include(CMakeParseArguments)

# Generates the resource XML controlling file from resource list (and saves it
# to xml_path). It's not recommended to use this function directly, since it
# doesn't handle invalid arguments. It is used by the function
# COMPILE_GRESOURCES() to create a custom command, so that this function is
# invoked at build-time in script mode from CMake.
function(GENERATE_GXML xml_path)
    # Available options:
    # COMPRESS_ALL, NO_COMPRESS_ALL       Overrides the COMPRESS flag in all
    #                                     registered resources.
    # STRIPBLANKS_ALL, NO_STRIPBLANKS_ALL Overrides the STRIPBLANKS flag in all
    #                                     registered resources.
    # TOPIXDATA_ALL, NO_TOPIXDATA_ALL     Overrides the TOPIXDATA flag in all
    #                                     registered resources.
    set(GXML_OPTIONS COMPRESS_ALL NO_COMPRESS_ALL
                     STRIPBLANKS_ALL NO_STRIPBLANKS_ALL
                     TOPIXDATA_ALL NO_TOPIXDATA_ALL)

    # Available one value options:
    # PREFIX     Overrides the resource prefix that is prepended to each
    #            relative file name in registered resources.
    set(GXML_ONEVALUEARGS PREFIX)

    # Available multi-value options:
    # RESOURCES The list of resource files. Whether absolute or relative path is
    #           equal, absolute paths are stripped down to relative ones. If the
    #           absolute path is not inside the given base directory SOURCE_DIR
    #           or CMAKE_CURRENT_SOURCE_DIR (if SOURCE_DIR is not overriden),
    #           this function aborts.
    set(GXML_MULTIVALUEARGS RESOURCES)

    # Parse the arguments.
    cmake_parse_arguments(GXML_ARG
                          "${GXML_OPTIONS}"
                          "${GXML_ONEVALUEARGS}"
                          "${GXML_MULTIVALUEARGS}"
                          "${ARGN}")

    # Variable to store the double-quote (") string. Since escaping
    # double-quotes in strings is not possible we need a helper variable that
    # does this job for us.
    set(Q \")

    # Process resources and generate XML file.
    # Begin with the XML header and header nodes.
    set(GXML_XML_FILE "<?xml version=${Q}1.0${Q} encoding=${Q}UTF-8${Q}?>")
    set(GXML_XML_FILE "${GXML_XML_FILE}<gresources><gresource prefix=${Q}")

    # Set the prefix for the resources. Depending on the user-override we choose
    # the standard prefix "/" or the override.
    if (GXML_ARG_PREFIX)
        set(GXML_XML_FILE "${GXML_XML_FILE}${GXML_ARG_PREFIX}")
    else()
        set(GXML_XML_FILE "${GXML_XML_FILE}/")
    endif()

    set(GXML_XML_FILE "${GXML_XML_FILE}${Q}>")

    # Process each resource.
    foreach(res ${GXML_ARG_RESOURCES})
        if ("${res}" STREQUAL "COMPRESS")
            set(GXML_COMPRESSION_FLAG ON)
        elseif ("${res}" STREQUAL "STRIPBLANKS")
            set(GXML_STRIPBLANKS_FLAG ON)
        elseif ("${res}" STREQUAL "TOPIXDATA")
            set(GXML_TOPIXDATA_FLAG ON)
        else()
            # The file name.
            set(GXML_RESOURCE_PATH "${res}")

            # Append to real resource file dependency list.
            list(APPEND GXML_RESOURCES_DEPENDENCIES ${GXML_RESOURCE_PATH})

            # Assemble <file> node.
            set(GXML_RES_LINE "<file")
            if ((GXML_ARG_COMPRESS_ALL OR GXML_COMPRESSION_FLAG) AND NOT
                    GXML_ARG_NO_COMPRESS_ALL)
                set(GXML_RES_LINE "${GXML_RES_LINE} compressed=${Q}true${Q}")
            endif()

            # Check preprocess flag validity.
            if ((GXML_ARG_STRIPBLANKS_ALL OR GXML_STRIPBLANKS_FLAG) AND
                    (GXML_ARG_TOPIXDATA_ALL OR GXML_TOPIXDATA_FLAG))
                set(GXML_ERRMSG "Resource preprocessing option conflict. Tried")
                set(GXML_ERRMSG "${GXML_ERRMSG} to specify both, STRIPBLANKS")
                set(GXML_ERRMSG "${GXML_ERRMSG} and TOPIXDATA. In resource")
                set(GXML_ERRMSG "${GXML_ERRMSG} ${GXML_RESOURCE_PATH} in")
                set(GXML_ERRMSG "${GXML_ERRMSG} function COMPILE_GRESOURCES.")
                message(FATAL_ERROR ${GXML_ERRMSG})
            endif()

            if ((GXML_ARG_STRIPBLANKS_ALL OR GXML_STRIPBLANKS_FLAG) AND NOT
                    GXML_ARG_NO_STRIPBLANKS_ALL)
                set(GXML_RES_LINE "${GXML_RES_LINE} preprocess=")
                set(GXML_RES_LINE "${GXML_RES_LINE}${Q}xml-stripblanks${Q}")
            elseif((GXML_ARG_TOPIXDATA_ALL OR GXML_TOPIXDATA_FLAG) AND NOT
                       GXML_ARG_NO_TOPIXDATA_ALL)
                set(GXML_RES_LINE "${GXML_RES_LINE} preprocess=")
                set(GXML_RES_LINE "${GXML_RES_LINE}${Q}to-pixdata${Q}")
            endif()

            set(GXML_RES_LINE "${GXML_RES_LINE}>${GXML_RESOURCE_PATH}</file>")

            # Append to file string.
            set(GXML_XML_FILE "${GXML_XML_FILE}${GXML_RES_LINE}")

            # Unset variables.
            unset(GXML_COMPRESSION_FLAG)
            unset(GXML_STRIPBLANKS_FLAG)
            unset(GXML_TOPIXDATA_FLAG)
        endif()

    endforeach()

    # Append closing nodes.
    set(GXML_XML_FILE "${GXML_XML_FILE}</gresource></gresources>")

    # Use "file" function to generate XML controlling file.
    get_filename_component(xml_path_only_name "${xml_path}" NAME)
    file(WRITE ${xml_path} ${GXML_XML_FILE})

endfunction()