import { MAT_FOOD, MAT_HOME, MAT_SAND } from "./constants";

// simple seeded PRNG for deterministic placement
function mulberry32(seed: number) {
    return () => {
        seed += 0x6d2b79f5;
        let t = seed;
        t = Math.imul(t ^ (t >>> 15), t | 1);
        t ^= t + Math.imul(t ^ (t >>> 7), t | 61);
        return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
    };
}

export function generateSideViewWorld(
    worldSize: number,
    seed: boolean,
): Float32Array {
    const data = new Float32Array(worldSize * worldSize * 4);
    const sandHeight = Math.floor(worldSize * 0.6);
    const surfaceRow = sandHeight - 1;

    // fill bottom 60% with sand
    for (let y = 0; y < sandHeight; y++) {
        for (let x = 0; x < worldSize; x++) {
            const idx = (y * worldSize + x) * 4;
            data[idx] = MAT_SAND;
        }
    }
    // top 40% stays MAT_AIR (Float32Array is zero-initialized)

    if (seed) {
        const rng = mulberry32(Date.now());
        // place home at random surface position (middle 60% of world width)
        const margin = Math.floor(worldSize * 0.2);
        const homeX = margin + Math.floor(rng() * (worldSize - 2 * margin));

        const homeIdx = (surfaceRow * worldSize + homeX) * 4;
        data[homeIdx] = MAT_HOME;

        // place food at a different random surface position
        let foodX = homeX;
        while (foodX === homeX) {
            foodX = margin + Math.floor(rng() * (worldSize - 2 * margin));
        }
        const foodIdx = (surfaceRow * worldSize + foodX) * 4;
        data[foodIdx] = MAT_FOOD;
    }

    return data;
}