#!/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 force_posix_locale():
    os.environ['LC_ALL'] = 'C'

def pkgdeps(pkgs):
    apt_cache = subprocess.Popen(
        ['apt-cache', 'depends', *pkgs],
        stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
        universal_newlines=True,
        preexec_fn=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):
    seen = set()
    todo = set([pkg])
    while todo:
        new = pkgdeps(todo)
        seen |= todo
        todo = set(new) - seen
    return seen

def localarchitectures():
    architectures = []
    dpkg_arch = subprocess.Popen(
        ['dpkg', '--print-architecture'],
        stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
        universal_newlines=True,
        preexec_fn=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,
            preexec_fn=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 = alldeps(pname)

    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)