# - Precompilation of Vala/Genie source files into C sources
# Makes use of the parallel build ability introduced in Vala 0.11.
# Filenames must be unique within a single compilation unit and that's fine.
# Props to other Vala module writers, I had to reengineer it to understand it.
#
#   vala_precompile (source... - .vala, .gs, .vapi
#     [DIRECTORY dir]          - Output directory (binary dir by default)
#     [PACKAGES package...]    - Package dependencies
#     [OPTIONS option...]      - Extra valac options
#     [OUTPUTS outputs_var]    - Output C sources
#     [HEADER id.h             - Generate id.h and id_internal.h
#       [VAPI id.vapi]         - Generate a vapi file
#       [SYMBOLS id.def]])     - Generate a list of public symbols
#

#=============================================================================
# Copyright (c) 2011, 2016, Přemysl Eric Janouch <p@janouch.name>
#
# Permission to use, copy, modify, and/or distribute this software for any
# purpose with or without fee is hereby granted.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
# SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
# OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
# CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
#=============================================================================

cmake_minimum_required (VERSION 2.8.0)
find_package (Vala 0.11 REQUIRED)
include (CMakeParseArguments)

macro (_vala_parse_source_path)
	get_filename_component (basename          "${file}" NAME)
	get_filename_component (without_extension "${file}" NAME_WE)
	set (output_vapi "${directory}/${without_extension}.vapi")
	set (output_c    "${directory}/${without_extension}.c")
endmacro ()

function (_vala_make_fast file)
	_vala_parse_source_path ()

	# See `cmake --help-policy CMP0058` for a rather nice explanation
	set (_stamp "${output_vapi}")
	set (_byproducts)
	if (NOT "${CMAKE_VERSION}" VERSION_LESS "3.0.2")
		set (_stamp "${output_vapi}.stamp")
		set (_byproducts BYPRODUCTS "${output_vapi}")
		set (stamp_target ${stamp_target} "${_stamp}" PARENT_SCOPE)
	endif ()

	add_custom_command (OUTPUT "${_stamp}"
		${_byproducts}
		COMMAND ${VALA_COMPILER} "${file}" "--fast-vapi=${output_vapi}"
		COMMAND ${CMAKE_COMMAND} -E touch "${_stamp}"
		DEPENDS "${file}"
		COMMENT "Generating a fast vapi for ${basename}" VERBATIM)
	set (fast_vapi_deps ${fast_vapi_deps} "${output_vapi}" PARENT_SCOPE)
	set (fast_vapi_args ${fast_vapi_args}
		"--use-fast-vapi=${output_vapi}" PARENT_SCOPE)
endfunction ()

function (_vala_make_c file)
	_vala_parse_source_path ()

	# We need to filter the current file back out or else it creates conflicts
	set (_fast_vapis ${fast_vapi_args})
	list (REMOVE_ITEM _fast_vapis "--use-fast-vapi=${output_vapi}")

	add_custom_command (OUTPUT "${output_c}"
		COMMAND ${VALA_COMPILER} "${file}" -C ${compiler_args} ${_fast_vapis}
		COMMAND ${CMAKE_COMMAND} -E touch "${output_c}"
		DEPENDS "${file}" ${fast_vapi_deps} ${vapis} ${stamp_target}
		WORKING_DIRECTORY "${directory}"
		COMMENT "Precompiling ${basename}" VERBATIM)
	set (c_outputs ${c_outputs} "${output_c}" PARENT_SCOPE)
endfunction ()

set (_vala_counter 0)
function (vala_precompile)
	# So that the user doesn't need to name any targets, we can do it ourselves
	math (EXPR counter "${_vala_counter} + 1")
	set (_vala_counter "${counter}" PARENT_SCOPE)

	set (_single_value DIRECTORY OUTPUTS HEADER VAPI SYMBOLS)
	set (_multi_value PACKAGES OPTIONS)
	cmake_parse_arguments (arg "" "${_single_value}" "${_multi_value}" ${ARGN})

