/*
 * Copyright (c) 2020 Samsung Electronics Co., Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */
#include "particle-view.h"
#include "utils.h"
#include "dali/public-api/animation/constraints.h"

//#define ENABLE_DEBUG_VOLUME

#define USE_GLSL_VERSION(version) "#version " #version "\n"

using namespace Dali;

namespace
{

const uint32_t POPULATION_GRANULARITY = 128;

///@brief Shader for billboarded particles, where the vertices of the particles
/// are supplied as vec3 position (particle position) + vec2 sub-position.
const char* const PARTICLES_VSH = USE_GLSL_VERSION(300 es)
DALI_COMPOSE_SHADER(
  precision lowp float;
  uniform mat4 uModelView; // DALi
  uniform mat4 uProjection; // DALi
  uniform vec3 uSize; // DALi
  uniform vec4 uColor; // DALi

  uniform vec3 uSecondaryColor;
  uniform vec2 uDepthRange; // x is zNear, y is 1.f / (zFar - zNear)
  uniform float uTwinkleFrequency;
  uniform float uTwinkleSizeScale;
  uniform float uTwinkleOpacityWeight;
  uniform float uTime;
  uniform float uFocalLength;
  uniform float uAperture;
  uniform float uPopulation;

  struct Scatter
  {
    float radiusSqr;
    float amount;
    vec3 ray;
  };

  const int SCATTER_VARS = 6; // Must match ParticleView::mScatterProps' size.
  uniform Scatter uScatter[SCATTER_VARS];

  const int POPULATION_GRANULARITY = 128;
  uniform float uOrderLookUp[POPULATION_GRANULARITY];

  in vec3 aPosition;
  in float aSeed;
  in vec4 aPath;
  in vec2 aSubPosition;
  in float aSize;

  flat out float vDepth;
  flat out float vFocalDistance;
  out vec2 vUvUnit;
  flat out float vOpacity;
  flat out vec3 vColor; // ignore alpha

  float bezier(vec3 control, float alpha)
  {
    return mix(mix(control.x, control.y, alpha), mix(control.y, control.z, alpha), alpha);
  }

  void main() {
    // Get random order from the look-up table, based on particle ID.
    int particleId = gl_VertexID / 6;
    float order = uOrderLookUp[particleId & (POPULATION_GRANULARITY - 1)];

    // Get twinkle scalar
    float twinkle = sin(uTime * floor(uTwinkleFrequency * aSeed) + fract(aSeed * 1.17137));

    // Add Motion
    float s = sin(uTime + aSeed) * .5f + .5f;	// different phase for all
    // NOTE: you'd think that taking the bezier() calls apart would save 4 mix() calls, since
    // the mix()es (of xy / yz / zw / wx) are all calculated twice. It turns out that the MALI
    // compiler is already doing this; leaving it as is for readability.
    float bx0 = bezier(aPath.xyz, s);
    float bx1 = bezier(aPath.zwx, s);
    float by0 = bezier(aPath.yzw, s);
    float by1 = bezier(aPath.wxy, s);
    vec3 motion = vec3(mix(bx0, bx1, s), mix(by0, by1, s), 0.f);

    // Model to view position
    vec3 position3 = aPosition * uSize + motion;

    vec4 position = uModelView * vec4(position3, 1.f);

    // Add scatter - calculated in view space, using view ray
    vec3 normalizedPos = position.xyz / uSize;
    for (int i = 0; i < SCATTER_VARS; ++i)
    {
      vec2 scatterDist = (normalizedPos - uScatter[i].ray * dot(uScatter[i].ray, normalizedPos)).xy;

      // NOTE: replacing the division with a multiplication (by inverse) oddly results in more instructions (MALI).
      float scatter = max(0.f, uScatter[i].radiusSqr - dot(scatterDist, scatterDist)) *
        uScatter[i].amount / aSize;
      position.xy += scatter * normalize(scatterDist) * uSize.xy;
    }

    // Calculate normalised depth and distance from focal plane
    float depth = (position.z - uDepthRange.x) * uDepthRange.y;
    vDepth = depth;

    float focalDist = (uFocalLength - depth) * uAperture;
    focalDist *= focalDist;
    vFocalDistance = max(focalDist, 1e-6f);	// NOTE: was clamp(..., 1.f); side effect: out of focus particles get squashed at higher aperture values.

