#
# Makefile for utl Unit test
#
# Copyright (C) 2019-2020 Christos Choutouridis <christos@choutouridis.net>
#
# 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/>.
#

#   ult notes:
# ==============
# This makefile provides support for unix-like local builds and
# docker based builds for gcc and clang.
# ** msvc is not currently supported.
#
# Use cases:
# 1) build localy using **local rules** in terminal.
#    example: 
#       make -j4 MK_ARG="-std=c++14 -fconcepts" build-gcc
#
# 2) build localy using **docker based rules** via terminal or script
#    in order to compile for all compilers/versions/dialects.
#    example in bash:
#       #!/bin/bash
#       for im in gcc:8 gcc:9 gcc:10; do
#          for dial in -std=c++14 -std=c++17; do
#             make IMAGE="$im" MK_ARG="$dial" dock-gcc
#          done
#       done
#
# 3) build inside a docker instance using **local rules** in order to
#    build and test using a CD/CI system.
#    example in a yml file:
#       image: gcc:8
#       build:
#          stage: build
#          - make MK_ARG="-std=c++14" build-gcc
#          - make MK_ARG="-std=c++14 -fconcepts" build-gcc
#          - make MK_ARG="-std=c++17" build-gcc
#          - make MK_ARG="-std=c++17 -fconcepts" build-gcc
#          - make MK_ARG="-std=c++2a" build-gcc
#          ... etc
#       test:
#          stage: test
#          - bin/utlTest
#          ... etc


# ============== Project settings ==============
# Project's name
PROJECT         := utl
# Excecutable's name
TARGET          := utlTest
# Source directories list(space seperated).
# Relative path, under current directory only
SRC_DIR_LIST    := tests gtest
# Include directories list(space seperated).
# Relative path
INC_DIR_LIST    := ../include gtest
# Exclude files list(space seperated). Filenames only.
# EXC_FILE_LIST := bad.cpp old.cpp

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

# ============== Compiler settings ==============
CLANGXX         := clang++
GCCXX           := g++
CSIZE           := size
# Compiler flags for debug and release
DEB_CFLAGS      := -DDEBUG -g3 -Wall -Wextra
REL_CFLAGS      := -Wall -Wextra -O2
# Pre-defines
# PRE_DEFS := MYCAB=1729 SUPER_MODE

# ============== Linker settings ==============
# Linker flags
LDFLAGS         := -pthread
# Map output file
MAP_FILE        := output.map
MAP_FLAG        := -Xlinker -Map=$(BUILD_DIR)/$(MAP_FILE)

# ============== Docker settings ==============
# We need:
#  1) Bind the entire project directory(the dir that icludes all the code) as volume.
#  2) In docker instance change to working directory(where the makefile is). 
# For utl we use the directories `${PWD%/*}` and `test`.
# We double-$$ for double evaluating.
DOCKER_VOL_DIR  := "$${PWD%/*}"
DOCKER_WRK_DIR  := test
DOCKER_RUN      := docker run --rm -v $(DOCKER_VOL_DIR):/usr/src/$(PROJECT) -w /usr/src/$(PROJECT)/$(DOCKER_WRK_DIR)

# ============== Default settings ==============
# compiler and compiler flags. By default docker is not used.
CFLAGS          := $(DEB_CFLAGS)
CXX             := $(GCCXX)
DOCKER          := 

#
# =========== Main body and Patterns ===========
#
ifeq ($(OS), Windows_NT)
	TARGET := $(TARGET).exe
endif
INC     := $(foreach dir,$(INC_DIR_LIST),-I$(dir))
DEF     := $(foreach def,$(PRE_DEFS),-D$(def))
EXC     := $(foreach fil,$(EXC_FILE_LIST),                              \
               $(foreach dir,$(SRC_DIR_LIST),$(wildcard $(dir)/$(fil))) \
           )
# source files, object and dependencies list
# recursive search into current and source directories
SRC     := $(wildcard *.cpp)
SRC     += $(foreach dir,$(SRC_DIR_LIST),$(wildcard $(dir)/*.cpp))
SRC     += $(foreach dir,$(SRC_DIR_LIST),$(wildcard $(dir)/**/*.cpp))
#SRC     := $(abspath $(filter-out $(EXC),$(SRC)))
SRC     := $(filter-out $(EXC),$(SRC))

OBJ     := $(foreach file,$(SRC:%.cpp=%.o),$(OBJ_DIR)/$(file))
DEP     := $(foreach file,$(SRC:%.cpp=%.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: %.cpp
	@mkdir -p $(@D)
	@$(DOCKER) $(CXX) -E $(CFLAGS) $(INC) $(DEF) -MM -MT $(OBJ_DIR)/$(<:.cpp=.o) -MF $@ $<

# objects depent on .cpp AND dependency files, which have an empty recipe 
$(OBJ_DIR)/%.o: %.cpp $(DEP_DIR)/%.d
	@mkdir -p $(@D)
	$(DOCKER) $(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 $(DOCKER) $(CXX) $(LDFLAGS) $(MAP_FLAG) -o $(@D)/$(TARGET) '$$(OBJ)'
	@$(DOCKER) $(CXX) $(LDFLAGS) $(MAP_FLAG) -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)


#
# ================ Local build rules =================
# examples:
# make MK_ARG="-std=c++14 -fconcepts" build-gcc
# make MK_ARG="-std=c++17" build-clang
#
.PHONY: build-gcc
build-gcc: CFLAGS += $(MK_ARG)
build-gcc: $(BUILD_DIR)/$(TARGET)

.PHONY: build-clang
build-clang: CXX := $(CLANGXX)
build-clang: CFLAGS += $(MK_ARG)
build-clang: $(BUILD_DIR)/$(TARGET)

.PHONY: debug
debug: $(BUILD_DIR)/$(TARGET)

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

.PHONY: all
all: clean release

#
# ================ Docker based rules ================ 
# examples:
# make IMAGE="gcc:8.3" MK_ARG="-std=c++14 -fconcepts" dock-gcc
# make IMAGE="a-clang-image" MK_ARG="-std=c++17" dock-clang
#
.PHONY: dock-gcc
dock-gcc: DOCKER := $(DOCKER_RUN) $(IMAGE)
dock-gcc: CFLAGS += $(MK_ARG)
dock-gcc: $(BUILD_DIR)/$(TARGET)

.PHONY: dock-clang
dock-clang: CXX := $(CLANGXX)
dock-clang: DOCKER := $(DOCKER_RUN) $(IMAGE)
dock-clang: CFLAGS += $(MK_ARG)
dock-clang: $(BUILD_DIR)/$(TARGET)