsc, wich is a string name
    of a dsc package. dsc itself is included'''
    package = debian.deb822.Dsc(file(dsc))
    internal_files = map( lambda(x): x['name'], package['Files'])
    internal_files.append(dsc)
    return internal_files

def build(package):
    with current_directory(package):
        cl = debian.changelog.Changelog(file('debian/changelog'))
        package_name = cl.package
        package_version = str(cl.version)
        orig_tgz = package_name+'_'+ cl.upstream_version + ".orig.tar.gz"
        dsc_name = package_name+"_"+package_version + ".dsc"
        source_format = command_output(('dpkg-source', '--print-format', '.'))
        if "native" not in source_format:
            run_cmd( ('pristine-tar', 'checkout', '../'+orig_tgz))
    package_path = os.path.split(package)
    with current_directory(os.path.join ('.', *package_path[0:len(package_path)-1])) :
        package_path = package_path[len(package_path)-1]
        try:
            run_cmd(("dpkg-source", '-b', '-i', package_path))
            for f in dsc_files(dsc_name):
                copy(f, build_place)
        finally:
            for f in dsc_files(dsc_name):
                try: os.unlink(f)
                except OSError: pass
    with current_directory(build_place):
        run_cmd(('sbuild', '-d', distribution, '--setup-hook',
    build_place + '/add_source',
                 dsc_name))

def gen_package_files() :
    '''Generate package files in build_place and a script
    build_place/add_source that can be used as a sbuild setup hook to
    include the package files. Unfortunately, apt doesn't have a
    mechanism for asserting that a package file is trusted when it is
    local. We could generate a unique gpg key, generate signed
    releases files and trust that key. It's easier to simply touch the
    release.gpg in apt's lists directory, which turns out to do what
    we need.'''
    # Rather than substuting the release file directly, we create gpg
    # release files for any  local package list. That's easier than
    # encoding apt's ideas about what characters to escape.
    script = '''#!/bin/sh
    set -e
    echo deb file:{build_place} ./ >>/etc/apt/sources.list
    apt-get update
    touch $(ls /var/lib/apt/lists/_*Packages \
        |sed -e s:Packages\$:Release.gpg:)
    '''.format (
        build_place = build_place
        )
    f = file(build_place + "/add_source", "w")
    f.write(script)
    f.close()
    with current_directory(build_place):
        run_cmd(('chmod', 'a+x', 'add_source'))
        run_cmd( 'dpkg-scanpackages . >Packages',
                 shell = True)
        
try:
    for p in packages:
        gen_package_files()
        build(p)
except CommandError as c:
    print "Error:" + str(c.args)
    exit(1)