    // Calculate expiring scale - for size and opacity.
    float expiringScale = smoothstep(order + 1.f, order, uPopulation);

    // Calculate billboard position and size
    vec2 subPosition = aSubPosition * aSize *
      (1.f + twinkle * aSeed * uTwinkleSizeScale) *
      expiringScale;

    // Insist on hacking the size? Do it here...
    float sizeHack = depth + .5f;
    // NOTE: sizeHack *= sizeHack looked slightly better.
    subPosition *= sizeHack;

    vec3 subPositionView = vec3(subPosition, 0.);

    // Add billboards to view position.
    position += vec4(subPositionView, 0.f);

    // subPosition doubles as normalized (-1..1) UV.
    vUvUnit = aSubPosition;

    // Vary opacity (actor alpha) by time as well as expiring scale.
    vOpacity = uColor.a * expiringScale *
      (1.0f + aSeed + twinkle * uTwinkleOpacityWeight) / (2.0f + uTwinkleOpacityWeight);

    // Randomize RGB using seed.
    vec3 mixColor = vec3(fract(aSeed), fract(aSeed * 16.f), fract(aSeed * 256.f));
    vColor = mix(uColor.rgb, uSecondaryColor, mixColor);

    gl_Position = uProjection * position;
  });

///@brief Fragment shader for particles, which simulates depth of field
/// using a combination of procedural texturing, alpha testing and alpha
/// blending.
const char* const PARTICLES_FSH = USE_GLSL_VERSION(300 es)
DALI_COMPOSE_SHADER(
  precision lowp float;
  uniform float uAlphaTestRefValue;
  uniform vec2 uFadeRange; // near, far
  in vec2 vUvUnit;
  flat in float vDepth;
  flat in float vFocalDistance;
  flat in float vOpacity;
  flat in vec3 vColor;
  out vec4 oFragColor;

  const float REF_VALUE_THRESHOLD = 1. / 64.;

  void main() {
    // Softened disc pattern from normalized UVs
    float value = 1.f - dot(vUvUnit, vUvUnit);

    // Decrease area of particles 'in-focus'.
    float refValue = (1.f - vFocalDistance) * .5f;
    float threshold = REF_VALUE_THRESHOLD * (1.f + vDepth);
    float alpha = pow(value, vFocalDistance) * smoothstep(refValue - threshold, refValue + threshold, value);
    if (alpha < uAlphaTestRefValue)
    {
      discard;
    }

    // Apply opacity
    alpha *= vOpacity;
    alpha *= alpha;

    // Fade particles out as they get close to the near and far clipping planes
    alpha *= smoothstep(.0f, uFadeRange.x, vDepth) * smoothstep(1.f, uFadeRange.y, vDepth);

    oFragColor = vec4(vColor, alpha);
  });

///@brief Shader for simple textured geometry.
const char* const SIMPLE_VSH = USE_GLSL_VERSION(300 es)
DALI_COMPOSE_SHADER(
  precision mediump float;
  uniform mat4 uMvpMatrix;//by DALi
  uniform vec3 uSize;  // by DALi
  in vec3 aPosition;
  void main() {
    gl_Position = uMvpMatrix * vec4(aPosition * uSize, 1.f);
  });

///@brief Shader for an unlit, unfogged, textured mesh.
const char* const SIMPLE_FSH = USE_GLSL_VERSION(300 es)
DALI_COMPOSE_SHADER(
  precision mediump float;
  uniform vec4 uColor;
  out vec4 oFragColor;

  void main() {
    oFragColor = uColor;
  });


uint32_t GetSkipValue(uint32_t count, uint32_t prime)
{
  uint32_t skip = 0;
  do
  {
    skip = (rand() % prime) * count * count + (rand() % prime) * count + (rand() % prime);
  }
  while (skip % prime == 0);
  return skip;
}

}

ParticleView::ParticleView(const ParticleField& field, Dali::Actor world, Dali::CameraActor camera,
  Dali::Geometry particleGeom)
: mWorld(world),
  mParticleBoxSize(field.mBoxSize)
{
  if (!particleGeom)
  {
    // create particles
    particleGeom = field.MakeGeometry();
  }

  // create shader
  Shader particleShader = Shader::New(PARTICLES_VSH, PARTICLES_FSH, Shader::Hint::MODIFIES_GEOMETRY);

  float zNear = camera.GetNearClippingPlane();
  float zFar = camera.GetFarClippingPlane();
  const Vector2 depthRange(zNear, 1.f / (zFar - zNear));
  particleShader.RegisterProperty("uDepthRange", depthRange);

  particleShader.RegisterProperty("uTwinkleFrequency", field.mTwinkleFrequency);
  particleShader.RegisterProperty("uTwinkleSizeScale", field.mTwinkleSizeScale);
  particleShader.RegisterProperty("uTwinkleOpacityWeight", field.mTwinkleOpacityWeight);

  mPropPopulation = particleShader.RegisterProperty("uPopulation", 1.f);
  mPropFocalLength = particleShader.RegisterProperty("uFocalLength", .5f);
  mPropAperture = particleShader.RegisterProperty("uAperture", 8.f);
  mPropAlphaTestRefValue = particleShader.RegisterProperty("uAlphaTestRefValue", 0.f);
  mPropFadeRange = particleShader.RegisterProperty("uFadeRange", Vector2(0.f, 1.f));

