DEFAULT_HOST:=i686-elf
HOST?=DEFAULT_HOST
HOSTARCH:=i386

CFLAGS?= -O2 -g
CPPFLAGS?=
LDFLAGS?=
LIBS?=

DESTDIR?=
PREFIX?=/usr/local
EXEC_PREFIX?=$(PREFIX)
BOOTDIR?=$(EXEC_PREFIX)/boot
INCLUDEDIR?=$(PREFIX)/include

CFLAGS:=$(CFLAGS) -ffreestanding -Wall -Wextra
CPPFLAGS:=$(CPPFLAGS) -D__is_kernel -Iinclude
LDFLAGS:=$(LDFLAGS)
LIBS:=$(LIBS) -nostdlib -lgcc

ARCHDIR=arch/$(HOSTARCH)

include $(ARCHDIR)/make.config

CFLAGS:=$(CFLAGS) $(KERNEL_ARCH_CFLAGS)
CPPFLAGS:=$(CPPFLAGS) $(KERNEL_ARCH_CPPFLAGS)
LDFLAGS:=$(LDFLAGS) $(KERNEL_ARCH_LDFLAGS)
LIBS:=$(LIBS) $(KERNEL_ARCH_LIBS)

KERNEL_OBJS=           \
$(KERNEL_ARCH_OBJS)    \
kernel/utils.o         \
kernel/serial.o        \
kernel/gdt.o           \
kernel/idt.o           \
kernel/kernel.o        

OBJS=\
$(ARCHDIR)/crti.o     \
$(ARCHDIR)/crtbegin.o \
$(KERNEL_OBJS)        \
$(ARCHDIR)/crtend.o   \
$(ARCHDIR)/crtn.o

LINK_LIST=\
$(LDFLAGS)            \
$(ARCHDIR)/crti.o     \
$(ARCHDIR)/crtbegin.o \
$(KERNEL_OBJS)        \
$(LIBS)               \
$(ARCHDIR)/crtend.o   \
$(ARCHDIR)/crtn.o

.PHONY: all clean install install-headers install-kernel
.SUFFIXES: .o .c .s

all: red.kernel

red.kernel: $(OBJS) $(ARCHDIR)/linker.ld
	$(CC) -T $(ARCHDIR)/linker.ld -o $@ $(CFLAGS) $(LINK_LIST)

$(ARCHDIR)/crtbegin.o $(ARCHDIR)/crtend.o:
	OBJ=`$(CC) $(CFLAGS)  $(LDFLAGS) -print-file-name=$(@F)` && cp "$$OBJ" $@
	
$(ARCHDIR)/gdt.o:
	nasm -f elf $(ARCHDIR)/gdt.s
		
.c.o:
	$(CC) -MD -c $< -o $@ -std=gnu11 $(CFLAGS) $(CPPFLAGS)
.s.o:
	$(CC) -MD -c $< -o $@ $(CFLAGS) $(CPPFLAGS)
		
clean:
	rm -f red.kernel
	rm -f $(OBJS) *.o */*.o */*/*.o
	rm -f $(OBJS:.o=.d) *.d */*.d */*/*.d

install: install-headers install-kernel gen-iso

install-headers:
	mkdir -p $(DESTDIR)$(INCLUDEDIR)
	cp -R --preserve=timestamps include/. $(DESTDIR)$(INCLUDEDIR)/.
	
install-kernel: red.kernel
	mkdir -p $(DESTDIR)$(BOOTDIR)
	cp red.kernel $(DESTDIR)$(BOOTDIR)
	
gen-iso: 
	rm -f red.iso 
	cp red.kernel iso/boot/kernel.elf 
	genisoimage -R                    \
		-b boot/grub/stage2_eltorito  \
		-no-emul-boot                 \
		-A ProjectRED                 \
		-input-charset utf8           \
		-quiet                        \
		-boot-info-table              \
		-o red.iso                    \
		iso
	
-include $(OBJS:.o=.d)