#!/bin/sh
# Copyright (C) 2014  Codethink Limited
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 2 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#
# =*= License: GPL-2 =*=
#
#
# This is a write extension for making a package that can be used to
# install the produced system. Ideally we'd instead have Baserock
# everywhere to do the deployment, but we need to support this workflow
# until that is possible.
#
# This write extension produces a tarball, which contains:
#    - a tarball of the configured system root file system
#    - any supporting files listed in BOOTLOADER_BLOBS
#    - any supporting scripts, generated from templates listed in
#      INCLUDE_SCRIPTS
#
# The extension requires the following environment variables to be set:
#
#   * BOOTLOADER_BLOBS: files to include besides rootfs tarball,
#                       paths are relative to the root of the built rootfs
#                       works on any kind of file in the rootfs, named
#                       BOOTLOADER_BLOBS since that's the common use-case
#                       :-separated by default
#   * INCLUDE_SCRIPTS:  script templates that are included in the package
#                       after being filled out
#                       file paths are relative to the definitions repository
#                       :-separated by default
#
# The script templates may contain any of the following strings, which
# will be replaced with a string which will expand to the appropriate
# value as a shell word:
#    - @@SCRIPT_DIR@@:      the path the script files are installed to
#    - @@IMAGE_DIR@@:       the path BOOTLOADER_BLOBS are installed to
#    - @@ROOTFS_TAR_PATH@@: path to the rootfs tarball
#
# The interpolated strings may run commands dependant on the current
# working directory, so if `cd` is required, bind these values to a
# variable beforehand.
#
# The following optional variables can be set as well:
#
#   * INCLUDE_SCRIPTS_SEPARATOR: character to separate INCLUDE_SCRIPTS with (default: :)
#   * BOOTLOADER_BLOBS_SEPARATOR: character to separate BOOTLOADER_BLOBS with (default: :)
#   * SCRIPT_SUBDIR: where in the package processed scripts are installed to (default: tools)
#   * IMAGE_SUBDIR:  where in the package BOOTLOADER_BLOBS are copied to (default: image_files)
#   * ROOTFS_TAR:    name to call the rootfs tarball inside IMAGE_SUBDIR (default: rootfs.tar)
#   * OUTPUT_COMPRESS: compression used for output tarball (default: none)
#   * ROOTFS_COMPRESS: compression used for rootfs (default: none)

set -eu

die(){
    echo "$@" >&2
    exit 1
}

warn(){
    echo "$@" >&2
}

info(){
    echo "$@" >&2
}

shellescape(){
    echo "'$(echo "$1" | sed -e "s/'/'\\''/g")'"
}

sedescape(){
    # Escape the passed in string so it can be safely interpolated into
    # a sed expression as a literal value.
    echo "$1" | sed -e 's/[\/&]/\\&/g'
}

ROOTDIR="$1"
OUTPUT_TAR="$2"
td="$(mktemp -d)"
IMAGE_SUBDIR="${IMAGE_SUBDIR-image_files}"
SCRIPT_SUBDIR="${SCRIPT_SUBDIR-tools}"
ROOTFS_TAR="${ROOTFS_TAR-rootfs.tar}"

# Generate shell snippets that will expand to paths to various resources
# needed by the scripts.
# They expand to a single shell word, so constructs like the following work
#     SCRIPT_DIR=@@SCRIPT_DIR@@
#     dd if="$SCRIPT_DIR/mbr" of="$disk" count=1
#     tar -C "$mountpoint" -xf @@ROOTFS_TAR_PATH@@ .
find_script_dir='"$(readlink -f "$(dirname "$0")")"'
image_dir="$find_script_dir/../$(shellescape "$IMAGE_SUBDIR")"
rootfs_tar_path="$image_dir/$(shellescape "$ROOTFS_TAR")"

install_script(){
    local source_file="$1"
    local output_dir="$2"
    local target_file="$output_dir/$SCRIPT_SUBDIR/$(basename "$source_file" .in)"
    sed -e "s/@@SCRIPT_DIR@@/$(sedescape "$find_script_dir")/g" \
        -e "s/@@IMAGE_DIR@@/$(sedescape "$image_dir")/g" \
        -e "s/@@ROOTFS_TAR_PATH@@/$(sedescape "$rootfs_tar_path")/g" \
        "$source_file" \
    |   install -D -m 755 /proc/self/fd/0 "$target_file"
}

install_scripts(){
    local output_dir="$1"
    (
        IFS="${INCLUDE_SCRIPTS_SEPARATOR-:}"
        for script in $INCLUDE_SCRIPTS; do
            local script_path="$(pwd)/$script"
            if [ ! -e "$script_path" ]; then
                warn Script "$script" not found, ignoring
                continue
            fi
            install_script "$script" "$output_dir"
        done
    )
}

install_bootloader_blobs(){
    local output_dir="$1"
    local image_dir="$output_dir/$IMAGE_SUBDIR"
    (
        IFS="${BOOTLOADER_BLOBS_SEPARATOR-:}"
        for blob in $BOOTLOADER_BLOBS; do
            local blob_path="$ROOTDIR/$blob"
            if [ ! -e "$blob_path" ]; then
                warn Bootloader blob "$blob" not found, ignoring
                continue
            fi
            install -D -m644 "$blob_path" "$image_dir/$(basename "$blob_path")"
        done
    )
}

# Determine a basename for our directory as the same as our tarball with
# extensions removed. This is needed, since tarball packages usually
# have a base directory of its contents, rather then extracting into the
# current directory.
output_dir="$(basename "$OUTPUT_TAR")"
for ext in .xz .bz2 .gzip .gz .tgz .tar; do
    output_dir="${output_dir%$ext}"
done

info Installing scripts
install_scripts "$td/$output_dir"

info Installing bootloader blobs
install_bootloader_blobs "$td/$output_dir"

info Writing rootfs tar to "$IMAGE_SUBDIR/$ROOTFS_TAR"
tar -C "$ROOTDIR" -c . \
| sh -c "${ROOTFS_COMPRESS-cat}" >"$td/$output_dir/$IMAGE_SUBDIR/$ROOTFS_TAR"

info Writing image package tar to "$OUTPUT_TAR"
tar -C "$td" -c "$output_dir" | sh -c "${OUTPUT_COMPRESS-cat}" >"$OUTPUT_TAR"