import * as THREE from 'three';
import { TransformControls } from 'three/addons/controls/TransformControls.js';

/**
 * Posing. Each bone is driven as a rotation *relative to its rest pose*, so
 * every bone reads 0/0/0 in the original stance and a saved pose stays valid
 * even if the model is re-exported with different bone orientations.
 *
 * `bone.quaternion = rest * delta` and `delta = rest⁻¹ * quaternion`, with the
 * delta expressed as XYZ Euler angles in degrees for the UI.
 */

const RAD = Math.PI / 180;
const DEG = 180 / Math.PI;

/** three sanitises node names, so `armsupport.l` arrives as `armsupportl`. */
const normalizeName = (name) => (name ?? '').replace(/[.\s]/g, '').toLowerCase();

/**
 * The same angle shifted by whole turns to sit next to `reference`. On an exact
 * half-turn tie the lower (smaller-magnitude) value wins, which keeps the
 * canonical -180..180 reading when two are equally close.
 */
const nearestAngle = (angle, reference) => {
  const turns = (reference - angle) / 360;
  const low = angle + 360 * Math.floor(turns);
  const high = angle + 360 * Math.ceil(turns);
  return Math.abs(low - reference) <= Math.abs(high - reference) ? low : high;
};

/** True when two quaternions describe the same rotation (double cover included). */
const sameRotation = (a, b) => Math.abs(Math.abs(a.dot(b)) - 1) < 1e-6;

export class Rig {
  constructor({ bones, scene, camera, domElement, orbit, pickTargets, onChange = null }) {
    this.bones = bones;
    this.byName = new Map();
    for (const entry of bones) {
      this.byName.set(entry.name, entry);
      const alias = normalizeName(entry.name);
      if (!this.byName.has(alias)) this.byName.set(alias, entry);
    }
    this.scene = scene;
    this.domElement = domElement;
    this.orbit = orbit;
    this.pickTargets = pickTargets;
    this.onChange = onChange;
    this.selected = null;
    // The delta last handed to (or written by) the UI, in degrees. An XYZ Euler
    // has several equivalent triples for one rotation, so getDelta returns the
    // one closest to this. That keeps a single-axis drag smooth through the
    // wrap at 90 deg (the middle axis) instead of jumping to the gimbal-flipped
    // twin, which made the sliders and the next setDelta spin the character.
    this.lastDelta = new Map();

    this.controls = new TransformControls(camera, domElement);
    this.controls.setMode('rotate');
    this.controls.setSpace('local');
    this.controls.setSize(0.8);
    // A *hidden* TransformControls still grabs the pointer in three: its picker
    // stays raycastable even when the helper is not drawn, so grabbing the body
    // (the rings sit on the `master` bone, right where you grab) silently turned
    // the character. Keep the controls disabled until the gizmo is actually
    // shown, so the mouse can only move the character (see setGizmoVisible).
    this.controls.enabled = false;
    this.helper = this.controls.getHelper();
    this.helper.visible = false;
    // Whether the user wants the gizmo at all. It starts OFF: the model is the
    // point, and the rings sat on top of it until you went looking for them.
    // Selecting a bone must not switch it back on by itself, so `select()`
    // consults this instead of always showing the helper.
    this.gizmoWanted = false;
    scene.add(this.helper);

    this.controls.addEventListener('dragging-changed', (event) => {
      this.orbit.enabled = !event.value;
    });
    this.controls.addEventListener('objectChange', () => {
      if (this.selected) this.onChange?.(this.selected);
    });
  }

  /* ------------------------------------------------------------ selection */

  select(name, { silent = false } = {}) {
    if (name && !this.byName.has(name)) return;
    this.selected = name ?? null;
    if (name) {
      this.controls.attach(this.byName.get(name).bone);
      this.helper.visible = this.gizmoWanted;
    } else {
      this.controls.detach();
      this.helper.visible = false;
    }
    // Only an actually-shown gizmo may take the pointer (see the constructor).
    this.controls.enabled = this.helper.visible;
    if (!silent) this.onChange?.(this.selected);
  }

  // Clicking the model no longer reaches for a bone: the mouse is for composing
  // (see the drag handling in src/main.js), and bones are picked from the panel's
  // bone list, which calls `select()` directly. So there is no pointer handler on
  // the canvas here at all.

