@timohausmann/quadtree-ts/src/Rectangle.ts

import type { NodeGeometry, Indexable } from './types';

/**
 * Rectangle Geometry
 * @beta
 * 
 * @remarks
 * This interface simply represents a rectangle geometry.
 */
export interface RectangleGeometry {

    /**
     * X start of the rectangle (top left).
     */
    x: number

    /**
     * Y start of the rectangle (top left).
     */
    y: number

    /**
     * Width of the rectangle.
     */
    width: number

    /**
     * Height of the rectangle.
     */
    height: number
}

/**
 * Rectangle Constructor Properties
 * @beta
 * @typeParam CustomDataType - Type of the custom data property (optional, inferred automatically).
 */
export interface RectangleProps<CustomDataType = void> extends RectangleGeometry {

    /**
     * Custom data
     */
    data?: CustomDataType
}

/**
 * Class representing a Rectangle
 * @typeParam CustomDataType - Type of the custom data property (optional, inferred automatically).
 * 
 * @example Without custom data (JS/TS):
 * ```typescript
 * const rectangle = new Rectangle({ 
 *   x: 10, 
 *   y: 20, 
 *   width: 30,
 *   height: 40,
 * });
 * ```
 * 
 * @example With custom data (JS/TS):
 * ```javascript
 * const rectangle = new Rectangle({ 
 *   x: 10, 
 *   y: 20, 
 *   width: 30,
 *   height: 40,
 *   data: { 
 *     name: 'Jane', 
 *     health: 100,
 *   },
 * });
 * ```
 * 
 * @example With custom data (TS):
 * ```typescript
 * interface ObjectData {
 *   name: string
 *   health: number
 * }
 * const entity: ObjectData = {
 *   name: 'Jane',
 *   health: 100,
 * };
 * 
 * // Typescript will infer the type of the data property
 * const rectangle1 = new Rectangle({
 *   x: 10, 
 *   y: 20, 
 *   width: 30,
 *   height: 40,
 *   data: entity,
 * });
 * 
 * // You can also pass in a generic type for the data property
 * const rectangle2 = new Rectangle<ObjectData>({ 
 *   x: 10, 
 *   y: 20, 
 *   width: 30,
 *   height: 40,
 * });
 * rectangle2.data = entity;
 * ```
 * 
 * @example With custom class extending Rectangle (implements {@link RectangleGeometry} (x, y, width, height)):
 * ```javascript
 * // extending inherits the qtIndex method
 * class Box extends Rectangle {
 *   
 *   constructor(props) {
 *     // call super to set x, y, width, height (and data, if given)
 *     super(props);
 *     this.content = props.content;
 *   }
 * }
 * 
 * const box = new Box({
 *   content: 'Gravity Boots',
 *   x: 10, 
 *   y: 20, 
 *   width: 30,
 *   height: 40,
 * });
 * ```
 * 
 * @example With custom class and mapping {@link RectangleGeometry}:
 * ```javascript
 * // no need to extend if you don't implement RectangleGeometry
 * class Box {
 *   
 *   constructor(content) {
 *     this.content = content;
 *     this.position = [10, 20];
 *     this.size = [30, 40];
 *   }
 *   
 *   // add a qtIndex method to your class
 *   qtIndex(node) {
 *     // map your properties to RectangleGeometry
 *     return Rectangle.prototype.qtIndex.call({
 *       x: this.position[0],
 *       y: this.position[1],
 *       width: this.size[0],
 *       height: this.size[1],
 *     }, node);
 *   }
 * }
 * 
 * const box = new Box('Gravity Boots');
 * ```
 * 
 * @example With custom object that implements {@link RectangleGeometry}:
 * ```javascript
 * const player = {
 *   name: 'Jane', 
 *   health: 100,
 *   x: 10, 
 *   y: 20, 
 *   width: 30,
 *   height: 30,
 *   qtIndex: Rectangle.prototype.qtIndex,
 * });
 * ```
 * 
 * @example With custom object and mapping {@link RectangleGeometry}:
 * ```javascript
 * // Note: this is not recommended but possible. 
 * // Using this technique, each object would have it's own qtIndex method. 
 * // Rather add qtIndex to your prototype, e.g. by using classes like shown above.
 * const player = {
 *   name: 'Jane', 
 *   health: 100,
 *   position: [10, 20], 
 *   size: [30, 40], 
 *   qtIndex: function(node) {
 *     return Rectangle.prototype.qtIndex.call({
 *       x: this.position[0],
 *       y: this.position[1],
 *       width: this.size[0],
 *       height: this.size[1],
 *     }, node);
 *   },
 * });
 * ```
 */
export class Rectangle<CustomDataType = void> implements RectangleGeometry, Indexable {

    /**
     * X start of the rectangle (top left).
     */
    x: number;

    /**
     * Y start of the rectangle (top left).
     */
    y: number;

    /**
     * Width of the rectangle.
     */
    width: number;

    /**
     * Height of the rectangle.
     */
    height: number;

    /**
     * Custom data.
     */
    data?: CustomDataType;

    constructor(props:RectangleProps<CustomDataType>) {
        
        this.x = props.x;
        this.y = props.y;
        this.width = props.width;
        this.height = props.height;
        this.data = props.data;
    }
    
    /**
     * Determine which quadrant this rectangle belongs to.
     * @param node - Quadtree node to be checked
     * @returns Array containing indexes of intersecting subnodes (0-3 = top-right, top-left, bottom-left, bottom-right)
     */
    qtIndex(node:NodeGeometry): number[] {
        
        const indexes:number[] = [],
            boundsCenterX   = node.x + (node.width/2),
            boundsCenterY   = node.y + (node.height/2);

        const startIsNorth  = this.y < boundsCenterY,
            startIsWest     = this.x < boundsCenterX,
            endIsEast       = this.x + this.width > boundsCenterX,
            endIsSouth      = this.y + this.height > boundsCenterY;

        //top-right quad
        if(startIsNorth && endIsEast) {
            indexes.push(0);
        }
        
        //top-left quad
        if(startIsWest && startIsNorth) {
            indexes.push(1);
        }

        //bottom-left quad
        if(startIsWest && endIsSouth) {
            indexes.push(2);
        }

        //bottom-right quad
        if(endIsEast && endIsSouth) {
            indexes.push(3);
        }
     
        return indexes;
    }
}