#!/bin/bash

# play save
set -e
set -u

# version of this script
backports_dsc_version=0.2

############
# Defaults #
############

bp_distribution=${BACKPORT_DISTRIBUTION:-squeeze-backports}
bp_version_prefix=${BACKPORT_VERSION_PREFIX:-\~}
bp_version_suffix=${BACKPORT_VERSION_SUFFIX:-bpo60}
bp_maintainer_name=${DEBFULLNAME:-unamed}
bp_maintainer_email=${DEBEMAIL:-unknown}
bp_update_maintainer=1
# whether or not to apply backport patches found in a package
bp_apply_patches=1
# produce fancy colored output
bp_color_output=1
# enables additional status message if set to true
bp_verbose=0
# sed expressions to modify debian/control
bp_mod_control=""


# source config files
if [ -f /etc/backport-dsc ]; then
    . /etc/backport-dsc
fi

# source user config files
if [ -f "$HOME/.backport-dsc" ]; then
    . $HOME/.backport-dsc
fi


print_version()
{
cat << EOT
backport-dsc $backports_dsc_version

Copyright (C) 2010-2012 Michael Hanke <michael.hanke@gmail.com>

Licensed under GNU Public License version 2 or later.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Written by Michael Hanke for the NeuroDebian project.

EOT
}


print_short_description()
{
cat << EOT
Helper to aid backporting a Debian source package to an arbitrary distribution
release.

backport-dsc aids backporting by appropriately mangling the source package
version, adjusting the maintainer of a package and compiling an informative
changelog entry. Moreover, it supports distribution specific patches (plain, or
for format 3.0 (quilt) source packages) and allow modification of debian/control
via arbitrary 'sed' expressions.

Backport relevant patches can be embedded in source packages for use with
backport-dsc. The distribution name (see --target-distribution) serves as an
identifier to search for patches in the source package that shall be applied
for a particular distribution. For packages using format the 3.0 (quilt),
backport-dsc will look for debian/patches/series-<distname> and append it to
the main patch series. Moreover, backport-dsc will also look for patches
matching /debian/patches/<distname>-dsc-patch* and apply them to the source
package. The latter patches, unlike the former quilt series, can also be used
to modify the debian/ directory itself.

EOT
}


print_help()
{
cat << EOT

Usage:  backport-dsc [OPTIONS] <dsc-file>


Options:

-d <distname>, --target-distribution <distname>
  Arbitrary distribution name (e.g. squeeze-backports). This will be the target
  distribution used for the backport changelog entry. The distribution name
  also serves as an identifier to search for backport patches in the source
  package.

-h, --help
  Print short description, usage summary and option list.

--maint-email <email>
  Specify the backport maintainer's email address. Alternatively, backport-dsc
  will use the DEBEMAIL environment setting.

--maint-name <name>
  Specify the backport maintainer's real name. Alternatively, backport-dsc will
  use the DEBFULLNAME environment setting.

--mod-control <expression>
  sed expression to modify debian/control. The option can be given multiple
  times and all expressions will be passed to sed in the order of appearance.
  This can be used to, e.g. change build or runtime dependencies.

--no-backport-patches
  If set, potentially existing backport patches will not be applied/activated.

--no-colored
  If set, backport-dsc won't colorize its status and error messages.

--no-maintainer-update
  If set, the orginal maintainer is preserved in the backported source package.
  This should only be done if original maintainer and backporter are identical.
  Otherwise the porter should take responsibility for the source package
  backport and identify herself as the maintainer.

-s <string>, --version-suffix <string>
  Version suffix that will be appended to the original source package version,
  ideally indicating the backport target distribution. The resulting package
  version will follow this schema:

  <originalversion><prefix><suffix>+<digit>

  e.g.: 1.2.3-4~bpo60+1 with default <prefix>=~

-p <string>, --version-prefix <string>
  Version prefix that will be prepended to the backport version.  By default it
  is ~ but want to be changed (e.g. to +) for forward-porting to next releases.

--verbose
  Enable additional status messages.

--verbose-help
  Print all available help.

--version
  Print version information and exit.

