import * as THREE from 'three';
import type { PierModel, Vec2 } from '../core/geometry';
import type { TerrainGrid } from '../core/ground-model';
import { buildPierScene, type PierScene } from './scene';
import { terrainGeometry } from './terrain';

/**
 * Scene offset of a pier's group inside the shared frame of the reference pier. Each pier's scene is centred on its own
 * pivot, so moving it by the pivot difference puts it at its national-grid place (x = E, z = −N, as in stretchMatrix).
 */
export function pierOffset(pivot: Vec2, reference: Vec2): { x: number; z: number } {
  return { x: pivot.e - reference.e, z: reference.n - pivot.n };
}

export interface AllPiers {
  /** Holds every pier's group, placed by pierOffset. Used for the camera fit and picking. */
  piers: THREE.Group;
  /** Shared terrain grid in the reference frame, or null without a terrain model. */
  terrain: THREE.Mesh | null;
  /** Scene of each pier, keyed by the pier name. Parts are shown per pier. */
  scenes: Map<string, PierScene>;
  /** Scene with the same shape the single-pier view expects (root = pier group, size = whole span). */
  view: PierScene;
}

/**
 * Builds the concrete members of several piers in one frame (전체 보기, 콘크리트만: no rebar). The first entry is the
 * reference. With a terrain grid it is drawn once and the per-pier ground lines are hidden.
 */
export function buildAllPiers(entries: { name: string; model: PierModel; groundEl?: number | null }[], terrain?: TerrainGrid): AllPiers {
  const piers = new THREE.Group();
  const scenes = new Map<string, PierScene>();
  const reference = entries[0].model.pivot;
  const terrainSurface = terrain ? terrainGeometry(terrain, reference) : undefined;
  const hasTerrainSurface = Boolean(terrainSurface && (terrainSurface.getIndex()?.count ?? 0) > 0);
  for (const { name, model, groundEl } of entries) {
    const scene = buildPierScene(model, undefined, groundEl);
    // Without terrain each pier keeps its own 지반고 line; with terrain the shared grid replaces them.
    scene.parts.ground.visible = !hasTerrainSurface;
    const { x, z } = pierOffset(model.pivot, reference);
    scene.root.position.set(x, 0, z);
    scene.root.userData.pier = name;
    piers.add(scene.root);
    scenes.set(name, scene);
  }
  let terrainMesh: THREE.Mesh | null = null;
  if (terrainSurface && hasTerrainSurface) {
    const material = new THREE.MeshStandardMaterial({ color: 0xb8c7b0, roughness: 0.9, metalness: 0, transparent: true, opacity: 0.35, depthWrite: false, side: THREE.DoubleSide });
    terrainMesh = new THREE.Mesh(terrainSurface, material);
  }
  const box = new THREE.Box3().setFromObject(piers);
  const size = box.getSize(new THREE.Vector3()).length();
  const view: PierScene = { root: piers, parts: scenes.get(entries[0].name)!.parts, size };
  return { piers, terrain: terrainMesh, scenes, view };
}