  // scatter variables
  char nameBuffer[64];
  char* writep = nameBuffer + sprintf(nameBuffer, "uScatter[");
  for (uint32_t i = 0; i < std::extent<decltype(mScatterProps)>::value; ++i)
  {
    char* writep2 = writep + sprintf(writep, "%d].", i);

    sprintf(writep2, "radiusSqr");
    mScatterProps[i].mPropRadius = particleShader.RegisterProperty(nameBuffer, 0.f);

    sprintf(writep2, "amount");
    mScatterProps[i].mPropAmount = particleShader.RegisterProperty(nameBuffer, 0.f);

    sprintf(writep2, "ray");
    mScatterProps[i].mPropRay = particleShader.RegisterProperty(nameBuffer, Vector3::ZERO);
  }

  // Create a look-up table for pseudo-random traversal of particles.
  // Our particle mesh is sorted in Z; changing the population should remove
  // particles "randomly", not from one end.
  // Algorithm described in Mike McShaffry & al: Game Coding Complete.
  const uint32_t prime = 131;	// next prime after POPULATION_GRANULARITY
  const uint32_t skip = GetSkipValue(POPULATION_GRANULARITY, prime);
  uint32_t next = 0;

  writep = nameBuffer + sprintf(nameBuffer, "uOrderLookUp[");
  for (uint32_t i = 0; i < POPULATION_GRANULARITY; ++i)
  {
    do {
      next += skip;
      next %= prime;
    }
    while (next == 0 || next > POPULATION_GRANULARITY);

    sprintf(writep, "%d]", i);
    particleShader.RegisterProperty(nameBuffer, float(next - 1));
  }

  // create animation for time in shader
  auto propTime = particleShader.RegisterProperty("uTime", 0.f);

  Animation animTime = Animation::New(field.mMotionCycleLength);
  animTime.AnimateTo(Property(particleShader, propTime), static_cast<float>(M_PI * 2.f));
  animTime.SetLoopCount(0);
  animTime.Play();

  mParticleShader = particleShader;

  auto renderer = CreateRenderer(TextureSet::New(), particleGeom, particleShader, OPTION_BLEND);
  auto masterParticles = CreateActor();
  masterParticles.SetProperty(Actor::Property::SIZE, field.mBoxSize);
  masterParticles.SetProperty(Actor::Property::VISIBLE, true);
  masterParticles.AddRenderer(renderer);

  mPropSecondaryColor = masterParticles.RegisterProperty("uSecondaryColor", Vector3::XAXIS);

#ifdef ENABLE_DEBUG_VOLUME
  Geometry cubeGeom = CreateCuboidWireframeGeometry();
  renderer = CreateRenderer(renderer.GetTextures(), cubeGeom, Shader::New(SIMPLE_VSH, SIMPLE_FSH));
  masterParticles.AddRenderer(renderer);
#endif

  world.Add(masterParticles);
  mMasterParticles = masterParticles;
}

ParticleView::~ParticleView()
{
  UnparentAndReset(mMasterParticles);
  UnparentAndReset(mSlaveParticles);

  for (auto anim: { mAngularAnim, mLinearAnim })
  {
    if (anim)
    {
      anim.Stop();
      anim.Reset();
    }
  }

  for (auto& s: mScatterProps)
  {
    auto& anim = s.mAnim;
    if (anim)
    {
      anim.Stop();
      anim.Reset();
    }
  }
}

void ParticleView::SetColorRange(const ColorRange& range)
{
  mMasterParticles.SetProperty(Actor::Property::COLOR_RED, range.rgb0.r);
  mMasterParticles.SetProperty(Actor::Property::COLOR_GREEN, range.rgb0.g);
  mMasterParticles.SetProperty(Actor::Property::COLOR_BLUE, range.rgb0.b);

  mMasterParticles.SetProperty(mPropSecondaryColor, range.rgb1);
}

void ParticleView::SetPopulation(float percentage)
{
  percentage = 1.f - std::min(1.f, std::max(0.f, percentage));
  mParticleShader.SetProperty(mPropPopulation, POPULATION_GRANULARITY * percentage);
}

