import { Euler } from './Euler';
import { MathUtils } from '../MathUtils';
import { Matrix4 } from './Matrix4';
import { Vector3 } from './Vector3';

class Quaternion {
  static slerp(qa: Quaternion, qb: Quaternion, qm: Quaternion, t: number) {
    return qm.copy(qa).slerp(qb, t);
  }

  static slerpFlat(dst: number[], dstOffset: number, src0: number[], srcOffset0: number, src1: number[], srcOffset1: number, t: number) {
    // fuzz-free, array-based Quaternion SLERP operation

    let x0 = src0[srcOffset0 + 0];
    let y0 = src0[srcOffset0 + 1];
    let z0 = src0[srcOffset0 + 2];
    let w0 = src0[srcOffset0 + 3];

    const x1 = src1[srcOffset1 + 0];
    const y1 = src1[srcOffset1 + 1];
    const z1 = src1[srcOffset1 + 2];
    const w1 = src1[srcOffset1 + 3];

    if (t === 0) {
      dst[dstOffset + 0] = x0;
      dst[dstOffset + 1] = y0;
      dst[dstOffset + 2] = z0;
      dst[dstOffset + 3] = w0;
      return;
    }

    if (t === 1) {
      dst[dstOffset + 0] = x1;
      dst[dstOffset + 1] = y1;
      dst[dstOffset + 2] = z1;
      dst[dstOffset + 3] = w1;
      return;
    }

    if (w0 !== w1 || x0 !== x1 || y0 !== y1 || z0 !== z1) {
      let s = 1 - t;
      const cos = x0 * x1 + y0 * y1 + z0 * z1 + w0 * w1;
      const dir = (cos >= 0 ? 1 : -1);
      const sqrSin = 1 - cos * cos;

      // Skip the Slerp for tiny steps to avoid numeric problems:
      if (sqrSin > Number.EPSILON) {
        const sin = Math.sqrt(sqrSin);
        const len = Math.atan2(sin, cos * dir);

        s = Math.sin(s * len) / sin;
        t = Math.sin(t * len) / sin;
      }

      const tDir = t * dir;

      x0 = x0 * s + x1 * tDir;
      y0 = y0 * s + y1 * tDir;
      z0 = z0 * s + z1 * tDir;
      w0 = w0 * s + w1 * tDir;

      // Normalize in case we just did a lerp:
      if (s === 1 - t) {
        const f = 1 / Math.sqrt(x0 * x0 + y0 * y0 + z0 * z0 + w0 * w0);

        x0 *= f;
        y0 *= f;
        z0 *= f;
        w0 *= f;
      }
    }

    dst[dstOffset] = x0;
    dst[dstOffset + 1] = y0;
    dst[dstOffset + 2] = z0;
    dst[dstOffset + 3] = w0;
  }

  static multiplyQuaternionsFlat(dst: number[], dstOffset: number, src0: number[], srcOffset0: number, src1: number[], srcOffset1: number) {
    const x0 = src0[srcOffset0];
    const y0 = src0[srcOffset0 + 1];
    const z0 = src0[srcOffset0 + 2];
    const w0 = src0[srcOffset0 + 3];

    const x1 = src1[srcOffset1];
    const y1 = src1[srcOffset1 + 1];
    const z1 = src1[srcOffset1 + 2];
    const w1 = src1[srcOffset1 + 3];

    dst[dstOffset] = x0 * w1 + w0 * x1 + y0 * z1 - z0 * y1;
    dst[dstOffset + 1] = y0 * w1 + w0 * y1 + z0 * x1 - x0 * z1;
    dst[dstOffset + 2] = z0 * w1 + w0 * z1 + x0 * y1 - y0 * x1;
    dst[dstOffset + 3] = w0 * w1 - x0 * x1 - y0 * y1 - z0 * z1;

    return dst;
  }

  readonly isQuaternion: boolean;
  _x: number;
  _y: number;
  _z: number;
  _w: number;