  /* ----------------------------------------------------------------- pose */

  getDelta(name) {
    const entry = this.byName.get(name);
    if (!entry) return { x: 0, y: 0, z: 0 };
    const delta = entry.rest.clone().invert().multiply(entry.bone.quaternion);
    const base = new THREE.Euler().setFromQuaternion(delta, 'XYZ');
    const reference = this.lastDelta.get(entry) ?? { x: 0, y: 0, z: 0 };

    // For one rotation an XYZ Euler has a second solution - its "flipped" twin
    // `(x+180, 180-y, z+180)`. Three always returns the one whose middle angle
    // stays within +/-90, so past 90 the twin is what continues the drag; offer
    // both and keep whichever is closest to the last value. Near gimbal lock the
    // twin no longer reproduces the rotation, so it is dropped by the check.
    const candidates = [{ x: base.x, y: base.y, z: base.z }];
    const flipped = new THREE.Euler(base.x + Math.PI, Math.PI - base.y, base.z + Math.PI, 'XYZ');
    if (sameRotation(delta, new THREE.Quaternion().setFromEuler(flipped))) {
      candidates.push({ x: flipped.x, y: flipped.y, z: flipped.z });
    }

    let best = { x: 0, y: 0, z: 0 };
    let bestDistance = Infinity;
    for (const candidate of candidates) {
      const x = nearestAngle(candidate.x * DEG, reference.x);
      const y = nearestAngle(candidate.y * DEG, reference.y);
      const z = nearestAngle(candidate.z * DEG, reference.z);
      const distance = (x - reference.x) ** 2 + (y - reference.y) ** 2 + (z - reference.z) ** 2;
      if (distance < bestDistance) {
        bestDistance = distance;
        best = { x, y, z };
      }
    }

    this.lastDelta.set(entry, best);
    return { ...best };
  }

  setDelta(name, { x = 0, y = 0, z = 0 }) {
    const entry = this.byName.get(name);
    if (!entry) return;
    const delta = new THREE.Quaternion().setFromEuler(
      new THREE.Euler(x * RAD, y * RAD, z * RAD, 'XYZ'),
    );
    entry.bone.quaternion.copy(entry.rest).multiply(delta);
    // Remember exactly what the UI asked for so getDelta can hand it straight
    // back (this keeps applyPose/getPose an exact round-trip). Keyed by the bone
    // entry, not the name, so a raw name and its normalised alias agree.
    this.lastDelta.set(entry, { x, y, z });
  }

  /** `pose.bones` maps a bone name to `[x, y, z]` degrees; `pose.root` is a translation. */
  applyPose(pose = {}) {
    // Presets and saved files use the glTF bone names (`armsupport.l`) while
    // three sanitises them to `armsupportl`, so compare on the normalised form -
    // otherwise every preset that touches an arm or leg is silently ignored.
    const rotations = new Map();
    for (const [key, value] of Object.entries(pose.bones ?? {})) {
      rotations.set(normalizeName(key), value);
    }
    for (const entry of this.bones) {
      const value = rotations.get(normalizeName(entry.name));
      if (Array.isArray(value)) this.setDelta(entry.name, { x: value[0], y: value[1], z: value[2] });
      else this.setDelta(entry.name, { x: 0, y: 0, z: 0 });
    }
  }

  getPose({ onlyMoved = true } = {}) {
    const rotations = {};
    for (const entry of this.bones) {
      const { x, y, z } = this.getDelta(entry.name);
      const rounded = [round1(x), round1(y), round1(z)];
      if (onlyMoved && rounded.every((value) => value === 0)) continue;
      rotations[entry.name] = rounded;
    }
    return { bones: rotations };
  }

  reset(name) {
    if (name) {
      this.setDelta(name, { x: 0, y: 0, z: 0 });
      return;
    }
    for (const entry of this.bones) this.setDelta(entry.name, { x: 0, y: 0, z: 0 });
  }

  /** True when every bone sits at its rest rotation. */
  isRestPose() {
    return this.bones.every((entry) => {
      const { x, y, z } = this.getDelta(entry.name);
      return Math.abs(x) < 0.01 && Math.abs(y) < 0.01 && Math.abs(z) < 0.01;
    });
  }

  setGizmoVisible(visible) {
    this.gizmoWanted = visible !== false;
    this.helper.visible = this.gizmoWanted && this.selected != null;
    // A hidden gizmo must not grab the pointer (see the constructor).
    this.controls.enabled = this.helper.visible;
  }

  dispose() {
    this.controls.detach();
    this.controls.dispose();
    this.helper.removeFromParent();
  }
}

const round1 = (value) => Math.round(value * 10) / 10;