export const canvas = document.getElementById('gameCanvas');
export const ctx = canvas.getContext('2d', { alpha: false });

export const cellSize = 5;
export let cols = 0;
export let rows = 0;
export let grid = [];
export let selectedType = 'sand';
export let brushSize = 4;
export let currentFrame = 1;
export let cursor = { x: -1, y: -1, visible: false };

export function incrementFrame() {
    currentFrame++;
    if (currentFrame > 2000000000) currentFrame = 1;
}

export function setSelectedType(type) {
    selectedType = type;
}

export function setBrushSize(size) {
    brushSize = Math.max(1, Math.min(30, Math.round(size)));
}

export function setGrid(newGrid) {
    grid = newGrid;
}

export function createEmptyGrid(newCols, newRows) {
    const newGrid = new Array(newCols);
    for (let x = 0; x < newCols; x++) {
        newGrid[x] = new Array(newRows).fill(null);
    }
    return newGrid;
}

export function clearGrid() {
    grid = createEmptyGrid(cols, rows);
}

export function resize() {
    const newWidth = window.innerWidth;
    const newHeight = window.innerHeight;
    canvas.width = newWidth;
    canvas.height = newHeight;
    
    const newCols = Math.floor(newWidth / cellSize);
    const newRows = Math.floor(newHeight / cellSize);
    
    if (newCols === cols && newRows === rows && grid.length > 0) {
        return;
    }
    
    const oldGrid = grid;
    const oldCols = cols;
    const oldRows = rows;
    
    cols = newCols;
    rows = newRows;
    grid = createEmptyGrid(cols, rows);
    
    // Non-destructive resize: preserve existing particles
    if (oldGrid && oldCols > 0 && oldRows > 0) {
        const copyCols = Math.min(oldCols, cols);
        const copyRows = Math.min(oldRows, rows);
        for (let x = 0; x < copyCols; x++) {
            for (let y = 0; y < copyRows; y++) {
                grid[x][y] = oldGrid[x][y];
            }
        }
    }
}