	set (directory ${CMAKE_CURRENT_BINARY_DIR})
	if (arg_DIRECTORY)
		set (directory ${arg_DIRECTORY})
		if (NOT IS_DIRECTORY ${directory})
			file (MAKE_DIRECTORY ${directory})
		endif (NOT IS_DIRECTORY ${directory})
	endif ()

	set (sources)
	set (vapis)
	foreach (_source ${arg_UNPARSED_ARGUMENTS})
		if (NOT IS_ABSOLUTE "${_source}")
			set (_source "${CMAKE_CURRENT_SOURCE_DIR}/${_source}")
		endif ()
		if (${_source} MATCHES "\\.vapi$")
			list (APPEND vapis "${_source}")
		else ()
			list (APPEND sources "${_source}")
		endif ()
	endforeach ()

# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

	set (fast_vapi_deps)
	set (fast_vapi_args)
	set (stamp_target)
	foreach (_source ${sources})
		_vala_make_fast ("${_source}")
	endforeach ()

	# The target is actually required, or else it may trigger CMP0058
	if (stamp_target)
		add_custom_target ("vala_fast_vapis_${counter}" DEPENDS ${stamp_target})
		set (stamp_target "vala_fast_vapis_${counter}")
	endif ()

	set (compiler_args)
	foreach (_pkg ${arg_PACKAGES})
		list (APPEND compiler_args "--pkg=${_pkg}")
	endforeach ()
	list (APPEND compiler_args ${arg_OPTIONS} ${vapis})

	set (c_outputs)
	foreach (_source ${sources})
		_vala_make_c ("${_source}")
	endforeach ()
	if (arg_OUTPUTS)
		set (${arg_OUTPUTS} ${c_outputs} PARENT_SCOPE)
	endif (arg_OUTPUTS)

# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

	set (extra_outputs)
	if (arg_VAPI)
		if (NOT IS_ABSOLUTE "${arg_VAPI}")
			set (arg_VAPI "${directory}/${arg_VAPI}")
		endif ()
		list (APPEND extra_outputs "${arg_VAPI}")
		list (APPEND compiler_args "--internal-vapi=${arg_VAPI}")
		if (NOT arg_HEADER)
			message (FATAL_ERROR "HEADER generation required for vapi")
		endif ()
	endif ()
	if (arg_SYMBOLS)
		if (NOT IS_ABSOLUTE "${arg_SYMBOLS}")
			set (arg_SYMBOLS "${directory}/${arg_SYMBOLS}")
		endif ()
		list (APPEND extra_outputs "${arg_SYMBOLS}")
		list (APPEND compiler_args "--symbols=${arg_SYMBOLS}")
		if (NOT arg_HEADER)
			message (FATAL_ERROR "HEADER generation required for symbols")
		endif ()
	endif ()
	if (arg_HEADER)
		if (NOT IS_ABSOLUTE "${arg_HEADER}")
			set (arg_HEADER "${directory}/${arg_HEADER}")
		endif ()
		get_filename_component (header_path "${arg_HEADER}" PATH)
		get_filename_component (header_name "${arg_HEADER}" NAME_WE)
		set (header_base "${header_path}/${header_name}")
		get_filename_component (header_ext "${arg_HEADER}" EXT)

		list (APPEND extra_outputs
			"${header_base}${header_ext}"
			"${header_base}_internal${header_ext}")
		list (APPEND compiler_args
			"--header=${header_base}${header_ext}"
			"--internal-header=${header_base}_internal${header_ext}")
	endif ()
	if (extra_outputs)
		add_custom_command (OUTPUT ${extra_outputs}
			COMMAND ${VALA_COMPILER} -C ${compiler_args} ${fast_vapi_args}
			DEPENDS ${fast_vapi_deps} ${vapis}
			COMMENT "Generating vapi/headers/symbols" VERBATIM)
	endif ()
endfunction ()