import styles from './screen.module.css'
import Cursor from './Cursor'

import type { Point, Dimensions } from './types';


export type State  = Dimensions

export const INITIAL_STATE: State = {
  width: 0,
  height: 0,
}


function getElementsFromInternalPoint(doc: Document, { x, y }: Point): Element[] {
  // @ts-ignore (IE, Edge)
  if (typeof doc.msElementsFromRect === 'function') {
    // @ts-ignore
    return Array.prototype.slice.call(doc.msElementsFromRect(x,y)) || []
  }

  if (typeof doc.elementsFromPoint === 'function') {
    return doc.elementsFromPoint(x, y)
  }
  const el = doc.elementFromPoint(x, y)
  return el ? [ el ] : []
}

function getElementsFromInternalPointDeep(doc: Document, point: Point): Element[] {
  const elements = getElementsFromInternalPoint(doc, point)
  // is it performant though??
  for (let i = 0; i < elements.length; i++) {
    const el = elements[i]
    if (isIframe(el)){
      const iDoc = el.contentDocument
      if (iDoc) {
        const iPoint: Point = {
          x: point.x - el.clientLeft,
          y: point.y - el.clientTop,
        }
        elements.push(...getElementsFromInternalPointDeep(iDoc, iPoint))
      }
    }
  }
  return elements
}

function isIframe(el: Element): el is HTMLIFrameElement {
  return el.tagName === "IFRAME"
}

export default class Screen {
  readonly overlay: HTMLDivElement
  readonly cursor: Cursor

  private readonly iframe: HTMLIFrameElement;
  private readonly screen: HTMLDivElement;
  private parentElement: HTMLElement | null = null;

  constructor(isMobile: boolean, coldStart?: boolean) {
    if (coldStart) return;

    const iframe = document.createElement('iframe');
    iframe.className = styles.iframe;
    this.iframe = iframe;

    const overlay = document.createElement('div');
    overlay.className = styles.overlay;
    this.overlay = overlay;

    const screen = document.createElement('div');

    screen.className = styles.screen;
    screen.appendChild(iframe);
    screen.appendChild(overlay);
    this.screen = screen;

    this.cursor = new Cursor(this.overlay, isMobile) // TODO: move outside
  }

  attach(parentElement: HTMLElement) {
    if (this.parentElement) {
      this.parentElement = undefined
      console.error("BaseScreen: Trying to attach an attached screen.");
    }

    parentElement.appendChild(this.screen);

    this.parentElement = parentElement;

    /* == For the Inspecting Document content  == */
    this.overlay.addEventListener('contextmenu', () => {
      this.overlay.style.display = 'none'
      const doc = this.document
      if (!doc) { return }
      const returnOverlay = () => {
        this.overlay.style.display = 'block'
        doc.removeEventListener('mousemove', returnOverlay)
        doc.removeEventListener('mouseclick', returnOverlay) // TODO: prevent default in case of input selection
      }
      doc.addEventListener('mousemove', returnOverlay)
      doc.addEventListener('mouseclick', returnOverlay)
    })
  }

  getParentElement():  HTMLElement | null {
    return this.parentElement
  }

  setBorderStyle(style: { border: string }) {
    return Object.assign(this.screen.style, style)
  }

  get window(): WindowProxy | null {
    return this.iframe.contentWindow;
  }

  get document(): Document | null {
    return this.iframe.contentDocument;
  }

  get iframeStylesRef(): CSSStyleDeclaration {
    return this.iframe.style
  }

  private boundingRect: DOMRect | null  = null;
  private getBoundingClientRect(): DOMRect {
     if (this.boundingRect === null) {
      return this.boundingRect = this.overlay.getBoundingClientRect() // expensive operation?
    }
    return this.boundingRect
  }

  getInternalViewportCoordinates({ x, y }: Point): Point {
    const { x: overlayX, y: overlayY, width } = this.getBoundingClientRect();

    const screenWidth = this.overlay.offsetWidth;

    const scale = screenWidth / width;
    const screenX = (x - overlayX) * scale;
    const screenY = (y - overlayY) * scale;

    return { x: Math.round(screenX), y: Math.round(screenY) };
  }

  getCurrentScroll(): Point {
    const docEl = this.document?.documentElement
    const x = docEl ? docEl.scrollLeft : 0
    const y = docEl ? docEl.scrollTop : 0
    return { x, y }
  }

  getInternalCoordinates(p: Point): Point {
    const { x, y } = this.getInternalViewportCoordinates(p);

    const sc = this.getCurrentScroll()

    return { x: x+sc.x, y: y+sc.y };
  }

  getElementFromInternalPoint({ x, y }: Point): Element | null {
    // elementFromPoint && elementFromPoints require viewpoint-related coordinates,
    //                                                 not document-related
    return this.document?.elementFromPoint(x, y) || null;
  }

  getElementsFromInternalPoint(point: Point): Element[] {
    const doc = this.document
    if (!doc) { return [] }
    return getElementsFromInternalPointDeep(doc, point)
  }

  getElementFromPoint(point: Point): Element | null {
    return this.getElementFromInternalPoint(this.getInternalViewportCoordinates(point));
  }

  getElementsFromPoint(point: Point): Element[] {
    return this.getElementsFromInternalPoint(this.getInternalViewportCoordinates(point));
  }

  getElementBySelector(selector: string) {
    if (!selector) return null;
    try {
      const safeSelector = selector.replace(/:/g, '\\\\3A ').replace(/\//g, '\\/');
      return this.document?.querySelector<HTMLElement>(safeSelector) || null;
    } catch (e) {
      console.error("Can not select element. ", e)
      return null
    }
  }

  display(flag: boolean = true) {
    this.screen.style.display = flag ? '' : 'none';
  }

  displayFrame(flag: boolean = true) {
    this.iframe.style.display = flag ? '' : 'none';
  }

  private scaleRatio: number = 1;
  getScale() {
    return this.scaleRatio;
  }

  scale({ height, width }: Dimensions) {
    if (!this.parentElement) return;
    const { offsetWidth, offsetHeight } = this.parentElement;

    this.scaleRatio = Math.min(offsetWidth / width, offsetHeight / height);
    if (this.scaleRatio > 1) {
      this.scaleRatio = 1;
    } else {
      this.scaleRatio = Math.round(this.scaleRatio * 1e3) / 1e3;
    }
    this.screen.style.transform =  `scale(${ this.scaleRatio }) translate(-50%, -50%)`;
    this.screen.style.width = width + 'px';
    this.screen.style.height =  height + 'px';
    this.iframe.style.width = width + 'px';
    this.iframe.style.height = height + 'px';

    this.boundingRect = this.overlay.getBoundingClientRect();
  }

  scaleFullPage() {
    if (!this.parentElement) return;
    const { width: boxWidth } = this.parentElement.getBoundingClientRect();
    const { height, width } = this.document.body.getBoundingClientRect();
    this.overlay.remove()

    this.scaleRatio = boxWidth/width;
    if (this.scaleRatio > 1) {
      this.scaleRatio = 1;
    } else {
      this.scaleRatio = Math.round(this.scaleRatio * 1e3) / 1e3;
    }

    Object.assign(this.screen.style, {
      top: '0',
      left: '0',
      height: height + 'px',
      width: width + 'px',
      transform: `scale(${this.scaleRatio})`,
    })
    Object.assign(this.iframe.style, {
      width: width + 'px',
      height: height + 'px',
    })
  }

}