#!/bin/bash -e
# Tiny Linux Bootloader
# (c) 2014- Dr Gareth Owen (www.ghowen.me). All rights reserved.

#    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, either version 3 of the License, or
#    (at your option) any later version.
#
#    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, see <http://www.gnu.org/licenses/>.

export SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
cd "${SCRIPT_DIR}"

INPUT="bflop.asm"
KERN="${1:-bzImage}"
OUTPUT="${2:-boot-disk.img}"
PAD_TO_FLOPPY="${PAD_TO_FLOPPY:-y}"

#size of kern + ramdisk
K_SZ="$(stat -c %s "${KERN}")"

#padding to make it up to a sector
K_PAD="$((512 - "${K_SZ}" % 512))"

nasm -o "${OUTPUT}" "${INPUT}"

cat "${KERN}" >> "${OUTPUT}"
if [[ "${K_PAD}" -lt 512 ]]; then
    dd if=/dev/zero bs=1 count="${K_PAD}" >> "${OUTPUT}"
fi

TOTAL="$(stat -c %s "${OUTPUT}")"
if [[ "${TOTAL}" -gt 1474560 ]]; then
	echo "Warning: Image exceeds floppy size by $(( TOTAL - 1474560  )) bytes"
	exit 1
else
	echo "Free bytes on floppy image: $(( 1474560 - TOTAL ))"
fi

if [ "$PAD_TO_FLOPPY" = y ]; then
	dd if=/dev/zero bs=1 count="$((1474560 - TOTAL))" >> "${OUTPUT}" 2>/dev/null
fi