#!/usr/bin/python3
#  which-pkg-broke: help find offending packages when something breaks
#  Placed in the public domain by Bill Gribble <grib@billgribble.com>

import sys
import os
import subprocess
import time
from string import *
from stat import *

def pkgdeps(pkg):
    apt_cache = subprocess.Popen(
        ['apt-cache', 'depends', pkg],
        stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
        universal_newlines=True,
        env={} # force POSIX locale
    )
    deps = []
    for myline in apt_cache.stdout:
        elts = list(s.strip() for s in myline.split(':'))
        if len(elts) == 2:
            how, pkg = elts
            how = how.replace('|', '')
            if how in ('Depends', 'PreDepends'):
                deps.append(pkg)
    apt_cache.wait()
    return deps

def alldeps(pkg, ignore):
    deps = {}
    imm_deps = pkgdeps(pkg)
    for i in imm_deps:
        if ignore.get(i) is None:
            deps[i] = 1
            ignore[i] = 1
            childeps = alldeps(i, ignore)
            for c in childeps:
                deps[c] = 1
                ignore[i] = 1

    dlist = list(deps.keys())
    return dlist


def localarchitectures():
    architectures = []
    dpkg_arch = subprocess.Popen(
        ['dpkg', '--print-architecture'],
        stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
        universal_newlines=True,
        env={} # force POSIX locale
    )
    for arch in dpkg_arch.stdout.readlines():
        architectures.append(arch.rstrip())

    try:
        dpkg_archs = subprocess.Popen(
            ['dpkg', '--print-foreign-architecture'],
            stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
            universal_newlines=True,
            env={} # force POSIX locale
            )
        for arch in dpkg_archs.stdout.readlines():
            architectures.append(arch.rstrip())

    except OSError:
        pass # non-multiarchy dpkg, which is ok

    return architectures

def pkginstalltime(pkg, architectures):
    times = []
    for arch in architectures:
        listfile = '/var/lib/dpkg/info/' + pkg + ':' + arch + '.list'
        try:
            times.append([pkg + ':' + arch, os.stat(listfile)[ST_MTIME]])
        except OSError:
            pass

    if not times:
        listfile = '/var/lib/dpkg/info/' + pkg + '.list'
        try:
            times.append([pkg, os.stat(listfile)[ST_MTIME]])
        except OSError:
            print("Package", pkg, "has no install time info")

    return times

def what_broke(pname):
    pkgs = [ pname ]
    pkgs.extend(alldeps(sys.argv[1], {}))

    architectures = localarchitectures()

    itimes = []
    for p in pkgs:
        itimes.extend(pkginstalltime(p, architectures))
    itimes.sort(key=lambda k: k[1])
    for i in itimes:
        p, t = i
        if t is not None:
            print(p.ljust(54), time.asctime(time.localtime(float(t))))

if (len(sys.argv) != 2 or sys.argv[1][0] == '-'):
    print("Usage: which-pkg-broke <pkg-name>")
    sys.exit(-1)
else:
    what_broke(sys.argv[1])
    sys.exit(0)