import { ClassFlag } from "./ClassFlag";
import { HTMLNodeTreeWalker } from '../graphs/HTMLNodeTreeWalker';
import { Box2 } from "../geometry/Box2";
import { Vector2 } from "../geometry/Vector2";
import { ElementAttribute } from "./ElementAttribute";
import { MapList } from "../tools/MapList";

export type above_sight = "above-sight";
export type in_sight    = "in-sight";
export type below_sight = "below-sight";

export type InsighStateType = above_sight | in_sight | below_sight;

export class InsighState
{
  static readonly above_sight:above_sight = "above-sight";
  static readonly in_sight:in_sight       = "in-sight";
  static readonly below_sight:below_sight = "below-sight";
}

export class InsightData
{
  insight:Insight;
  isInsight = false;
  wasInsight = false;
  viewBox:Box2 = null;
  elementBox:Box2 = new Box2();
  changeTime:number = 0;
}

export class InsightElement extends Element
{

  _insightData:InsightData;

  static ensure( element:Element )
  {
    let insightElement = element as InsightElement;

    if ( ! insightElement._insightData )
    {
      insightElement._insightData = new InsightData();
    }

    return insightElement;
  }

  static forAllInsightElements( root:Element, callback:( insightElement:InsightElement )=>void )
  {
    let walker = HTMLNodeTreeWalker.$;

    walker.forAll( root, 
      n =>
      {
        let insightElement = n as InsightElement;

        if ( insightElement._insightData )
        {
          callback( insightElement );
        }
      } 
    );
  }
}

export type InsightCallback = ()=>void;
export type CallbackMapList = Map<Element,InsightCallback[]>;


export class Insight
{
  static attribute = new ElementAttribute( "insight" );
  static wasSeenFlag = new ClassFlag( "was-in-sight" );
  static maxHeight = new ElementAttribute( "max-insight-height" );

  static readonly above_sight = new ClassFlag( InsighState.above_sight );
  static readonly in_sight    = new ClassFlag( InsighState.in_sight );
  static readonly below_sight = new ClassFlag( InsighState.below_sight );

  static changeFrequencyMS = 200; 
  private _elements:Element[] = []; 
  private _offsightCallbackElements:CallbackMapList;
  private _insightCallbackElements:CallbackMapList;

  private _viewBoxSize:Vector2 = null;
  private _hasScreenUpdate = false;
  private _lastYOffset = 0;
  private _yTresholdForChanges = 15;
  private _lastGrabbedTime = 0;
  private _afterGrabingUpdateDurationMS = 3000; 

  static _allInstances:Insight[] = [];

  static updateAll()
  {
    this._allInstances.forEach( i => { i._hasScreenUpdate = true; i.update() } );
  }

  constructor( publishGlobally:boolean = true )
  {
    if ( publishGlobally )
    {
      Insight._allInstances.push( this );
    }
  }

  onInsight( element:Element, callback:InsightCallback )
  {
    MapList.add( this._insightCallbackElements, element, callback );
  }

  onOffsight( element:Element, callback:InsightCallback )
  {
    MapList.add( this._offsightCallbackElements, element, callback );
  }

  grabElements()
  {     
    this._lastGrabbedTime = new Date().getTime();

    this._elements.forEach( 
      e => 
      {
        let element = InsightElement.ensure( e ); 
        element._insightData.insight = null;
      }
    
    );

    this._elements = Insight.attribute.queryAll( document.body ); 
    this._offsightCallbackElements = new Map<Element,InsightCallback[]>();
    this._insightCallbackElements = new Map<Element,InsightCallback[]>();

    this._elements.forEach( 
      e => 
      {
        let element = InsightElement.ensure( e ); 
        element._insightData.insight = this;
      }
    
    );

    //console.log( this._elements );
  }

  update()
  {
    this._updateViewBox();

    let currentTime = new Date().getTime();
    let elapsedSinceGrabbing = currentTime - this._lastGrabbedTime;
    
    if ( elapsedSinceGrabbing < this._afterGrabingUpdateDurationMS )
    {
      this._hasScreenUpdate = true;
    }


    let yChange = window.pageYOffset - this._lastYOffset;

    if ( Math.abs( yChange ) > this._yTresholdForChanges  )
    {
      this._hasScreenUpdate = true;
    }

    if ( ! this._hasScreenUpdate )
    {
      return;
    }

    this._lastYOffset = window.pageYOffset;
    this._hasScreenUpdate = false;

    let now = new Date().getTime();
    this._elements.forEach( e => this.updateElement( e, now ) );
  }

  updateElement( e:Element, updateTime:number )
  {
    let insightElement = InsightElement.ensure( e );
    let insightData =  insightElement._insightData;    

    let viewBox = insightData.viewBox;
    
    if ( ! viewBox )
    {
      viewBox = this._getViewBox( e );
      insightData.viewBox = viewBox;
    }

    let elementBox = insightData.elementBox;


