import { ctx, canvas, grid, cols, rows, cellSize, brushSize, cursor } from './state.js';
import { config } from './config.js';

let offscreenCanvas = document.createElement('canvas');
let offscreenCtx = offscreenCanvas.getContext('2d', { willReadFrequently: false });
let imgData = null;
let pixelBuffer = null;
let lastCols = 0;
let lastRows = 0;

const BG_COLOR = 0xFF151211; // 0xAABBGGRR for #111215

function ensureBuffer() {
    if (cols !== lastCols || rows !== lastRows || !imgData) {
        lastCols = cols;
        lastRows = rows;
        offscreenCanvas.width = cols;
        offscreenCanvas.height = rows;
        imgData = offscreenCtx.createImageData(cols, rows);
        pixelBuffer = new Uint32Array(imgData.data.buffer);
    }
}

export function draw() {
    if (cols <= 0 || rows <= 0) return;
    ensureBuffer();

    const totalPixels = cols * rows;
    const style = config.visual.style;

    // Fast-fill background or render particles
    for (let y = 0; y < rows; y++) {
        const rowOffset = y * cols;
        for (let x = 0; x < cols; x++) {
            const cell = grid[x][y];
            if (cell) {
                pixelBuffer[rowOffset + x] = cell.u32Color || 0xFFFFFFFF;
            } else {
                pixelBuffer[rowOffset + x] = BG_COLOR;
            }
        }
    }

    offscreenCtx.putImageData(imgData, 0, 0);

    // Blit to main canvas with desired smoothing
    ctx.imageSmoothingEnabled = (style === 'fuzzy' || style === 'bloby');
    if (style === 'fuzzy') {
        ctx.filter = 'blur(1px)';
    } else {
        ctx.filter = 'none';
    }

    ctx.drawImage(offscreenCanvas, 0, 0, canvas.width, canvas.height);

    if (style === 'fuzzy') {
        ctx.filter = 'none';
    }

    // Brush cursor indicator
    if (cursor.visible && cursor.x >= 0 && cursor.y >= 0) {
        ctx.save();
        ctx.beginPath();
        const screenRadius = Math.max(cellSize, brushSize * cellSize);
        ctx.arc(cursor.x, cursor.y, screenRadius, 0, Math.PI * 2);
        ctx.strokeStyle = 'rgba(255, 255, 255, 0.45)';
        ctx.lineWidth = 1.5;
        ctx.setLineDash([4, 4]);
        ctx.stroke();
        ctx.restore();
    }
}