  constructor(x = 0, y = 0, z = 0, w = 1) {
    this.isQuaternion = true;
    this._x = x;
    this._y = y;
    this._z = z;
    this._w = w;
  }

  get x() {
    return this._x;
  }

  set x(value) {
    this._x = value;
    this._onChangeCallback();
  }

  get y() {
    return this._y;
  }

  set y(value) {
    this._y = value;
    this._onChangeCallback();
  }

  get z() {
    return this._z;
  }

  set z(value) {
    this._z = value;
    this._onChangeCallback();
  }

  get w() {
    return this._w;
  }

  set w(value) {
    this._w = value;
    this._onChangeCallback();
  }

  set(x: number, y: number, z: number, w: number) {
    this._x = x;
    this._y = y;
    this._z = z;
    this._w = w;
    this._onChangeCallback();

    return this;
  }

  clone() {
    return new Quaternion(this._x, this._y, this._z, this._w);
  }

  copy(quaternion: Quaternion) {
    this._x = quaternion.x;
    this._y = quaternion.y;
    this._z = quaternion.z;
    this._w = quaternion.w;

    this._onChangeCallback();

    return this;
  }

  setFromEuler(euler: Euler) {
    const x = euler._x; const y = euler._y; const z = euler._z; const
      order = euler._order;

    // http://www.mathworks.com/matlabcentral/fileexchange/
    // 20696-function-to-convert-between-dcm-euler-angles-quaternions-and-euler-vectors/
    // content/SpinCalc.m

    const cos = Math.cos;
    const sin = Math.sin;

    const c1 = cos(x / 2);
    const c2 = cos(y / 2);
    const c3 = cos(z / 2);

    const s1 = sin(x / 2);
    const s2 = sin(y / 2);
    const s3 = sin(z / 2);

    switch (order) {
    case 'XYZ':
      this._x = s1 * c2 * c3 + c1 * s2 * s3;
      this._y = c1 * s2 * c3 - s1 * c2 * s3;
      this._z = c1 * c2 * s3 + s1 * s2 * c3;
      this._w = c1 * c2 * c3 - s1 * s2 * s3;
      break;

    case 'YXZ':
      this._x = s1 * c2 * c3 + c1 * s2 * s3;
      this._y = c1 * s2 * c3 - s1 * c2 * s3;
      this._z = c1 * c2 * s3 - s1 * s2 * c3;
      this._w = c1 * c2 * c3 + s1 * s2 * s3;
      break;

    case 'ZXY':
      this._x = s1 * c2 * c3 - c1 * s2 * s3;
      this._y = c1 * s2 * c3 + s1 * c2 * s3;
      this._z = c1 * c2 * s3 + s1 * s2 * c3;
      this._w = c1 * c2 * c3 - s1 * s2 * s3;
      break;

    case 'ZYX':
      this._x = s1 * c2 * c3 - c1 * s2 * s3;
      this._y = c1 * s2 * c3 + s1 * c2 * s3;
      this._z = c1 * c2 * s3 - s1 * s2 * c3;
      this._w = c1 * c2 * c3 + s1 * s2 * s3;
      break;

    case 'YZX':
      this._x = s1 * c2 * c3 + c1 * s2 * s3;
      this._y = c1 * s2 * c3 + s1 * c2 * s3;
      this._z = c1 * c2 * s3 - s1 * s2 * c3;
      this._w = c1 * c2 * c3 - s1 * s2 * s3;
      break;

    case 'XZY':
      this._x = s1 * c2 * c3 - c1 * s2 * s3;
      this._y = c1 * s2 * c3 - s1 * c2 * s3;
      this._z = c1 * c2 * s3 + s1 * s2 * c3;
      this._w = c1 * c2 * c3 + s1 * s2 * s3;
      break;

    default:
      console.warn(`THREE.Quaternion: .setFromEuler() encountered an unknown order: ${order}`);
    }

    this._onChangeCallback();

    return this;
  }

  setFromAxisAngle(axis: Vector3, angle: number) {
    // http://www.euclideanspace.com/maths/geometry/rotations/conversions/angleToQuaternion/index.htm
    // assumes axis is normalized

    const halfAngle = angle / 2; const
      s = Math.sin(halfAngle);

    this._x = axis.x * s;
    this._y = axis.y * s;
    this._z = axis.z * s;
    this._w = Math.cos(halfAngle);

    this._onChangeCallback();

    return this;
  }

  setFromRotationMatrix(m: Matrix4) {
    // http://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToQuaternion/index.htm

