import * as THREE from 'three';
const {
  document,
	window,
	HTMLCanvasElement,
	requestAnimationFrame,
	cancelAnimationFrame,
core,
	Event,
  Event0
} = THREE .DHTML

import Stats from 'three/examples/jsm/libs/stats.module.js';
import { GUI } from 'three/examples/jsm/libs/lil-gui.module.min.js';

import { OrbitControls } from 'three/examples/jsm/controls/OrbitControls.js';
import { OrbitControls0 } from 'three/examples/jsm/controls/OrbitControls0.js';
import { GPUComputationRenderer } from 'three/examples/jsm/misc/GPUComputationRenderer.js';
const computeShaderPosition = `

#define delta ( 1.0 / 60.0 )

void main() {

  vec2 uv = gl_FragCoord.xy / resolution.xy;

  vec4 tmpPos = texture2D( texturePosition, uv );
  vec3 pos = tmpPos.xyz;

  vec4 tmpVel = texture2D( textureVelocity, uv );
  vec3 vel = tmpVel.xyz;
  float mass = tmpVel.w;

  if ( mass == 0.0 ) {
    vel = vec3( 0.0 );
  }

  // Dynamics
  pos += vel * delta;

  gl_FragColor = vec4( pos, 1.0 );

}
`
const computeShaderVelocity = `

// For PI declaration:
#include <common>

#define delta ( 1.0 / 60.0 )

uniform float gravityConstant;
uniform float density;

const float width = resolution.x;
const float height = resolution.y;

float radiusFromMass( float mass ) {
  // Calculate radius of a sphere from mass and density
  return pow( ( 3.0 / ( 4.0 * PI ) ) * mass / density, 1.0 / 3.0 );
}

void main()	{

  vec2 uv = gl_FragCoord.xy / resolution.xy;
  float idParticle = uv.y * resolution.x + uv.x;

  vec4 tmpPos = texture2D( texturePosition, uv );
  vec3 pos = tmpPos.xyz;

  vec4 tmpVel = texture2D( textureVelocity, uv );
  vec3 vel = tmpVel.xyz;
  float mass = tmpVel.w;

  if ( mass > 0.0 ) {

    float radius = radiusFromMass( mass );

    vec3 acceleration = vec3( 0.0 );

    // Gravity interaction
    for ( float y = 0.0; y < height; y++ ) {

      for ( float x = 0.0; x < width; x++ ) {

        vec2 secondParticleCoords = vec2( x + 0.5, y + 0.5 ) / resolution.xy;
        vec3 pos2 = texture2D( texturePosition, secondParticleCoords ).xyz;
        vec4 velTemp2 = texture2D( textureVelocity, secondParticleCoords );
        vec3 vel2 = velTemp2.xyz;
        float mass2 = velTemp2.w;

        float idParticle2 = secondParticleCoords.y * resolution.x + secondParticleCoords.x;

        if ( idParticle == idParticle2 ) {
          continue;
        }

        if ( mass2 == 0.0 ) {
          continue;
        }

        vec3 dPos = pos2 - pos;
        float distance = length( dPos );
        float radius2 = radiusFromMass( mass2 );

        if ( distance == 0.0 ) {
          continue;
        }

        // Checks collision

        if ( distance < radius + radius2 ) {

          if ( idParticle < idParticle2 ) {

            // This particle is aggregated by the other
            vel = ( vel * mass + vel2 * mass2 ) / ( mass + mass2 );
            mass += mass2;
            radius = radiusFromMass( mass );

          }
          else {

            // This particle dies
            mass = 0.0;
            radius = 0.0;
            vel = vec3( 0.0 );
            break;

          }

        }

        float distanceSq = distance * distance;

        float gravityField = gravityConstant * mass2 / distanceSq;

        gravityField = min( gravityField, 1000.0 );

        acceleration += gravityField * normalize( dPos );

      }

      if ( mass == 0.0 ) {
        break;
      }
    }

    // Dynamics
    vel += delta * acceleration;

