import * as THREE from 'three';
import type { PierModel } from '../core/geometry';

export type PartName = 'coping' | 'columns' | 'footings' | 'piles' | 'blinding' | 'blocks' | 'pads' | 'ground';

export const PART_LABELS: Record<PartName, string> = {
  coping: '코핑',
  columns: '기둥',
  footings: '확대기초',
  piles: '말뚝',
  blinding: '버림콘크리트',
  blocks: '받침블럭',
  pads: '모르타르 패드',
  ground: '지반',
};

const COLORS: Record<PartName, number> = {
  coping: 0xb8c2cc,
  columns: 0x9aa7b4,
  footings: 0x7d8a99,
  piles: 0x5b6878,
  blinding: 0xe6e2d8,
  blocks: 0xd6dde5,
  pads: 0x8898aa,
  ground: 0x6b8f4e,
};

/**
 * Maps the model's local frame (x = along axis s, y = absolute EL, z = across axis n) to the scene.
 * The scene uses y as up and places the first column centre at the origin (spec §1).
 * Basis vectors: X = (u.e, 0, -u.n), Z = (nrm.e, 0, -nrm.n). The determinant is +1, so faces keep their winding.
 */
export function stretchMatrix(m: PierModel, k: number): THREE.Matrix4 {
  const st = m.stretches[k];
  const X = new THREE.Vector3(st.u.e, 0, -st.u.n);
  const Y = new THREE.Vector3(0, 1, 0);
  const Z = new THREE.Vector3(st.nrm.e, 0, -st.nrm.n);
  const origin = new THREE.Vector3(st.origin.e - m.pivot.e, 0, -(st.origin.n - m.pivot.n));
  return new THREE.Matrix4().makeBasis(X, Y, Z).setPosition(origin);
}

/**
 * Mitre plane at the bend point. Stretch 0 keeps the side (p − kink)·mitre ≤ 0 and stretch 1 the other side,
 * so each stretch's full-length slab is trimmed to its own half and the two meet at the mitred joint.
 * Three.js keeps fragments with a non-negative distance from the plane, hence the sign flip for stretch 0.
 */
/** Mitre plane for one stretch as a list, or undefined on a straight axis. */
export function planesOf(m: PierModel, k: number): THREE.Plane[] | undefined {
  const plane = mitrePlane(m, k);
  return plane ? [plane] : undefined;
}

/** Straight-frame matrix (stretch 0). */
export function frameMatrix(m: PierModel): THREE.Matrix4 {
  return stretchMatrix(m, 0);
}

export function mitrePlane(m: PierModel, k: number): THREE.Plane | undefined {
  if (!m.kink || !m.mitre) return undefined;
  const normal = new THREE.Vector3(m.mitre.e, 0, -m.mitre.n).multiplyScalar(k === 0 ? -1 : 1);
  const point = new THREE.Vector3(m.kink.e - m.pivot.e, 0, -(m.kink.n - m.pivot.n));
  return new THREE.Plane().setFromNormalAndCoplanarPoint(normal, point);
}

export interface PierScene {
  root: THREE.Group;
  parts: Record<PartName, THREE.Group>;
  size: number;
}

export function buildPierScene(m: PierModel): PierScene {
  const Ms = m.stretches.map((_, k) => stretchMatrix(m, k));
  const parts = {} as Record<PartName, THREE.Group>;
  for (const key of Object.keys(PART_LABELS) as PartName[]) {
    parts[key] = new THREE.Group();
    parts[key].name = key;
  }

  const add = (part: PartName, geometry: THREE.BufferGeometry, opacity = 1, k = 0, clippingPlanes?: THREE.Plane[]) => {
    geometry.applyMatrix4(Ms[k]);
    const material = new THREE.MeshStandardMaterial({
      color: COLORS[part],
      roughness: 0.75,
      metalness: 0.05,
      transparent: opacity < 1,
      opacity,
      side: THREE.DoubleSide,
      clippingPlanes,
    });
    material.userData.baseOpacity = opacity;
    parts[part].add(new THREE.Mesh(geometry, material));
  };

