assets_include.cmake

# credit goes to https://github.com/Lauriethefish for this
# Directory where our arbitrary asset files are stored
set(ASSETS_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/assets)
# Directory to save the object files generated by llvm-objcopy
set(ASSET_BINARIES_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/binaryAssets)
# Directory to save the prepended files to
set(PREPENDED_ASSETS_DIR ${CMAKE_CURRENT_BINARY_DIR}/prependedAssets)
set(ASSET_HEADER_PATH "${CMAKE_CURRENT_SOURCE_DIR}/include/assets.hpp")

# Define a macro which we will use for defining the symbols to access our asset files below
set(ASSET_HEADER_DATA 
"#pragma once
struct IncludedAsset {

    IncludedAsset(uint8_t* start, uint8_t* end) : array(reinterpret_cast<Array<uint8_t>*>(start)) {
        array->klass = nullptr;
        array->monitor = nullptr;
        array->bounds = nullptr;
        array->max_length = end - start - 32;
    }
    
    operator ArrayW<uint8_t>() const {
        init();
        return array;
    }

    operator std::string_view() const {
        return { reinterpret_cast<char*>(array->_values), array->get_Length() };
    }
    
    operator std::span<uint8_t>() const {
        return { array->_values, array->get_Length() };
    }

    void init() const {
        if(!array->klass)
            array->klass = classof(Array<uint8_t>*);
    }

    private:
        Array<uint8_t>* array;

};

#define DECLARE_FILE(name)                         \\
    extern \"C\" uint8_t _binary_##name##_start[];  \\
    extern \"C\" uint8_t _binary_##name##_end[];    \\
    const IncludedAsset name { _binary_##name##_start, _binary_##name##_end};

namespace IncludedAssets {
\n")

if (EXISTS ${ASSETS_DIRECTORY}) 
    file(MAKE_DIRECTORY ${ASSET_BINARIES_DIRECTORY})
    file(MAKE_DIRECTORY ${PREPENDED_ASSETS_DIR})
    file(GLOB ASSETS LIST_DIRECTORIES false ${ASSETS_DIRECTORY}/*)

    # Iterate through each file in the assets directory. TODO: This could be recursive
    foreach(FILE IN LISTS ASSETS)
        message("-- Including asset: ${FILE}")
        get_filename_component(ASSET ${FILE} NAME) # Find the asset's file name

        # make a copy of the file with 32 bytes added in the build dir
        add_custom_command(
            OUTPUT ${PREPENDED_ASSETS_DIR}/${ASSET}
            COMMAND ${CMAKE_COMMAND} -E echo_append "                                " > ${PREPENDED_ASSETS_DIR}/${ASSET}
            COMMAND ${CMAKE_COMMAND} -E cat ${ASSETS_DIRECTORY}/${ASSET} >> ${PREPENDED_ASSETS_DIR}/${ASSET}
            DEPENDS ${ASSETS_DIRECTORY}/${ASSET}
        )

        set(OUTPUT_FILE "${ASSET_BINARIES_DIRECTORY}/${ASSET}.o") # Save our asset in the asset binaries directory

        # Use llvm-objcopy to create an object file that stores our binary asset
        # The resulting file contains 3 symbols: _binary_<file_name>_start, _binary_<file_name>_size and _binary_<file_name>_end
        # We only use the first two
        add_custom_command(
                OUTPUT ${OUTPUT_FILE}
                COMMAND ${CMAKE_OBJCOPY} ${ASSET} ${OUTPUT_FILE} --input-target binary --output-target elf64-aarch64 --set-section-flags binary=strings
                DEPENDS ${PREPENDED_ASSETS_DIR}/${ASSET}
                WORKING_DIRECTORY ${PREPENDED_ASSETS_DIR}
        )
        list(APPEND BINARY_ASSET_FILES ${OUTPUT_FILE})

        # Find the correct objcopy symbol name, this is always the file name with any non-alphanumeric characters replaced with _
        string(REGEX REPLACE "[^a-zA-Z0-9]" "_" FIXED_ASSET ${ASSET})
        # Add to our assets header
        set(ASSET_HEADER_DATA "${ASSET_HEADER_DATA}\tDECLARE_FILE(${FIXED_ASSET})\n")
    endforeach()
    set(ASSET_HEADER_DATA "${ASSET_HEADER_DATA}\n}\n")

    # check if at least 1 asset file, otherwise ignore
    list(LENGTH BINARY_ASSET_FILES COUNT)
    if (${COUNT} GREATER 0)
        # Generate the assets header file
        file(GENERATE OUTPUT ${ASSET_HEADER_PATH} CONTENT "${ASSET_HEADER_DATA}")

        # Add our assets files to the final SO
        add_library(asset_files OBJECT ${BINARY_ASSET_FILES})
        set_target_properties(asset_files PROPERTIES LINKER_LANGUAGE CXX)
        target_link_libraries(${COMPILE_ID} PRIVATE asset_files ${BINARY_ASSET_FILES})
    endif()
else()
    message("-- Removing '${ASSET_HEADER_PATH}' as no assets have been found in '${ASSETS_DIRECTORY}'")
    file(REMOVE ${ASSET_HEADER_PATH})
endif()