debpack

#!/usr/bin/env bash
set -euo pipefail

# Only output color if stdout is a TTY
color_echo() {
    if [[ -t 1 ]]; then
        printf "\e[$1m==> %s\e[0m\n" "$2"
    else
        echo "==> $2"
    fi
}

green() {
    color_echo "1;32" "$1"
}

yellow() {
    color_echo "1;33" "$1"
}

fatal() {
    color_echo "1;31" "$1"
    exit 1
}

# Parses package control file field into $key and $value
parse_control_field() {
    key=$(echo "$1" | cut -d: -f1)
    value=$(echo "$1" | cut -d: -f2- | sed "s/^[[:space:]]*//")
    if [[ $1 != *:* ]] || [[ -z $key ]] || [[ -z $value ]]; then
        fatal "Invalid format: $1"
    fi
}

patch_control() {
    parse_control_field "$2"
    grep -Fiv "${key}:" "$1" > "$1.tmp" || true
    echo "${key}: ${value}" >> "$1.tmp"
    mv "$1.tmp" "$1"
}

# https://www.debian.org/doc/debian-policy/ch-files.html#permissions-and-owners
normalize_perms() {
    find "$1" | while IFS= read -r filename; do
        if [[ -d ${filename} ]] || [[ -x ${filename} ]]; then
            chmod 0755 "${filename}"
        elif [[ -f ${filename} ]]; then
            chmod 0644 "${filename}"
        else
            fatal "${filename} is neither a file nor a directory"
        fi
    done
}

build() {
    # Cleanup
    if [[ -d .debpack ]]; then
        rm -r .debpack
    fi

    green "Copying files"
    mkdir -p .debpack/DEBIAN/
    if [[ -d ${src_debian} ]]; then
        cp -R "${src_debian}/." .debpack/DEBIAN/
    fi

    # Allow in case all fields are set through args
    if [[ ! -f .debpack/DEBIAN/control ]]; then
        yellow "Package control file not found; assuming empty"
    fi

    # Copy files in Debpackfile
    # Don't allow empty packages
    if [[ ! -e ${debpackfile_path} ]]; then
        fatal "${debpackfile_path} not found"
    fi
    while IFS= read -r line || [[ -n ${line} ]]; do
        # Ignore empty and comment lines
        if [[ -z ${line} ]] || [[ ${line} == \#* ]]; then
            continue
        fi
        # Make sure we have a tab character
        if [[ ${line} != *$(printf "\t")* ]]; then
            fatal "Invalid format: ${line}"
        fi
        src=$(echo "${line}" | cut -f1)
        dst=.debpack$(echo "${line}" | cut -f2)
        # Create directories up to last slash
        mkdir -p "${dst%/*}"
        # Allow source wildcards
        # shellcheck disable=SC2086
        cp -R ${src} "${dst}"
    done < "${debpackfile_path}"

    green "Patching package control file"
    for field in "$@"; do
        patch_control .debpack/DEBIAN/control "${field}"
    done

    green "Normalizing permissions"
    normalize_perms .debpack

    green "Building package"
    fakeroot dpkg-deb -b -Zgzip -z9 .debpack

    dpkg --info .debpack.deb
    dpkg --contents .debpack.deb
    dpkg-name --overwrite .debpack.deb

    green "Done"
}

print_usage() {
    cat << EOF
Usage: debpack [-h] [options] [fields...]

Super simple Debian packages.

Options:
  -h       Show this message
  -d PATH  Control files directory (default: debian)
  -f FILE  Debpackfile path (- for stdin) (default: Debpackfile)

The package control file can be modified at build-time by
specifying fields in the key:value format. For example:

  debpack Version:1.0 Architecture:i386
EOF
}

debpackfile_path=Debpackfile
src_debian=debian

while getopts ":hf:d:" opt; do
    case ${opt} in
        h)
            print_usage
            exit
            ;;
        f)
            if [[ ${OPTARG} == - ]]; then
                debpackfile_path=/dev/stdin
            else
                debpackfile_path=${OPTARG}
            fi
            ;;
        d)
            src_debian=${OPTARG}
            ;;
        \?|*)
            print_usage
            exit 1
            ;;
    esac
done

# Unprocessed opts are control fields
shift $(( OPTIND - 1 ))
build "$@"