let vehicle1;
let vehicle2;

function setup() {
    cursor(CROSS);
    createCanvas(600, 600);
    vehicle1 = new Vehicle(300, 300, "#CCCCCC");
    vehicle2 = new Vehicle(300, 300, "#CC3333");
    vehicle2.velocity = randomVector(5);
}

function draw() {
    // 追逐鼠标();
    // 逃避鼠标();
    // 巡游小车();
    小车追逐();
}

function 追逐鼠标() {
    background(64);
    vehicle1.seek({ position: createVector(mouseX, mouseY) });
    vehicle1.move();
    vehicle1.turn();
    vehicle1.drawPath();
    vehicle1.show();
}

function 逃避鼠标() {
    background(64);
    vehicle1.flee({ position: createVector(mouseX, mouseY) });
    vehicle1.move();
    vehicle1.turn();
    vehicle1.drawPath();
    vehicle1.show();
}

function 巡游小车() {
    background(64);
    vehicle1.wander();
    vehicle1.move();
    vehicle1.turn();
    vehicle1.drawPath();
    vehicle1.show();
}

function 小车追逐() {
    background(64);
    vehicle1.seek(vehicle2, 20);
    vehicle2.move();
    vehicle1.move();
    if (vehicle2.turn()) vehicle2.velocity = randomVector(random(2, 5));
    vehicle1.turn();
    vehicle1.drawPath();
    vehicle2.show();
    vehicle1.show();
}

/**
 * 返回可指定大小的随机二维向量
 * @param {number} magnitude 向量大小
 * @return {p5.Vector} vector 随机二维向量
 */
function randomVector(magnitude) {
    let vector = p5.Vector.random2D();
    return magnitude ? vector.mult(magnitude) : vector;
}

class Vehicle {
    constructor(x, y, color) {
        this.color = color;
        this.position = createVector(x, y);
        this.path = [];
        this.pathes = [];
        this.velocity = createVector(0, 0);
        this.heading = this.velocity.heading();
        this.acceleration = createVector(0, 0);
        this.maxVelocity = 5;
        this.maxAcceleration = 1;
    }

    seek(target, slowdownDistance = 100) {
        const desired = p5.Vector.sub(target.position, this.position);
        const distance = desired.mag();
        const magnitude =
            slowdownDistance > 0 && distance <= slowdownDistance
                ? map(distance, 0, slowdownDistance, 0, this.maxVelocity)
                : this.maxVelocity;
        desired.setMag(magnitude);
        const steering = p5.Vector.sub(desired, this.velocity);
        this.acceleration.add(steering);
    }

    flee(target, fleeDistance = 100) {
        const desired = p5.Vector.sub(this.position, target.position);
        const distance = desired.mag();
        const magnitude =
            !fleeDistance || fleeDistance <= 0
                ? this.maxVelocity
                : distance <= fleeDistance
                ? map(distance, 0, fleeDistance, this.maxVelocity, 0)
                : 0;
        desired.setMag(magnitude);
        const steering = p5.Vector.sub(desired, this.velocity);
        this.acceleration.add(steering);
    }

    wander() {
        const target = this.velocity.copy();
        target.setMag(50).add(this.position);

        // stroke(128);
        // const x1 = target.x + -25 * cos(PI / 2 + this.heading);
        // const y1 = target.y + -25 * sin(PI / 2 + this.heading);
        // const x2 = target.x + 25 * cos(PI / 2 + this.heading);
        // const y2 = target.y + 25 * sin(PI / 2 + this.heading);
        // line(x1, y1, x2, y2);

        const offset = map(noise(Date.now() / 1000), 0, 1, -50, 50);
        const x = offset * cos(PI / 2 + this.heading);
        const y = offset * sin(PI / 2 + this.heading);
        target.add(x, y);

        // noStroke();
        // fill("#F063A4");
        // circle(target.x, target.y, 5);

        const steering = target.sub(this.position);
        this.acceleration.add(steering);
    }

    move() {
        this.acceleration.limit(this.maxAcceleration);
        this.velocity.add(this.acceleration);
        if (this.velocity.mag() > 0) this.heading = this.velocity.heading();
        this.velocity.limit(this.maxVelocity);
        this.position.add(this.velocity);
        this.acceleration.set(0, 0);
        this.path.push(this.position.copy());
    }

    turn() {
        let x = this.position.x;
        let y = this.position.y;
        while (x < 0 || x >= width) x = (x + width) % width;
        while (y < 0 || y >= height) y = (y + height) % height;
        const edgeCrossed = x != this.position.x || y != this.position.y;
        if (edgeCrossed) {
            this.pathes.push(this.path);
            this.path = [];
        }
        this.position.x = x;
        this.position.y = y;
        return edgeCrossed;
    }

    // bounce() {
    //     if (this.position.x <= this.size / 2) {
    //         this.position.x = this.size / 2;
    //         this.velocity.x *= -1;
    //         return true;
    //     } else if (this.position.x > canvasWidth - this.size / 2) {
    //         this.position.x = canvasWidth - this.size / 2;
    //         this.velocity.x *= -1;
    //         return true;
    //     }
    //     if (this.position.y <= this.size / 2) {
    //         this.position.y = this.size / 2;
    //         this.velocity.y *= -1;
    //         return true;
    //     } else if (this.position.y >= canvasHeight - this.size / 2) {
    //         this.position.y = canvasHeight - this.size / 2;
    //         this.velocity.y *= -1;
    //         return true;
    //     }
    //     return false;
    // }

    drawPath() {
        push();
        noFill();
        stroke(50);
        strokeWeight(1);
        // if (this.pathes.length >= 10) this.pathes.shift();
        [...this.pathes, this.path].forEach((path) => {
            beginShape();
            path.forEach((v) => vertex(v.x, v.y));
            endShape();
        });
        pop();
    }

    show() {
        push();
        translate(this.position.x, this.position.y);
        rotate(this.heading);
        stroke(this.color);
        fill(this.color);
        triangle(0, 0, -10, 2.5, -10, -2.5);
        pop();
    }
}