#
# Makefile
#
# Copyright (C) 2020 Christos Choutouridis <cchoutou@ece.auth.gr>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as
# published by the Free Software Foundation, either version 3
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#

# ========== Project settings ==========
TARGET      := matmul
SRC_DIR     := src
INC_DIR     := 
EXC_FILE    := 

# build directories
BUILD_DIR   := bin
OBJ_DIR     := $(BUILD_DIR)/obj
DEP_DIR     := $(BUILD_DIR)/.dep

# ========== Compiler settings ==========
CXX         := gcc
CPP         := gcc -E
CSIZE       := size

CFLAGS      := -std=gnu99 -Wall -Wextra
DEB_FLAGS   := -DDEBUG -g3
REL_FLAGS   := -O3
LDFLAGS     := -lm

PRE_DEFS    := 

#
# =========== Main body and Patterns ===========
#
INC         := $(foreach dir,$(INC_DIR),-I$(dir))
DEF         := $(foreach def,$(PRE_DEFS),-D$(def))

# source files
# recursive search into current and source directories
SRC         := $(wildcard *.c)
SRC         += $(foreach dir,$(SRC_DIR),$(wildcard $(dir)/*.c))
SRC         += $(foreach dir,$(SRC_DIR),$(wildcard $(dir)/**/*.c))
# exclude every file from the exclude file list
SRC         := $(filter-out $(wildcard $(EXC_FILE)),$(SRC))

OBJ         := $(foreach file,$(SRC:%.c=%.o),$(OBJ_DIR)/$(file))
DEP         := $(foreach file,$(SRC:%.c=%.d),$(DEP_DIR)/$(file))


# Make Dependencies pattern.
# This little trick enables recompilation only when dependencies change
# and it does so for changes both in source AND header files ;)
# 
# It is based on Tom Tromey's method.
# 
# Invoke cpp to create makefile rules with dependencies for each source file
$(DEP_DIR)/%.d: %.c
	@mkdir -p $(@D)
	@$(CPP) $(CFLAGS) $(INC) $(DEF) -MM -MT $(OBJ_DIR)/$(<:.c=.o) -MF $@ $<


# objects depent on .c AND dependency files, which have an empty recipe 
$(OBJ_DIR)/%.o: %.c $(DEP_DIR)/%.d
	@mkdir -p $(@D)
	$(CXX) -c $(CFLAGS) $(INC) $(DEF) -o $@ $<

# empty recipe for dependency files. This prevents make errors
$(DEP):

# now include all dependencies
# After all they are makefile dependency rules ;)
include $(wildcard $(DEP))

# main target rule
$(BUILD_DIR)/$(TARGET): $(OBJ)
	@mkdir -p $(@D)
	@echo Linking to target: $(TARGET)
	@echo $(CXX) $(LDFLAGS) -o $(@D)/$(TARGET) '$$(OBJ)'
	@$(CXX) $(LDFLAGS) -o $(@D)/$(TARGET) $(OBJ)
	@echo
	@echo Print size information
	@$(CSIZE) $(@D)/$(TARGET)
	@echo Done


.PHONY: clean
clean:
	@echo Cleaning build directories
	@rm -rf $(OBJ_DIR)
	@rm -rf $(DEP_DIR)
	@rm -rf $(BUILD_DIR)

#
# ============ User Rules =============
#

.PHONY: debug
debug: CFLAGS += $(DEB_FLAGS)
debug: $(BUILD_DIR)/$(TARGET)


.PHONY: release
release: CFLAGS += $(REL_FLAGS)
release: $(BUILD_DIR)/$(TARGET)


.PHONY: all
all: clean release