DEFAULT: _target

nul_:=
comma_:= ,
space_:= ${nul_} ${nul_}

.PHONY: clean .FORCE
.PHONY: _config_raspi _partition_raspi
.PHONY: _qemu _bootstrap _install _copy _config_raspi _config _bootloader _squash
.PHONY: _target _partition _format _mount _sparse _umount _partcopy _mbr

ARCH := amd64
KEYRING := keys/debian-archive-stretch-stable.gpg
BOOTSTRAP := http://cdn.debian.net/debian

# Partition Table (2M) + Boot Partition (126M)+ Root Partition + Slack Space (1M) = 2048M
BOOT_MB := 62
ROOT_MB := 959

define SOURCES = 
deb	http://cdn.debian.net/debian stretch main
endef

PACKAGES := ${PACKAGES} apt busybox-static debian-archive-keyring init systemd

config.mk:
	cp "config.example" "$@"

include config.mk

ifdef disk
VOLUME := ${disk}
PBOOT := ${disk}1
PROOT := ${disk}2
SYSROOT := hdd_mount/
CFGROOT := hdd_mount/

_target: _mbr _umount _config _install _partition

_partition:
_format: _partition
_mount: _format
_bootstrap: _mount
_install: _bootstrap _mount
_config: _install _mount
_bootloader: _mount
_umount: _mount _config _bootloader
_mbr: _umount _bootloader

else ifdef image
VOLUME := ${image}
PBOOT := part_boot.img
PROOT := part_root.img
SYSROOT := sys_root/
CFGROOT := img_mount/

_target: _mbr _umount _partcopy _config _install

_bootstrap:
_install: _bootstrap
_sparse:
_format: _sparse
_mount: _format
_copy: _install _mount
_config: _copy _mount
_bootloader: _mount
_umount: _mount _config _bootloader
_partition:
_partcopy: _partition _umount
_mbr: _partcopy _bootloader

else ifdef squash
SQUASH := ${squash}
SYSROOT := sys_root/
CFGROOT := cfg_root/

_target: _squash _install _config

_bootstrap:
_install: _bootstrap
_copy: _install
_config: _copy
_squash: _config

else ifdef raspi
VOLUME := ${raspi}
PBOOT := rpi_boot.img
PROOT := rpi_root.img
SYSROOT := rpi_root/
CFGROOT := img_mount/

ARCH := armhf
KEYRING := keys/raspbian-archive-keyring.gpg
BOOTSTRAP := http://raspbian.raspberrypi.org/raspbian

define SOURCES =
deb	http://raspbian.raspberrypi.org/raspbian stretch main non-free firmware rpi
deb	http://archive.raspberrypi.org/debian stretch main
endef

PACKAGES := ${PACKAGES} firmware-brcm80211 libraspberrypi-bin libraspberrypi0 pi-bluetooth raspberrypi-bootloader raspberrypi-kernel

_target: _umount _partcopy _config _install

_qemu:
_bootstrap: _qemu
_install: _bootstrap
_sparse:
_format: _sparse
_mount: _format
_copy: _install _mount
_config_raspi: _copy _mount
_config: _copy _mount _config_raspi
_umount: _mount _config
_partition_raspi:
_partcopy: _partition_raspi _umount

else
_target:
	false

endif

include modules/default.mk
ifdef modules
include $(addsuffix .mk, $(addprefix modules/, $(subst ${comma_},${space_},${modules})))
endif

ifeq "${ARCH}" "amd64"
PACKAGES := ${PACKAGES} linux-image-amd64
else ifeq "${ARCH}" "i386"
PACKAGES := ${PACKAGES} linux-image-686
endif

export SOURCES SYSROOT CFGROOT VOLUME PBOOT PROOT SQUASH ARCH KEYRING BOOTSTRAP

sys_root/:
	btrfs subvol create "$@" || mkdir -p "$@"
	chmod 755 "$@"

cfg_root/: sys_root/ _install
	btrfs sub snap "$<" "$@" || mkdir -p "$@"
	chmod 755 "$@"

rpi_root/:
	btrfs subvol create "$@" || mkdir -p "$@"
	chmod 755 "$@"

img_mount/:
	mkdir -p -m 755 "$@"
	chmod 755 "$@"

hdd_mount/:
	mkdir -p -m 755 "$@"

