# Compile GLSL (.comp/.vert/.frag) into SPIR-V at build time.
#
# Usage:
#   simv_compile_shaders(simv_shaders
#       shaders/editor/mesh.vert
#       shaders/editor/mesh.frag
#       INCLUDES shaders
#   )
#
# Produces ${CMAKE_BINARY_DIR}/spirv/<relative_dir>/<name>.spv as a custom target.

function(simv_compile_shaders TARGET)
    cmake_parse_arguments(SCS "" "" "INCLUDES" ${ARGN})

    set(SOURCES ${SCS_UNPARSED_ARGUMENTS})
    set(SPIRV_OUT_DIR "${CMAKE_BINARY_DIR}/spirv")
    file(MAKE_DIRECTORY "${SPIRV_OUT_DIR}")

    set(SPV_OUTPUTS "")
    foreach(SRC IN LISTS SOURCES)
        get_filename_component(SHADER_NAME "${SRC}" NAME)
        file(RELATIVE_PATH REL_PATH "${CMAKE_CURRENT_SOURCE_DIR}" "${SRC}")
        get_filename_component(REL_DIR "${REL_PATH}" DIRECTORY)
        set(OUT_PATH "${SPIRV_OUT_DIR}/${REL_DIR}/${SHADER_NAME}.spv")

        get_filename_component(OUT_DIR "${OUT_PATH}" DIRECTORY)
        file(MAKE_DIRECTORY "${OUT_DIR}")

        set(INCLUDE_FLAGS "")
        foreach(INC IN LISTS SCS_INCLUDES)
            # glslangValidator requires -I<dir> with NO whitespace.
            list(APPEND INCLUDE_FLAGS "-I${INC}")
        endforeach()

        add_custom_command(
            OUTPUT  "${OUT_PATH}"
            COMMAND "${Vulkan_GLSLANG_VALIDATOR_EXECUTABLE}" -V --target-env vulkan1.3
                    ${INCLUDE_FLAGS} -o "${OUT_PATH}" "${SRC}"
            DEPENDS "${SRC}"
            COMMENT "GLSL → SPIR-V: ${REL_PATH}"
            VERBATIM
        )
        list(APPEND SPV_OUTPUTS "${OUT_PATH}")
    endforeach()

    add_custom_target(${TARGET} ALL DEPENDS ${SPV_OUTPUTS})
    set_target_properties(${TARGET} PROPERTIES
        SIMV_SPIRV_DIR "${SPIRV_OUT_DIR}"
    )
endfunction()