// ====== [GLOBAL VARIABLES] ======
let trail = [];
let velocities = [];

let particles = [];
let flashAlpha = 0;
let lastSliceTime = 0;

let coconut = {
    x: 400,
    y: 300,
    r: 50
};

// ====== [SETUP] ======
function setup() {
    createCanvas(800, 600);
}

// ====== [DRAW LOOP] ======
function draw() {
    background(30);

    drawTrail();
    drawCoconut();
    checkSlice();

    // ====== PARTICLES ======
    for (let i = particles.length - 1; i >= 0; i--) {
        particles[i].update();
        particles[i].draw();

        if (particles[i].life <= 0) {
            particles.splice(i, 1);
        }
    }

    // ====== FLASH EFFECT ======
    if (flashAlpha > 0) {
        fill(255, flashAlpha);
        rect(0, 0, width, height);
        flashAlpha -= 20;
    }
}

// ====== [INPUT: KNIFE TRACKING] ======
function mouseDragged() {
    let pos = createVector(mouseX, mouseY);
    trail.push(pos);

    if (trail.length > 1) {
        let v = p5.Vector.sub(
            trail[trail.length - 1],
            trail[trail.length - 2]
        );
        velocities.push(v.mag());
    }

    if (trail.length > 20) trail.shift();
    if (velocities.length > 20) velocities.shift();
}

// ====== [DRAW TRAIL] ======
function drawTrail() {
    noFill();

    for (let i = 1; i < trail.length; i++) {
        let speed = velocities[i] || 0;
        let thickness = map(speed, 0, 50, 1, 10);

        strokeWeight(thickness);
        stroke(255, 200);

        line(
            trail[i - 1].x,
            trail[i - 1].y,
            trail[i].x,
            trail[i].y
        );
    }
}

// ====== [DRAW COCONUT] ======
function drawCoconut() {
    fill(100, 255, 100);
    noStroke();
    ellipse(coconut.x, coconut.y, coconut.r * 2);
}

// ====== [SLICE CHECK] ======
function checkSlice() {
    for (let i = 1; i < trail.length; i++) {
        let hit = lineCircle(
            trail[i - 1],
            trail[i],
            coconut.x,
            coconut.y,
            coconut.r
        );

        if (hit && millis() - lastSliceTime > 100) {
            lastSliceTime = millis();

            let speed = velocities[i] || 10;

            console.log("SLICE!");

            spawnParticles(coconut.x, coconut.y, speed);
            flashAlpha = map(speed, 0, 50, 50, 150);
        }
    }
}

// ====== [COLLISION: LINE vs CIRCLE] ======
function lineCircle(p1, p2, cx, cy, r) {
    let ac = createVector(cx - p1.x, cy - p1.y);
    let ab = p5.Vector.sub(p2, p1);

    let ab2 = ab.magSq();
    let acab = ac.dot(ab);

    let t = constrain(acab / ab2, 0, 1);

    let h = createVector(
        p1.x + ab.x * t,
        p1.y + ab.y * t
    );

    let distSq = (h.x - cx) ** 2 + (h.y - cy) ** 2;

    return distSq <= r * r;
}

// ====== [PARTICLE CLASS] ======
class Particle {
    constructor(x, y, speed) {
        this.pos = createVector(x, y);
        this.vel = p5.Vector.random2D().mult(random(1, speed * 0.3));
        this.life = 255;
    }

    update() {
        this.pos.add(this.vel);
        this.life -= 5;
    }

    draw() {
        noStroke();
        fill(200, 255, 200, this.life);
        ellipse(this.pos.x, this.pos.y, 5);
    }
}

// ====== [SPAWN PARTICLES] ======
function spawnParticles(x, y, speed) {
    let count = map(speed, 0, 50, 5, 25);

    for (let i = 0; i < count; i++) {
        particles.push(new Particle(x, y, speed));
    }
}