#!/bin/sh
#############################################################################
##
## Copyright (C) 2016 The Qt Company Ltd.
## Contact: https://www.qt.io/licensing/
##
## This file is part of the Qt OTA Update module of the Qt Toolkit.
##
## $QT_BEGIN_LICENSE:GPL$
## Commercial License Usage
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## accordance with the commercial license agreement provided with the
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##
## GNU General Public License Usage
## Alternatively, this file may be used under the terms of the GNU
## General Public License version 3 or (at your option) any later version
## approved by the KDE Free Qt Foundation. The licenses are as published by
## the Free Software Foundation and appearing in the file LICENSE.GPL3
## included in the packaging of this file. Please review the following
## information to ensure the GNU General Public License requirements will
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#############################################################################

# This script is called by ostree/src/libostree/ostree-bootloader-grub2.c whenever
# boot loader configuration file needs to be updated. It can be used as a template
# for a custom grub.cfg generator. When writing a custom grub.cfg generator:
#
# 1) cp ostree-grub-generator ostree-grub-generator-mydevice
# 2) Edit ostree-grub-generator-mydevice
# 3) Pass ostree-grub-generator-mydevice to qt-ostree via --grub2-cfg-generator
# 4) Examine the generated grub.cfg file in the OTA sysroot (created by --create-ota-sysroot)
#
# WARNINGS:
#
#   - Do not modify populate_menu() function, unless you know what you are doing. This function
#   converts boot loader entries (https://www.freedesktop.org/wiki/Specifications/BootLoaderSpec/)
#   into GRUB2 menuentry sections.
#
#   - Be aware that this script is executed not only on a host machine, but also on a
#   target device, thus think about shell portability. Target device for example might
#   be using busybox with a limited shell.

set -e

script=$(basename ${0})
# Atomically safe location where to generete grub.cfg when executing OTA update.
new_grub2_cfg=${2}
entries_path=$(dirname $new_grub2_cfg)/entries

read_config()
{
    config_file=${1}
    title=""
    initrd=""
    options=""
    linux=""

    while read -r line
    do
        record=$(echo ${line} | cut -f 1 -d ' ')
        value=$(echo ${line} | cut -s -f2- -d ' ')
        case "${record}" in
            "title")
                title=${value}
                ;;
            "initrd")
                initrd=${value}
                ;;
            "linux")
                linux=${value}
                ;;
            "options")
                options=${value}
                ;;
        esac
    done < ${config_file}

    if [ -z "${title}" ]; then
        title="(Untitled)"
    fi
}

populate_menu()
{
    # We need to prepend "boot/" prefix when boot/ directory is on the same
    # partition as usr/ - this is the layout we have on Intel NUC boards, the
    # only board with GRUB boot loader that we support at the moment. When there
    # will be more boards, determine boot_prefix at runtime.
    boot_prefix="/boot"

    for config in $(ls $entries_path/*.conf); do
        read_config ${config}
        menu="${menu}menuentry '${title}' {\n"
        menu="${menu}\t linux ${boot_prefix}/${linux} ${options}\n"
        if [ -n "${initrd}" ] ; then
            menu="${menu}\t initrd ${boot_prefix}/${initrd}\n"
        fi
        menu="${menu}}\n\n"
    done
    # printf seems to be more reliable across shells for special character (\n, \t) evaluation
    printf "$menu" >> ${new_grub2_cfg}
}

populate_warning()
{
cat >> ${new_grub2_cfg} <<EOF
# This file was generated by ${script}. Do not modify the generated file - all
# changes will be lost when this file will be regenerated by OSTree. For more
# details refer to ${script} script.
EOF
}

populate_header()
{
cat >> ${new_grub2_cfg} <<EOF
serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
default=boot
timeout=10

EOF
}

generate_grub2_cfg()
{
    populate_warning
    populate_header
    populate_menu
}

generate_grub2_cfg