persistable sclass G22NetworkElement > MetaWithChangeListeners {
  // network element belongs to
  settable G22Network network;
  
  // position in visual representation
  settable Rect bounds;
  
  // identifier in network (optional)
  settableWithVar S identifier;
  
  // script code to adapt element and to create instance
  settableWithVar S code;
  
  {
    onChange(-> { network?.change(); });
  }
  
  class Port {
    // position on element's border (0 to 1, 0 to 1)
    settable DoublePt position;
    
    // name of port
    settable S name;
    
    // cable attached to this port
    settable G22NetworkCable cable;
    
    G22NetworkElement element() { ret G22NetworkElement.this; }
  }
  
  L<Port> ports = syncL();
  
  LASCompileResult newCompileResult() { ret new LASCompileResult; }
  
  transient LASCompileResult compileResult;
  LASCompileResult compile(G22Utils g22utils) {
    S code = this.code;
    if (code == null) null;
    var cr = compileResult;
    if (cr != null && eq(cr.script, code)) ret cr;
    cr = newCompileResult();
    var parser = g22utils.leftArrowParser();
    configureParser(parser);
    cr.script(code).parser(parser).compile();
    ret compileResult = cr;
  }
  
  void configureParser(GazelleV_LeftArrowScriptParser parser) {
    parser.addVar("blueprint");
  }
  
  O makeInstance(G22Utils g22utils) null on exception {
    var compiled = compile(g22utils);
    if (compiled == null) null;
    var compiled2 = compiled!;
    if (!compiled.runnable()) null;
    new FlexibleVarContext ctx;
    ctx.put("blueprint", this);
    ret compiled2.get(ctx);
  }
  
  toString { ret or2(identifier(), "Unnamed element"); }
  
  Port getPort(S name) {
    ret firstThat(ports, p -> eq(p.name, name));
  }
  
  void addPort aka addSlot(S name, DoublePt etc position) {
    Port p = getPort(name);
    if (p == null)
      ports.add(p = new Port().name(name));
    p.position(position);
    change();
  }
  
  void removePorts {
    ports.clear();
    change();
  }
}