#!/bin/bash

set -e

PROGRAM=$(basename $0)
BASEDIR=/var/cache/mdt
REPOSITORY_PATH=$BASEDIR/packages
LOCKFILE=$BASEDIR/mdt-lock

# Exits the program gracefully with an error message.
#
function die
{
    echo $PROGRAM: $@
    exit 1
}

# Given a package filename, returns the actual Debian base package name,
# excluding the version number.
#
function get-package-name
{
    local package_filename="$1"; shift

    dpkg-deb -I $package_filename \
        | grep -E '^ Package: ' \
        | awk '{ print $2 }'
}

# Given a package filename, copies the package into the local MDT package
# repository for later installation.
#
function add-package
{
    local package_filename="$1"; shift

    if [[ ! -f $package_filename ]]; then
        die No such file or directory: $package_filename
    fi

    local package_name=$(get-package-name $package_filename)

    (
        flock -n -E 254 200
        (
            cp $package_filename $REPOSITORY_PATH
            cd $REPOSITORY_PATH
            apt-ftparchive packages . > Packages
        )
    ) 200>$LOCKFILE

    local exitcode=$?
    if [[ $exitcode == 254 ]]; then
        die Couldn\'t acquire lockfile: $LOCKFILE
    fi

    return $exitcode
}

# Given a package filename, removes the package from the local MDT package
# repository.
#
function remove-package
{
    local package_filename="$1"; shift
    local package_basename=$(basename $package_filename)
    local package_path=$REPOSITORY_PATH/$package_basename

    if [[ ! -f $package_path ]]; then
        die No such file or directory: $package_path
    fi

    (
        flock -n -E 254 200
        (
            rm -f $package_path
            cd $BASEDIR
            apt-ftparchive packages packages > Packages
        )
    ) 200>$LOCKFILE

    local exitcode=$?
    if [[ $exitcode == 254 ]]; then
        die Couldn\'t acquire lockfile: $LOCKFILE
    fi

    return $exitcode
}

function main
{
    local package_to_install="$1"; shift

    if [[ -z $package_to_install ]]; then
        echo "Usage: mdt-install-package <package>"
        echo 
        echo "Installs a given Debian package to the system using a local repository"
        echo "to help install all dependent packages. Forces reinstalls."
        echo
        exit 1
    fi

    if [[ ! -f $package_to_install ]]; then
        die No such file or directory: $PACKAGE_TO_INSTALL
    fi

    if [[ ! -d $REPOSITORY_PATH ]]; then
        die Can\'t find local repository: $REPOSITORY_PATH
    fi

    if [[ ! -x /usr/bin/apt-ftparchive ]]; then
        die apt-utils is not installed: can\'t find apt-ftparchive
    fi

    add-package $package_to_install \
        || die failed to add package to repository: $package_to_install

    local package_name=$(get-package-name $package_to_install)

    apt-get -qq update \
            --no-list-cleanup \
            -o Dir::Etc::SourceList="sources.list.d/00-mdt-services.list" \
            -o Dir::Etc::SourceParts="-"

    apt-get install -y --reinstall $package_name

    remove-package $package_to_install \
        || die failed to remove package from repository: $package
}

main "$@"