import OpenSimplexNoise from 'open-simplex-noise'
import { vec3 } from 'gl-matrix'
import Resource from '../../resource'

class HeightMap {
  constructor (size) {
    this.size = size
  }

  static async fromFile (file, amplitude) {
    let img = await Resource.loadImage(file)
    if (img.width / img.height !== 1) throw new Error('Height Map needs to be of 1:1 aspect ratio.')

    let hmap = new HeightMap(img.width)
    let sampler = Resource.imageToSampler(img)

    for (let x = 0; x < img.width; x++) {
      for (let y = 0; y < img.width; y++) {
        hmap['h' + x + ';' + y] = (sampler(x, y)[0] / 255 * 2 - 1) * amplitude
      }
    }

    sampler = null

    return hmap
  }

  getHeight (x, y) {
    if (x > this.size || y > this.size || x < 0 || y < 0) return 0
    if (!this['h' + x + ';' + y]) return 0
    return this['h' + x + ';' + y]
  }

  getNormal (x, y) {
    let hL = this.getHeight(x - 1, y)
    let hR = this.getHeight(x + 1, y)
    let hD = this.getHeight(x, y - 1)
    let hU = this.getHeight(x, y + 1)
    let normal = vec3.fromValues(hL - hR, 2.0, hD - hU)
    vec3.normalize(normal, normal)
    return normal
  }
}

class SimplexHeightMap extends HeightMap {
  constructor (offsetX, offsetY, size, seed) {
    super(size)
    this.ix = offsetX
    this.iy = offsetY
    this.seed = seed

    this.osn = new OpenSimplexNoise(seed)
  }

  getNoise (relX, relY) {
    let x = ((this.ix * this.size) + relX) / this.size - 0.5
    let y = ((this.iy * this.size) + relY) / this.size - 0.5

    let total = this.osn.noise2D(2 * x, 2 * y) +
      0.5 * this.osn.noise2D(4 * x, 4 * y) +
      0.25 * this.osn.noise2D(2 * x, 2 * y)

    total *= 10
    return total
  }

  getHeight (x, y) {
    return this.getNoise(x, y)
  }
}

export { HeightMap, SimplexHeightMap }