#!/usr/bin/env bash

# Copyright (C) 2017,2018 Andrew Robbins <contact@andrewrobbins.info>
#
# 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/>.

ARCH='arch'
CONFIG='config'
FONTS='fonts'
FONT_FILE='font-file'
FONT_PROJECT='font-project'
FORMAT='format'
MODMIN='modules-minimal'
PLATFORM='platform'
PREFIX='prefix'
SIZE='size'

grub_arch() {
	project_file_contents "$project" "$CONFIGS" "$ARCH" "$@"
}

grub_font_file() {
	project_file_contents "$project" "$CONFIGS" "$FONT_FILE" "$@"
}

grub_font_project() {
	project_file_contents "$project" "$CONFIGS" "$FONT_PROJECT" "$@"
}

grub_format() {
	project_file_contents "$project" "$CONFIGS" "$FORMAT" "$@"
}

grub_platform() {
	project_file_contents "$project" "$CONFIGS" "$PLATFORM" "$@"
}

grub_prefix() {
	project_file_contents "$project" "$CONFIGS" "$PREFIX" "$@"
}

grub_size() {
	project_file_contents "$project" "$CONFIGS" "$SIZE" "$@"
}

grub_config_path() {
	project_file_path "$project" "$CONFIGS" "$CONFIG" "$@"
}

grub_modmin_path() {
	project_file_path "$project" "$CONFIGS" "$MODMIN" "$@"
}

grub_bo_search() {
    local pattern="$1"
    local comparand="$2"

    grep -Fbof <(grub_bo_dump "$pattern") <(grub_bo_dump "$comparand") | cut -d: -f1
}

grub_bo_dump() {
    local file="$1"

    od -Anx -t x1 -w16 -v "$file" | paste -sd '' | tr -d ' '
}

grub_bo() {
    local pattern="$1"
    local comparand="$2"

    local nibble_offset="$(grub_bo_search "$pattern" "$comparand")"

    if [[ -n "$nibble_offset" ]]; then
	printf '0x%X\n' $((nibble_offset / 2))
    else
	return 1
    fi
}

grub_blocklist_format() {
	local blocklist="$1"
	local byte

	while read -N 2 byte; do
		printf '%s' "\\x$byte"
	done <<< "$blocklist"
}

grub_blocklist_generate() {
	local -i byte_offset="$1"

	printf '%04x' $((byte_offset / 512)) | tac -rs ..
}

grub_copy_modules() {
	local grub_module_dir="$sources_path/grub-core"
	local keep_dir="$build_path/$(grub_format "$target" "$@")"

	mkdir -p "$keep_dir"

	cp -a "$grub_module_dir"/*.@(mod|lst) "$keep_dir"
}

grub_build_font() {
	# Font project-specific filenames and paths
	local font_file="$(grub_font_file "$FONTS" "$@")"
	local font_project="$(grub_font_project "$FONTS" "$@")"
	local font_build_dir="$root/$BUILD/$font_project"

	local grub_mkfont="$sources_path/grub-mkfont"

	# GRUB font directory for outputting the built PF2 file
	mkdir -p "$build_path/$FONTS"

	"$grub_mkfont" --output="$build_path/$FONTS/${font_file%.*}.pf2" \
			"$font_build_dir/$font_file"
}

grub_build_utils() {
	(
		# If arch and/or platform files don't exist,
		# the configure script will pick a reasonable default
		local arch="$(grub_arch "$target" "$@")"
		local platform="$(grub_platform "$target" "$@")"

		cd "$sources_path" || return

		if git_project_check "$repository"; then
			./autogen.sh
		fi

		./configure --target="$arch" --with-platform="$platform"

		make -j"$TASKS"
	)
}

grub_build_layout() {
	local raw_layout="${1##*/}"
	local raw_layout_path="$1"
	local keymap_out_path="$build_path/keymaps"
	local grub_mklayout="$sources_path/grub-mklayout"
	local grub_kbd_layout="$keymap_out_path/$raw_layout.gkb"

	if ! [[ -e "$keymap_out_path" ]]; then
		mkdir -p "$keymap_out_path"
	elif ! [[ -d "$keymap_out_path" ]]; then
		printf '\n%s\n' "Error: File $keymap_out_path is not a directory" 1>&2

		return 1
	fi

	"$grub_mklayout" --output="$grub_kbd_layout" --input="$raw_layout_path"
}

grub_build_bootable_image() {
	local arch="$(grub_arch "$target" "$@")"
	local format="$(grub_format "$target" "$@")"
	local prefix="$(grub_prefix "$target" "$@")"
	local config_path="$(grub_config_path "$target" "$@")"
	local modmin_path="$(grub_modmin_path "$target" "$@")"

	local -a modmin=($(< "$modmin_path"))

	local grub_mkimage="$sources_path/grub-mkimage"
	local grub_module_dir="$sources_path/grub-core"

	local grub_bootimg="$grub_module_dir/boot.img"
	local grub_coreimg="$build_path/core.img"

