# See: https://github.com/xpack-dev-tools/riscv-none-elf-gcc-xpack/releases
# See: https://github.com/xpack-dev-tools/qemu-riscv-xpack/releases
GCC_VER  := 14.2.0-3
QEMU_VER := 8.2.6-1

SYS_TOOLPREFIX ?= riscv64-linux-gnu

GCC_PATH := toolchain/gcc/bin
LOCAL_TOOLPREFIX := $(GCC_PATH)/riscv-none-elf

# TODO: Some wildcard condition to detect prefix
TOOLPREFIX := $(LOCAL_TOOLPREFIX)
# TOOLPREFIX := $(SYS_TOOLPREFIX)

QEMU_PATH := toolchain/qemu/bin
QEMU = $(QEMU_PATH)/qemu-system-riscv64

CC = $(TOOLPREFIX)-gcc
AS = $(TOOLPREFIX)-as
LD = $(TOOLPREFIX)-ld
OBJCOPY = $(TOOLPREFIX)-objcopy
OBJDUMP = $(TOOLPREFIX)-objdump

ASFLAGS = -march=rv64gc -mabi=lp64

LDFLAGS = -Tkern/kernel.ld
LDFLAGS += -m elf64lriscv

CFLAGS = -Wall -Werror -O
CFLAGS += -Wno-unused-result
CFLAGS += -mcmodel=medany
CFLAGS += -march=rv64gc -mabi=lp64
CFLAGS += -ffreestanding
CFLAGS += -fno-common
CFLAGS += -nostdlib
CFLAGS += -mno-relax
CFLAGS += -std=gnu99

CFLAGS += -fno-stack-protector # Prevents code that needs libc / runtime support
CFLAGS += -MD # Generate header dependency files (.d)
CFLAGS += -fno-pie -no-pie # Fixed address linking
CFLAGS += -ggdb -gdwarf-2 # GDB debug info
CFLAGS += -fno-omit-frame-pointer # More reliable backtraces in GDB

CFLAGS += -I.
CFLAGS += -I./kern
CFLAGS += -I./kern/libkern

all: kern/kernel.elf
build: all

quickstart:
	make get_toolchain && bear -- make -j$(nproc) && make qemu

KERNEL_OBJ := \
	kern/entry.o \
	kern/start.o \
	kern/kalloc.o \
	kern/libkern/string.o \
	kern/libkern/proc.o \
	kern/libkern/uart.o \
	kern/libkern/panic.o \
	kern/libkern/memory.o \
	kern/libkern/spinlock.o \
	kern/libkern/mini-printf.o \
	kern/libkern/stdio.o \
	kern/libkern/badrand.o

kern/kernel.elf: $(KERNEL_OBJ)
	@echo LD $@
	@$(LD) $(LDFLAGS) -o $@ $^

%.o: %.c
	@echo CC $@
	@$(CC) $(CFLAGS) -nostdinc -I. -c $< -o $@

%.o: %.S
	@echo AS $@
	@$(AS) $(ASFLAGS) -o $@ $<

qemu: kern/kernel.elf
	@echo QEMU $<
	@$(QEMU) -machine virt -bios none -nographic -m 128M -smp 4 -kernel $<

clean:
	find . -type f -name '*.[od(elf)]' -exec rm -f {} +

format:
	find kern -type f -name '*.[ch]' -exec clang-format -i {} \;

help:
	@echo "Available targets:"
	@echo "  quickstart    – Runs get_toolchain, build and qemu in sequence. Generates compile-commands.json. RUN ONLY ONCE"
	@echo "  build         - Build the project"
	@echo "  qemu          - Run the kernel in qemu"
	@echo "  clean         – Remove build artifacts (*.o, *.d, *.elf)"
	@echo "  distclean     – Same as clean, but also purges toolchain"
	@echo "  format        – Run clang-format over all kernel sources"
	@echo "  get_toolchain – Fetchest the toolchain and extracts it into ./toolchain"
	@echo "  info          – Get some general info on toolchain versions and flags"

TOOLCHAIN_DIR := toolchain

QEMU_TARBALL := xpack-qemu-riscv-$(QEMU_VER)-linux-x64.tar.gz
GCC_TARBALL  := xpack-riscv-none-elf-gcc-$(GCC_VER)-linux-x64.tar.gz

QEMU_URL := https://github.com/xpack-dev-tools/qemu-riscv-xpack/releases/download/v$(QEMU_VER)/$(QEMU_TARBALL)
GCC_URL  := https://github.com/xpack-dev-tools/riscv-none-elf-gcc-xpack/releases/download/v$(GCC_VER)/$(GCC_TARBALL)

QEMU_TARPATH := toolchain/$(QEMU_TARBALL)
GCC_TARPATH := toolchain/$(GCC_TARBALL)

QEMU_SYM_DIR := xpack-qemu-riscv-$(QEMU_VER)
GCC_SYM_DIR  := xpack-riscv-none-elf-gcc-$(GCC_VER)

$(TOOLCHAIN_DIR):
	@mkdir -p $@

$(QEMU_TARPATH): $(TOOLCHAIN_DIR)
	@echo "Fetching qemu-riscv-xpack: v$(QEMU_VER)"
	@curl -# -L -o $@ $(QEMU_URL)

$(GCC_TARPATH): $(TOOLCHAIN_DIR)
	@echo "Fetching riscv-none-elf-gcc-xpack: v$(GCC_VER)"
	@curl -# -L -o $@ $(GCC_URL)

get_toolchain: $(TOOLCHAIN_DIR) $(GCC_TARPATH) $(QEMU_TARPATH)
	@echo "Unpacking qemu..."
	@cd toolchain && tar xf $(QEMU_TARBALL)
	@echo "Unpacking gcc..."
	@cd toolchain && tar xf $(GCC_TARBALL)
	@cd $(TOOLCHAIN_DIR) && ln -sfn $(QEMU_SYM_DIR) qemu
	@cd $(TOOLCHAIN_DIR) && ln -sfn $(GCC_SYM_DIR) gcc
	@echo "Toolchain in place, ready to make!"

distclean: clean
	rm -rf $(TOOLCHAIN_DIR)

info:
	@echo "Using qemu v$(QEMU_VER): $(QEMU)"
	@echo "Using toolchain gcc v$(GCC_VER): $(TOOLPREFIX)"
	@echo "CFLAGS:"
	@for flag in $(CFLAGS); do \
	    printf "  %s\n" "$$flag"; \
	done
	@echo "LDFLAGS:"
	@for flag in $(LDFLAGS); do \
	    printf "  %s\n" "$$flag"; \
	done

-include *.d

.PHONY: all qemu info quickstart help build