eno-example/components/collapse.tsx

import React from "react";

export default (props:{open:boolean, children:React.JSX.Element|React.JSX.Element[]})=>
{
  const [openGet, openSet] = React.useState(props.open);
  const [doneGet, doneSet] = React.useState(true);
  const refEl:React.RefObject<HTMLElement> = React.useRef(null);
  const refCollapse:React.RefObject<CollapseControls> = React.useRef(null);

  React.useEffect(()=>
  {
    if(refEl.current)
    {
      refCollapse.current = Collapser(refEl.current, openGet);
    }
    return ()=> refCollapse.current && refCollapse.current();
  }
  , []);
  const Handler =()=>
  {
      openSet((old)=>
      {
        if(refCollapse.current)
        {
          doneSet(false);
          refCollapse.current(!old, 1000, ()=>doneSet(true));
        }
        return !old;
      });
  };

  return <div>
    <button onClick={Handler}>{openGet ? "Close this" : "Open it"}{doneGet ? "." : "..."}</button>
    <div ref={refEl as React.RefObject<HTMLDivElement>}>
      {!(!openGet && doneGet) && props.children}
    </div>
  </div>
};

export function useAway(inRef:React.Ref<HTMLElement>, inHandler:(inAway:boolean)=>void)
{
  const handlerRef = React.useRef(inHandler);
  handlerRef.current = inHandler;
  React.useEffect(()=>
  {
    const iterate = (element:EventTarget)=>element === inRef.current;
    const handler = (event:MouseEvent)=> handlerRef.current( event.composedPath().find(iterate) ? false : true );
    document.body.addEventListener("click", handler);
    return ()=> document.body.removeEventListener("click", handler);
  }
  , []);
}

type CollapseStateGet = {Done:boolean, Open:boolean, Away:boolean};
type CollapseStateSet = (args:{Done?:boolean, Open?:boolean, Away?:boolean})=>void;
type CollapseStateBinding = [state:CollapseStateGet, update:CollapseStateSet];
const CollapseContext = React.createContext([{Done:true, Open:true, Away:false}, (args)=>{}] as CollapseStateBinding);
export const CollapseGroup =({children}:{children:React.JSX.Element|React.JSX.Element[]})=>
{
  const [stateGet, stateSet] = React.useState({Done:true, Open:false, Away:false} as CollapseStateGet);
  const setAny:CollapseStateSet =(params)=> stateSet((old)=> ({...old, ...params}));
  React.useEffect(()=>{stateGet.Away && setAny({Open:false})}, [stateGet.Away]);
  return <CollapseContext.Provider value={[stateGet, setAny]}>{children}</CollapseContext.Provider>;
};

export const CollapseButton =()=>
{
  const [stateGet, stateSet] = React.useContext(CollapseContext);
  const buttonRef:React.Ref<HTMLElement> = React.useRef(null);
  useAway(buttonRef, (Away)=>stateSet({Away}));
  return <button onClick={e=>stateSet({Open:!stateGet.Open})} ref={buttonRef as React.Ref<HTMLButtonElement>}>
    click it! {JSON.stringify(stateGet)}
  </button>
}

type DoneCallback =(openState:boolean)=>void;
export type CollapseControls =(inOpen?:boolean, inMs?:number, inDone?:DoneCallback)=>void;
export function Collapser(inElement:HTMLElement, initialState = false)
{
    let userDone:DoneCallback = (openState) => {};
    let userMode = initialState;
    let frameRequest = 0;

    const done = (inEvent:TransitionEvent)=>
    {
      if (inEvent.propertyName == "height" && inEvent.target == inElement)
      {
        inEvent.stopPropagation();
        if (userMode)
        {
          inElement.style.height = "auto";
          inElement.style.overflow = "visible";
        }
        userDone(userMode);
      }
    };
    inElement.addEventListener("transitionend", done);

    return function(inOpen, inMs, inDone)
    {
      cancelAnimationFrame(frameRequest);

      if(arguments.length)
      {
        userDone = inDone|| ((m)=>{}) as DoneCallback;
        userMode = inOpen === true;

        inElement.style.height = inElement.clientHeight + "px";
        inElement.style.overflow = "hidden";
        inElement.style.transition = "none";
        frameRequest = requestAnimationFrame(()=>
        {
          inElement.style.transition = `height ${(inMs||1000) / 1000}s`;
          frameRequest = requestAnimationFrame(()=>
          {
            inElement.style.height = `${inOpen ? inElement.scrollHeight : 0}px`;
          });
          
        });
      }
      else
      {
        inElement.removeEventListener("transitionend", done);
      }
    } as CollapseControls;
}