"use strict";

/******************************************************
 ************** Simple ES6 Vector Class  **************
 ******************************************************
 * Author: Starbeamrainbowlabs
 * Twitter: @SBRLabs
 * Email: feedback at starbeamrainbowlabs dot com
 * 
 * From https://gist.github.com/sbrl/69a8fa588865cacef9c0
 ******************************************************
 * Originally written for my 2D Graphics ACW at Hull
 * University.
 ******************************************************
 * Changelog
 ******************************************************
 * 19th December 2015:
 * Added this changelog.
 * 28th December 2015:
 * Rewrite tests with klud.js + Node.js
 * 30th January 2016:
 * Tweak angleFrom function to make it work properly.
 * 31st January 2016:
 * Add the moveTowards function.
 * Add the minComponent getter.
 * Add the maxComponent getter.
 * Add the equalTo function.
 * Tests still need to be written for all of the above.
 * 19th September 2016:
 * Added Vector support to the multiply method.
 */

class Vector {
    // Constructor
    constructor(inX, inY) {
        if (typeof inX != "number") throw new Error("Invalid x value.");
        if (typeof inY != "number") throw new Error("Invalid y value.");

        // Store the (x, y) coordinates
        this.x = inX;
        this.y = inY;
    }

    /**
     * Add another vector to this vector.
     * @param {Vector} v The vector to add.
     * @return {Vector}   The current vector. useful for daisy-chaining calls.
     */
    add(v) {
        this.x += v.x;
        this.y += v.y;

        return this;
    }

    /**
     * Take another vector from this vector.
     * @param  {Vector} v The vector to subtrace from this one.
     * @return {Vector}   The current vector. useful for daisy-chaining calls.
     */
    subtract(v) {
        this.x -= v.x;
        this.y -= v.y;

        return this;
    }

    /**
     * Divide the current vector by a given value.
     * @param  {number} value The value to divide by.
     * @return {Vector}	   The current vector. Useful for daisy-chaining calls.
     */
    divide(value) {
        if (typeof value != "number") throw new Error("Can't divide by non-number value.");

        this.x /= value;
        this.y /= value;

        return this;
    }

    /**
     * Multiply the current vector by a given value.
     * @param  {(number|Vector)} value The number (or Vector) to multiply the current vector by.
     * @return {Vector}	   The current vector. useful for daisy-chaining calls.
     */
    multiply(value) {
        if (value instanceof Vector) {
            this.x *= value.x;
            this.y *= value.y;
        } else if (typeof value == "number") {
            this.x *= value;
            this.y *= value;
        } else throw new Error("Can't multiply by non-number value.");

        return this;
    }

    /**
     * Move the vector towards the given vector by the given amount.
     * @param  {Vector} v      The vector to move towards.
     * @param  {number} amount The distance to move towards the given vector.
     */
    moveTowards(v, amount) {
        // From http://stackoverflow.com/a/2625107/1460422
        var dir = new Vector(
        v.x - this.x,
        v.y - this.y).limitTo(amount);
        this.x += dir.x;
        this.y += dir.y;

        return this;
    }

    /**
     * Limit the length of the current vector to value without changing the
     * direction in which the vector is pointing.
     * @param  {number} value The number to limit the current vector's length to.
     * @return {Vector}	   The current vector. useful for daisy-chaining calls.
     */
    limitTo(value) {
        if (typeof value != "number") throw new Error("Can't limit to non-number value.");

        this.divide(this.length);
        this.multiply(value);

        return this;
    }

    /**
     * Return the dot product of the current vector and another vector.
     * @param  {Vector} v   The other vector we should calculate the dot product with.
     * @return {Vector}	 The current vector. useful for daisy-chaining calls.
     */
    dotProduct(v) {
        return (this.x * v.x) + (this.y * v.y);
    }

    /**
     * Calculate the angle, in radians, from north to another vector.
     * @param  {Vector} v The other vector to which to calculate the angle.
     * @return {Vector}	 The current vector. useful for daisy-chaining calls.
     */
    angleFrom(v) {
        // From http://stackoverflow.com/a/16340752/1460422
        var angle = Math.atan2(v.y - this.y, v.x - this.x) - (Math.PI / 2);
        angle += Math.PI / 2;
        if (angle < 0) angle += Math.PI * 2;
        return angle;
    }

    /**
     * Clones the current vector.
     * @return {Vector} A clone of the current vector. Very useful for passing around copies of a vector if you don't want the original to be altered.
     */
    clone() {
        return new Vector(this.x, this.y);
    }

    /*
     * Returns a representation of the current vector as a string.
     * @returns {string} A representation of the current vector as a string.
     */
    toString() {
        return` ($ {
            this.x
        }, $ {
            this.y
        })`;
    }

    /**
     * Whether the vector is equal to another vector.
     * @param  {Vector} v The vector to compare to.
     * @return {boolean}  Whether the current vector is equal to the given vector.
     */
    equalTo(v) {
        if (this.x == v.x && this.y == v.y) return true;
        else return false;
    }

    /**
     * Get the unit vector of the current vector - that is a vector poiting in the same direction with a length of 1. Note that this does *not* alter the original vector.
     * @return {Vector} The current vector's unit form.
     */
    get unitVector() {
        var length = this.length;
        return new Vector(
        this.x / length,
        this.y / length);
    }

    /**
     * Get the length of the current vector.
     * @return {number} The length of the current vector.
     */
    get length() {
        return Math.sqrt((this.x * this.x) + (this.y * this.y));
    }

    /**
     * Get the value of the minimum component of the vector.
     * @return {number} The minimum component of the vector.
     */
    get minComponent() {
        return Math.min(this.x, this.y);
    }

    /**
     * Get the value of the maximum component of the vector.
     * @return {number} The maximum component of the vector.
     */
    get maxComponent() {
        return Math.min(this.x, this.y);
    }
}
// Make Vector.js Node.js friendly
export default Vector;