import * as THREE from "three";

/**
 * VoxelManager.js
 * Handles the Three.js rendering of the VoxelGrid.
 * Uses InstancedMesh for performance (1 draw call for 10,000 blocks).
 */
export class VoxelManager {
  constructor(grid, scene) {
    this.grid = grid;
    this.scene = scene;
    this.mesh = null;

    // Define Material Palette (ID -> Color)
    this.palette = [
      null, // 0: Air (Invisible)
      new THREE.Color(0x888888), // 1: Stone (Grey)
      new THREE.Color(0x8b4513), // 2: Dirt (Brown)
      new THREE.Color(0x228b22), // 3: Grass (Green)
      new THREE.Color(0x00f0ff), // 4: Aether Crystal (Cyan)
    ];

    this.init();
  }

  init() {
    // Create geometry once
    const geometry = new THREE.BoxGeometry(1, 1, 1);

    // Basic material allows for coloring individual instances
    const material = new THREE.MeshLambertMaterial({ color: 0xffffff });

    // Calculate max capacity based on grid size
    const count = this.grid.width * this.grid.height * this.grid.depth;

    // Create the InstancedMesh
    this.mesh = new THREE.InstancedMesh(geometry, material, count);
    this.mesh.instanceMatrix.setUsage(THREE.DynamicDrawUsage);

    // Add to scene
    this.scene.add(this.mesh);
  }

  /**
   * Rebuilds the visual mesh based on the grid data.
   * Call this in the game loop if grid.dirty is true.
   */
  update() {
    if (!this.grid.dirty) return;

    let instanceId = 0;
    const dummy = new THREE.Object3D();

    for (let y = 0; y < this.grid.height; y++) {
      for (let z = 0; z < this.grid.depth; z++) {
        for (let x = 0; x < this.grid.width; x++) {
          const typeId = this.grid.getVoxel(x, y, z);

          if (typeId !== 0) {
            // Position the dummy object
            dummy.position.set(x, y, z);
            dummy.updateMatrix();

            // Update the instance matrix
            this.mesh.setMatrixAt(instanceId, dummy.matrix);

            // Update the instance color based on ID
            const color = this.palette[typeId] || new THREE.Color(0xff00ff); // Magenta = Error
            this.mesh.setColorAt(instanceId, color);

            instanceId++;
          }
        }
      }
    }

    // Hide unused instances by scaling them to zero (or moving them to infinity)
    // For simplicity in this prototype, we define count as max possible,
    // but in production, we would manage the count property more dynamically.
    this.mesh.count = instanceId;

    this.mesh.instanceMatrix.needsUpdate = true;

    // instanceColor is lazy-created by Three.js only when setColorAt is called.
    // If the grid is empty, instanceColor might be null.
    if (this.mesh.instanceColor) {
      this.mesh.instanceColor.needsUpdate = true;
    }

    this.grid.dirty = false;
  }
}