# https://www.gnu.org/software/make/manual/html_node/Setting.html
# :=	expanded variable, right-hand side can contain variables
# ?=	only set if it doesn't have a value
# !=	execute a shell script on the right-hand side and assign its result to the left-hand side

export TARGET := i686-elf

export AR := llvm-ar
export NASM := nasm
export LD := ld.lld
export CXX := clang++
export CXX_FLAGS := -std=c++20 -ffreestanding -nostdinc -fno-exceptions -fno-rtti -Wall -Wextra -O2
CXX_INCLUDE := libk
CXX_OBJ := kernel.o vga.o

# $@ is target
# $< is first dependency
# $^ is all dependencies

default: myos.bin

myos.bin: boot.o $(CXX_OBJ) libk/libk.a
	$(LD) -T linker.ld -o myos.bin boot.o $(CXX_OBJ) -Llibk -lk

boot.o: boot.asm
	$(NASM) -felf32 -o $@ $^

$(CXX_OBJ): %.o : %.cc
	$(CXX) -target $(TARGET) $(CXX_FLAGS) -I$(CXX_INCLUDE) -c $^ -o $@

libk/libk.a:
	$(MAKE) -C libk libk.a

iso: myos.bin
	mkdir -p isodir/boot/grub
	cp myos.bin isodir/boot/myos.bin
	cp grub.cfg isodir/boot/grub/grub.cfg
	grub-mkrescue -o myos.iso isodir

run: myos.bin
	qemu-system-i386 -kernel myos.bin

clean:
	rm boot.o $(CXX_OBJ) myos.bin
	$(MAKE) -C libk clean

clean-iso:
	rm -rf isodir