EOT
}


print_additional_description()
{
cat << EOT

Examples:

backport-dsc examplepkg_1.2.3-4.dsc
  Create backport suitable for backports.org

backport-dsc -d myown-backports -v mo2010 examplepkg_1.2.3-4.dsc
  Create backport for some custom distribution with custom version suffix.

backport-dsc -d ubuntu-lucid -v myppa --mod-control "-e 's/iceweasel/firefox/g'" examplepkg_1.2.3-4.dsc
  Create a backport for a fake Ubuntu PPA repository, replacing all occurrences
  of iceweasel in debian/control with firefox.


Files:

backport-dsc reads configuration from two files: system-wide from
/etc/backports-dsc and per user settings from \$HOME/.backport-dsc
(in that order). Both files have to be valid bash scripts that will
be sourced by backport-dsc. The following variables (each shown with an
example setting) can be used to pre-configure backport-dsc:

bp_distribution="squeeze-backports"
  Backport target distribution (see --backport-distribution)

bp_version_prefix="~"
  Version prefix (see --version-prefix)

bp_version_suffix="bpo60"
  Version suffix (see --version-suffix)

bp_maintainer_name="Unknown fellow"
  Name of the backport maintainer (see --maint-name)

bp_maintainer_email="user@example.net"
  Email address of backport maintainer (see --maint-email)

bp_apply_patches=1
  Whether or not to apply backport patches found in a source package.
  (see --no-backport-patches)

bp_color_output=1
  Enable or disable colored status output (see --no-color)

bp_verbose=0
  Enable verbose status output (see --verbose)

bp_mod_control="--mod-control 's/^Depends:.*$/&, mypackage/'"
  sed expressions to modify debian/control, for example to add dependencies
  (see --mod-control)

bp_update_maintainer=1
  Whether or not to replace the original maintainer in the backported source
  package (see --no-maintainer-update)


Environment:

backport-dsc acknowledges the common environment variables DEBFULLNAME and
DEBEMAIL to specify the maintainer.



Report bugs to <michael.hanke@gmail.com>.

EOT
}



################################
# Commandline options handling #
################################

# Parse commandline options (taken from the getopt examples from the Debian util-linux package)
# Note that we use `"$@"' to let each command-line parameter expand to a
# separate word. The quotes around `$@' are essential!
# We need CLOPTS as the `eval set --' would nuke the return value of getopt.
CLOPTS=`getopt -o h,d:,s:,p: --long help,verbose-help,version,target-distribution:,version-suffix:,version-prefix:,maint-name:,maint-email:,no-color,no-backport-patches,verbose,mod-control:,no-maintainer-update, -n 'backport-dsc' -- "$@"`

if [ $? != 0 ] ; then
  echo "Terminating..." >&2
  exit 1
fi

# Note the quotes around `$CLOPTS': they are essential!
eval set -- "$CLOPTS"

while true ; do
  case "$1" in
	  -d|--target-distribution) shift; bp_distribution=$1; shift;;
	  -s|--version-suffix) shift; bp_version_suffix=$1; shift;;
	  -p|--version-prefix) shift; bp_version_prefix=$1; shift;;
	  --maint-name) shift; bp_maintainer_name=$1; shift;;
	  --maint-email) shift; bp_maintainer_email=$1; shift;;
	  --no-maintainer-update) bp_update_maintainer=0; shift;;
	  --no-backport-patches) apply_patches=0; shift;;
	  --no-color) bp_color_output=0; shift;;
	  --verbose) bp_verbose=1; shift;;
	  --mod-control) shift; bp_mod_control="$bp_mod_control -e '$1'"; shift;;
	  -h|--help) print_short_description; print_help; exit 0;;
	  --verbose-help) print_short_description; print_help; print_additional_description; exit 0;;
	  --version) print_version; exit 0;;
	  --) shift ; break ;;
	  *) echo "Internal error! ($1)"; exit 1;;
  esac
done

# colorful output requested?
if [ "$bp_color_output" = 1 ]; then
  black='\e[0;30m'; Black='\e[1;30m'
  red='\e[0;31m'; Red='\e[1;31m'
  green='\e[0;32m'; Green='\e[1;32m'
  yellow='\e[0;33m'; Yellow='\e[1;33m'
  blue='\e[0;34m'; Blue='\e[1;34m'
  cyan='\e[0;36m'; Cyan='\e[1;36m'
  white='\e[0;37m'; White='\e[1;37m'
  NC='\e[0m' #no color
else
  black=''; Black=''
  red=''; Red=''
  green=''; Green=''
  yellow=''; Yellow=''
  blue=''; Blue=''
  cyan=''; Cyan=''
  white=''; White=''
  NC='' #no color
fi


if [ $# -ne 1 ]; then
  printf "${Red}Error: This command needs exactly one positional argument.\n${NC}"
  exit 1
fi

