// World: Chunk-Storage, Block-Zugriff, Generierung, Mesh-Verwaltung, Streaming.
import * as THREE from 'three';
import {
  CHUNK_SIZE, CHUNK_HEIGHT, BLOCK, isSolid,
} from './constants.js';
import { generateChunk } from './worldgen.js';
import { buildChunkGeometry } from './mesher.js';

class Chunk {
  constructor(cx, cz) {
    this.cx = cx;
    this.cz = cz;
    // Index: y * (S*S) + z * S + x
    this.blocks = new Uint8Array(CHUNK_SIZE * CHUNK_HEIGHT * CHUNK_SIZE);
    this.meshes = null;     // { opaque: Mesh|null, water: Mesh|null }
    this.dirty = true;      // Mesh muss (neu) gebaut werden
  }
  idx(x, y, z) { return y * CHUNK_SIZE * CHUNK_SIZE + z * CHUNK_SIZE + x; }
  get(x, y, z) { return this.blocks[this.idx(x, y, z)]; }
  set(x, y, z, v) { this.blocks[this.idx(x, y, z)] = v; }
}

export class World {
  constructor(scene, materials, seed) {
    this.scene = scene;
    this.materials = materials; // { opaque: Material, water: Material }
    this.seed = seed;
    this.chunks = new Map();
  }

  key(cx, cz) { return cx + ',' + cz; }

  getChunk(cx, cz) { return this.chunks.get(this.key(cx, cz)); }

  // Generiert den Chunk (falls nicht vorhanden) inkl. Terrain+Baeume.
  // Da der Chunk VOR dem Generieren in die Map eingetragen wird, ist die
  // Rekursion (Baeume in Nachbar-Chunks) beschraenkt und terminiert.
  ensureChunk(cx, cz) {
    const k = this.key(cx, cz);
    let c = this.chunks.get(k);
    if (c) return c;
    c = new Chunk(cx, cz);
    this.chunks.set(k, c);
    generateChunk(this, c);
    return c;
  }

  // Block-Lesezugriff OHNE Generierung (fuer Rendering/Physik/Raycast).
  getBlock(wx, wy, wz) {
    if (wy < 0 || wy >= CHUNK_HEIGHT) return BLOCK.AIR;
    const cx = Math.floor(wx / CHUNK_SIZE);
    const cz = Math.floor(wz / CHUNK_SIZE);
    const c = this.getChunk(cx, cz);
    if (!c) return BLOCK.AIR;
    return c.get(wx - cx * CHUNK_SIZE, wy, wz - cz * CHUNK_SIZE);
  }

  // Lesezugriff MIT Generierung (fuer Weltgenerierung / Baeume).
  getGen(wx, wy, wz) {
    if (wy < 0 || wy >= CHUNK_HEIGHT) return BLOCK.AIR;
    const cx = Math.floor(wx / CHUNK_SIZE);
    const cz = Math.floor(wz / CHUNK_SIZE);
    const c = this.ensureChunk(cx, cz);
    return c.get(wx - cx * CHUNK_SIZE, wy, wz - cz * CHUNK_SIZE);
  }

  // Schreibzugriff waehrend Generierung.
  setGen(wx, wy, wz, v) {
    if (wy < 0 || wy >= CHUNK_HEIGHT) return;
    const cx = Math.floor(wx / CHUNK_SIZE);
    const cz = Math.floor(wz / CHUNK_SIZE);
    const c = this.ensureChunk(cx, cz);
    c.set(wx - cx * CHUNK_SIZE, wy, wz - cz * CHUNK_SIZE, v);
  }

  // Spieler-Setzen/Abbauen: schreibt Block und markiert betroffene Chunks dirty.
  setBlock(wx, wy, wz, v) {
    if (wy < 0 || wy >= CHUNK_HEIGHT) return false;
    const cx = Math.floor(wx / CHUNK_SIZE);
    const cz = Math.floor(wz / CHUNK_SIZE);
    const lx = wx - cx * CHUNK_SIZE;
    const lz = wz - cz * CHUNK_SIZE;
    const c = this.ensureChunk(cx, cz);
    if (c.get(lx, wy, lz) === v) return false;
    c.set(lx, wy, lz, v);
    c.dirty = true;
    // An Chunk-Grenzen Nachbar-Chunks ebenfalls aktualisieren
    if (lx === 0) this._markDirty(cx - 1, cz);
    if (lx === CHUNK_SIZE - 1) this._markDirty(cx + 1, cz);
    if (lz === 0) this._markDirty(cx, cz - 1);
    if (lz === CHUNK_SIZE - 1) this._markDirty(cx, cz + 1);
    return true;
  }

