#!/bin/sh
#
# apt-mtime-for - list available versions of packages with modification time
#
# $Id$

# first version - I have no idea how reliable this is!

# NOTE: this isn't necessarily the repository it was actually installed from
# (which information appears to be impossible to obtain on Ubuntu!)

# the algorithm:
# 1) run apt-cache policy <pkg>
# 2) extract each repository URL for the candidate version,
#    one per line with the space-separated fields
#    - package name
#    - package status (can be absent|newer|current)
#    - candidate version
#    - repository URL
# 3) run apache-cache show <pkg>, match the Version: and produce the Filename:,
# 4) append it to each URL and fetch the remote HTTP mtime
# 5) and insert it as the fourth field
#
# example output for 1):
#
#   $ apt-cache policy ansible
#   ansible:
#     Installed: 2.8.10-1ppa~bionic
#     Candidate: 2.8.18-1ppa~bionic
#     Version table:
#        2.8.18-1ppa~bionic 500
#           500 http://ppa.launchpad.net/ansible/ansible-2.8/ubuntu bionic/main amd64 Packages
#           500 http://ppa.launchpad.net/ansible/ansible-2.8/ubuntu bionic/main i386 Packages
#    *** 2.8.10-1ppa~bionic 100
#           100 /var/lib/dpkg/status
#        2.5.1+dfsg-1ubuntu0.1 500
#           500 http://nl.archive.ubuntu.com/ubuntu bionic-updates/universe amd64 Packages
#           500 http://nl.archive.ubuntu.com/ubuntu bionic-updates/universe i386 Packages
#           500 http://security.ubuntu.com/ubuntu bionic-security/universe amd64 Packages
#           500 http://security.ubuntu.com/ubuntu bionic-security/universe i386 Packages
#        2.5.1+dfsg-1 500
#           500 http://nl.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages
#           500 http://nl.archive.ubuntu.com/ubuntu bionic/universe i386 Packages

Policy2UrlLines()
{
  perl -e '
    use strict;
    use warnings;

    my ($name, $installed, $candidate, $priority, @repourl);

    sub output_urls
    {
      @repourl or return;
      my $status = ($installed eq $candidate) ? "current" : ($installed eq "(none)") ? "absent" : "newer";
      printf("%s %s %s %s\n", $name, $status, $candidate, $_) for @repourl
    }

    while (<>)
    {
      if (/^(\S+):/)
      {
        output_urls();
        $name = $1;
        undef $_ for ($installed, $candidate, $priority, @repourl)
      }
      elsif (/^\s+Installed: (\S+)/)
      {
        $installed = $1
      }
      elsif (/^\s+Candidate: (\S+)/)
      {
        $candidate = $1
      }
      elsif (/^[*\s]+(\S+) (\d+)/)
      {
        undef($priority);

        if ($1 eq $candidate)
        {
          $priority = $2
        }
      }
      elsif (m#^\s+(\d+) (\S+://\S+)#)
      {
        if ($priority // 0 == $1)
        {
          push(@repourl, $2)
        }
      }
    }

    output_urls()
  ' |
  perl -ne '$seen{$_}++ or print'  # deduplicate
}

Show2Filenames()
{
  perl -ne '
    if (/^(\S+):\s+(\S+)/)
    {
      $prop{$1} = $2;

      if ($1 eq "Filename")
      {
        printf("%s %s %s\n", @prop{Package, Version, Filename});
        undef %prop
      }
    }
  '
}

UrlMtime()
{
  for url in "$@"
  do
    wget -q -nd -S --spider "$url" 2>&1 |
    perl -lne '/^\s*Last-Modified:\s+(.*\S)/i and $mtime = $1; END {print $mtime}' |
    perl -MTime::Piece -lpe '$_ = Time::Piece->strptime($_, "%a, %d %b %Y %H:%M:%S GMT")->strftime("%FT%T")'
  done
}

for pkg in "$@"
do
  apt-cache policy "$pkg" |
  Policy2UrlLines |
  while read name status version url
  do
    apt-cache show $name |
    Show2Filenames |
    while read name2 version2 filepath
    do
      if [ X"$version" = X"$version2" ]
      then
        echo $name2 $status $version `UrlMtime $url/$filepath` $url/$filepath
      fi
    done
  done
done