LOCAL_PATH := $(dir $(lastword $(MAKEFILE_LIST)))
INSTALL_SH := $(abspath $(LOCAL_PATH)/scripts/install.sh)

all:
.PHONY: help all clean

ifneq ($(V),1)
_@ :=@
endif

INC_DIRS ?=
SRC_DIR ?= ./src
TEST_PREFIX ?= test_
OUT_DIR ?= ./out
OS := $(shell uname)

ifeq ($(DOCKER),1)
$(warning DOCKER=1 is experimential and may not work as advertised)
LLVM_DIR = $(LOCAL_PATH)llvm-docker/
LLVM_SYSTEM_INC_DIRS := /usr/local/lib/clang/8.0.0/include
else
LLVM_DIR = $(LOCAL_PATH)llvm-native/
LLVM_SYSTEM_INC_DIRS := $(LLVM_DIR)/lib/clang/8.0.0/include
endif

ifdef LLVM_DIR
CC := $(LLVM_DIR)/bin/clang
CXX := $(LLVM_DIR)/bin/clang++
LLD := $(LLVM_DIR)/bin/ld.lld
OBJ_DUMP := $(LLVM_DIR)/bin/llvm-objdump
endif

SYSTEM_INC_DIRS := \
  $(LOCAL_PATH)inc \
  $(LLVM_SYSTEM_INC_DIRS) \

C_FLAGS := \
  -Werror \
  -O2 \
  -fno-builtin \
  -std=c17 \
  $(addprefix -isystem,$(SYSTEM_INC_DIRS)) \
  $(addprefix -I,$(INC_DIRS))

CXX_FLAGS := \
  $(C_FLAGS) \
  -std=c++17 \

BPF_C_FLAGS := \
  $(C_FLAGS) \
  -target bpf \
  -fPIC \

BPF_CXX_FLAGS := \
  $(CXX_FLAGS) \
  -target bpf \
  -fPIC \
  -fomit-frame-pointer \
  -fno-exceptions \
  -fno-asynchronous-unwind-tables \
  -fno-unwind-tables \

BPF_LLD_FLAGS := \
  -z notext \
  -shared \
  --Bdynamic \
  $(LOCAL_PATH)bpf.ld \
  --entry entrypoint \

OBJ_DUMP_FLAGS := \
  -color \
  -source \
  -disassemble \

TESTFRAMEWORK_RPATH := $(abspath $(LOCAL_PATH)criterion/lib)
TESTFRAMEWORK_FLAGS := \
  -DSOL_TEST \
  -isystem $(LOCAL_PATH)criterion/include \
  -L $(LOCAL_PATH)criterion/lib \
  -rpath $(TESTFRAMEWORK_RPATH) \
  -lcriterion \

# The "-rpath" in TESTFRAMEWORK_FLAGS doesn't work in macOS so rewrite the name
# post-link.
# TODO: Find a better way
MACOS_ADJUST_TEST_DYLIB := \
$(if $(filter $(OS),Darwin),\
 $(_@)install_name_tool -change libcriterion.3.dylib $(TESTFRAMEWORK_RPATH)/libcriterion.3.dylib, \
 : \
)

TEST_C_FLAGS := \
  $(C_FLAGS) \
  $(TESTFRAMEWORK_FLAGS) \

TEST_CXX_FLAGS := \
  $(CXX_FLAGS) \
  $(TESTFRAMEWORK_FLAGS) \

help:
	@echo ''
	@echo 'BPF Program makefile'
	@echo ''
	@echo 'This makefile will build BPF Programs from C or C++ source files into ELFs'
	@echo ''
	@echo 'Assumptions:'
	@echo '  - Programs are located in the source directory: $(SRC_DIR)/<program name>'
	@echo '  - Programs are named by their directory name (eg. directory name:src/foo/ -> program name:foo)'
	@echo '  - Tests are located in their corresponding program directory and must being with "test_"'
	@echo '  - Output files will be placed in the directory: $(OUT_DIR)'
	@echo ''
	@echo 'User settings'
	@echo '  - The following setting are overridable on the command line, default values shown:'
	@echo '    - Show commands while building: V=1'
	@echo '      V=$(V)'
	@echo '    - List of include directories:'
	@echo '      INC_DIRS=$(INC_DIRS)'
	@echo '    - List of system include directories:'
	@echo '      SYSTEM_INC_DIRS=$(SYSTEM_INC_DIRS)'
	@echo '    - Location of source directories:'
	@echo '      SRC_DIR=$(SRC_DIR)'
	@echo '    - Location to place output files:'
	@echo '      OUT_DIR=$(OUT_DIR)'
	@echo '    - Location of LLVM:'
	@echo '      LLVM_DIR=$(LLVM_DIR)'
	@echo ''
	@echo 'Usage:'
	@echo '  - make help - This help message'
	@echo '  - make all - Build all the programs and tests, run the tests'
	@echo '  - make programs - Build all the programs'
	@echo '  - make tests - Build and run all tests'
	@echo '  - make dump_<program name> - Dumps the contents of the program to stdout'
	@echo '  - make <program name> - Build a single program by name'
	@echo '  - make <test name> - Build and run a single test by name'
	@echo ''
	@echo 'Available programs:'
	$(foreach name, $(PROGRAM_NAMES), @echo '  - $(name)'$(\n))
	@echo ''
	@echo 'Available tests:'
	$(foreach name, $(TEST_NAMES), @echo '  - $(name)'$(\n))
	@echo ''
	@echo 'Example:'
	@echo '  - Assuming a programed named foo (src/foo/foo.c)'
	@echo '    - make foo'
	@echo '    - make dump_foo'
	@echo ''

