/**
 * LANE-RENDER — the Bitstream, made visible.
 *
 * Isometric factory view. Sim is truth: we render snapshots and never simulate.
 * Composition: registry (assets + MODELBEAST hot-swap) -> ground / belts / entities /
 * belt items / ghost layers -> ortho iso camera.
 */
import * as THREE from 'three';
import type { Dir, GameData, MachineDef, Renderer, SimSnapshot, Vec2 } from '../contracts';
import { AssetRegistry } from './registry';
import { CAM_DIST, CameraRig, WORLD_HALF } from './camera';
import { createGround, createVignette } from './ground';
import { EntityLayer } from './entities';
import { BeltLayer } from './belts';
import { BeltItemLayer } from './beltitems';
import { GhostLayer } from './ghost';
import { DevScene, devSceneEnabled, devSceneStress } from './devscene';
import { BeltTopology } from './topology';
import { WORLD } from './palette';

const KEY_INTENSITY = 1.9;
const FILL_INTENSITY = 0.7;
const AMBIENT_INTENSITY = 1.1;
/** ACES rolls mid-tones down hard; this lifts the factory back off a near-black ground. */
const BASE_EXPOSURE = 1.35;

export function createRenderer(): Renderer {
  let gl: THREE.WebGLRenderer;
  let scene: THREE.Scene;
  let rig: CameraRig;
  let registry: AssetRegistry;
  let entities: EntityLayer;
  let belts: BeltLayer;
  let cargo: BeltItemLayer;
  let ghost: GhostLayer;
  let dev: DevScene | null = null;
  let defs: Map<string, MachineDef>;
  const topo = new BeltTopology();

  const raycaster = new THREE.Raycaster();
  const groundPlane = new THREE.Plane(new THREE.Vector3(0, 1, 0), 0);
  const ndc = new THREE.Vector2();
  const hit = new THREE.Vector3();
  const clock = new THREE.Clock();
  let dim = 1; // smoothed brownout level
  /** Dev-only frame-cost sampler. Measures CPU ms per frame, which — unlike frame
   *  RATE — stays honest even when the tab is backgrounded and rAF is throttled. */
  const stats = { ms: 0, avg: 0, frames: 0 };

  return {
    async init(container: HTMLElement, data: GameData) {
      defs = new Map(data.machines.map((m) => [m.id, m]));

      gl = new THREE.WebGLRenderer({ antialias: true, powerPreference: 'high-performance' });
      gl.setPixelRatio(Math.min(devicePixelRatio, 2));
      gl.setSize(container.clientWidth, container.clientHeight);
      gl.shadowMap.enabled = true;
      gl.shadowMap.type = THREE.PCFSoftShadowMap;
      gl.toneMapping = THREE.ACESFilmicToneMapping;
      container.appendChild(gl.domElement);
      container.appendChild(createVignette());

      scene = new THREE.Scene();
      scene.background = new THREE.Color(WORLD.bg);
      // Fog distances are measured from the CAMERA, which an ortho iso rig parks
      // CAM_DIST away from everything — so the band starts past the focal point and
      // only bites at the far reaches. Absolute values here would fog the whole world
      // into the background.
      scene.fog = new THREE.Fog(WORLD.bg, CAM_DIST + 12, CAM_DIST + 78);
      scene.add(createGround());

      const key = new THREE.DirectionalLight(0xbfc8ff, KEY_INTENSITY);
      key.position.set(18, 30, 12);
      key.castShadow = true;
      key.shadow.mapSize.set(2048, 2048);
      key.shadow.camera.near = 1;
      key.shadow.camera.far = 90;
      const s = 26;
      key.shadow.camera.left = -s;
      key.shadow.camera.right = s;
      key.shadow.camera.top = s;
      key.shadow.camera.bottom = -s;
      key.shadow.bias = -0.0012;
      scene.add(key);
      // Cool bounce from below-ish so machine flanks don't go pure black.
      const fill = new THREE.DirectionalLight(0x4a3f7a, FILL_INTENSITY);
      fill.position.set(-14, 8, -16);
      scene.add(fill);
      scene.add(new THREE.AmbientLight(0x8f8fbf, AMBIENT_INTENSITY));

      rig = new CameraRig(container, gl.domElement);

      registry = new AssetRegistry();
      await registry.init(data);

      belts = new BeltLayer(registry, defs, topo);
      entities = new EntityLayer(registry, defs);
      cargo = new BeltItemLayer(data, topo);
      ghost = new GhostLayer(registry, defs);
      scene.add(belts.group, entities.group, cargo.group, ghost.group);

      if (devSceneEnabled()) {
        const d = new DevScene(data, devSceneStress());
        if (d.usable) {
          dev = d;
          console.info('[render] devscene active — mock line until LANE-SIM lands entities');
          // Dev-only introspection hook (devscene builds only). Never touched in prod.
          (window as unknown as { __render: unknown }).__render = {
            scene, camera: rig.camera, stats, gl, dev, topo, cargo, entities,
          };
        }
      }

      const onResize = () => {
        gl.setSize(container.clientWidth, container.clientHeight);
        rig.resize();
      };
      addEventListener('resize', onResize);
      new ResizeObserver(onResize).observe(container);
    },

    render(snap: SimSnapshot, alpha: number) {
      if (!gl) return;
      const t0 = dev ? performance.now() : 0;
      const dt = clock.getDelta();
      const t = clock.elapsedTime;

      // Dev scaffold yields the instant the real sim has anything to show.
      const view = dev && snap.entities.length === 0 ? dev.snapshot(snap.tick) : snap;

      rig.update(dt);
      // Topology is shared by belts (which piece to draw) and cargo (which path the
      // items take), so it is rebuilt once here rather than twice downstream.
      topo.rebuild(view, defs);
      belts.sync(view, t);
      entities.sync(view, t, dt);
      cargo.sync(view, alpha, t);
      ghost.update(view, t);

      // Brownout: drop the whole scene ~30% and flicker. Driven through tone-mapping
      // exposure so emissives dim too — a brownout that left the glow at full would
      // read as a lighting bug rather than a power failure.
      const target = view.bandwidth.brownout ? 0.7 : 1;
      dim += (target - dim) * Math.min(1, dt * 6);
      const flicker = view.bandwidth.brownout
        ? 0.88 + Math.sin(t * 37) * 0.08 + (Math.sin(t * 13.3) > 0.72 ? -0.22 : 0)
        : 1;
      gl.toneMappingExposure = BASE_EXPOSURE * dim * flicker;

      gl.render(scene, rig.camera);

      if (dev) {
        stats.ms = performance.now() - t0;
        stats.frames++;
        stats.avg += (stats.ms - stats.avg) * 0.05; // rolling
      }
    },

    pickTile(clientX: number, clientY: number): Vec2 | null {
      if (!gl) return null;
      const rect = gl.domElement.getBoundingClientRect();
      ndc.x = ((clientX - rect.left) / rect.width) * 2 - 1;
      ndc.y = -((clientY - rect.top) / rect.height) * 2 + 1;
      raycaster.setFromCamera(ndc, rig.camera);
      if (!raycaster.ray.intersectPlane(groundPlane, hit)) return null;
      const x = Math.floor(hit.x);
      const y = Math.floor(hit.z);
      if (x < -WORLD_HALF || x >= WORLD_HALF || y < -WORLD_HALF || y >= WORLD_HALF) return null;
      return { x, y };
    },

    setGhost(def: string | null, pos: Vec2 | null, dir: Dir) {
      ghost?.set(def, pos, dir);
    },
  };
}