# Copyright (c) 2026 Dominic Masters
#
# This software is released under the MIT License.
# https://opensource.org/licenses/MIT

# Asset building. Include this from the root CMakeLists.txt.
#
# Assets are registered with add_asset() and built by dusk_assets_finalize().
# Each asset is dispatched on its file extension to a handler function named
# dusk_asset_<extension> (e.g. dusk_asset_obj), defined in its own file in this
# directory. Extensions without a handler fall back to a plain copy.

include(${CMAKE_CURRENT_LIST_DIR}/copy.cmake)
include(${CMAKE_CURRENT_LIST_DIR}/obj.cmake)

# Registers an asset to be built into the project. The path is relative to the
# calling CMakeLists.txt, and is kept relative to the root assets directory in
# the output, so assets/models/a.obj ends up at <build>/assets/models/a.obj.
#
# This only records the asset. The build rules are created by
# dusk_assets_finalize() from the root CMakeLists.txt, because a custom command
# output can only be used by targets in the directory it was defined in.
function(add_asset ASSET_PATH)
  set(ASSET_SOURCE "${CMAKE_CURRENT_SOURCE_DIR}/${ASSET_PATH}")
  if(NOT EXISTS "${ASSET_SOURCE}")
    message(FATAL_ERROR "add_asset: ${ASSET_SOURCE} does not exist")
  endif()

  set_property(GLOBAL APPEND PROPERTY DUSK_ASSET_SOURCES "${ASSET_SOURCE}")
endfunction()

# Determines the lowercase extension of an asset, without the leading dot.
function(dusk_asset_extension ASSET_SOURCE OUT_VAR)
  get_filename_component(ASSET_EXT "${ASSET_SOURCE}" LAST_EXT)
  string(TOLOWER "${ASSET_EXT}" ASSET_EXT)
  string(REGEX REPLACE "^\\." "" ASSET_EXT "${ASSET_EXT}")
  set(${OUT_VAR} "${ASSET_EXT}" PARENT_SCOPE)
endfunction()

# Creates the TARGET_NAME target, which builds every asset registered with
# add_asset(). Call once from the root CMakeLists.txt after adding the assets.
function(dusk_assets_finalize TARGET_NAME)
  get_property(ASSET_SOURCES GLOBAL PROPERTY DUSK_ASSET_SOURCES)

  set(ASSET_OUTPUTS "")
  foreach(ASSET_SOURCE IN LISTS ASSET_SOURCES)
    file(RELATIVE_PATH ASSET_RELATIVE "${DUSK_ASSETS_DIR}" "${ASSET_SOURCE}")
    dusk_asset_extension("${ASSET_SOURCE}" ASSET_EXT)

    # Dispatch on the extension, falling back to a plain copy.
    set(ASSET_OUTPUT "")
    if(COMMAND dusk_asset_${ASSET_EXT})
      cmake_language(CALL dusk_asset_${ASSET_EXT}
        "${ASSET_SOURCE}" "${ASSET_RELATIVE}" ASSET_OUTPUT
      )
    else()
      message(STATUS "Asset ${ASSET_RELATIVE}: no handler for '.${ASSET_EXT}', copying")
      dusk_asset_copy("${ASSET_SOURCE}" "${ASSET_RELATIVE}" ASSET_OUTPUT)
    endif()

    list(APPEND ASSET_OUTPUTS "${ASSET_OUTPUT}")
  endforeach()

  add_custom_target(${TARGET_NAME} ALL DEPENDS ${ASSET_OUTPUTS})
endfunction()