  // Coping: each part's elevation outline extruded across its width (no boolean operations), trimmed by the mitre plane.
  for (const part of m.copingParts) {
    const shape = new THREE.Shape(part.profile.map(([s, z]) => new THREE.Vector2(s, z)));
    const coping = new THREE.ExtrudeGeometry(shape, { depth: part.nTo - part.nFrom, bevelEnabled: false });
    coping.translate(0, 0, part.nFrom);
    const plane = mitrePlane(m, part.k);
    add('coping', coping, 1, part.k, plane ? [plane] : undefined);
  }

  for (const c of m.columns) {
    const g = new THREE.CylinderGeometry(c.diameter / 2, c.diameter / 2, c.top - c.bottom, 48);
    g.translate(c.s, (c.top + c.bottom) / 2, 0);
    add('columns', g, 1, c.k);
  }

  for (const f of m.footings) {
    const g = new THREE.BoxGeometry(f.length, f.top - f.bottom, f.width);
    g.translate(f.s, (f.top + f.bottom) / 2, 0);
    add('footings', g, 1, f.k, planesOf(m, f.k));
  }

  for (const b of m.blindings) {
    const g = new THREE.BoxGeometry(b.length, b.thickness, b.width);
    g.translate(b.s, b.top - b.thickness / 2, 0);
    add('blinding', g, 1, b.k, planesOf(m, b.k));
  }

  for (const p of m.piles) {
    const g = new THREE.CylinderGeometry(p.diameter / 2, p.diameter / 2, p.top - p.bottom, 20);
    g.translate(p.s, (p.top + p.bottom) / 2, p.n);
    add('piles', g, 1, p.k, planesOf(m, p.k));
  }

  for (const b of m.blocks) {
    // Turn the block so its sides follow the bearing row (rowSkewDeg); the 3D turn is rotateY(−skew).
    const turn = (-b.rowSkewDeg * Math.PI) / 180;
    const h = b.top - b.bottom;
    const g = new THREE.BoxGeometry(1.2, h, 1.2);
    g.rotateY(turn);
    g.translate(b.s, b.bottom + h / 2, b.n);
    add('blocks', g, 1, b.k);
    const pad = new THREE.BoxGeometry(1.0, 0.05, 1.0);
    pad.rotateY(turn);
    pad.translate(b.s, b.padTop - 0.025, b.n);
    add('pads', pad, 1, b.k);
  }

  // Ground: a translucent plane at the ground EL, used only to judge soil cover (not a computed input).
  const ground = new THREE.PlaneGeometry(60, 60);
  ground.rotateX(-Math.PI / 2);
  ground.translate(m.copingL / 2, m.groundEl, 0);
  add('ground', ground, 0.35);

  const root = new THREE.Group();
  for (const key of Object.keys(parts) as PartName[]) root.add(parts[key]);
  const box = new THREE.Box3().setFromObject(root);
  const size = Math.max(...box.getSize(new THREE.Vector3()).toArray());
  return { root, parts, size };
}

/** ③ rebar view: members and the ground at half opacity so the bars show through (승인 2026-10-23). */
const REBAR_VIEW_ALPHA = 0.5;

/** Turns the ③ rebar view on or off. Off restores each part's own opacity. Depth writes stop while on, so bars behind a member stay visible. */
export function setRebarView(scene: PierScene, on: boolean): void {
  for (const group of Object.values(scene.parts)) {
    group.traverse((o) => {
      if (!(o instanceof THREE.Mesh)) return;
      const mat = o.material as THREE.MeshStandardMaterial;
      const base = mat.userData.baseOpacity as number;
      mat.opacity = on ? REBAR_VIEW_ALPHA : base;
      mat.transparent = on || base < 1;
      mat.depthWrite = !on;
      mat.needsUpdate = true;
    });
  }
}

export type ViewKind = 'iso' | 'front' | 'side' | 'top';

/** Camera position for one of the four view presets, looking at the centre of the model. */
export function viewPosition(scene: PierScene, kind: ViewKind, m: PierModel): { position: THREE.Vector3; target: THREE.Vector3 } {
  const box = new THREE.Box3().setFromObject(scene.root);
  const target = box.getCenter(new THREE.Vector3());
  const dist = scene.size * 1.6;
  const X = new THREE.Vector3(m.u.e, 0, -m.u.n);
  const Z = new THREE.Vector3(m.nrm.e, 0, -m.nrm.n);
  const dirs: Record<ViewKind, THREE.Vector3> = {
    iso: new THREE.Vector3(1, 0.7, 1).normalize(),
    front: Z.clone().add(new THREE.Vector3(0, 0.15, 0)).normalize(),
    side: X.clone().add(new THREE.Vector3(0, 0.15, 0)).normalize(),
    top: new THREE.Vector3(0, 1, 0.001).normalize(),
  };
  return { position: target.clone().add(dirs[kind].multiplyScalar(dist)), target };
}