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

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

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

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

# Usage:
# $(1): Library name
# $(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