.POSIX:
.SUFFIXES:

# Path to the development kit (devkitARM) and the GBA library.
DEVKITPRO  := /opt/devkitpro
DEVKITARM  := /opt/devkitpro/devkitARM
PATH       := $(DEVKITARM)/bin:$(PATH)
LIBGBA_DIR := $(DEVKITPRO)/libgba
LIBGBA_SRC := /opt/devkitpro/libgba/include/
LIBGBA     := $(LIBGBA_DIR)/lib/libgba.a
LIBGBA     += $(LIBGBA_DIR)/lib/libfat.a
LIBGBA     += $(LIBGBA_DIR)/lib/libmm.a

# Source code location and files to watch for changes.
SRC_DIR        := src
SRC_MAIN       := $(SRC_DIR)/main.c
ASM_FILES      := $(wildcard $(SRC_DIR)/*.s)
WATCH_SRC      := $(wildcard $(SRC_DIR)/*.c)
WATCH_SRC      += $(wildcard $(SRC_DIR)/*.h)
WATCH_SRC      += $(wildcard $(SRC_DIR)/*.s)

# Output library names and executables.
TARGET         := experiments
BUILD_DIR      := build
ELF            := $(BUILD_DIR)/$(TARGET).elf
BIN            := $(BUILD_DIR)/$(TARGET).gba

# Compiler and linker configuration.
CC             := arm-none-eabi-gcc
OBJCOPY        := arm-none-eabi-objcopy
ARCH           := -mthumb -mthumb-interwork
SPECS          := -specs=gba.specs
CFLAGS         := -Wall -Wextra -pedantic -fno-strict-aliasing -Wno-incompatible-pointer-types
CFLAGS         += -mcpu=arm7tdmi -mtune=arm7tdmi $(ARCH)
CFLAGS         += -I$(LIBGBA_SRC)
LDFLAGS        := $(ARCH) $(SPECS)
LDLIBS         := $(LIBGBA)
RELEASE_CFLAGS := -DNDEBUG -O2 -g
DEBUG_CFLAGS   := -DDEBUG -O2 -g

.PHONY: clean run

# Setup debug/release builds.
#     make clean && make <target> DEBUG=0
#     make clean && make <target> DEBUG=1
DEBUG ?= 0
ifeq ($(DEBUG), 1)
    CFLAGS += $(DEBUG_CFLAGS)
else
    CFLAGS += $(RELEASE_CFLAGS)
endif

main: $(BUILD_DIR) $(BIN)

# Strip and fix header to create final .gba file.
$(BIN): $(ELF)
	$(OBJCOPY) -v -O binary $(ELF) $(BIN)
	gbafix $(BIN)

# Link files.
$(ELF): $(SRC_MAIN) $(WATCH_SRC)
	$(CC) $(CFLAGS) $(LDFLAGS) -o $(ELF) $(SRC_MAIN) $(ASM_FILES) $(LDLIBS)

# Create build directory if needed.
$(BUILD_DIR):
	mkdir -p $(BUILD_DIR)

# Test the output .gba in an emulator.
run: main
	mgba-qt $(BIN)

# Remove build directory.
clean:
	rm -r $(BUILD_DIR)