# to be processed source package
dsc_file=$1

if [ ! -f "$dsc_file" ]; then
  printf "${Red}Error: Cannot find DSC file at '$dsc_file'.\n${NC}"
  exit 1
fi

# determine basic DSC properties
src_name=$(basename "${dsc_file%%_*}")
src_version=${dsc_file#*_}
src_version=${src_version%%.dsc}

wdir=$(mktemp -d -t backport-dsc.XXXXXX)
sdir=$wdir/${src_name}-${src_version}

bp_version="${bp_version_prefix}${bp_version_suffix}+"


# setup environment for dpkg
DEBEMAIL="$bp_maintainer_email"
DEBFULLNAME="$bp_maintainer_name"
export DEBEMAIL DEBFULLNAME

if [ "$bp_verbose" = 1 ]; then
  printf "${green}DSC name: '$src_name'\nDSC version: '$src_version'\n${NC}"
  printf "${green}Backporting to '$bp_distribution', version suffix '$bp_version'\n${NC}"
  printf "${green}Extracting source package to '$sdir'\n${NC}"
fi

# common debchange call
bp_dch_cmd="dch --noconf --force-distribution --force-bad-version -c $sdir/debian/changelog"

# extract the original source package
dpkg-source -x $dsc_file $sdir
# note backport in changelog
# This will create a new changelog entry
# All subsequent calls to dch should use -a to assure that those entries
# are appended to the existing entry (otherwise with wheezy new entries will be added)
$bp_dch_cmd -D ${bp_distribution} -l "${bp_version}" "Backported for ${bp_distribution}."

if [ "$bp_update_maintainer" = 1 ]; then
  if [ "$bp_verbose" = 1 ]; then
    printf "${green}Set backport maintainer to: '$bp_maintainer_name <$bp_maintainer_email>'\n${NC}"
  fi
  bp_mod_control="$bp_mod_control -e 's/^Maintainer:.*$/Maintainer: $bp_maintainer_name <$bp_maintainer_email>\nX-Original-&/'"
fi

# handle patches if desired
if [ "$bp_apply_patches" = 1 ]; then
  dsc_format=$(dpkg-source --print-format $sdir)
  # per each supported source package format
  if [ "$dsc_format" = "3.0 (quilt)" -a -f "$sdir/debian/patches/series-$bp_distribution" ]; then
    if [ "$bp_verbose" = 1 ]; then
      printf "${green}Enabling additional quilt patch series for $bp_distribution.\n${NC}"
    fi
    cat $sdir/debian/patches/series-$bp_distribution >> $sdir/debian/patches/series
    $bp_dch_cmd -a "Added 'series-$bp_distribution' in quilt patch series."
  fi
  # look for backport patches
  for p in $(ls -1 $sdir/debian/patches/$bp_distribution-dsc-patch* 2> /dev/null || true); do
    if [ "$bp_verbose" = 1 ]; then
      printf "${green}Applying additional patch $(basename "$p").\n${NC}"
    fi
    patch -p1 --directory=$sdir < "$p"
    $bp_dch_cmd -a "Applied additional patch from debian/patches/$(basename "$p")."
  done
fi

# modify control file
if [ -n "$bp_mod_control" ]; then
  if [ "$bp_verbose" = 1 ]; then
    printf "${green}Modifying debian/control with given instructions.\n${NC}"
  fi
  bash -c "sed -i $bp_mod_control $sdir/debian/control"
  $bp_dch_cmd -a "Used following sed expression to modify debian/control:$bp_mod_control."
fi

# extract final version
final_version=$(dpkg-parsechangelog -l$sdir/debian/changelog | egrep '^Version: ' | cut -d ' ' -f 2,2)
# build backported source package
bash -c "cd $wdir && dpkg-source -b $sdir"
# remove extracted source tree
rm -rf $sdir
# move generated source package into working dir
mv $wdir/* .
# cleanup
rm -rf $wdir

if [ "$bp_verbose" = 1 ]; then
  printf "${green}Backported source package is at '${src_name}_$final_version.dsc'\n${NC}"
fi