setTimeout(async () => {
  const mapTexture = await loadTexture('https://s3-us-west-2.amazonaws.com/s.cdpn.io/292951/winter.jpg')
  const entities = [
    new Plane(mapTexture),
    new THREE.AxisHelper(50)
  ]
  ReactDOM.render((
    <Simulation
        fov={45}
        cameraPosition={new THREE.Vector3(40, 18, -82)}
        {...{ entities }}
    />
  ), document.getElementById('js-app'))
}, 0)

const loadTexture = (assetUri) => {
  return new Promise((resolve) => {
    const textureLoader = new THREE.TextureLoader()
    textureLoader.crossOrigin = ''
    textureLoader.load(assetUri, image => resolve(image))
  })
}

const buildPoints = (edgeCount, rotationOffset = 0) => {
  const stepSize = (Math.PI * 2) / edgeCount;
  return Array(...(new Array(edgeCount))).map((_, edgeIndex) => [
    Math.cos(edgeIndex * stepSize + rotationOffset),
    Math.sin(edgeIndex * stepSize + rotationOffset)
  ]);
}

class Plane extends THREE.Mesh {
  uTime = null

  constructor (mapTexture) {
    const pointsUp = buildPoints(3, Math.PI * 1.5)
    const uvs = [
      pointsUp[0].map(i => (i + 1) / 2).map(i => 1 - i),
      pointsUp[1].map(i => (i + 1) / 2).map(i => 1 - i),
      pointsUp[2].map(i => (i + 1) / 2).map(i => 1 - i)
    ]
    const geometry = Plane.createGeometry(uvs)
    const material = Plane.createMaterial(mapTexture, uvs)
    material.uniforms.uMap.value = mapTexture
    super(geometry, material)
  }

  get time () {
    return this.uTime
  }

  set time (newTime) {
    this.uTime = newTime
  }

  static elevationGenerator (scaling = 20, s = Math.random()) {
    const colorLookup = {}
    const seed = 5625463739 * s
    return (vertex) => {
      const key = `${vertex.x}&${vertex.y}&${vertex.z}`
      if (colorLookup[key] === undefined) {
        const elevation = (noise.simplex3(
          (vertex.x + seed) / scaling,
          (vertex.y + seed) / scaling,
          (vertex.z + seed) / scaling
        ) + 1) / 2 // this will be a value between 0 and 1
        let elevationIndex = 0
        if (elevation > 0.3) { // ocean
          elevationIndex = 1
        }
        if (elevation > 0.45) { // sand
          elevationIndex = 2
        }
        if (elevation > 0.62) { // grass
          elevationIndex = 3
        }
        if (elevation > 0.8) { // dense grass
          elevationIndex = 4
        }
        colorLookup[key] = elevationIndex
      }
      return colorLookup[key]
    }
  }

  static createGeometry (uvs) {
    const getElevation = Plane.elevationGenerator()
    const model = new THREE.IcosahedronGeometry(20, 4)
    THREE.BAS.Utils.separateFaces(model) // this splits each face into its own 3 vertices, allowing us to add elevations to them (i think)
    const barycentricCombinations = [
      [1, 0, 0],
      [0, 1, 0],
      [0, 0, 1]
    ]
    const geometry = new THREE.BAS.ModelBufferGeometry(model)
    const aUv = geometry.createAttribute('aUv', 2)
    const aElevation = geometry.createAttribute('aElevation', 4)
    let offsetUv = 0
    let offsetElevation = 0
    ;[...new Array(geometry.faceCount)].forEach((_, faceIndex) => {
      const face = geometry.modelGeometry.faces[faceIndex]
      const {
        a,
        b,
        c
      } = face
      const {
        vertices
      } = geometry.modelGeometry
      const [
        elevationA,
        elevationB,
        elevationC
      ] = [a, b, c].map((vertexIndex) => {
        const vertex = vertices[vertexIndex]
        return getElevation(vertex)
      })
      const elevationD = Plane.getFaceCenterColor(elevationA, elevationB, elevationC)
      for (let i = 0; i < 3; i++) {
        aUv.array[offsetUv++] = uvs[i][0]
        aUv.array[offsetUv++] = uvs[i][1]
        aElevation.array[offsetElevation++] = elevationA
        aElevation.array[offsetElevation++] = elevationB
        aElevation.array[offsetElevation++] = elevationC
        aElevation.array[offsetElevation++] = elevationD
      }
    })
    return geometry
  }

  static getFaceCenterColor (elevationA, elevationB, elevationC) { // TODO refactor, probably a better way to do this
    return (elevationA + elevationB + elevationC) / 3
  }

