import type { Point } from './Point.js'

/** 二维向量 */
export class Vector2
{
  x: number
  y: number
  readonly isVector2: boolean = true
  constructor(x: number = 0, y: number = 0)
  {
    this.x = x
    this.y = y
  }

  get width(): number { return this.x }
  set width(value: number) { this.x = value }
  get height(): number { return this.y }
  set height(value: number) { this.y = value }
  set(x: number, y: number): Vector2
  {
    this.x = x
    this.y = y
    return this
  }

  setScalar(scalar: number): Vector2
  {
    this.x = scalar
    this.y = scalar
    return this
  }

  setX(x: number): Vector2
  {
    this.x = x
    return this
  }

  setY(y: number): Vector2
  {
    this.y = y
    return this
  }

  setComponent(index: number, value: number): Vector2
  {
    switch (index)
    {
      case 0: this.x = value; break
      case 1: this.y = value; break
      default: throw new Error(`index is out of range: ${index}`)
    }
    return this
  }

  getComponent(index: number): number
  {
    switch (index)
    {
      case 0: return this.x
      case 1: return this.y
      default: throw new Error(`index is out of range: ${index}`)
    }
  }

  clone(): Vector2
  {
    return new (this.constructor as any)().copy(this)
  }

  copy(v: Vector2): Vector2
  {
    this.x = v.x
    this.y = v.y
    return this
  }

  add(v: Point): Vector2
  {
    this.x += v.x
    this.y += v.y
    return this
  }

  addScalar(s: number): Vector2
  {
    this.x += s
    this.y += s
    return this
  }

  addVectors(a: Vector2, b: Vector2): Vector2
  {
    this.x = a.x + b.x
    this.y = a.y + b.y
    return this
  }

  addScaledVector(v: Vector2, s: number): Vector2
  {
    this.x += v.x * s
    this.y += v.y * s
    return this
  }

  sub(v: Vector2): Vector2
  {
    this.x -= v.x
    this.y -= v.y
    return this
  }

  subScalar(s: number): Vector2
  {
    this.x -= s
    this.y -= s
    return this
  }

  subVectors(a: Vector2, b: Vector2): Vector2
  {
    this.x = a.x - b.x
    this.y = a.y - b.y
    return this
  }

  multiply(v: Vector2): Vector2
  {
    this.x *= v.x
    this.y *= v.y
    return this
  }

  multiplyScalar(scalar: number): Vector2
  {
    if (Number.isFinite(scalar))
    {
      this.x *= scalar
      this.y *= scalar
    } else
    {
      this.x = 0
      this.y = 0
    }
    return this
  }

  divide(v: Vector2): Vector2
  {
    this.x /= v.x
    this.y /= v.y
    return this
  }

  divideScalar(scalar: number): Vector2
  {
    return this.multiplyScalar(1 / scalar)
  }

  min(v: Point): Vector2
  {
    this.x = Math.min(this.x, v.x)
    this.y = Math.min(this.y, v.y)
    return this
  }

  max(v: Point): Vector2
  {
    this.x = Math.max(this.x, v.x)
    this.y = Math.max(this.y, v.y)
    return this
  }

  clamp(min: Vector2, max: Vector2): Vector2
  {
    // This function assumes min < max, if this assumption isn't true it will not operate correctly
    this.x = Math.max(min.x, Math.min(max.x, this.x))
    this.y = Math.max(min.y, Math.min(max.y, this.y))
    return this
  }

  private static clampScalar_min = new Vector2()
  private static clampScalar_max = new Vector2()
  clampScalar(minVal: number, maxVal: number): Vector2
  {
    const min: Vector2 = Vector2.clampScalar_min.set(minVal, minVal)
    const max: Vector2 = Vector2.clampScalar_max.set(maxVal, maxVal)
    return this.clamp(min, max)
  }

  clampLength(min: number, max: number): Vector2
  {
    const length: number = this.length()
    return this.multiplyScalar(Math.max(min, Math.min(max, length)) / length)
  }

  floor(): Vector2
  {
    this.x = Math.floor(this.x)
    this.y = Math.floor(this.y)
    return this
  }

  ceil(): Vector2
  {
    this.x = Math.ceil(this.x)
    this.y = Math.ceil(this.y)
    return this
  }

  round(): Vector2
  {
    this.x = Math.round(this.x)
    this.y = Math.round(this.y)
    return this
  }

  roundToZero(): Vector2
  {
    this.x = (this.x < 0) ? Math.ceil(this.x) : Math.floor(this.x)
    this.y = (this.y < 0) ? Math.ceil(this.y) : Math.floor(this.y)
    return this
  }

  negate(): Vector2
  {
    this.x = -this.x
    this.y = -this.y
    return this
  }

  dot(v: Vector2): number
  {
    return this.x * v.x + this.y * v.y
  }

  lengthSq(): number
  {
    return this.x * this.x + this.y * this.y
  }

  length(): number
  {
    return Math.sqrt(this.x * this.x + this.y * this.y)
  }

  lengthManhattan(): number
  {
    return Math.abs(this.x) + Math.abs(this.y)
  }

  normalize(): Vector2
  {
    return this.divideScalar(this.length())
  }

  angle(): number
  {
    // computes the angle in radians with respect to the positive x-axis
    let angle: number = Math.atan2(this.y, this.x)
    if (angle < 0)
      angle += 2 * Math.PI
    return angle
  }

  distanceTo(v: Vector2): number
  {
    return Math.sqrt(this.distanceToSquared(v))
  }

  distanceToSquared(v: Vector2): number
  {
    const dx: number = this.x - v.x; const dy: number = this.y - v.y
    return dx * dx + dy * dy
  }

  distanceToManhattan(v: Vector2): number
  {
    return Math.abs(this.x - v.x) + Math.abs(this.y - v.y)
  }

  setLength(length: number): Vector2
  {
    return this.multiplyScalar(length / this.length())
  }

  lerp(v: Vector2, alpha: number): Vector2
  {
    this.x += (v.x - this.x) * alpha
    this.y += (v.y - this.y) * alpha
    return this
  }

  lerpVectors(v1: Vector2, v2: Vector2, alpha: number): Vector2
  {
    return this.subVectors(v2, v1).multiplyScalar(alpha).add(v1)
  }

  equals(v: Vector2): boolean
  {
    return ((v.x === this.x) && (v.y === this.y))
  }

  fromArray(array: Float32Array | number[], offset: number = 0): Vector2
  {
    this.x = array[offset]
    this.y = array[offset + 1]
    return this
  }

  toArray(array: Float32Array | number[] = [], offset: number = 0): Float32Array | number[]
  {
    array[offset] = this.x
    array[offset + 1] = this.y
    return array
  }

  fromAttribute(attribute: any, index: number, offset: number = 0): Vector2
  {
    index = index * attribute.itemSize + offset
    this.x = attribute.array[index]
    this.y = attribute.array[index + 1]
    return this
  }

  rotateAround(center: Vector2, angle: number): Vector2
  {
    const c: number = Math.cos(angle); const s: number = Math.sin(angle)
    const x: number = this.x - center.x
    const y: number = this.y - center.y
    this.x = x * c - y * s + center.x
    this.y = x * s + y * c + center.y
    return this
  }
}