WORKING_DIR?=$(shell pwd)
EXTERNAL_DIR?=$(WORKING_DIR)/external
BUILD_DIR?=$(WORKING_DIR)/build
LINUX_DIR?=$(EXTERNAL_DIR)/linux
LINUX_REPO?=https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
BUSYBOX_DIR?=$(EXTERNAL_DIR)/busybox
BUSYBOX_REPO?=https://git.busybox.net/busybox
INITRAMFS_INIT?=initramfs_init
ROOTFS_DIR?=$(BUILD_DIR)/rootfs
INITRAMFS_DIR?=$(BUILD_DIR)/initramfs
LIMINE_REPO?=https://github.com/limine-bootloader/limine.git
LIMINE_BRANCH?=v8.x-binary
ISO_ROOT?=$(BUILD_DIR)/iso_root 
LIMINE_DIR?=$(EXTERNAL_DIR)/limine
ISO_PATH?=$(BUILD_DIR)/yerba-linux.iso

.PHONY: all kernel initramfs rootfs iso run clean

all: iso

$(EXTERNAL_DIR):
	@mkdir -p $(EXTERNAL_DIR)

$(BUILD_DIR):
	@mkdir -p $(BUILD_DIR)

$(LINUX_DIR): $(EXTERNAL_DIR)
	@if [ -d $(LINUX_DIR) ]; then \
		echo "[yerba] Linux kernel already cloned, skipping..."; \
	else \
		echo "[yerba] cloning Linux kernel..."; \
		git clone --depth 1 $(LINUX_REPO) $(LINUX_DIR); \
	fi

kernel: $(LINUX_DIR) $(BUILD_DIR)
	@if [ -f $(BUILD_DIR)/bzImage ]; then \
		echo "[yerba] bzImage already exists, skipping kernel build..."; \
	else \
		echo "[yerba] building kernel (default defconfig)..."; \
		rm -f $(LINUX_DIR)/.config; \
		cp $(WORKING_DIR)/linux_config $(LINUX_DIR)/.config; \
		$(MAKE) -C $(LINUX_DIR) -j$(shell nproc) bzImage; \
		cp $(LINUX_DIR)/arch/x86/boot/bzImage $(BUILD_DIR)/bzImage; \
	fi


initramfs: busybox kernel | $(BUILD_DIR)
	@if [ -f $(BUILD_DIR)/initramfs.cpio.gz ]; then \
		echo "[yerba] initramfs already created, skipping..."; \
	else \
		echo "[yerba] creating initramfs..."; \
		rm -rf $(INITRAMFS_DIR); \
		mkdir -p $(INITRAMFS_DIR)/bin; \
		mkdir -p $(INITRAMFS_DIR)/sbin; \
		mkdir -p $(INITRAMFS_DIR)/etc; \
		mkdir -p $(INITRAMFS_DIR)/proc; \
		mkdir -p $(INITRAMFS_DIR)/sys; \
		mkdir -p $(INITRAMFS_DIR)/dev; \
		cp -a $(BUSYBOX_DIR)/_install/. $(INITRAMFS_DIR)/; \
		cp $(WORKING_DIR)/initramfs_init $(INITRAMFS_DIR)/init; \
		chmod +x $(INITRAMFS_DIR)/init; \
		cd $(INITRAMFS_DIR) && find . | cpio -o -H newc | gzip > $(BUILD_DIR)/initramfs.cpio.gz; \
	fi

$(ROOTFS_DIR): $(BUILD_DIR)
	mkdir -p $(ROOTFS_DIR)

rootfs: $(ROOTFS_DIR) kernel initramfs busybox
	@if [ -f $(BUILD_DIR)/rootfs.squashfs ]; then \
		echo "[yerba] rootfs squashfs image already exists, skipping..."; \
	else \
		rm -rf $(ROOTFS_DIR); \
		mkdir -p $(ROOTFS_DIR); \
		echo "[yerba] creating rootfs..."; \
		mkdir -p $(ROOTFS_DIR)/bin; \
		mkdir -p $(ROOTFS_DIR)/sbin; \
		mkdir -p $(ROOTFS_DIR)/etc; \
		mkdir -p $(ROOTFS_DIR)/proc; \
		mkdir -p $(ROOTFS_DIR)/sys; \
		mkdir -p $(ROOTFS_DIR)/dev; \
		mkdir -p $(ROOTFS_DIR)/home; \
		mkdir -p $(ROOTFS_DIR)/var; \
		mkdir -p $(ROOTFS_DIR)/usr; \
		mkdir -p $(ROOTFS_DIR)/root; \
		mkdir -p $(ROOTFS_DIR)/mnt; \
		mkdir -p $(ROOTFS_DIR)/tmp; \
		cp -a $(BUSYBOX_DIR)/_install/. $(ROOTFS_DIR)/; \
		ln -sf sbin/init $(ROOTFS_DIR)/init; \
		echo "proc /proc proc defaults 0 0" > $(ROOTFS_DIR)/etc/fstab; \
		echo "sysfs /sys sysfs defaults 0 0" >> $(ROOTFS_DIR)/etc/fstab; \
		echo "devtmpfs /dev devtmpfs defaults 0 0" >> $(ROOTFS_DIR)/etc/fstab; \
		echo "::sysinit:/bin/mount -a" > $(ROOTFS_DIR)/etc/inittab; \
		echo "::askfirst:/bin/sh" >> $(ROOTFS_DIR)/etc/inittab; \
		echo "::ctrlaltdel:/sbin/reboot" >> $(ROOTFS_DIR)/etc/inittab; \
		echo "[yerba] creating squashfs image..."; \
		mksquashfs $(ROOTFS_DIR) $(BUILD_DIR)/rootfs.squashfs -comp zstd -noappend; \
	fi