  static createMaterial (mapTexture, uvs) {
    return new THREE.BAS.PhongAnimationMaterial({
      shading: THREE.FlatShading,
      side: THREE.FrontSide,
      uniforms: {
        uTime: { value: 0 },
        uMap: { value: null },
        uUvA: { value: uvs[0] },
        uUvB: { value: uvs[1] },
        uUvC: { value: uvs[2] }
      },
      uniformValues: {
      },
      vertexParameters: [`
        // vertexParamters
        attribute vec2 aUv;
        attribute vec3 aBarycentric;
        attribute vec4 aElevation;
        uniform float uTime;
      `],
      varyingParameters: [`
        // varyingParameters
        varying vec2 vUv;
        varying vec4 vElevation;
      `],
      vertexFunctions: [`
        // vertexFunctions
      `],
      vertexInit: [`
        // vertexInit
      `],
      vertexNormal: [`
        // vertexNormal
      `],
      vertexPosition: [`
        // vertexPosition
      `],
      vertexColor: [`
        // vertexColor
        vUv = aUv;
        vElevation = aElevation;
      `],
      fragmentParameters: [`
        // fragmentParameters
        uniform vec2 uUvA;
        uniform vec2 uUvB;
        uniform vec2 uUvC;
      `],
      fragmentFunctions: [`
        // fragmentFunctions
        float terrainShininess (float elev) {
          float landShininess = 10.0;
          float waterShininess = 100.0;
          if (elev >= 4.0) {
            return landShininess; // dense grass
          }
          if (elev >= 3.0) {
            return landShininess; // grass
          }
          if (elev >= 2.0) {
            return landShininess; // sand
          }
          if (elev >= 1.0) {
            return waterShininess; // ocean
          }
          return waterShininess; // deep ocean
        }

        vec3 terrainColor (float elev) {
          if (elev >= 4.0) {
            return vec3(0, 0.533, 0); // dense grass 008800 (0, 136, 0)
          }
          if (elev >= 3.0) {
            return vec3(0, 0.619, 0); // grass 009e00 (0, 158, 0)
          }
          if (elev >= 2.0) {
            return vec3(0.76, 0.698, 0.435); // sand c2b26f (194, 178, 111)
          }
          if (elev >= 1.0) {
            return vec3(0.188, 0.619, 0.752); // ocean 309ec0 (48, 158, 192)
          }
          return vec3(0.16, 0.533, 0.682); // deep ocean 2988ae (41, 136, 174)
        }

        vec3 cartesianToBarycentric (vec2 p1, vec2 p2, vec2 p3, vec2 p) { // http://totologic.blogspot.com/2014/01/accurate-point-in-triangle-test.html
          float denominator = ((p2.y - p3.y) * (p.x - p3.x) + (p3.x - p2.x) * (p1.y - p3.y));
          float a = ((p2.y - p3.y) * (p.x - p3.x) + (p3.x - p2.x) * (p.y - p3.y)) / denominator;
          float b = ((p3.y - p1.y) * (p.x - p3.x) + (p1.x - p3.x) * (p.y - p3.y)) / denominator;
          float c = 1.0 - a - b;
          return vec3(a, b, c);
        }

        float getPointElevation (vec4 elevation, vec3 barycentric) {
          if (barycentric.x > barycentric.y + barycentric.z) {
            return elevation.x;
          } else if (barycentric.y > barycentric.x + barycentric.z) {
            return elevation.y;
          } else if (barycentric.z > barycentric.x + barycentric.y) {
            return elevation.z;
          }
          return elevation.w;
        }

        vec3 perturbNormalArb (vec3 surf_pos, vec3 surf_norm, vec2 dHdxy) {
          vec3 vSigmaX = vec3(dFdx(surf_pos.x), dFdx(surf_pos.y), dFdx(surf_pos.z));
          vec3 vSigmaY = vec3(dFdy(surf_pos.x), dFdy(surf_pos.y), dFdy(surf_pos.z));
          vec3 vN = surf_norm;
          vec3 R1 = cross(vSigmaY, vN);
          vec3 R2 = cross(vN, vSigmaX);
          float fDet = dot(vSigmaX, R1);
          vec3 vGrad = sign(fDet) * (dHdxy.x * R1 + dHdxy.y * R2);
          return normalize(abs(fDet) * surf_norm - vGrad);
        }

