import { CLASS_CONTAINER, EVENT_HIDDEN, EVENT_VISIBLE, EventInterface, SlideComponent, Splide } from '@splidejs/splide';
import { child, pad, queryAll, removeAttribute, setAttribute, style, unit } from '@splidejs/splide/src/js/utils';
import { CLASS_SLIDE_COL, CLASS_SLIDE_ROW } from '../../constants/classes';
import { GridOptions } from '../../types/options';
import { DimensionComponent } from './Dimension';


/**
 * The interface for the Layout subcomponent.
 *
 * @since 0.5.0
 */
export interface LayoutComponent {
  mount(): void;
  destroy(): void;
}

/**
 * The subcomponent to layout grids.
 *
 * @since 0.5.0
 *
 * @param Splide      - A Splide instance.
 * @param gridOptions - Initialized grid options.
 * @param Dimension   - A Dimension subcomponent.
 *
 * @return A Layout subcomponent object.
 */
export function Layout( Splide: Splide, gridOptions: GridOptions, Dimension: DimensionComponent ): LayoutComponent {
  const { on, destroy: destroyEvent } = EventInterface( Splide );
  const { Components, options } = Splide;
  const { resolve } = Components.Direction;
  const { forEach } = Components.Slides;

  /**
   * Initializes the component.
   */
  function mount(): void {
    layout();

    if ( options.slideFocus ) {
      on( EVENT_VISIBLE, onVisible );
      on( EVENT_HIDDEN, onHidden );
    }
  }

  /**
   * Destroys the component.
   */
  function destroy(): void {
    forEach( Slide => {
      const { slide } = Slide;
      toggleTabIndex( slide, false );

      getRowsIn( slide ).forEach( cell => {
        removeAttribute( cell, 'style' );
      } );

      getColsIn( slide ).forEach( colSlide => {
        cover( colSlide, true );
        removeAttribute( colSlide, 'style' );
      } );
    } );

    destroyEvent();
  }

  /**
   * Layouts grid elements.
   */
  function layout(): void {
    forEach( Slide => {
      const { slide } = Slide;
      const [ rows, cols ] = Dimension.get( Slide.isClone ? Slide.slideIndex : Slide.index );

      layoutRow( rows, slide );
      layoutCol( cols, slide );

      getColsIn( Slide.slide ).forEach( ( colSlide, index ) => {
        colSlide.id = `${ Slide.slide.id }-col${ pad( index + 1 ) }`;

        if ( Splide.options.cover ) {
          cover( colSlide );
        }
      } );
    } );
  }

  /**
   * Layouts row elements by CSS.
   *
   * @param rows  - A number of rows.
   * @param slide - A slide element.
   */
  function layoutRow( rows: number, slide: HTMLElement ): void {
    const { row: rowGap } = gridOptions.gap;
    const height  = `calc(${ 100 / rows }%${ rowGap ? ` - ${ unit( rowGap ) } * ${ ( rows - 1 ) / rows }` : '' })`;

    getRowsIn( slide ).forEach( ( rowElm, index, rowElms ) => {
      style( rowElm, 'height', height );
      style( rowElm, 'display', 'flex' );
      style( rowElm, 'margin', `0 0 ${ unit( rowGap ) } 0` );
      style( rowElm, 'padding', 0 );

      if ( index === rowElms.length - 1 ) {
        style( rowElm, 'marginBottom', 0 );
      }
    } );
  }

  /**
   * Layouts col elements by CSS.
   *
   * @param cols  - A number of cols.
   * @param slide - A slide element.
   */
  function layoutCol( cols: number, slide: HTMLElement ): void {
    const { col: colGap } = gridOptions.gap;
    const width = `calc(${ 100 / cols }%${ colGap ? ` - ${ unit( colGap ) } * ${ ( cols - 1 ) / cols }` : '' })`;

    getColsIn( slide ).forEach( ( colElm, index, colElms ) => {
      style( colElm, 'width', width );

      if ( index !== colElms.length - 1 ) {
        style( colElm, resolve( 'marginRight' ), unit( colGap ) );
      }
    } );
  }

  /**
   * Sets the background image to the col element by its own image element.
   *
   * @param colSlide - A col slide element.
   * @param uncover  - Optional. If `true`, reset the cover mode.
   */
  function cover( colSlide: HTMLElement, uncover?: boolean ): void {
    const container = child( colSlide, `.${ CLASS_CONTAINER }` );
    const img       = child<HTMLImageElement>( container || colSlide, 'img' );

    if ( img && img.src ) {
      style( container || colSlide, 'background', uncover ? '' : `center/cover no-repeat url("${ img.src }")` );
      style( img, 'display', uncover ? '' : 'none' );
    }
  }

  /**
   * Returns row elements in the provided slide.
   *
   * @param slide - A slide element.
   *
   * @return An array with row elements.
   */
  function getRowsIn( slide: HTMLElement ): HTMLElement[] {
    return queryAll<HTMLElement>( slide, `.${ CLASS_SLIDE_ROW }` );
  }

  /**
   * Returns col elements in the provided slide.
   *
   * @param slide - A slide element.
   *
   * @return An array with col elements.
   */
  function getColsIn( slide: HTMLElement ): HTMLElement[] {
    return queryAll<HTMLElement>( slide, `.${ CLASS_SLIDE_COL }` );
  }

  /**
   * Toggles the tab index of col elements.
   *
   * @param slide - A slide element.
   * @param add   - Optional. Determines whether to add or remove tab index.
   */
  function toggleTabIndex( slide: HTMLElement, add?: boolean ): void {
    getColsIn( slide ).forEach( colSlide => {
      setAttribute( colSlide, 'tabindex', add ? 0 : null );
    } );
  }

  /**
   * Called when any slide becomes visible.
   *
   * @param Slide - A Slide component.
   */
  function onVisible( Slide: SlideComponent ): void {
    toggleTabIndex( Slide.slide, true );
  }

  /**
   * Called when any slide gets hidden.
   *
   * @param Slide - A Slide component.
   */
  function onHidden( Slide: SlideComponent ): void {
    toggleTabIndex( Slide.slide, false );
  }

  return {
    mount,
    destroy,
  };
}