  _markDirty(cx, cz) {
    const c = this.getChunk(cx, cz);
    if (c) c.dirty = true;
  }

  // Alle geladenen Chunks für einen Neubau markieren – z.B. wenn ein global
  // mesh-relevanter Wert (AO_LEVEL) live geändert wird. updateStreaming baut
  // sie dann über mehrere Frames (maxOpsPerFrame) verteilt neu.
  markAllDirty() {
    for (const c of this.chunks.values()) c.dirty = true;
  }

  // --- Meshing ---
  getBlockWorld = (wx, wy, wz) => this.getBlock(wx, wy, wz);

  buildChunkMesh(chunk) {
    // Fuer korrektes Border-Culling Nachbarn sicherstellen (Blockdaten).
    for (let dz = -1; dz <= 1; dz++) {
      for (let dx = -1; dx <= 1; dx++) {
        this.ensureChunk(chunk.cx + dx, chunk.cz + dz);
      }
    }
    const { opaque, transparent } = buildChunkGeometry(this.getBlockWorld, chunk);

    // alte Meshes entfernen
    this.disposeChunkMesh(chunk);

    const ox = chunk.cx * CHUNK_SIZE;
    const oz = chunk.cz * CHUNK_SIZE;
    const meshes = { opaque: null, water: null };

    if (opaque) {
      const m = new THREE.Mesh(opaque, this.materials.opaque);
      m.position.set(ox, 0, oz);
      m.frustumCulled = true;
      m.castShadow = true;
      m.receiveShadow = true;
      this.scene.add(m);
      meshes.opaque = m;
    }
    if (transparent) {
      const m = new THREE.Mesh(transparent, this.materials.water);
      m.position.set(ox, 0, oz);
      m.renderOrder = 1;
      m.receiveShadow = true; // Wasseroberflaeche kriegt Schatten; casten unnoetig
      this.scene.add(m);
      meshes.water = m;
    }
    chunk.meshes = meshes;
    chunk.dirty = false;
  }

  disposeChunkMesh(chunk) {
    if (!chunk.meshes) return;
    for (const key of ['opaque', 'water']) {
      const m = chunk.meshes[key];
      if (m) {
        this.scene.remove(m);
        m.geometry.dispose();
      }
    }
    chunk.meshes = null;
  }

  // --- Streaming: Chunks im Radius um Spieler halten ---
  updateStreaming(px, pz, renderDistance, maxOpsPerFrame) {
    const pcx = Math.floor(px / CHUNK_SIZE);
    const pcz = Math.floor(pz / CHUNK_SIZE);

    // 1) Entferne zu weit entfernte Chunks
    for (const [k, c] of this.chunks) {
      const dx = c.cx - pcx;
      const dz = c.cz - pcz;
      if (Math.max(Math.abs(dx), Math.abs(dz)) > renderDistance + 1) {
        this.disposeChunkMesh(c);
        this.chunks.delete(k);
      }
    }

    // 2) Sammle fehlende/dirty Chunks im Radius, sortiert nach Distanz
    const todo = [];
    for (let dz = -renderDistance; dz <= renderDistance; dz++) {
      for (let dx = -renderDistance; dx <= renderDistance; dx++) {
        const cx = pcx + dx;
        const cz = pcz + dz;
        const c = this.getChunk(cx, cz);
        if (!c) {
          todo.push({ cx, cz, d: dx * dx + dz * dz, gen: true });
        } else if (c.dirty) {
          todo.push({ cx, cz, d: dx * dx + dz * dz, gen: false });
        }
      }
    }
    todo.sort((a, b) => a.d - b.d);

    let ops = 0;
    for (const job of todo) {
      if (ops >= maxOpsPerFrame) break;
      const c = this.ensureChunk(job.cx, job.cz);
      this.buildChunkMesh(c);
      ops++;
    }
  }

  // Bei Spielstart: Chunk am Spawn sicherstellen (fuer sicheren Boden)
  highestSolidY(wx, wz) {
    const cx = Math.floor(wx / CHUNK_SIZE);
    const cz = Math.floor(wz / CHUNK_SIZE);
    const c = this.ensureChunk(cx, cz);
    const lx = wx - cx * CHUNK_SIZE;
    const lz = wz - cz * CHUNK_SIZE;
    for (let y = CHUNK_HEIGHT - 1; y >= 0; y--) {
      if (isSolid(c.get(lx, y, lz))) return y;
    }
    return CHUNK_HEIGHT - 1;
  }
}