  }

  gl_FragColor = vec4( vel, mass );

}`
const particleVertexShader = `

// For PI declaration:
#include <common>

uniform sampler2D texturePosition;
uniform sampler2D textureVelocity;

uniform float cameraConstant;
uniform float density;

varying vec4 vColor;

float radiusFromMass( float mass ) {
  // Calculate radius of a sphere from mass and density
  return pow( ( 3.0 / ( 4.0 * PI ) ) * mass / density, 1.0 / 3.0 );
}


void main() {


  vec4 posTemp = texture2D( texturePosition, uv );
  vec3 pos = posTemp.xyz;

  vec4 velTemp = texture2D( textureVelocity, uv );
  vec3 vel = velTemp.xyz;
  float mass = velTemp.w;

  vColor = vec4( 1.0, mass / 250.0, 0.0, 1.0 );

  vec4 mvPosition = modelViewMatrix * vec4( pos, 1.0 );

  // Calculate radius of a sphere from mass and density
  //float radius = pow( ( 3.0 / ( 4.0 * PI ) ) * mass / density, 1.0 / 3.0 );
  float radius = radiusFromMass( mass );

  // Apparent size in pixels
  if ( mass == 0.0 ) {
    gl_PointSize = 0.0;
  }
  else {
    gl_PointSize = radius * cameraConstant / ( - mvPosition.z );
  }

  gl_Position = projectionMatrix * mvPosition;

}`
const particleFragmentShader = `

varying vec4 vColor;

void main() {

  if ( vColor.y == 0.0 ) discard;

  float f = length( gl_PointCoord - vec2( 0.5, 0.5 ) );
  if ( f > 0.5 ) {
    discard;
  }
  gl_FragColor = vColor;

}
`
var requestId
Page({
	onUnload() {
		cancelAnimationFrame(requestId, this.canvas)
		this.worker && this.worker.terminate()
if(this.canvas) this.canvas = null
		setTimeout(() => {
			if (this.renderer instanceof THREE.WebGLRenderer) {
				this.renderer.dispose()
				this.renderer.forceContextLoss()
				this.renderer.context = null
				this.renderer.domElement = null
				this.renderer = null
			}
		}, 10)
	},
  webgl_touch(e){
		const web_e = (window.platform=="devtools"?Event:Event0).fix(e)
		this.canvas.dispatchEvent(web_e)
  },
  onLoad() {
		document.createElementAsync("canvas", "webgl2",this).then(canvas => {
      this.canvas = canvas
      this.body_load(canvas).then()
    })
  },
  async body_load(canvas3d) {

  // Texture width for simulation (each texel is a debris particle)
  const WIDTH = 64;

  let container, stats;
  let camera, scene, renderer, geometry;

  const PARTICLES = WIDTH * WIDTH;

  let gpuCompute;
  let velocityVariable;
  let positionVariable;
  let velocityUniforms;
  let particleUniforms;
  let effectController;

  init();
  animate();

  function init() {

    container = document.createElement( 'div' );
    document.body.appendChild( container );

    camera = new THREE.PerspectiveCamera( 75, window.innerWidth / window.innerHeight, 5, 15000 );
    camera.position.y = 120;
    camera.position.z = 400;

    scene = new THREE.Scene();

    renderer = new THREE.WebGLRenderer();
    renderer.setPixelRatio( window.devicePixelRatio );
    renderer.setSize( window.innerWidth, window.innerHeight );
    container.appendChild( renderer.domElement );

    const controls = new (window.platform=="devtools"?OrbitControls:OrbitControls0)( camera, renderer.domElement );
    controls.minDistance = 100;
    controls.maxDistance = 1000;

    effectController = {
      // Can be changed dynamically
      gravityConstant: 100.0,
      density: 0.45,

