#!/bin/sh
set -e

# grub-mkconfig helper script.
# Copyright (C) 2010  Alexander Kurtz <kurtz.alex@googlemail.com>
#
# GRUB 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, either version 3 of the License, or
# (at your option) any later version.
#
# GRUB 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 GRUB.  If not, see <http://www.gnu.org/licenses/>.

# Include the GRUB helper library for grub-mkconfig.
. /usr/share/grub/grub-mkconfig_lib

# We want to work in /boot/grub/ only.
test -d /boot/grub
cd /boot/grub

# Set the location of a possibly necessary cache file for the background image.
# NOTE: This MUST BE A DOTFILE to avoid confusing it with user-defined images.
BACKGROUND_CACHE=".background_cache"

set_default_theme() {
    case $GRUB_DISTRIBUTOR in
    Tanglu | Ubuntu | Kubuntu)
        # Set a monochromatic theme for Tanglu/Ubuntu.
        echo "${1}set menu_color_normal=white/black"
        echo "${1}set menu_color_highlight=black/light-gray"

        if [ -e /lib/plymouth/themes/default.grub ]; then
            sed "s/^/${1}/" /lib/plymouth/themes/default.grub
        fi
        ;;
    *)
        # Set the traditional Debian blue theme.
        echo "${1}set menu_color_normal=cyan/blue"
        echo "${1}set menu_color_highlight=white/blue"
        ;;
    esac
}

module_available() {
    local module
    for module in "${1}.mod" */"${1}.mod"; do
        if [ -f "${module}" ]; then
            return 0
        fi
    done
    return 1
}

set_background_image() {
    # Step #1: Search all available output modes ...
    local output
    for output in ${GRUB_TERMINAL_OUTPUT}; do
        if [ "x$output" = "xgfxterm" ]; then
            break
        fi
    done

    # ... and check if we are able to display a background image at all.
    if ! [ "x${output}" = "xgfxterm" ]; then
        return 1
    fi

    # Step #2: Check if the specified background image exists.
    if ! [ -f "${1}" ]; then
        return 2
    fi

    # Step #3: Search the correct GRUB module for our background image.
    local reader
    case "${1}" in
    *.jpg | *.JPG | *.jpeg | *.JPEG) reader="jpeg" ;;
    *.png | *.PNG) reader="png" ;;
    *.tga | *.TGA) reader="tga" ;;
    *) return 3 ;; # Unknown image type.
    esac

    # Step #4: Check if the necessary GRUB module is available.
    if ! module_available "${reader}"; then
        return 4
    fi

    # Step #5: Ensure GRUB can read the background image
    if cp "${1}" "${BACKGROUND_CACHE}.${reader}"; then
        set -- "${BACKGROUND_CACHE}.${reader}" "${2}" "${3}"
    else
        return 5
    fi

    # Step #6: Prepare GRUB to read the background image.
    if ! prepare_grub_to_access_device "$(${grub_probe} --target=device "${1}")"; then
        return 6
    fi

    # Step #7: Everything went fine, print out a message to stderr ...
    echo "Found background image: ${1}" >&2

    # ... and write our configuration snippet to stdout. Use the colors
    # desktop-base specified. If we're using a user-defined background, use
    # the default colors since we've got no idea how the image looks like.
    # If loading the background image fails, use the default theme.
    echo "insmod ${reader}"
    echo "if background_image $(make_system_path_relative_to_its_root "${1}"); then"
    if [ -n "${2}" ]; then
        echo "  set color_normal=${2}"
    fi
    if [ -n "${3}" ]; then
        echo "  set color_highlight=${3}"
    fi
    if [ -z "${2}" ] && [ -z "${3}" ]; then
        echo "  true"
    fi
    echo "else"
    set_default_theme "  "
    echo "fi"
}

# Earlier versions of grub-pc copied the default background image to /boot/grub
# during postinst. Remove those obsolete images if they haven't been touched by
# the user. They are still available under /usr/share/images/desktop-base/ if
# desktop-base is installed.
while read checksum background; do
    if [ -f "${background}" ] && [ "x$(sha1sum "${background}")" = "x${checksum}  ${background}" ]; then
        echo "Removing old background image: ${background}" >&2
        rm "${background}"
    fi
done << EOF
648ee65dd0c157a69b019a5372cbcfea4fc754a5  debian-blueish-wallpaper-640x480.png
0431e97a6c661084c59676c4baeeb8c2f602edb8  debian-blueish-wallpaper-640x480.png
968ecf6696c5638cfe80e8e70aba239526270864  debian-blueish-wallpaper-640x480.tga
11143e8c92a073401de0b0fd42d0c052af4ccd9b  moreblue-orbit-grub.png
d00d5e505ab63f2d53fa880bfac447e2d3bb197c  moreblue-orbit-grub.png
f5b12c1009ec0a3b029185f6b66cd0d7e5611019  moreblue-orbit-grub.png
EOF

# Include the configuration of desktop-base if available.
if [ -f "/usr/share/scibian/grub/scibian_background.sh" ]; then
    . "/usr/share/scibian/grub/scibian_background.sh"
fi

# First check whether the user has specified a background image explicitly.
# If so, try to use it. Don't try the other possibilities in that case
# (#608263).
if [ -n "${GRUB_BACKGROUND+x}" ]; then
    set_background_image "${GRUB_BACKGROUND}" || set_default_theme
    exit 0
fi

# Next search for pictures the user put into /boot/grub/ and use the first one.
for background in *.jpg *.JPG *.jpeg *.JPEG *.png *.PNG *.tga *.TGA; do
    if set_background_image "${background}"; then
        exit 0
    fi
done

# Next try to use the background image and colors specified by desktop-base.
if set_background_image "${WALLPAPER}" "${COLOR_NORMAL}" "${COLOR_HIGHLIGHT}"; then
    exit 0
fi

# If we haven't found a background image yet, use the default from desktop-base.
case $GRUB_DISTRIBUTOR in
Ubuntu | Kubuntu) ;;
Tanglu)
    if set_background_image "/usr/share/images/grub/grub.png"; then
        exit 0
    fi
    ;;
*)
    if set_background_image "/usr/share/images/desktop-base/desktop-grub.png"; then
        exit 0
    fi
    ;;
esac

# Finally, if all of the above fails, use the default theme.
set_default_theme
