#!/bin/sh
#
# dpkgdiff - diff a file against the version found in its Ubuntu package
#
# $Id$

me=`basename $0`

Ehm() { echo $me: "$@" >&2; }
Die() { Ehm "$@"; exit 1; }

HaveExecutable()
{
  for f in "$@"
  do
    type "$f" >/dev/null || Die Required executable not found: $f
  done
}

HaveExecutable dpkg realpath mktemp

makeorig=0

diffopts=

while [ $# -gt 0 ]
do
  case "$1" in
  -o) makeorig=1; shift;;
  -*) diffopts="$diffopts $1"; shift;;
  *) break;;
  esac
done

PlainFilesIn()
{
  for f in "$@"
  do
    r=`realpath "$f"`

    if [ -z "$r" ]
    then
      Ehm empty argument, skipped: $r
    elif [ ! -f "$r" ]
    then
      Ehm not a plain file, skipped: $r
    else
      echo "$f"
    fi
  done
}

WithProvidingPackage()
# given a list of files, outputs the ones provided by a package
# preceded by the package name
{
  while read f
  do
    dpkg -S "$f" |
    perl -lne '
      my ($pkgs,$f) = /^(.+):\s+(\S+)/ or next;
      $f eq "'"$f"'" or next;
      foreach my $p (split(/,/,$pkgs))  # there may be multiple packages
      {
        $p =~ s#:.*##;  # no :amd64, please
        print "$p $f"
      }'
  done
}

d=`mktemp -d /tmp/$me-XXXX`
[ -d "$d" ] || Die mktemp failed
trap "rm -rf $d" EXIT

DownloadPackageOnce()
(
  cd $d >/dev/null
  for pkg in $pkg
  do
    [ -d $pkg ] && continue  # assume it is already there
    mkdir $pkg && cd $pkg >/dev/null
    apt-get -q download $pkg >/dev/null
    # the exact filename is hard to describe due to colons in versions
    deb=`echo $pkg*.deb`
    #Ehm package $pkg has debfile $deb
    dpkg -x $deb .
  done 
)

PlainFilesIn "$@" |
WithProvidingPackage |
while read pkg f
do
  if [ X"$makeorig" = X1 ]
  then
    cp -p $d$r $r.orig
  else
    DownloadPackageOnce $pkg
    diff $diffopts $d/$pkg$f $f
  fi
done

#rm -rf "$d"  # done by the trap