$(BUSYBOX_DIR): $(EXTERNAL_DIR)
	@if [ -d $(BUSYBOX_DIR) ]; then \
		echo "[yerba] BusyBox already cloned, skipping..."; \
	else \
		echo "[yerba] cloning BusyBox..."; \
		git clone --depth 1 $(BUSYBOX_REPO) $(BUSYBOX_DIR); \
	fi

busybox: $(BUSYBOX_DIR) $(BUILD_DIR)
	@if [ -d $(BUSYBOX_DIR)/_install ]; then \
		echo "[yerba] BusyBox already built, skipping..."; \
	else \
		echo "[yerba] building BusyBox..."; \
		rm -f $(BUSYBOX_DIR)/.config; \
		cp $(WORKING_DIR)/busybox_config $(BUSYBOX_DIR)/.config; \
		$(MAKE) -C $(BUSYBOX_DIR) -j$(shell nproc); \
		$(MAKE) -C $(BUSYBOX_DIR) CONFIG_PREFIX=$(BUSYBOX_DIR)/_install install; \
	fi

$(LIMINE_DIR): $(EXTERNAL_DIR)
	@if [ -d $(LIMINE_DIR) ]; then \
		echo "[yerba] Limine already cloned, skipping..."; \
	else \
		echo "[yerba] cloning Limine..."; \
		git clone --depth 1 --branch=$(LIMINE_BRANCH) $(LIMINE_REPO) $(LIMINE_DIR); \
	fi

iso: kernel initramfs busybox rootfs $(LIMINE_DIR)
	@if [ -f $(ISO_PATH) ]; then \
		echo "[yerba] iso already created, skipping..."; \
	else \
		echo "[yerba] building Limine..."; \
		$(MAKE) -C $(LIMINE_DIR); \
		echo "[yerba] bootstrapping Limine and creating ISO..."; \
		mkdir -p $(ISO_ROOT)/boot/limine; \
		mkdir -p $(ISO_ROOT)/EFI/BOOT; \
		mkdir -p $(ISO_ROOT)/yerba; \
		cp $(BUILD_DIR)/bzImage $(ISO_ROOT)/boot/; \
		cp $(BUILD_DIR)/initramfs.cpio.gz $(ISO_ROOT)/boot/; \
		cp $(WORKING_DIR)/limine.conf $(ISO_ROOT)/boot/limine; \
		cp $(LIMINE_DIR)/limine-bios.sys $(LIMINE_DIR)/limine-bios-cd.bin $(LIMINE_DIR)/limine-uefi-cd.bin $(ISO_ROOT)/boot/limine; \
		cp $(LIMINE_DIR)/BOOTX64.EFI $(ISO_ROOT)/EFI/BOOT/; \
		cp $(LIMINE_DIR)/BOOTIA32.EFI $(ISO_ROOT)/EFI/BOOT/; \
		cp $(BUILD_DIR)/rootfs.squashfs $(ISO_ROOT)/yerba/; \
		xorriso -as mkisofs -R -r -J -b boot/limine/limine-bios-cd.bin -no-emul-boot -boot-load-size 4 -boot-info-table -hfsplus -apm-block-size 2048 --efi-boot boot/limine/limine-uefi-cd.bin -efi-boot-part --efi-boot-image --protective-msdos-label $(ISO_ROOT) -o $(ISO_PATH); \
		$(LIMINE_DIR)/limine bios-install $(ISO_PATH); \
	fi

clean:
	rm -rf $(EXTERNAL_DIR) $(BUILD_DIR)

run: iso
	@echo "[yerba] booting in QEMU..."
	qemu-system-x86_64 -cdrom $(ISO_PATH) -m 2G -cpu host -enable-kvm -vga std

setup: $(LINUX_DIR) $(LIMINE_DIR) $(BUSYBOX_DIR)
	@echo "[yerba] all repos fetched"