define C_RULE
$1: $2
	@echo "[cc] $1 ($2)"
	$(_@)mkdir -p $(dir $1)
	$(_@)$(CC) $(BPF_C_FLAGS) -o $1 -c $2 -MD -MF $(1:.o=.d)
endef

define CC_RULE
$1: $2 
	@echo "[cxx] $1 ($2)"
	$(_@)mkdir -p $(dir $1)
	$(_@)$(CXX) $(BPF_CXX_FLAGS) -o $1 -c $2 -MD -MF $(1:.o=.d)
endef

define O_RULE
$1: $2
	@echo "[llc] $1 ($2)"
	$(_@)mkdir -p $(dir $1)
	$(_@)$(LLC) $(BPF_LLC_FLAGS) -o $1 $2
endef

define SO_RULE
$1: $2
	@echo "[lld] $1 ($2)"
	$(_@)mkdir -p $(dir $1)
	$(_@)$(LLD) $(BPF_LLD_FLAGS) -o $1 $2
endef

define TEST_C_RULE
$1: $2
	@echo "[test cc] $1 ($2)"
	$(_@)mkdir -p $(dir $1)
	$(_@)$(CC) $(TEST_C_FLAGS) -o $1 $2 -MD -MF $(1:.o=.d)
	$(_@)$(MACOS_ADJUST_TEST_DYLIB) $1
endef

define TEST_CC_RULE
$1: $2
	@echo "[test cxx] $1 ($2)"
	$(_@)mkdir -p $(dir $1)
	$(_@)$(CXX) $(TEST_CXX_FLAGS) -o $1 $2 -MD -MF $(1:.o=.d)
	$(_@)$(MACOS_ADJUST_TEST_DYLIB) $1
endef

define TEST_EXEC_RULE
$1: $2
	$2$(\n)
endef

.PHONY: $(INSTALL_SH)
$(INSTALL_SH):
	$(_@)$(INSTALL_SH)

PROGRAM_NAMES := $(notdir $(basename $(wildcard $(SRC_DIR)/*)))

define \n


endef

all: programs tests

$(foreach PROGRAM, $(PROGRAM_NAMES), \
  $(eval -include $(wildcard $(OUT_DIR)/$(PROGRAM)/*.d)) \
  \
  $(eval $(PROGRAM): %: $(addprefix $(OUT_DIR)/, %.so)) \
  $(eval $(PROGRAM)_SRCS := \
    $(addprefix $(SRC_DIR)/$(PROGRAM)/, \
    $(filter-out $(TEST_PREFIX)%,$(notdir $(wildcard $(SRC_DIR)/$(PROGRAM)/*.c $(SRC_DIR)/$(PROGRAM)/*.cc))))) \
  $(eval $(PROGRAM)_OBJS := $(subst $(SRC_DIR), $(OUT_DIR), \
    $(patsubst %.c,%.o, \
    $(patsubst %.cc,%.o,$($(PROGRAM)_SRCS))))) \
	$(eval $($(PROGRAM)_SRCS): $(INSTALL_SH)) \
  $(eval $(call SO_RULE,$(OUT_DIR)/$(PROGRAM).so,$($(PROGRAM)_OBJS))) \
  $(foreach _,$(filter %.c,$($(PROGRAM)_SRCS)), \
    $(eval $(call C_RULE,$(subst $(SRC_DIR),$(OUT_DIR),$(_:%.c=%.o)),$_))) \
  $(foreach _,$(filter %.cc,$($(PROGRAM)_SRCS)), \
    $(eval $(call CC_RULE,$(subst $(SRC_DIR),$(OUT_DIR),$(_:%.cc=%.o)),$_))) \
  \
  $(eval TESTS := $(notdir $(basename $(wildcard $(SRC_DIR)/$(PROGRAM)/$(TEST_PREFIX)*.c)))) \
  $(eval $(TESTS) : %: $(addprefix $(OUT_DIR)/$(PROGRAM)/, %)) \
  $(eval TEST_NAMES := $(TEST_NAMES) $(TESTS)) \
  $(foreach TEST, $(TESTS), \
    $(eval $(TEST)_SRCS := \
      $(addprefix $(SRC_DIR)/$(PROGRAM)/, \
      $(notdir $(wildcard $(SRC_DIR)/$(PROGRAM)/$(TEST).c $(SRC_DIR)/$(PROGRAM)/$(TEST).cc)))) \
		$(eval $($(TEST)_SRCS): $(INSTALL_SH)) \
    $(foreach _,$(filter %.c,$($(TEST)_SRCS)), \
      $(eval $(call TEST_C_RULE,$(subst $(SRC_DIR),$(OUT_DIR),$(_:%.c=%)),$_))) \
    $(foreach _,$(filter %.cc, $($(TEST)_SRCS)), \
      $(eval $(call TEST_CC_RULE,$(subst $(SRC_DIR),$(OUT_DIR),$(_:%.cc=%)),$_))) \
    $(eval $(call TEST_EXEC_RULE,$(TEST),$(addprefix $(OUT_DIR)/$(PROGRAM)/, $(TEST)))) \
   ) \
)

.PHONY: $(PROGRAM_NAMES)
programs: $(PROGRAM_NAMES)

.PHONY: $(TEST_NAMES)
tests: $(TEST_NAMES)

dump_%: %
	$(_@)$(OBJ_DUMP) $(OBJ_DUMP_FLAGS) $(addprefix $(OUT_DIR)/, $(addsuffix .so, $<))

clean:
	rm -rf $(OUT_DIR)