    // assumes the upper 3x3 of m is a pure rotation matrix (i.e, unscaled)

    const te = m.elements;

    const m11 = te[0]; const m12 = te[4]; const m13 = te[8];
    const m21 = te[1]; const m22 = te[5]; const m23 = te[9];
    const m31 = te[2]; const m32 = te[6]; const m33 = te[10];

    const trace = m11 + m22 + m33;

    if (trace > 0) {
      const s = 0.5 / Math.sqrt(trace + 1.0);

      this._w = 0.25 / s;
      this._x = (m32 - m23) * s;
      this._y = (m13 - m31) * s;
      this._z = (m21 - m12) * s;
    } else if (m11 > m22 && m11 > m33) {
      const s = 2.0 * Math.sqrt(1.0 + m11 - m22 - m33);

      this._w = (m32 - m23) / s;
      this._x = 0.25 * s;
      this._y = (m12 + m21) / s;
      this._z = (m13 + m31) / s;
    } else if (m22 > m33) {
      const s = 2.0 * Math.sqrt(1.0 + m22 - m11 - m33);

      this._w = (m13 - m31) / s;
      this._x = (m12 + m21) / s;
      this._y = 0.25 * s;
      this._z = (m23 + m32) / s;
    } else {
      const s = 2.0 * Math.sqrt(1.0 + m33 - m11 - m22);

      this._w = (m21 - m12) / s;
      this._x = (m13 + m31) / s;
      this._y = (m23 + m32) / s;
      this._z = 0.25 * s;
    }

    this._onChangeCallback();

    return this;
  }

  setFromUnitVectors(vFrom: Vector3, vTo: Vector3) {
    // assumes direction vectors vFrom and vTo are normalized

    const EPS = 0.000001;

    let r = vFrom.dot(vTo) + 1;

    if (r < EPS) {
      r = 0;

      if (Math.abs(vFrom.x) > Math.abs(vFrom.z)) {
        this._x = -vFrom.y;
        this._y = vFrom.x;
        this._z = 0;
        this._w = r;
      } else {
        this._x = 0;
        this._y = -vFrom.z;
        this._z = vFrom.y;
        this._w = r;
      }
    } else {
      // crossVectors( vFrom, vTo ); // inlined to avoid cyclic dependency on Vector3

      this._x = vFrom.y * vTo.z - vFrom.z * vTo.y;
      this._y = vFrom.z * vTo.x - vFrom.x * vTo.z;
      this._z = vFrom.x * vTo.y - vFrom.y * vTo.x;
      this._w = r;
    }

    return this.normalize();
  }

  angleTo(q: Quaternion) {
    return 2 * Math.acos(Math.abs(MathUtils.clamp(this.dot(q), -1, 1)));
  }

  rotateTowards(q: Quaternion, step: number) {
    const angle = this.angleTo(q);

    if (angle === 0) return this;

    const t = Math.min(1, step / angle);

    this.slerp(q, t);

    return this;
  }

  identity() {
    return this.set(0, 0, 0, 1);
  }

  invert() {
    // quaternion is assumed to have unit length

    return this.conjugate();
  }

  conjugate() {
    this._x *= -1;
    this._y *= -1;
    this._z *= -1;

    this._onChangeCallback();

    return this;
  }

  dot(v: Quaternion) {
    return this._x * v._x + this._y * v._y + this._z * v._z + this._w * v._w;
  }

  lengthSq() {
    return this._x * this._x + this._y * this._y + this._z * this._z + this._w * this._w;
  }

  length() {
    return Math.sqrt(this._x * this._x + this._y * this._y + this._z * this._z + this._w * this._w);
  }

