// detachable_elements.ysl2
//
// compute what elements are required by pages
// and decide where to cut when removing/attaching 
// pages elements on page switch

// returns all directly or indirectly refered elements
def "func:refered_elements" {
    param "elems";
    const "descend", "$elems/descendant-or-self::svg:*";
    const "clones", "$descend[self::svg:use]";
    const "originals", "//svg:*[concat('#',@id) = $clones/@xlink:href]";
    choose {
        when "$originals"
            result "$descend | func:refered_elements($originals)";
        otherwise
            result "$descend";
    }
}

def "func:all_related_elements" {
    param "page";
    const "page_overlapping_geometry", "func:overlapping_geometry($page)";
    const "page_overlapping_elements", "//svg:*[@id = $page_overlapping_geometry/@Id]";
    const "page_sub_elements", "func:refered_elements($page | $page_overlapping_elements)";
    result "$page_sub_elements";
}

def "func:required_elements" {
    param "pages"; 
    choose{
        when "$pages"{
            result """func:all_related_elements($pages[1])
                      | func:required_elements($pages[position()!=1])""";
        }otherwise{
            result "/..";
        }
    }
}

const "required_elements",
    """//svg:defs/descendant-or-self::svg:*
       | func:required_elements($hmi_pages)/ancestor-or-self::svg:*""";

const "discardable_elements", "//svg:*[not(@id = $required_elements/@id)]";

def "func:sumarized_elements" {
    param "elements";
    const "short_list", "$elements[not(ancestor::*/@id = $elements/@id)]";
    const "filled_groups", """$short_list/parent::svg:*[
        not(descendant::*[
            not(self::svg:g) and
            not(@id = $discardable_elements/@id) and
            not(@id = $short_list/descendant-or-self::*[not(self::svg:g)]/@id)
        ])]""";
    const "groups_to_add", "$filled_groups[not(ancestor::*/@id = $filled_groups/@id)]";
    result "$groups_to_add | $short_list[not(ancestor::svg:g/@id = $filled_groups/@id)]";
}

def "func:detachable_elements" {
    param "pages";
    choose{
        when "$pages"{
            result """func:sumarized_elements(func:all_related_elements($pages[1]))
                      | func:detachable_elements($pages[position()!=1])""";
        }otherwise{
            result "/..";
        }
    }
}

// Avoid nested detachables
const "_detachable_elements", "func:detachable_elements($hmi_pages)";
const "detachable_elements", "$_detachable_elements[not(ancestor::*/@id = $_detachable_elements/@id)]";

function "debug_detachables" {
    foreach "$detachable_elements"{
        |  «@id»
    }
}
!debug_output_calls.append("debug_detachables")