        vec2 dHdxy_fwd (vec2 uvA, vec2 uvB, vec2 uvC, vec2 uv, vec4 elevation, float bumpScale) {
          vec2 dSTdx = dFdx(uv);
          vec2 dSTdy = dFdy(uv);
          float Hll = bumpScale * getPointElevation(elevation, cartesianToBarycentric(uvA, uvB, uvC, uv));
          float dBx = bumpScale * getPointElevation(elevation, cartesianToBarycentric(uvA, uvB, uvC, uv + dSTdx)) - Hll;
          float dBy = bumpScale * getPointElevation(elevation, cartesianToBarycentric(uvA, uvB, uvC, uv + dSTdy)) - Hll;
          return vec2(dBx, dBy);
        }
      `],
      fragmentInit: [`
        // fragmentInit
        vec4 elevation = ceil(vElevation + 0.5) - 1.0;
      `],
      fragmentDiffuse: [`
        // fragmentDiffuse
        vec3 barycentric = cartesianToBarycentric(uUvA, uUvB, uUvC, vUv);
        float pointElevation = getPointElevation(elevation, barycentric);
        diffuseColor.rgb = terrainColor(pointElevation);
      `],
      fragmentMap: [`
        // fragmentMap
      `],
      fragmentEmissive: [`
        // fragmentEmissive
        if (pointElevation > 1.0) {
          normal = perturbNormalArb(-vViewPosition, normal, dHdxy_fwd(uUvA, uUvB, uUvC, vUv, elevation, 0.5));
        }
      `],
      fragmentSpecular: [`
        // fragmentSpecular
        material.specularShininess = terrainShininess(pointElevation);
      `]
    })
  }
}

class Simulation extends React.Component {
  static defaultProps = {
    entities: [],
    fov: 80,
    cameraPosition: new THREE.Vector3(0, 0, 0)
  }

  shouldComponentUpdate () {
    return false
  }

  componentDidMount () {
    const camera = this.createCamera(
      this.props.fov,
      this.props.cameraPosition,
      window.innerWidth,
      window.innerHeight
    )
    camera.target = new THREE.Vector3(0, 0, 0)
    camera.lookAt(camera.target)
    const scene = new THREE.Scene()
    const renderer = new THREE.WebGLRenderer({
      antialias: false,
      alpha: false,
      canvas: this.canvas
    })
    const handleWindowResize = this.onWindowResize(camera, renderer)
    handleWindowResize()
    window.addEventListener('resize', handleWindowResize, false)
    const controls = this.createControls(camera)
    this.props.entities.forEach(e => scene.add(e))
    const {
      lights,
      pointLights
    } = this.createLights()
    lights.forEach(light => scene.add(light))
    this.animate(renderer, scene, camera, controls, this.props.entities, pointLights, +(new Date()))
  }

  createLights () {
    const ambientLight = new THREE.AmbientLight(0x333333)
    const pointLightA = new THREE.PointLight(0xffffff, 1, 200)
    const pointLightHelperA = new THREE.PointLightHelper(pointLightA, 1)
    const pointLightB = new THREE.PointLight(0xffffff, 1, 200)
    const pointLightHelperB = new THREE.PointLightHelper(pointLightB, 1)
    return {
      lights: [
        ambientLight,
        pointLightA,
        pointLightHelperA,
        // pointLightB,
        // pointLightHelperB
      ],
      pointLights: [
        pointLightA,
        // pointLightB
      ]
    }
  }

  createCamera (fov, pos, width, height) {
    const camera = new THREE.PerspectiveCamera(fov, width / height, 1, 1000)
    camera.position.x = pos.x
    camera.position.y = pos.y
    camera.position.z = pos.z
    return camera
  }

  createControls (camera) {
    const controls = new THREE.OrbitControls(camera)
    controls.target = camera.target
    controls.enableDamping = true
    controls.dampingFactor = 0.1
    controls.rotateSpeed = 0.1
    return controls
  }

  onWindowResize (camera, renderer) {
    return () => {
      const width = window.innerWidth
      const height = window.innerHeight
      camera.aspect = width / height
      camera.updateProjectionMatrix()
      renderer.setSize(width, height)
    }
  }

  animate (renderer, scene, camera, controls, entities, pointLights, lastTime) {
    const currentTime = +(new Date())
    const timeDelta = currentTime - lastTime
    entities.forEach(e => e.time += timeDelta / 1000)
    requestAnimationFrame(() => {
      this.animate(renderer, scene, camera, controls, entities, pointLights, currentTime)
    })
    pointLights.forEach((pointLight, index) => {
      index += 1
      const frequency = 1000 + index * 200
      const amplitude = 40
      const animationTime = Math.PI * frequency + currentTime * index;
      const cos = Math.cos(animationTime / frequency) * amplitude
      const sin = Math.sin(animationTime / frequency * 1) * amplitude / 1 // turn the 1s to 2s
      pointLight.position.set(
        sin,
        20,
        cos
      )
    })
    controls.update()
    renderer.render(scene, camera)
  }

  render () {
    return (
      <canvas ref={c => this.canvas = c} />
    )
  }
}