_qemu: ${SYSROOT}/usr/bin/qemu-arm-static
${SYSROOT}/usr/bin/qemu-arm-static: /usr/bin/qemu-arm-static ${SYSROOT}
	mkdir -p -m 755 "$${SYSROOT}"/usr/bin
	chmod 755 "$${SYSROOT}"/usr
	cp -p "$<" "$@"

_bootstrap: ${SYSROOT}/bin/sh
${SYSROOT}/bin/sh: | ${SYSROOT}
	debootstrap --variant=minbase --arch="$${ARCH}" \
		--keyring="$${KEYRING}" \
		stretch "$${SYSROOT}" "$${BOOTSTRAP}"

.PHONY: _aptkeys _norecommends
_aptkeys: ${SYSROOT}/etc/apt/trusted.gpg.d/
_norecommends: ${SYSROOT}/etc/apt/apt.conf.d/10norecommends

${SYSROOT}/etc/apt/apt.conf.d/10norecommends: ${SYSROOT}
	mkdir -p -m 755 "$(dir $@)"
	printf 'APT::Install-Recommends "false";\n' >"$@"
	chmod 644 "$@"

${SYSROOT}/etc/apt/trusted.gpg.d/: ${SYSROOT}
	mkdir -p -m 755 "$@"
	cp keys/*.gpg "$@"

_install: ${SYSROOT} _aptkeys _norecommends
	printf '%s\n' "$${SOURCES}" >"$${SYSROOT}/etc/apt/sources.list"
	-cp /etc/resolv.conf "$${SYSROOT}/etc/"
	-chroot "$${SYSROOT}" sh -c 'apt-mark showmanual |xargs apt-mark auto'
	-chroot "$${SYSROOT}" apt-get update
	chroot "$${SYSROOT}" ln -sf /bin/true /usr/local/sbin/invoke-rc.d
	chroot "$${SYSROOT}" apt-get --yes install ${PACKAGES}
	chroot "$${SYSROOT}" apt-get --yes --auto-remove purge
	-chroot "$${SYSROOT}" apt-get --yes --auto-remove upgrade
	chroot "$${SYSROOT}" apt-get clean
	chroot "$${SYSROOT}" rm /usr/local/sbin/invoke-rc.d

_copy: ${SYSROOT} ${CFGROOT}
	cp -au "$${SYSROOT}/." "$${CFGROOT}/"

_config_raspi: ${CFGROOT}/boot/cmdline.txt
${CFGROOT}/boot/cmdline.txt: ${CFGROOT}
	printf 'dwc_otg.lpm_enable=0 console=serial0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait quiet' >"$@"

.PHONY: _common_config
_config: _common_config
_common_config: ${CFGROOT}
	ln -sf /dev/null "$${CFGROOT}/etc/systemd/network/99-default.link"
	printf 'LABEL=FSROOT / ext4 auto,nofail,rw 0 0\nLABEL=BOOT /boot vfat auto,nofail,ro 0 0\n' \
		>"$${CFGROOT}/etc/fstab"

${SQUASH}: ${CFGROOT}
	-rm "$${SQUASH}"
	mksquashfs "$${CFGROOT}" "$${SQUASH}" -comp xz

_squash: ${SQUASH}

${VOLUME}: .FORCE
	! printf '%s\n' "$${VOLUME}" |grep -q '^/dev/'  # abort if volume should be real device
	dd count=0 of="$${VOLUME}"  # truncate
	dd bs=1M count=0 seek=$$((3 + ${BOOT_MB} + ${ROOT_MB})) of="$${VOLUME}"
	chmod g+w "$${VOLUME}"

${PBOOT}: .FORCE
	! printf '%s\n' "$${PBOOT}" |grep -q '^/dev/'  # abort if volume should be real device
	dd count=0 of="$${PBOOT}"  # truncate
	dd bs=1M count=0 seek=${BOOT_MB} of="$${PBOOT}"

