# Variables to override
#
# CC            C compiler
# CROSSCOMPILE	crosscompiler prefix, if any
# CFLAGS	compiler flags for compiling all C files
# ERL_CFLAGS	additional compiler flags for files using Erlang header files
# ERL_EI_LIBDIR path to libei.a
# LDFLAGS	linker flags for linking all binaries
# ERL_LDFLAGS	additional linker flags for projects referencing Erlang libraries

# Check that we're on a supported build platform
ifeq ($(CROSSCOMPILE),)
    # Not crosscompiling, so check that we're on Linux.
    ifneq ($(shell uname -s),Linux)
        $(warning input_event only works on Linux, but crosscompilation)
        $(warning is supported by defining $$CROSSCOMPILE, $$ERL_EI_INCLUDE_DIR,)
        $(warning and $$ERL_EI_LIBDIR. See Makefile for details. If using Nerves,)
        $(warning this should be done automatically.)
        $(warning .)
        $(warning Skipping C compilation unless targets explicitly passed to make.)
	  DEFAULT_TARGETS = priv
    endif
endif

DEFAULT_TARGETS ?= priv priv/input_event

# The paths to the EI library and header files are either passed in when
# compiled by Nerves (crosscompiled builds) or determined by mix.exs for
# host builds.
ifeq ($(ERL_EI_INCLUDE_DIR),)
$(error ERL_EI_INCLUDE_DIR not set. Invoke via mix)
endif
ifeq ($(ERL_EI_LIBDIR),)
$(error ERL_EI_LIBDIR not set. Invoke via mix)
endif

# Set Erlang-specific compile and linker flags
ERL_CFLAGS ?= -I$(ERL_EI_INCLUDE_DIR)
ERL_LDFLAGS ?= -L$(ERL_EI_LIBDIR) -lei

LDFLAGS +=
CFLAGS += -std=gnu99

# If not cross-compiling, then run sudo by default
ifeq ($(origin CROSSCOMPILE), undefined)
SUDO_ASKPASS ?= /usr/bin/ssh-askpass
SUDO ?= sudo
else
# If cross-compiling, then permissions need to be set some build system-dependent way
SUDO ?= true
endif

# Enable for debug messages
#CFLAGS += -DDEBUG

SRC=$(wildcard src/*.c)
OBJ=$(SRC:.c=.o)

.PHONY: all clean

all: priv priv/input_event

%.o: %.c
	$(CC) -c $(ERL_CFLAGS) $(CFLAGS) -o $@ $<

priv:
	mkdir -p priv

priv/input_event: $(OBJ)
	$(CC) $^ $(ERL_LDFLAGS) $(LDFLAGS) -o $@
	# For host builds, setuid root the input_event binary so that it can read /dev/input/event*
	SUDO_ASKPASS=$(SUDO_ASKPASS) $(SUDO) -- sh -c 'chown root:root $@; chmod +s $@'

clean:
	rm -f priv/input_event src/*.o