/* V13 Filters Module - Post-Processing Effects */
import { state } from './state.js';

/**
 * Apply all enabled filters to the canvas
 */
export function applyFilters(ctx, canvas) {
    if (state.glitchEnabled) {
        applyGlitch(ctx, canvas);
    }

    if (state.scanlinesEnabled) {
        applyScanlines(ctx, canvas);
    }

    if (state.vignetteEnabled) {
        applyVignette(ctx, canvas);
    }

    if (state.bloomEnabled) {
        applyBloom(ctx, canvas);
    }

    if (state.pixelateEnabled) {
        applyPixelate(ctx, canvas);
    }

    if (state.invertEnabled) {
        applyInvert(ctx, canvas);
    }
}

/**
 * Glitch Effect - RGB channel separation
 */
function applyGlitch(ctx, canvas) {
    const imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
    const data = imageData.data;

    // Random offset
    const offset = Math.floor(Math.random() * 10) - 5;

    // Shift red channel
    for (let i = 0; i < data.length; i += 4) {
        if (i + offset * 4 >= 0 && i + offset * 4 < data.length) {
            data[i] = data[i + offset * 4]; // R
        }
    }

    ctx.putImageData(imageData, 0, 0);
}

/**
 * Scanlines - CRT monitor effect
 */
function applyScanlines(ctx, canvas) {
    ctx.globalAlpha = 0.1;
    ctx.fillStyle = '#000000';

    for (let y = 0; y < canvas.height; y += 4) {
        ctx.fillRect(0, y, canvas.width, 2);
    }

    ctx.globalAlpha = 1.0;
}

/**
 * Vignette - Darkened edges
 */
function applyVignette(ctx, canvas) {
    const cx = canvas.width / 2;
    const cy = canvas.height / 2;
    const radius = Math.max(canvas.width, canvas.height) / 2;

    const gradient = ctx.createRadialGradient(cx, cy, radius * 0.3, cx, cy, radius);
    gradient.addColorStop(0, 'rgba(0,0,0,0)');
    gradient.addColorStop(1, 'rgba(0,0,0,0.7)');

    ctx.fillStyle = gradient;
    ctx.fillRect(0, 0, canvas.width, canvas.height);
}

/**
 * Bloom - Glow overflow effect
 * Note: This is a simplified version. True bloom requires multiple passes.
 */
function applyBloom(ctx, canvas) {
    ctx.save();
    ctx.globalCompositeOperation = 'screen';
    ctx.globalAlpha = 0.3;
    ctx.filter = 'blur(20px)';
    ctx.drawImage(canvas, 0, 0);
    ctx.filter = 'none';
    ctx.restore();
}

/**
 * Pixelate - Retro pixel art look
 */
function applyPixelate(ctx, canvas) {
    const pixelSize = 8;
    const w = canvas.width;
    const h = canvas.height;

    // Get current canvas
    const imageData = ctx.getImageData(0, 0, w, h);

    // Downsample
    ctx.imageSmoothingEnabled = false;
    const tempCanvas = document.createElement('canvas');
    tempCanvas.width = Math.floor(w / pixelSize);
    tempCanvas.height = Math.floor(h / pixelSize);
    const tempCtx = tempCanvas.getContext('2d');
    tempCtx.drawImage(canvas, 0, 0, tempCanvas.width, tempCanvas.height);

    // Upsample
    ctx.clearRect(0, 0, w, h);
    ctx.drawImage(tempCanvas, 0, 0, w, h);
    ctx.imageSmoothingEnabled = true;
}

/**
 * Invert Colors - Negative image
 */
function applyInvert(ctx, canvas) {
    const imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
    const data = imageData.data;

    for (let i = 0; i < data.length; i += 4) {
        data[i] = 255 - data[i];         // R
        data[i + 1] = 255 - data[i + 1]; // G
        data[i + 2] = 255 - data[i + 2]; // B
        // Alpha unchanged
    }

    ctx.putImageData(imageData, 0, 0);
}