${PROOT}: .FORCE
	! printf '%s\n' "$${PROOT}" |grep -q '^/dev/'  # abort if volume should be real device
	dd count=0 of="$${PROOT}"  # truncate
	dd bs=1M count=0 seek=${ROOT_MB} of="$${PROOT}"

_partition_raspi: ${VOLUME}
	printf 'label: dos\n\n: start=2MiB, size=%iMiB, type=c\n: start=%iMiB, size=%iMiB, type=83\n' \
		${BOOT_MB} "$$((${BOOT_MB} + 2))" ${ROOT_MB} | sfdisk "$${VOLUME}"

_partition: ${VOLUME}
	printf 'label: gpt\n\n: start=2MiB, size=%iMiB, type=1, attrs="LegacyBIOSBootable"\n: size=%iMiB, type=20\n' \
		${BOOT_MB} ${ROOT_MB} | sfdisk "$${VOLUME}"

_sparse: ${PBOOT} ${PROOT}

_format: ${PBOOT} ${PROOT}
	-umount "$${CFGROOT}/boot" "$${CFGROOT}"
	mkfs.fat -F 32 -n BOOT "$${PBOOT}"
	mkfs.ext4 -F -L FSROOT "$${PROOT}"

.PHONY: _syslinux_efi32 _syslinux_efi64 _syslinux_bios
.PHONY: _grub_efi32 _grub_efi64

_syslinux_efi32: ${CFGROOT}
	mkdir -p "$${CFGROOT}/boot/EFI/BOOT"
	cp /usr/lib/SYSLINUX.EFI/efi32/syslinux.efi "$${CFGROOT}/boot/EFI/BOOT/BOOTIA32.EFI"
	mkdir -p "$${CFGROOT}/boot/efi32"
	cp $(addprefix /usr/lib/syslinux/modules/efi32/, ldlinux.e32 menu.c32 libutil.c32) "$${CFGROOT}"/boot/efi32/
	cp /usr/lib/syslinux/modules/efi32/ldlinux.e32 "$${CFGROOT}/boot/EFI/BOOT/"  # workaround
	printf 'PATH /efi32\nINCLUDE /bootmenu.cfg\nMENU TITLE Syslinux EFI-32\n' >"$${CFGROOT}/boot/syslia32.cfg"

_syslinux_efi64: ${CFGROOT}
	mkdir -p "$${CFGROOT}/boot/EFI/BOOT"
	cp /usr/lib/SYSLINUX.EFI/efi64/syslinux.efi "$${CFGROOT}/boot/EFI/BOOT/BOOTX64.EFI"
	mkdir -p "$${CFGROOT}/boot/efi64"
	cp $(addprefix /usr/lib/syslinux/modules/efi64/, ldlinux.e64 menu.c32 libutil.c32) "$${CFGROOT}"/boot/efi64/
	cp /usr/lib/syslinux/modules/efi64/ldlinux.e64 "$${CFGROOT}/boot/EFI/BOOT/"  # workaround
	printf 'PATH /efi64\nINCLUDE /bootmenu.cfg\nMENU TITLE Syslinux EFI-64\n' >"$${CFGROOT}/boot/syslx64.cfg"

_syslinux_bios: ${CFGROOT}
	mkdir -p "$${CFGROOT}/boot/bios"
	cp $(addprefix /usr/lib/syslinux/modules/bios/,  menu.c32 libutil.c32) "$${CFGROOT}"/boot/bios/
	printf 'PATH bios\nINCLUDE bootmenu.cfg\nMENU TITLE Syslinux BIOS\n' >"$${CFGROOT}/boot/syslinux.cfg"

_grub_efi32: ${CFGROOT}
	mkdir -p "$${CFGROOT}/boot/EFI/BOOT"
	grub-mkimage -p / -O i386-efi   fat part_gpt normal linux all_video >"$${CFGROOT}/boot/EFI/BOOT/BOOTIA32.EFI"

_grub_efi64: ${CFGROOT}
	mkdir -p "$${CFGROOT}/boot/EFI/BOOT"
	grub-mkimage -p / -O x86_64-efi fat part_gpt normal linux all_video >"$${CFGROOT}/boot/EFI/BOOT/BOOTX64.EFI"