      // Must restart simulation
      radius: 300,
      height: 8,
      exponent: 0.4,
      maxMass: 15.0,
      velocity: 70,
      velocityExponent: 0.2,
      randVelocity: 0.001
    };

    initComputeRenderer();

    stats = new Stats();
    container.appendChild( stats.dom );

    window.addEventListener( 'resize', onWindowResize );

    initGUI();

    initProtoplanets();

    dynamicValuesChanger();

  }

  function initComputeRenderer() {

    gpuCompute = new GPUComputationRenderer( WIDTH, WIDTH, renderer );

    if ( renderer.capabilities.isWebGL2 === false ) {

      gpuCompute.setDataType( THREE.HalfFloatType );

    }

    const dtPosition = gpuCompute.createTexture();
    const dtVelocity = gpuCompute.createTexture();

    fillTextures( dtPosition, dtVelocity );

    velocityVariable = gpuCompute.addVariable( 'textureVelocity',computeShaderVelocity, dtVelocity );
    positionVariable = gpuCompute.addVariable( 'texturePosition',computeShaderPosition, dtPosition );

    gpuCompute.setVariableDependencies( velocityVariable, [ positionVariable, velocityVariable ] );
    gpuCompute.setVariableDependencies( positionVariable, [ positionVariable, velocityVariable ] );

    velocityUniforms = velocityVariable.material.uniforms;

    velocityUniforms[ 'gravityConstant' ] = { value: 0.0 };
    velocityUniforms[ 'density' ] = { value: 0.0 };

    const error = gpuCompute.init();

    if ( error !== null ) {

      console.error( error );

    }

  }

  function restartSimulation() {

    const dtPosition = gpuCompute.createTexture();
    const dtVelocity = gpuCompute.createTexture();

    fillTextures( dtPosition, dtVelocity );

    gpuCompute.renderTexture( dtPosition, positionVariable.renderTargets[ 0 ] );
    gpuCompute.renderTexture( dtPosition, positionVariable.renderTargets[ 1 ] );
    gpuCompute.renderTexture( dtVelocity, velocityVariable.renderTargets[ 0 ] );
    gpuCompute.renderTexture( dtVelocity, velocityVariable.renderTargets[ 1 ] );

  }

  function initProtoplanets() {

    geometry = new THREE.BufferGeometry();

    const positions = new Float32Array( PARTICLES * 3 );
    let p = 0;

    for ( let i = 0; i < PARTICLES; i ++ ) {

      positions[ p ++ ] = ( Math.random() * 2 - 1 ) * effectController.radius;
      positions[ p ++ ] = 0; //( Math.random() * 2 - 1 ) * effectController.radius;
      positions[ p ++ ] = ( Math.random() * 2 - 1 ) * effectController.radius;

    }

    const uvs = new Float32Array( PARTICLES * 2 );
    p = 0;

    for ( let j = 0; j < WIDTH; j ++ ) {

      for ( let i = 0; i < WIDTH; i ++ ) {

        uvs[ p ++ ] = i / ( WIDTH - 1 );
        uvs[ p ++ ] = j / ( WIDTH - 1 );

      }

    }

    geometry.setAttribute( 'position', new THREE.BufferAttribute( positions, 3 ) );
    geometry.setAttribute( 'uv', new THREE.BufferAttribute( uvs, 2 ) );

    particleUniforms = {
      'texturePosition': { value: null },
      'textureVelocity': { value: null },
      'cameraConstant': { value: getCameraConstant( camera ) },
      'density': { value: 0.0 }
    };

    // THREE.ShaderMaterial
    const material = new THREE.ShaderMaterial( {
      uniforms: particleUniforms,
      vertexShader:particleVertexShader,
      fragmentShader:particleFragmentShader
    } );

    material.extensions.drawBuffers = true;

    const particles = new THREE.Points( geometry, material );
    particles.matrixAutoUpdate = false;
    particles.updateMatrix();

    scene.add( particles );

