const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");

const widthInput = document.getElementById("width");
const heightInput = document.getElementById("height");
const resizeButton = document.getElementById("resize");

const colorInput = document.getElementById("color");
const brushInput = document.getElementById("brush");

let color = colorInput.value;
let size = Number(brushInput.value);
let painting = false;

function resize() {
    canvas.width = Number(widthInput.value);
    canvas.height = Number(heightInput.value);

    ctx.fillStyle = "#ffffff";
    ctx.fillRect(0, 0, canvas.width, canvas.height);
}

function wrap(value, size) {
    return ((value % size) + size) % size;
}

function paint(x, y) {
    x = wrap(x, canvas.width);
    y = wrap(y, canvas.height);

    const radius = size / 2;

    ctx.fillStyle = color;

    for (const dx of [-canvas.width, 0, canvas.width]) {
        for (const dy of [-canvas.height, 0, canvas.height]) {
            ctx.beginPath();
            ctx.arc(x + dx, y + dy, radius, 0, Math.PI * 2);
            ctx.fill();
        }
    }
}

function pointerPosition(event) {
    const rect = canvas.getBoundingClientRect();

    return {
        x: (event.clientX - rect.left) * canvas.width / rect.width,
        y: (event.clientY - rect.top) * canvas.height / rect.height,
    };
}

canvas.addEventListener("pointerdown", event => {
    painting = true;
    canvas.setPointerCapture(event.pointerId);

    const { x, y } = pointerPosition(event);
    paint(x, y);
});

canvas.addEventListener("pointermove", event => {
    if (!painting)
        return;

    const { x, y } = pointerPosition(event);
    paint(x, y);
});

canvas.addEventListener("pointerup", event => {
    painting = false;
    canvas.releasePointerCapture(event.pointerId);
});

canvas.addEventListener("pointercancel", () => {
    painting = false;
});

colorInput.addEventListener("input", () => {
    color = colorInput.value;
});

brushInput.addEventListener("input", () => {
    if (brushInput.value < 1)
        brushInput.value = 1;

    size = Number(brushInput.value);
});

resizeButton.addEventListener("click", resize);

resize();

const downloadButton = document.getElementById("download");

downloadButton.addEventListener("click", () => {
    canvas.toBlob(blob => {
        const url = URL.createObjectURL(blob);
        const link = document.createElement("a");

        link.href = url;
        link.download = "tile_image.png";
        link.click();

        URL.revokeObjectURL(url);
    }, "image/png");
});