SandGame/explosive.js

import { grid, cols, rows } from './state.js';
import { config } from './config.js';
import { createCell } from './physics.js';

let explosionQueue = [];
let isProcessingExplosions = false;

export function updateExplosive(x, y, cell) {
    const dxs = [0, 0, -1, 1];
    const dys = [1, -1, 0, 0];
    for (let i = 0; i < 4; i++) {
        const nx = x + dxs[i];
        const ny = y + dys[i];
        if (nx >= 0 && nx < cols && ny >= 0 && ny < rows && grid[nx][ny]) {
            if (grid[nx][ny].type === 'fire' || grid[nx][ny].type === 'lava') {
                explode(x, y);
                return;
            }
        }
    }
}

export function explode(startX, startY) {
    if (!grid[startX][startY] || grid[startX][startY].type !== 'explosive') return;

    explosionQueue.push({ x: startX, y: startY });
    if (isProcessingExplosions) return;

    isProcessingExplosions = true;

    while (explosionQueue.length > 0) {
        const origin = explosionQueue.shift();
        processSingleExplosion(origin.x, origin.y);
    }

    isProcessingExplosions = false;
}

function processSingleExplosion(startX, startY) {
    if (startX < 0 || startX >= cols || startY < 0 || startY >= rows) return;
    
    // BFS to find contiguous cluster of TNT
    const queue = [{ x: startX, y: startY }];
    const cluster = [];
    const visited = new Uint8Array(cols * rows);
    visited[startY * cols + startX] = 1;

    let head = 0;
    let minX = startX, maxX = startX, minY = startY, maxY = startY;

    while (head < queue.length) {
        const curr = queue[head++];
        cluster.push(curr);

        if (curr.x < minX) minX = curr.x;
        if (curr.x > maxX) maxX = curr.x;
        if (curr.y < minY) minY = curr.y;
        if (curr.y > maxY) maxY = curr.y;

        const dxs = [0, 0, -1, 1];
        const dys = [1, -1, 0, 0];
        for (let i = 0; i < 4; i++) {
            const nx = curr.x + dxs[i];
            const ny = curr.y + dys[i];
            if (nx >= 0 && nx < cols && ny >= 0 && ny < rows) {
                const idx = ny * cols + nx;
                if (!visited[idx]) {
                    visited[idx] = 1;
                    if (grid[nx][ny] && grid[nx][ny].type === 'explosive') {
                        queue.push({ x: nx, y: ny });
                    }
                }
            }
        }
    }

    // Clear the TNT cluster
    for (let i = 0; i < cluster.length; i++) {
        const p = cluster[i];
        grid[p.x][p.y] = null;
    }

    const reach = Math.round(config.explosive.radius);
    const totalMass = cluster.length;
    const forceMultiplier = config.explosive.force + Math.log(totalMass + 1) * 0.15;

    // Center of the explosion
    const centerX = Math.round((minX + maxX) / 2);
    const centerY = Math.round((minY + maxY) / 2);

    const blastMinX = Math.max(0, minX - reach);
    const blastMaxX = Math.min(cols - 1, maxX + reach);
    const blastMinY = Math.max(0, minY - reach);
    const blastMaxY = Math.min(rows - 1, maxY + reach);

    // Apply blast wave across the combined bounding area
    for (let ny = blastMinY; ny <= blastMaxY; ny++) {
        for (let nx = blastMinX; nx <= blastMaxX; nx++) {
            // Find distance to closest cluster block or center
            const dx = nx - centerX;
            const dy = ny - centerY;
            const dist = Math.sqrt(dx * dx + dy * dy);
            const effectiveReach = reach + Math.min(10, Math.sqrt(totalMass));

            if (dist <= effectiveReach) {
                const target = grid[nx][ny];
                if (target) {
                    const tt = target.type;
                    if (tt === 'explosive') {
                        // Queue chain reaction
                        explosionQueue.push({ x: nx, y: ny });
                    } else if (config.explosive.destroy[tt]) {
                        if (tt === 'wood' || tt === 'plant' || tt === 'grass') {
                            grid[nx][ny] = createCell(Math.random() < 0.5 ? 'fire' : 'smoke');
                        } else if (tt === 'dirt' || tt === 'sand') {
                            // Fling granular particles outward with blast force
                            const angle = Math.atan2(dy, dx);
                            const force = (effectiveReach - dist + 1) * forceMultiplier * 0.4;
                            target.vx = (target.vx || 0) + Math.cos(angle) * force;
                            target.vy = (target.vy || 0) + Math.sin(angle) * force - 1.5;
                        } else {
                            grid[nx][ny] = null;
                        }
                    } else if (tt === 'water' || tt === 'acid' || tt === 'oil') {
                        if (tt === 'water' && Math.random() < 0.35) {
                            grid[nx][ny] = createCell('steam');
                        } else if (tt === 'oil' && Math.random() < 0.5) {
                            grid[nx][ny] = createCell('fire');
                        } else {
                            const angle = Math.atan2(dy, dx);
                            const force = (effectiveReach - dist + 1) * forceMultiplier * 0.5;
                            target.vx = (target.vx || 0) + Math.cos(angle) * force;
                            target.vy = (target.vy || 0) + Math.sin(angle) * force - 1.0;
                        }
                    }
                } else if (Math.random() < 0.08 && !grid[nx][ny]) {
                    // Spawn fire or smoke in empty space within blast core
                    grid[nx][ny] = createCell(Math.random() < 0.4 ? 'fire' : 'smoke');
                }
            }
        }
    }
}