/**
 * @date     2020-04-15
 * @author   Converted to a class by Ikaros Kappler
 * @modified 2020-08-19 Ported this class from vanilla JS to TypeScript.
 * @version  1.0.1
 *
 * @file CatmullRomPath
 * @public
 **/

import { CubicBezierCurve } from "../../CubicBezierCurve";
import { Vertex } from "../../Vertex";


/**
 * @classdesc Compute the Catmull-Rom spline path from a sequence of points (vertices).
 *
 * For comparison to the HobbyCurve I wanted to add a Catmull-Rom path (to show that the
 * HobbyCurve is smoother).
 *
 * This demo implementation was inspired by this Codepen by Blake Bowen
 * https://codepen.io/osublake/pen/BowJed
 *
 * @requires CubicBezierCurve
 * @requires Vertex
 */
export class CatmullRomPath {

    /**
     * @member {Array<Vertex>} vertices
     * @memberof CatmullRomPath
     * @type {Array<Vertex>}
     * @instance
     **/
    private vertices : Array<Vertex>;


    /**
     * @constructor
     * @name CatmullRomPath
     * @param {Array<Vertex>=} vertices? - An optional array of vertices to initialize the path with.
     **/
    constructor( vertices?: Array<Vertex> ) {
	this.vertices = vertices ? vertices : [];	
    };


    /**
     * Add a new point to the end of the vertex sequence.
     *
     * @name addPoint
     * @memberof CatmullRomPath
     * @instance
     * @param {Vertex} p - The vertex (point) to add.
     **/
    addPoint (p: Vertex) : void {
	this.vertices.push( p );
    };

    
    /**
     * Generate a sequence of cubic Bézier curves from the point set.
     *
     * @name generateCurve
     * @memberof CatmullRomPath
     * @instance
     * @param {boolean=} circular - Specify if the path should be closed.
     * @param {number=1} tension - (default=0) An optional tension parameter.
     * @return Array<CubicBezierCurve>
     **/
    generateCurve ( circular?: boolean, tension?: number ) {
	if( typeof tension === 'undefined' )
	    tension = 1.0;

	if( circular )
	    return this.solveClosed( tension );
	else
	    return this.solveOpen( tension );	
    };
     
    private solveOpen (k:number) : Array<CubicBezierCurve> {
	var curves : Array<CubicBezierCurve> = [];	
	if (k == null || typeof k === 'undefined' ) k = 1;	
	var size : number = this.vertices.length;
	var last : number = size - 2;
	for (var i = 0; i < size - 1; i ++ ) {
	    var p0 : Vertex = i ? this.vertices[i - 1] : this.vertices[0];	    
	    var p1 : Vertex = this.vertices[i + 0];
	    var p2 : Vertex = this.vertices[i + 1];
	    var p3 : Vertex = i !== last ? this.vertices[i + 2] : p2;	    
	    var cp1 : Vertex = new Vertex( p1.x + (p2.x - p0.x) / 6 * k, p1.y + (p2.y - p0.y) / 6 * k );
	    var cp2 : Vertex = new Vertex( p2.x - (p3.x - p1.x) / 6 * k, p2.y - (p3.y - p1.y) / 6 * k );	    
	    curves.push( new CubicBezierCurve( p1, p2, cp1, cp2 ) );
	} 
	return curves;
    }; // END solveOpen

    private solveClosed (k:number) : Array<CubicBezierCurve> {
	var curves : Array<CubicBezierCurve> = [];	
	if (k == null || typeof k === 'undefined' ) k = 1;	
	var size : number = this.vertices.length;
	var last : number = size - 1;
	for (var i = 0; i < size; i ++ ) {
	    var p0 : Vertex = i ? this.vertices[i - 1] : this.vertices[last];	    
	    var p1 : Vertex = this.vertices[i + 0];
	    var p2 : Vertex = this.vertices[(i + 1) % size];
	    var p3 : Vertex = this.vertices[(i + 2) % size];	    
	    var cp1 : Vertex = new Vertex( p1.x + (p2.x - p0.x) / 6 * k, p1.y + (p2.y - p0.y) / 6 * k );
	    var cp2 : Vertex = new Vertex( p2.x - (p3.x - p1.x) / 6 * k, p2.y - (p3.y - p1.y) / 6 * k );	    
	    curves.push( new CubicBezierCurve( p1, p2, cp1, cp2 ) );
	} 
	return curves;
    }; // END solveClosed
}; // END class