#!/usr/bin/python

from __future__ import print_function

# List all reverse dependencies (recursively) for the specified packages.
# I.E. it displays what packages break if you remove the specified packages.
# In other words what packages should you remove in addition to those specified.

# Licence: LGPLv2
# Author:
#    http://www.pixelbeat.org/
# Notes:
#   1. It works on both rpm and deb distros.
#   2. We do a (recursive) simulated erase on the specified packages, as that
#      seems to be the only way to get the appropriate dependent packages as:
#     * rpm -q --whatrequires package
#        . Doesn't have a --recurse option.
#        . Doesn't include file dependencies.
#        . Doesn't handle provides appropriately.
#           For e.g. pygtk2 depends on the python2 package which
#           the python package provides. However `rpm -q --whatrequires python`
#           does not list the pygtk2 package (on fedora core 3 at least).
#     * apt-cache --recurse --installed rdepends package
#        . This includes all types of dependencies (suggests, conflicts, ...).
#          There is an --important option, but as of apt-0.6.40.1ubuntu9
#          that option is ignored for the rdepends subcommand.
# Changes:
#    V1.0      17 Jan 2006     Initial release
#    V1.1      01 Feb 2010
#      http://github.com/pixelb/scripts/commits/master/scripts/whatrequires


#TODO, Auto handle absolute paths as well as packages.
#TODO, rpm specifies versions while dpkg doesn't. Should make consistent.

debug=False

import sys
import os
import errno

# The following exits cleanly on Ctrl-C or EPIPE
# while treating other exceptions as before.
def std_exceptions(etype, value, tb):
    sys.excepthook=sys.__excepthook__
    if issubclass(etype, KeyboardInterrupt):
        pass
    elif issubclass(etype, IOError) and value.errno == errno.EPIPE:
        pass
    else:
        sys.__excepthook__(etype, value, tb)
sys.excepthook=std_exceptions

# Determine what type of distro we're on.
class distroType:
    def __init__(self):
        self.rpm = self.deb = False
        if os.path.exists("/etc/redhat-release"):
            self.rpm = True
        elif os.path.exists("/etc/debian_version"):
            self.deb = True
        else:
            self.rpm = (os.system("rpm --version >/dev/null 2>&1") == 0)
            if not self.rpm:
                self.deb = (os.system("dpkg --version >/dev/null 2>&1") == 0)
dist_type=distroType()

checked_pkgs={}

def whatRequires(packages,level=0):
    if not packages: return
    for package in packages:
        if debug: print ("\t"*level+package)
        checked_pkgs[package]=''
    if dist_type.rpm:
        cmd  = r"rpm -e --test " + ' '.join(packages) + r" 2>&1 | "
        cmd += r"sed -n 's/-[0-9]\{1,\}:/-/; " #strip epoch
        cmd += r"        s/.*is needed by (installed) \(.*\)/\1/p' | "
        cmd += r"LANG=C sort | uniq"
    elif dist_type.deb:
        cmd  = r"dpkg --purge --dry-run " + ' '.join(packages) + r" 2>&1 | "
        cmd += r"sed -n 's/ \(.*\) depends on.*/\1/p' | "
        cmd += r"LANG=C sort | uniq"
    else:
        raise "unknown distro"
    process = os.popen(cmd)
    requires = process.read()
    del(process)
    new_packages = [p for p in requires.split() if not checked_pkgs.has_key(p)]
    whatRequires(new_packages,level+1)

def notInstalled(packages):
    if dist_type.rpm:
        cmd  = r"rpm -q " + ' '.join(packages) + r" 2>&1 | "
        cmd += r"sed -n 's/.* \(.*\) is not installed/\1/p'"
    elif dist_type.deb:
        cmd  = r"dpkg -l " + ' '.join(packages) + r" 2>&1 | "
        cmd += r"sed -n 's/^No packages found matching \(.*\)\./\1/p'"
    process = os.popen(cmd)
    ni_list = process.read()
    del(process)
    return ni_list.split()

packages=sys.argv[1:]
if "--help" in packages or len(packages)==0:
    sys.stderr.write("Usage: %s package1 [package2 ...]\n" % os.path.split(sys.argv[0])[1])
    sys.stderr.close()
    sys.exit(1)

ni_list = notInstalled(packages)
if ni_list:
    sys.stderr.write("Error: The following packages are not installed:\n")
    sys.stderr.write("%s\n"%'\n'.join(ni_list))
    sys.stderr.close()
    sys.exit(1)

whatRequires(packages)
requires_packages = '\n'.join([p for p in checked_pkgs if p not in packages])
if requires_packages:
    sys.stdout.write("%s\n"%requires_packages)
    sys.stdout.close()