	"$grub_mkimage" \
		--config="$config_path" \
		--directory="$grub_module_dir" \
		--output="$grub_coreimg" \
		--format="$format" \
		--prefix="$prefix" \
		"${modmin[@]}"

	cp -a "$grub_bootimg" "$build_path"
}

grub_build_floppy_image() {
	local floppyimg="$build_path/floppy.img"
	local format="$(grub_format "$target" "$@")"
	local grub_module_dir="$sources_path/grub-core"
	local size="$(grub_size "$target" "$@")"

	local -a modules

	for module in "$grub_module_dir"/*.mod; do
		modules+=($module)
	done

	if ! grub_build_bootable_image "$@"; then
		printf '\n%s\n\n' "Error: Failed to build a GRUB image" 1>&2

		return 1
	fi

	# Pre-allocate a floppy-sized image with a FAT12 filesystem
	# SeaBIOS requires floppy images to have a "correct" size
	if ! [[ -e "$floppyimg" ]]; then
		mkfs.fat -C -D 0x00 -F 12 -M 0xF9 -n SEAGRUB --invariant "$floppyimg" "$size"
	else
		printf '\n%s\n\n' "Error: File $floppyimg already exists!" 1>&2

		return 1
	fi

	grub_floppy_image_mmd "$floppyimg" /boot /boot/grub "/boot/grub/$format"
	grub_floppy_image_mcopy "$floppyimg" "/boot/grub/$format" "${modules[@]}"
	grub_floppy_image_make_bootable "$floppyimg"
}

grub_build_standalone_image() {
	local arch="$(grub_arch "$target" "$@")"
	local format="$(grub_format "$target" "$@")"
	local prefix="$(grub_prefix "$target" "$@")"
	local config_path="$(grub_config_path "$target" "$@")"
	local modmin_path="$(grub_modmin_path "$target" "$@")"

	local -a modmin=($(< "$modmin_path"))

	local grubimg="$build_path/grub2"

	local grub_mkimage="$sources_path/grub-mkimage"
	local grub_mkstandalone="$sources_path/grub-mkstandalone"
	local grub_module_dir="$sources_path/grub-core"

	"$grub_mkstandalone" \
		--grub-mkimage="$grub_mkimage" \
		--fonts='' \
		--themes='' \
		--locales='' \
		--install-modules="${modmin[*]}" \
		--directory="$grub_module_dir" \
		--format="$format" \
		--output="$grubimg" \
		/boot/grub/grub.cfg="$config_path"
}

grub_floppy_image_mmd() {
	local img="$1"
	local -a dirs=("${@:2}")

	if [[ -n "$img" ]]; then
		mmd -i "$img" "${dirs[@]}"
	else
		return 1
	fi
}

grub_floppy_image_mcopy() {
	local img="$1"
	local target="$2"
	local -a files=("${@:3}")

	if [[ -z "$img" ]]; then
		return 1
	elif [[ -z "${files[@]}" ]]; then
		mcopy -i "$img" -pv "::$target"
	else
		mcopy -i "$img" -pQv "${files[@]}" "::$target"
	fi
}

grub_floppy_image_make_bootable() {
	local floppyimg="$1"
	local bootimg="$build_path/boot.img"
	local coreimg="$build_path/core.img"
	local oem_name='\x4C\x49\x42\x52\x45\x20\x20\x20'

	# write $floppyimg Bios Parameter Block to $bootimg first
	dd if="$floppyimg" of="$bootimg" bs=1 skip=11 seek=11 count=52 conv=notrunc
	dd if=<(printf "$oem_name") of="$bootimg" bs=1 seek=3 conv=notrunc
	dd if=/dev/zero of="$floppyimg" count=1 conv=notrunc
	dd if="$bootimg" of="$floppyimg" conv=notrunc

	grub_floppy_image_mcopy "$floppyimg" /boot/grub "$bootimg"
	grub_floppy_image_mcopy "$floppyimg" /boot/grub "$coreimg"

	grub_floppy_image_update_blocklists "$coreimg" "$floppyimg"
	rm -f "$bootimg" "$coreimg"
}

grub_floppy_image_update_blocklists() {
	local coreimg="$1"
	local floppyimg="$2"

	local -i coreimg_offset="$(grub_bo "$coreimg" "$floppyimg")"
	local -i coreimg_second_sector_offset=$((coreimg_offset + 0x200))

	local -i boot_record_blocklist_offset=0x5C
	local -i coreimg_blocklist_offset=$((coreimg_offset + 0x1F4))

	# blocklists (little endian) describe the $coreimg_offset in sectors
	local boot_record_blocklist="$(grub_blocklist_generate "$coreimg_offset")"
	local coreimg_blocklist="$(grub_blocklist_generate "$coreimg_second_sector_offset")"

	if [[ $coreimg_offset -gt 0 ]]; then
		dd if=<(printf "$(grub_blocklist_format "$boot_record_blocklist")") \
			of="$floppyimg" \
			bs=1 \
			seek="$boot_record_blocklist_offset" \
			conv=notrunc

		dd if=<(printf "$(grub_blocklist_format "$coreimg_blocklist")") \
			of="$floppyimg" \
			bs=1 \
			seek="$coreimg_blocklist_offset" \
			conv=notrunc
	else
		printf 1>&2 '%s\n' "Error: ${coreimg##*/} offset not found"

		return 1
	fi
}