  }

  function fillTextures( texturePosition, textureVelocity ) {

    const posArray = texturePosition.image.data;
    const velArray = textureVelocity.image.data;

    const radius = effectController.radius;
    const height = effectController.height;
    const exponent = effectController.exponent;
    const maxMass = effectController.maxMass * 1024 / PARTICLES;
    const maxVel = effectController.velocity;
    const velExponent = effectController.velocityExponent;
    const randVel = effectController.randVelocity;

    for ( let k = 0, kl = posArray.length; k < kl; k += 4 ) {

      // Position
      let x, z, rr;

      do {

        x = ( Math.random() * 2 - 1 );
        z = ( Math.random() * 2 - 1 );
        rr = x * x + z * z;

      } while ( rr > 1 );

      rr = Math.sqrt( rr );

      const rExp = radius * Math.pow( rr, exponent );

      // Velocity
      const vel = maxVel * Math.pow( rr, velExponent );

      const vx = vel * z + ( Math.random() * 2 - 1 ) * randVel;
      const vy = ( Math.random() * 2 - 1 ) * randVel * 0.05;
      const vz = - vel * x + ( Math.random() * 2 - 1 ) * randVel;

      x *= rExp;
      z *= rExp;
      const y = ( Math.random() * 2 - 1 ) * height;

      const mass = Math.random() * maxMass + 1;

      // Fill in texture values
      posArray[ k + 0 ] = x;
      posArray[ k + 1 ] = y;
      posArray[ k + 2 ] = z;
      posArray[ k + 3 ] = 1;

      velArray[ k + 0 ] = vx;
      velArray[ k + 1 ] = vy;
      velArray[ k + 2 ] = vz;
      velArray[ k + 3 ] = mass;

    }

  }

  function onWindowResize() {

    camera.aspect = window.innerWidth / window.innerHeight;
    camera.updateProjectionMatrix();

    renderer.setSize( window.innerWidth, window.innerHeight );

    particleUniforms[ 'cameraConstant' ].value = getCameraConstant( camera );

  }

  function dynamicValuesChanger() {

    velocityUniforms[ 'gravityConstant' ].value = effectController.gravityConstant;
    velocityUniforms[ 'density' ].value = effectController.density;
    particleUniforms[ 'density' ].value = effectController.density;

  }

  function initGUI() {

    const gui = new GUI( { width: 280 } );

    const folder1 = gui.addFolder( 'Dynamic parameters' );

    folder1.add( effectController, 'gravityConstant', 0.0, 1000.0, 0.05 ).onChange( dynamicValuesChanger );
    folder1.add( effectController, 'density', 0.0, 10.0, 0.001 ).onChange( dynamicValuesChanger );

    const folder2 = gui.addFolder( 'Static parameters' );

    folder2.add( effectController, 'radius', 10.0, 1000.0, 1.0 );
    folder2.add( effectController, 'height', 0.0, 50.0, 0.01 );
    folder2.add( effectController, 'exponent', 0.0, 2.0, 0.001 );
    folder2.add( effectController, 'maxMass', 1.0, 50.0, 0.1 );
    folder2.add( effectController, 'velocity', 0.0, 150.0, 0.1 );
    folder2.add( effectController, 'velocityExponent', 0.0, 1.0, 0.01 );
    folder2.add( effectController, 'randVelocity', 0.0, 50.0, 0.1 );

    const buttonRestart = {
      restartSimulation: function () {

        restartSimulation();

      }
    };

    folder2.add( buttonRestart, 'restartSimulation' );

    folder1.open();
    folder2.open();

  }

  function getCameraConstant( camera ) {

    return window.innerHeight / ( Math.tan( THREE.MathUtils.DEG2RAD * 0.5 * camera.fov ) / camera.zoom );

  }


  function animate() {

    requestId = requestAnimationFrame( animate );

    render();
    stats.update();

  }

  function render() {

    gpuCompute.compute();

    particleUniforms[ 'texturePosition' ].value = gpuCompute.getCurrentRenderTarget( positionVariable ).texture;
    particleUniforms[ 'textureVelocity' ].value = gpuCompute.getCurrentRenderTarget( velocityVariable ).texture;

    renderer.render( scene, camera );

  }
  }
})