export abstract class ContextMenuItem
{
  readonly parent: ContextMenuDirectory | null;

  constructor( parent: ContextMenuDirectory | null )
  {
    this.parent = parent;
  }

  abstract createEl(): HTMLElement;
}

export class ContextMenuSeparator extends ContextMenuItem
{
  createEl(): HTMLElement
  {
    const el = document.createElement( 'div' );
    el.className = 'ctx-separator';
    return el;
  }
}

export class ContextMenuReadOnlyEntry extends ContextMenuItem
{
  label: string;

  constructor( parent: ContextMenuDirectory | null, label: string )
  {
    super( parent );
    this.label = label;
  }

  createEl(): HTMLElement
  {
    const el = document.createElement( 'div' );
    el.className = 'ctx-readonly';
    el.textContent = this.label;
    return el;
  }
}

export class ContextMenuEntry extends ContextMenuItem
{
  label: string;
  _action: () => void;
  noClose: boolean;

  constructor( parent: ContextMenuDirectory | null, label: string, action: () => void, noClose = false )
  {
    super( parent );
    this.label = label;
    this._action = action;
    this.noClose = noClose;
  }

  createEl(): HTMLElement
  {
    const el = document.createElement( 'div' );
    el.className = 'ctx-entry';
    el.textContent = this.label;
    el.addEventListener( 'click', ( e ) =>
    {
      e.stopPropagation();
      this._action();

      if ( ! this.noClose )
      {
        let dir: ContextMenuDirectory = this.parent;
        while ( dir.parent ) dir = dir.parent;
        dir.close();
      }
    } );
    return el;
  }
}

export class ContextMenuDirectory extends ContextMenuItem
{
  label: string | null;
  items: ContextMenuItem[] = [];
  _menuEl: HTMLElement = null;
  _closeTimer: number = 0;

  constructor( parent: ContextMenuDirectory | null, label: string | null = null )
  {
    super( parent );
    this.label = label;
  }

  add( item: ContextMenuItem ): this
  {
    this.items.push( item );
    return this;
  }

  show( x: number, y: number ): void
  {
    this.clearCloseUpwards();

    if ( this._menuEl )
    {
      return;
    }

    const menu = document.createElement( 'div' );
    menu.className = 'ctx-menu';
    menu.style.cssText = 'position:fixed;visibility:hidden';

    for ( const item of this.items )
    {
      menu.appendChild( item.createEl() );
    }

    document.body.appendChild( menu );
    this._menuEl = menu;

    const w = menu.offsetWidth;
    const h = menu.offsetHeight;
    const vw = window.innerWidth;
    const vh = window.innerHeight;

    const left = ( x + w > vw && x - w >= 0 ) ? x - w : x;
    const top  = ( y + h > vh && y - h >= 0 ) ? y - h : y;

    menu.style.left = `${left}px`;
    menu.style.top  = `${top}px`;
    menu.style.visibility = '';

    menu.addEventListener( 'mouseenter', () => this.clearCloseUpwards() );
    menu.addEventListener( 'mouseleave', () => this.scheduleClose() );

    if ( ! this.parent )
    {
      const onOutside = ( e: MouseEvent ) =>
      {
        if ( ! menu.contains( e.target as Node ) )
        {
          this.close();
          document.removeEventListener( 'click', onOutside, { capture: true } );
        }
      };
      setTimeout( () => document.addEventListener( 'click', onOutside, { capture: true } ), 0 );
    }
  }

  close(): void
  {
    for ( const item of this.items )
    {
      if ( item instanceof ContextMenuDirectory ) item.close();
    }

    this._menuEl?.remove();
    this._menuEl = null;
  }

  scheduleClose(): void
  {
    this._closeTimer = window.setTimeout( () => this.close(), 150 );
  }

  clearClose(): void
  {
    clearTimeout( this._closeTimer );
  }

  clearCloseUpwards(): void
  {
    let dir: ContextMenuDirectory = this;

    while ( dir )
    {
      dir.clearClose();
      dir = dir.parent;
    }
  }

  createEl(): HTMLElement
  {
    const el = document.createElement( 'div' );
    el.className = 'ctx-entry ctx-entry-dir';
    el.innerHTML = `<span class="ctx-label">${this.label ?? ''}</span><span class="ctx-arrow">▶</span>`;

    el.addEventListener( 'mouseenter', () =>
    {
      if ( this.parent )
      {
        for ( const item of this.parent.items )
        {
          if ( item instanceof ContextMenuDirectory && item !== this ) item.close();
        }
      }

      const rect = el.getBoundingClientRect();
      this.show( rect.right, rect.top );
    } );

    el.addEventListener( 'mouseleave', () => this.scheduleClose() );

    return el;
  }
}