_bootloader: ${CFGROOT} _grub_efi32 _grub_efi64 _syslinux_bios #_syslinux_efi32 _syslinux_efi64
	printf 'UI menu.c32\nDEFAULT stretch\nTIMEOUT 30\n' >"$${CFGROOT}/boot/bootmenu.cfg"
	printf 'set timeout=3\ndefault=stretch\n\n' >"$${CFGROOT}/boot/grub.cfg"
	k="$$(printf ' %s' "$${CFGROOT}/boot/"vmlinuz-*)"; k="$${k##*/}"; \
	i="$$(printf ' %s' "$${CFGROOT}/boot/"initrd.img-*)";  i="$${i##*/}"; \
	printf '\nLABEL stretch\n MENU LABEL Debian Stretch\n KERNEL /%s\n INITRD /%s\n APPEND root=LABEL=FSROOT\n' \
		"$$k" "$$i" >>"$${CFGROOT}/boot/bootmenu.cfg"; \
	printf '\nLABEL rescue\n MENU LABEL Rescue\n KERNEL /%s\n INITRD /%s\n APPEND root=LABEL=FSROOT init=/bin/sh\n' \
		"$$k" "$$i" >>"$${CFGROOT}/boot/bootmenu.cfg"; \
	printf "menuentry 'Debian Stretch' --id 'stretch' {\n linux '/%s' root=LABEL=FSROOT\n initrd '/%s'\n}\n" \
		"$$k" "$$i" >>"$${CFGROOT}/boot/grub.cfg"; \
	printf "menuentry 'Rescue' --id 'rescue' {\n linux '/%s' root=LABEL=FSROOT init=/bin/sh\n initrd '/%s'\n}\n" \
		"$$k" "$$i" >>"$${CFGROOT}/boot/grub.cfg"

.PHONY: _syslinux_mbr _grub_mbr

_syslinux_mbr: ${VOLUME}
	syslinux -t 2097152 -i "$${VOLUME}"
	dd conv=notrunc if=/usr/lib/syslinux/mbr/gptmbr.bin of="$${VOLUME}"

_grub_mbr: ${VOLUME}
	# grub-mkimage -p / -O i386-pc fat part_gpt normal linux all_video |dd conv=notrunc of="$${VOLUME}"

_mbr: _syslinux_mbr # _grub_mbr

_partcopy: ${VOLUME} ${PROOT} ${PBOOT}
	dd conv=notrunc,sparse bs=1M seek=2 if="$${PBOOT}" of="$${VOLUME}"
	dd conv=notrunc,sparse bs=1M seek=$$((2 + ${BOOT_MB})) if="$${PROOT}" of="$${VOLUME}"

_mount: ${PBOOT} ${PROOT} ${CFG_ROOT}
	mount -t ext4 "$${PROOT}" "$${CFGROOT}"
	chmod 755 "$${CFGROOT}"
	mkdir -p -m 755 "$${CFGROOT}/boot"
	mount -t vfat "$${PBOOT}" "$${CFGROOT}/boot"

_umount: ${CFGROOT}
	-umount "$${CFGROOT}/boot"
	umount "$${CFGROOT}" && rmdir "$${CFGROOT}"

clean:
	[ "$${SYSROOT#/}" ] && [ "$${CFGROOT#/}" ] || false  # (abort receipe)
	-umount img_mount/boot
	-umount img_mount
	-rmdir img_mount
	-umount hdd_mount/boot
	-umount hdd_mount
	-rmdir hdd_mount
	if [ -d "sys_root/" ]; then btrfs sub del "sys_root/" || echo rm -r "sys_root/"; fi
	if [ -d "cfg_root/" ]; then btrfs sub del "cfg_root/" || echo rm -r "cfg_root/"; fi
	if [ -d "rpi_root/" ]; then btrfs sub del "rpi_root/" || echo rm -r "rpi_root/"; fi
	-rm part_boot.img
	-rm part_root.img
	-rm rpi_boot.img
	-rm rpi_root.img
	-[ -f "$${SQUASH}" ] && rm "$${SQUASH}"
	-[ -f "$${VOLUME}" ] && rm "$${VOLUME}"