  normalize() {
    let l = this.length();

    if (l === 0) {
      this._x = 0;
      this._y = 0;
      this._z = 0;
      this._w = 1;
    } else {
      l = 1 / l;

      this._x *= l;
      this._y *= l;
      this._z *= l;
      this._w *= l;
    }

    this._onChangeCallback();

    return this;
  }

  multiply(q: Quaternion) {
    return this.multiplyQuaternions(this, q);
  }

  premultiply(q: Quaternion) {
    return this.multiplyQuaternions(q, this);
  }

  multiplyQuaternions(a: Quaternion, b: Quaternion) {
    // from http://www.euclideanspace.com/maths/algebra/realNormedAlgebra/quaternions/code/index.htm

    const qax = a._x; const qay = a._y; const qaz = a._z; const
      qaw = a._w;
    const qbx = b._x; const qby = b._y; const qbz = b._z; const
      qbw = b._w;

    this._x = qax * qbw + qaw * qbx + qay * qbz - qaz * qby;
    this._y = qay * qbw + qaw * qby + qaz * qbx - qax * qbz;
    this._z = qaz * qbw + qaw * qbz + qax * qby - qay * qbx;
    this._w = qaw * qbw - qax * qbx - qay * qby - qaz * qbz;

    this._onChangeCallback();

    return this;
  }

  slerp(qb: Quaternion, t: number) {
    if (t === 0) return this;
    if (t === 1) return this.copy(qb);

    const x = this._x; const y = this._y; const z = this._z; const
      w = this._w;

    // http://www.euclideanspace.com/maths/algebra/realNormedAlgebra/quaternions/slerp/

    let cosHalfTheta = w * qb._w + x * qb._x + y * qb._y + z * qb._z;

    if (cosHalfTheta < 0) {
      this._w = -qb._w;
      this._x = -qb._x;
      this._y = -qb._y;
      this._z = -qb._z;

      cosHalfTheta = -cosHalfTheta;
    } else {
      this.copy(qb);
    }

    if (cosHalfTheta >= 1.0) {
      this._w = w;
      this._x = x;
      this._y = y;
      this._z = z;

      return this;
    }

    const sqrSinHalfTheta = 1.0 - cosHalfTheta * cosHalfTheta;

    if (sqrSinHalfTheta <= Number.EPSILON) {
      const s = 1 - t;
      this._w = s * w + t * this._w;
      this._x = s * x + t * this._x;
      this._y = s * y + t * this._y;
      this._z = s * z + t * this._z;

      this.normalize();
      this._onChangeCallback();

      return this;
    }

    const sinHalfTheta = Math.sqrt(sqrSinHalfTheta);
    const halfTheta = Math.atan2(sinHalfTheta, cosHalfTheta);
    const ratioA = Math.sin((1 - t) * halfTheta) / sinHalfTheta;
    const ratioB = Math.sin(t * halfTheta) / sinHalfTheta;

    this._w = (w * ratioA + this._w * ratioB);
    this._x = (x * ratioA + this._x * ratioB);
    this._y = (y * ratioA + this._y * ratioB);
    this._z = (z * ratioA + this._z * ratioB);

    this._onChangeCallback();

    return this;
  }

  equals(quaternion: Quaternion) {
    return (quaternion._x === this._x) && (quaternion._y === this._y) && (quaternion._z === this._z) && (quaternion._w === this._w);
  }

  fromArray(array: number[] | ArrayLike<number>, offset = 0) {
    this._x = array[offset];
    this._y = array[offset + 1];
    this._z = array[offset + 2];
    this._w = array[offset + 3];

    this._onChangeCallback();

    return this;
  }

  toArray(array: number[] = [], offset = 0) {
    array[offset] = this._x;
    array[offset + 1] = this._y;
    array[offset + 2] = this._z;
    array[offset + 3] = this._w;

    return array;
  }

  _onChange(callback: Function) {
    this._onChangeCallback = callback;

    return this;
  }

  _onChangeCallback: Function = () => {
    //
  };
}

export { Quaternion };