library-ts/browser/random/RandomEngine.ts

import { HTMLColor } from '../colors/HTMLColor';
import { HSLColor } from '../colors/HSLColor';
import { RGBColor } from "../colors/RGBColor";
import { Range } from '../geometry/Range';


export abstract class RandomEngine
{
  abstract next():number;
  
  value( scalar:number ):number 
  {
    return this.next() * scalar;
  }

  range( a:number, b:number ):number 
  {
    return this.next()*( b - a ) + a;
  }

  in( range:Range ):number
  {
    return this.range( range.min, range.max );
  }

  polarOne():number 
  {
    return this.next() * 2 - 1;
  }
  
  polar( value:number ):number 
  {
    return this.polarOne() * value;
  }

  bool():boolean 
  {
    return this.next() > 0.5;
  }

  percentageVariation( variation:number ):Range 
  {
    var value = ( 100 - variation ) / 100;
    return new Range( value, 1 / value );  
  }

  withChanceOf( value:number ):boolean 
  {
    return ( this.next() * 100 ) <= value ;
  }


  randomHue( saturation:number = 1, luminance:number = 0.5):HTMLColor
  {
    let hue = this.range( 0, 360 );
    let color = new HSLColor( hue, saturation, luminance );
    return color;
  }

  lerpRGB( colors:HTMLColor[]):HTMLColor
  {
    if ( colors.length ==  1 )
    {
      return colors[ 0 ];
    }
    
    return RGBColor.lerpFrom( colors, this.next() );
  }
  
  /*
  inCubeOne():Vector3 
  {
    return new Vector3( this.polarOne(), this.polarOne(), this.polarOne() );
  }    

  inCube( size:number ):Vector3 
  {
    return this.inCubeOne().multiplyScalar( size * 0.5 );
  }

  inSphereOne():Vector3 
  {
    var inCube = this.inCubeOne();

    if ( inCube.lengthSq() > 1 )
    {
      inCube.normalize().multiplyScalar( this.next() );
    }

    return inCube;
  }

  inSphere( size:number ):Vector3 
  {
    return this.inSphereOne().multiplyScalar( size * 0.5 );
  }

  */
 
  integerInclusive( min:number, max:number ):number  
  {
    return ( Math.floor( this.next() * ( max - min + 1 ) ) + min ) ;
  }

  integerInclusiveFromZero( max:number ):number 
  {
    return this.integerInclusive( 0, max );
  }


  integerExclusive( min:number, max:number ):number  
  {
    var nextValue = this.next();
    var randomValue = nextValue * ( max - min ) + min;
    
    var value =  ( Math.floor( randomValue ) );
    return Math.min( max - 1, value );
  }

  integerExclusiveFromZero( max:number ):number 
  {
    return this.integerExclusive( 0, max );
  }
  

  fromString( text: string, alternative:string = null ):string
  {
    if ( ! text || text.length === 0 )
    {
      return alternative;
    }

    let index = this.integerExclusive( 0, text.length );
    return text[ index ];
  }

  from<T>( array: T[], alternative:T = null ):T
  {
    if ( array.length == 0 )
    {
      return alternative;
    }

    var index = this.integerExclusive( 0, array.length );
    return array[ index ];
  }

  arrayFrom<T>( numElements:number,  array: T[], alternative:T = null ):T[]
  {
    let randomArray:T[] = [];
    
    for ( let i = 0; i < numElements; i++ )
    {
      randomArray.push( this.from<T>( array, alternative ) );
    } 

    return randomArray;
  }

  fromValues<T>( first:T, ...values:T[] ):T
  {
    if ( values.length == 0 )
    {
      return first;
    }

    var index = this.integerExclusive( 0, values.length + 1 );

    return index == 0 ? first : values[ index - 1];
  }

  arrayFromValues<T>( numElements:number, first:T, ...values:T[] ):T[]
  {
    let randomArray:T[] = [];

    for ( let i = 0; i < numElements; i++ )
    {
      randomArray.push( this.from<T>( [first].concat( values ) ) );
    } 

    return randomArray;
  }

  fromSet<T>( set:Set<T> )
  {
    let index = this.integerExclusiveFromZero( set.size );
    let i = 0;

    for ( let t of set )
    {
      if ( index === i )
      {
        return t;
      }

      i++;
    }

    return null;
  }
  

}

export abstract class SeedableRandomEngine<S> extends RandomEngine
{
  abstract setSeed( seed:number ):void;
  abstract getSeedState():S;
  abstract setSeedState( seedState:S ):void;
  
}