/* global document */
/** Debug utility to draw FBO contents onto screen */
// eslint-disable-next-line
export const debugFBO = function (fbo, { minimap, opaque } = {}) {
    const color = fbo.device.readPixelsToArrayWebGL(fbo);
    let canvas = document.getElementById('fbo-canvas');
    const canvasHeight = (minimap ? 2 : 1) * fbo.height;
    if (!canvas) {
        canvas = document.createElement('canvas');
        canvas.id = 'fbo-canvas';
        canvas.style.zIndex = '100';
        canvas.style.position = 'absolute';
        canvas.style.top = '0';
        canvas.style.right = '0';
        canvas.style.border = 'blue 1px solid';
        canvas.style.transform = 'scaleY(-1)';
        document.body.appendChild(canvas);
    }
    if (canvas.width !== fbo.width || canvas.height !== canvasHeight) {
        canvas.width = fbo.width;
        canvas.height = canvasHeight;
        canvas.style.width = '400px';
    }
    const ctx = canvas.getContext('2d');
    const imageData = ctx.createImageData(canvas.width, canvas.height);
    // Minimap
    if (minimap) {
        const zoom = 8; // Zoom factor for minimap
        const { width, height } = canvas;
        for (let y = 0; y < height; y++) {
            for (let x = 0; x < width; x++) {
                const d = 4 * (x + y * width); // destination pixel
                const s = 4 * (Math.floor(x / zoom) + Math.floor(y / zoom) * width); // source
                imageData.data[d + 0] = color[s + 0];
                imageData.data[d + 1] = color[s + 1];
                imageData.data[d + 2] = color[s + 2];
                imageData.data[d + 3] = opaque ? 255 : color[s + 3];
            }
        }
    }
    // Full map
    const offset = minimap ? color.length : 0;
    for (let i = 0; i < color.length; i += 4) {
        imageData.data[offset + i + 0] = color[i + 0];
        imageData.data[offset + i + 1] = color[i + 1];
        imageData.data[offset + i + 2] = color[i + 2];
        imageData.data[offset + i + 3] = opaque ? 255 : color[i + 3];
    }
    ctx.putImageData(imageData, 0, 0);
};