const canvasWidth = 800;
const canvasHeight = 800;
const backgroundColor = "#333333";
let vehicle;
let target;
let demo = "wander";

function setup() {
    createCanvas(canvasWidth, canvasHeight);
    cursor(CROSS);
    vehicle = new Vehicle(0, 0);
    target = new Target(canvasWidth / 2, canvasHeight / 2);
    if (demo == "wander") {
        vehicle.maxVelocity = 5;
        vehicle.maxSteering = 3;
        vehicle.velocity = createVector(1, 1);
    }
}

function draw() {
    background(backgroundColor);
    switch (demo) {
        case "seek2":
            demoSeek2();
            break;
        case "arrive":
            demoSeek(true);
            break;
        case "wander":
            demoWander();
            break;
        default:
            demoSeek();
    }
}

class Vehicle {
    constructor(x, y) {
        this.position = createVector(x, y);
        this.velocity = createVector(0, 0);
        this.acceleration = createVector(0, 0);
        this.color = "#FFFFFF";
        this.size = 32;
        this.maxVelocity = 6;
        this.maxSteering = 0.25;
        this.path = [];
        this.drawPath = true;
        this.pathes = [];
    }

    seek(target, arrive = false) {
        let steering = p5.Vector.sub(target.position, this.position);

        let desiredVelocity = this.maxVelocity;
        if (arrive) {
            let slowdownDistance = this.size * 3;
            let distance = steering.mag();
            if (distance < slowdownDistance) {
                desiredVelocity = map(distance, 0, 100, 0, this.maxVelocity);
            }
        }

        steering.setMag(desiredVelocity);
        steering.sub(this.velocity);
        return steering;
    }

    flee(target) {
        let steering = this.seek(target).mult(-1);
        return steering;
    }

    wander() {
        let wanderPoint = this.velocity.copy();
        wanderPoint.setMag(100);
        wanderPoint.add(this.position);

        // stroke(255);
        // let x1 = wanderPoint.x + -25 * cos(PI / 2 + this.velocity.heading());
        // let y1 = wanderPoint.y + -25 * sin(PI / 2 + this.velocity.heading());
        // let x2 = wanderPoint.x + 25 * cos(PI / 2 + this.velocity.heading());
        // let y2 = wanderPoint.y + 25 * sin(PI / 2 + this.velocity.heading());
        // line(x1, y1, x2, y2);

        noStroke();
        fill("#F063A4");
        let offset = map(noise(Date.now() / 1000), 0, 1, -50, 50);
        let x = offset * cos(PI / 2 + this.velocity.heading());
        let y = offset * sin(PI / 2 + this.velocity.heading());
        wanderPoint.add(x, y);
        circle(wanderPoint.x, wanderPoint.y, 8);
        let steering = wanderPoint.sub(this.position);
        return steering;
    }

    update(steering) {
        if (steering) {
            steering.limit(this.maxSteering);
            this.acceleration.add(steering);
        }
        this.velocity.add(this.acceleration);
        this.velocity.limit(this.maxVelocity);
        this.position.add(this.velocity);
        this.acceleration.set(0);
    }

    show() {
        noFill();
        if (this.pathes.length >= 10) this.pathes.shift();
        stroke(255);
        strokeWeight(2);
        [...this.pathes, this.path].forEach((path, i) => {
            let c = map(i, 0, this.pathes.length, 127, 255);
            let w = map(i, 0, this.pathes.length, 1, 5);
            stroke(c);
            strokeWeight(w);
            beginShape();
            path.forEach((v) => vertex(v.x, v.y));
            endShape();
        });

        // stroke(255);
        // strokeWeight(4);
        // beginShape();
        // this.path.forEach((v) => {
        //     vertex(v.x, v.y);
        // });
        // endShape();

        push();
        noStroke();
        fill(this.color);
        translate(this.position.x, this.position.y);
        rotate(this.velocity.heading());
        triangle(
            this.size / 2,
            0,
            -this.size / 2,
            -this.size / 4,
            -this.size / 2,
            this.size / 4
        );
        pop();
    }

    edges() {
        if (this.position.x < 0) {
            this.position.x = canvasWidth;
            return true;
        } else if (this.position.x >= canvasWidth) {
            this.position.x = 0;
            return true;
        }
        if (this.position.y < 0) {
            this.position.y = canvasHeight;
            return true;
        } else if (this.position.y >= canvasHeight) {
            this.position.y = 0;
            return true;
        }
        return false;
    }

    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;
    }
}

class Target extends Vehicle {
    constructor(x, y) {
        super(x, y);
        this.position = createVector(random(canvasWidth), random(canvasHeight));
        this.color = "#F063A4";
        this.size = 32;
        this.maxVelocity = 6;
        this.maxSteering = 1;
    }

    show() {
        push();
        stroke(255);
        strokeWeight(1);
        fill(this.color);
        circle(this.position.x, this.position.y, this.size);
        pop();
    }
}

function demoSeek(arrive) {
    target.position.x = mouseX;
    target.position.y = mouseY;
    let steering = vehicle.seek(target, arrive);
    vehicle.update(steering);
    target.show();
    vehicle.show();
}

function demoWander() {
    let steering = vehicle.wander();
    vehicle.update(steering);
    if (vehicle.edges()) {
        vehicle.pathes.push(vehicle.path);
        vehicle.path = [];
    }
    if (frameCount % 1 == 0) vehicle.path.push(vehicle.position.copy());
    vehicle.show();
}

function demoSeek2() {
    let distance = p5.Vector.dist(vehicle.position, target.position);
    if (distance < target.size / 2) {
        target.position = createVector(
            random(canvasWidth),
            random(canvasHeight)
        );
        target.acceleration = createVector(0, 0);
        target.velocity = createVector(0, 0);
    }

    let seekSteering = vehicle.seek(target);
    let fleeSteering = target.flee(vehicle);
    vehicle.update(seekSteering);
    target.update(fleeSteering);
    target.bounce();
    target.show();
    vehicle.show();
}

/**
 * 获取随机向量，可指定大小
 * @param {number} magnitude 向量大小
 * @return {p5.Vector} vector 随机向量
 */
function randomVector(magnitude) {
    let vector = p5.Vector.random2D();
    if (magnitude) vector.mult(magnitude);
    return vector;
}