# Note: Your cross-compilation toolchain must be in PATH for this
# to work. Change these variables if it isn't (it should be, trust me)

.SUFFIXES:

CC := i386-elf-gcc
GDB := i386-elf-gdb
LD := i386-elf-ld
AS := nasm
IDIR := include
SRCDIR := src
BUILDDIR := build
OBJDIR := obj
DISTDIR := dist
GDB := gdb
CFLAGS := -o0 -ggdb -I $(IDIR) -Wall -pedantic -Wno-builtin-declaration-mismatch -ffreestanding
KERNEL_SOURCES := $(shell find src/kernel -name '*.c' -type f)
KERNEL_OBJS := $(KERNEL_SOURCES:.c=.o)
KERNEL_OBJS := $(subst src/,$(OBJDIR)/,$(KERNEL_OBJS))

DRIVERS_SOURCES := $(shell find src/kernel/drivers -name '*.c' -type f)
DRIVERS_OBJS := $(DRIVERS_SOURCES:.c=.o)
DRIVERS_OBJS := $(subst src/,$(OBJDIR)/,$(DRIVERS_OBJS))


BOOTLOADER_SOURCES := $(shell find src/boot -name '*.s' -type f)
BOOTLOADER_OBJS := $(BOOTLOADER_SOURCES:.s=.o)
BOOTLOADER_OBJS := $(subst src/,$(OBJDIR)/,$(BOOTLOADER_OBJS))


BUILD_PATHS := $(subst src/,$(OBJDIR),$(dir $(KERNEL_OBJS)))
BUILD_PATHS += $(subst src/,$(OBJDIR),$(dir $(DRIVERS_OBJS)))


prepare:
	mkdir -p $(BUILD_PATHS) build obj dist 


clean:
	rm -rf obj/
	rm -rf build/
	rm -rf dist/


# Produce obj/path/to/file.o in the ELF format 
# if src/path/to/file.s exists
$(OBJDIR)/%.o: prepare $(SRCDIR)/%.s
	$(AS) -f elf $(word 2,$^) -o $@


# Produce build/path/to/file.bin in the binary
# format if src/path/to/file.s exists
$(BUILDDIR)/%.bin: prepare $(SRCDIR)/%.s
	$(AS) -f bin $(word 2,$^) -o $@


# Special case for our master boot record
$(BUILDDIR)/mbr.bin: prepare $(SRCDIR)/boot/mbr.s
	$(AS) -f bin $(word 2,$^) -o $(BUILDDIR)/mbr.bin


# Produce obj/path/to/file.o using gcc if
# src/path/to/file.c exists
$(OBJDIR)/%.o: prepare $(SRCDIR)/%.c
	$(CC) $(CFLAGS) -c $(word 2,$^) -o $@


# Compile kernel drivers
drivers: $(DRIVERS_OBJS)


# Compile and link the kernel
$(BUILDDIR)/kernel.bin: $(OBJDIR)/entrypoint.o $(KERNEL_OBJS) $(DRIVERS_OBJS)
	$(LD) -o $@ -Ttext 0x1000 $^ --oformat binary

# Compile and link the kernel with debug symbols
$(BUILDDIR)/kernel.elf: $(OBJDIR)/entrypoint.o $(KERNEL_OBJS) $(DRIVERS_OBJS)
	$(LD) -o $@ -Ttext 0x1000 $^


kernel: $(BUILDDIR)/kernel.bin

# Compile the bootloader
bootloader: $(BUILDDIR)/mbr.bin


# Compile and link everything
all: bootloader drivers kernel


image: $(BUILDDIR)/mbr.bin $(BUILDDIR)/kernel.bin
	mkdir -p $(DISTDIR)/
	cat $^ > $(DISTDIR)/os.img


run: image
	qemu-system-i386 -drive format=raw,file=$(DISTDIR)/os.img,index=0,media=disk


debug: $(BUILDDIR)/kernel.elf image
	qemu-system-i386 -drive format=raw,file=$(DISTDIR)/os.img,index=0,media=disk -gdb tcp:localhost:8080 -S