    Box2.updatefromClientRect( insightData.elementBox, e.getBoundingClientRect() );
    
    if ( Insight.maxHeight.in( e ) )
    {
      let maxHeight = Insight.maxHeight.from( e );
      let isPercentage = /\%/.test( maxHeight );
      let maxHeightPixel = parseFloat( maxHeight.replace( /\%|px/, "" ) );
      
      if ( isPercentage )
      {
        maxHeightPixel *= window.innerHeight / 100;
      }
      
      let size = elementBox.size;
      
      if ( size.y > maxHeightPixel )
      {
        let center = elementBox.center;
        let offset = maxHeightPixel / 2;
        elementBox.min.y = center.y - offset;
        elementBox.max.y = center.y + offset;  
      }

    }

    let insight = viewBox.intersectsBox( elementBox );
    /*
    console.log( 
      "Is in sight", insight,
      "DOCUMENT VIEW BOX:", viewBox, 
      "ELEMENT BOX:", elementBox,
      "ELEMENT", e 
    );*/

    if ( insight === insightData.isInsight )
    {
      return;
    }

    let timeElapsedSinceLastChange = updateTime - insightData.changeTime;
    
    
    if ( timeElapsedSinceLastChange <= Insight.changeFrequencyMS )
    {
      return;
    }

    insightData.changeTime = updateTime;
    insightData.isInsight = insight;
    
    if ( insight )
    {
      Insight.in_sight.setAs( e, true ); 
      Insight.above_sight.setAs( e, false); 
      Insight.below_sight.setAs( e, false ); 
      
      if ( this._insightCallbackElements.has( e ) )
      {
        this._insightCallbackElements.get( e ).forEach( c => c() );
      }
    }
    else
    {
      let isAbove = elementBox.max.y < viewBox.min.y; 
      Insight.in_sight.setAs( e, false ); 
      Insight.above_sight.setAs( e, isAbove); 
      Insight.below_sight.setAs( e, ! isAbove ); 

      if ( this._offsightCallbackElements.has( e ) )
      {
        this._offsightCallbackElements.get( e ).forEach( c => c() );
      }
    }
        
    

    if ( insightData.wasInsight )
    {
      return;
    }

    setTimeout( ()=>{ Insight.wasSeenFlag.set( e ); }, 200 );
    
  } 
  

  private _updateViewBox()
  {
    if ( ! this._elements )
    {
      return;
    }

    if ( ! this._needsViewBoxUpdate() )
    {
      return;
    }

    this._hasScreenUpdate = true;

    this._viewBoxSize.x = window.innerWidth;
    this._viewBoxSize.y = window.innerHeight;

    this._elements.forEach( 
      e => 
      {
        let insightElement = InsightElement.ensure( e );
        let data = insightElement._insightData;
        data.viewBox = this._getViewBox( e );;
      }
    );

  }

  private _needsViewBoxUpdate()
  {
    if ( this._viewBoxSize == null )
    {
      this._viewBoxSize = new Vector2( 0, 0 );
      return true;
    }

    if ( this._viewBoxSize.x !== window.innerWidth || this._viewBoxSize.y !== window.innerHeight )
    {
      return true;
    }

    return false;
  }
  
  

  private _getViewBox( e:Element ):Box2
  {

    let relativeStart = 15;
    let relativeEnd = 100 - relativeStart;

    let coords = Insight.attribute.from( e );
    
    if ( coords && coords.length > 0 )
    {
      let numbers = coords.split( "," );

      if ( numbers.length == 1 )
      {
        relativeStart = parseFloat( numbers[ 0 ] );
        relativeEnd = 100 - relativeStart;
      }
      else if ( numbers.length == 2 )
      {
        relativeStart = parseFloat( numbers[ 0 ] );
        relativeEnd = 100 - parseFloat( numbers[ 1 ] );
      }
    }

    if ( isNaN( relativeStart ) )
    {
      relativeStart = 15;
    }

    if ( isNaN( relativeEnd ) )
    {
      relativeEnd = 100 - relativeStart;
    }


    //console.log( "VIEW BOX START/END", relativeStart, relativeEnd );

    let startY = window.innerHeight * relativeStart / 100;
    let endY   = window.innerHeight * relativeEnd  / 100;      

    return new Box2( new Vector2( -10000, startY ), new Vector2( 10000, endY ) );

   
  }
}