# Usage:
# $(1): Target prefix
#
# Generate build rules for files in variable <PREFIX>_SRCS. Use <PREFIX>_CFLAGS,
# <PREFIX>_CXXFLAGS, <PREFIX>_ASFLAGS to control build flags.
# Object files will be put into $BUILDDIR
# E.g: 
# $(eval $(call COMPILE_RULES,AM_))
define COMPILE_RULES
$(1)OBJS += $$(addprefix $$(BUILDDIR)/, $$(addsuffix .o, $$($(1)SRCS)))
### Rule (compile): a single `.c` -> `.c.o` (gcc)
$$(filter %.c.o, $$($(1)OBJS)): $$(BUILDDIR)/%.c.o: %.c
	@mkdir -p $$(dir $$@) && echo + CC $$<
	@$$(CC) $$($(1)CFLAGS) -c -o $$@ $$(realpath $$<)

### Rule (compile): a single `.cc` -> `.cc.o` (g++)
$$(filter %.cc.o, $$($(1)OBJS)): $$(BUILDDIR)/%.cc.o: %.cc
	@mkdir -p $$(dir $$@) && echo + CXX $$<
	@$$(CXX) $$($(1)CXXFLAGS) -c -o $$@ $$(realpath $$<)

### Rule (compile): a single `.cpp` -> `.cpp.o` (g++)
$$(filter %.cpp.o, $$($(1)OBJS)): $$(BUILDDIR)/%.cpp.o: %.cpp
	@mkdir -p $$(dir $$@) && echo + CXX $$<
	@$$(CXX) $$($(1)CXXFLAGS) -c -o $$@ $$(realpath $$<)

### Rule (compile): a single `.S` -> `.S.o` (gcc, which preprocesses and calls as)
$$(filter %.S.o, $$($(1)OBJS)): $$(BUILDDIR)/%.S.o: %.S
	@mkdir -p $$(dir $$@) && echo + AS $$<
	@$$(AS) $$($(1)ASFLAGS) -c -o $$@ $$(realpath $$<)

### Rule (`#include` dependencies): paste in `.d` files generated by gcc on `-MMD`
-include $$(addprefix $$(BUILDDIR)/, $$(addsuffix .d, $$(filter %.c %.cc, $$($(1)SRCS))))
endef

# Usage:
# $(1): Library build path
# $(2): Library variable prefix
# E.g: 
# $(eval $(call ADD_LIBRARY,am-riscv,AM_))
define ADD_LIBRARY
$(eval $(call COMPILE_RULES,$(2)))
$(1): $$($(2)OBJS) 
	@mkdir -p $$(dir $$@)
	@echo + AR "->" $$(patsubst $$(CURDIR)/%,%,$(1))
	@$$(AR) rcs $$@ $$($(2)OBJS)
endef

# Usage:
# $(1): Image build path
# $(2): Image variable prefix
# E.g: 
# $(eval $(call ADD_IMAGE,dummy,DUMMY_))
define ADD_IMAGE
$(eval $(call COMPILE_RULES,$(2)))
$(1).elf: $$($(2)OBJS) 
	@mkdir -p $$(dir $$@)
	@echo + LD "->" $$(patsubst $$(CURDIR)/%,%,$(1).elf)
	@$$(LD) -o $$@ $$(filter-out -l%,$$($(2)LDFLAGS)) --start-group $$($(2)OBJS) $$(filter -l%,$$($(2)LDFLAGS)) --end-group  
$(1).bin: $(1).elf
	@echo + OBJCOPY "->" $$(patsubst $$(CURDIR)/%,%,$(1).bin)
	@$$(OBJCOPY) -S --set-section-flags .bss=alloc,contents -O binary $(1).elf $(1).bin
endef