void ParticleView::SetFocalLength(float f)
{
  mParticleShader.SetProperty(mPropFocalLength, f);
}

void ParticleView::SetAperture(float a)
{
  mParticleShader.SetProperty(mPropAperture, a);
}

void ParticleView::SetAlphaTestRefValue(float rv)
{
  mParticleShader.SetProperty(mPropAlphaTestRefValue, rv);
}

void ParticleView::SetFadeRange(float near, float far)
{
  mParticleShader.SetProperty(mPropFadeRange, Vector2(near, far));
}

void ParticleView::SetAngularVelocity(float v)
{
  if (mAngularAnim)
  {
    mAngularAnim.Stop();
    mAngularAnim.Clear();
    mAngularAnim.Reset();
  }

  if (v * v > .0f)
  {
    float sign = Sign(v);
    auto anim = Animation::New(std::abs(2. * M_PI / v));
    anim.AnimateTo(Property(mMasterParticles, Actor::Property::ORIENTATION),
      Quaternion(Radian(Degree(120. * sign)), Vector3::ZAXIS), TimePeriod(0., anim.GetDuration() / 3.));
    anim.AnimateTo(Property(mMasterParticles, Actor::Property::ORIENTATION),
      Quaternion(Radian(Degree(240. * sign)), Vector3::ZAXIS), TimePeriod(anim.GetDuration() / 3., anim.GetDuration() / 3.));
    anim.AnimateTo(Property(mMasterParticles, Actor::Property::ORIENTATION),
      Quaternion(Radian(Degree(360. * sign)), Vector3::ZAXIS), TimePeriod(2. * anim.GetDuration() / 3., anim.GetDuration() / 3.));
    anim.SetLoopCount(0);
    anim.Play();

    mAngularAnim = anim;
  }
}

void ParticleView::SetLinearVelocity(float v)
{
  if (mLinearAnim)
  {
    mLinearAnim.Stop();
    mLinearAnim.Clear();
    mLinearAnim.Reset();
  }
  UnparentAndReset(mSlaveParticles);

  if (v * v > .0f)
  {
    float sign = Sign(v);
    float directedSize = sign * mParticleBoxSize.z;

    Actor slaveParticles = CloneActor(mMasterParticles);
    Vector3 position = mMasterParticles.GetCurrentProperty(Actor::Property::POSITION).Get<Vector3>();
    slaveParticles.SetProperty(Actor::Property::POSITION, position + Vector3(0., 0., directedSize));

    auto propSecondaryColor = slaveParticles.RegisterProperty("uSecondaryColor", Vector3::XAXIS);

    Actor world = mWorld.GetHandle();
    world.Add(slaveParticles);

    if (sign < 0.)	// fix draw order
    {
      world.Remove(mMasterParticles);
      world.Add(mMasterParticles);
    }

    Constraint constraint = Constraint::New<Vector4>(slaveParticles, Actor::Property::COLOR,
      EqualToConstraint());
    constraint.AddSource(Source(mMasterParticles, Actor::Property::COLOR));
    constraint.Apply();

    constraint = Constraint::New<Vector3>(slaveParticles, propSecondaryColor,
      EqualToConstraint());
    constraint.AddSource(Source(mMasterParticles, mPropSecondaryColor));
    constraint.Apply();

    constraint = Constraint::New<Quaternion>(slaveParticles, Actor::Property::ORIENTATION,
      EqualToConstraint());
    constraint.AddSource(Source(mMasterParticles, Actor::Property::ORIENTATION));
    constraint.Apply();

    auto anim = Animation::New(std::abs(directedSize / v));
    anim.AnimateTo(Property(mMasterParticles, Actor::Property::POSITION_Z), position.z - directedSize);
    anim.AnimateTo(Property(slaveParticles, Actor::Property::POSITION_Z), position.z);
    anim.SetLoopCount(0);
    anim.Play();

    mLinearAnim = anim;
    mSlaveParticles = slaveParticles;
  }
}

void ParticleView::Scatter(float radius, float amount, float durationOut, float durationIn)
{
  mActiveScatter = (mActiveScatter + 1) % std::extent<decltype(mScatterProps)>::value;

  auto& scatter = mScatterProps[mActiveScatter];
  if (scatter.mAnim)
  {
    scatter.mAnim.Stop();
  }

  radius /= mParticleBoxSize.y;
  radius *= radius;
  mParticleShader.SetProperty(scatter.mPropRadius, radius);

  Animation anim = Animation::New(durationOut + durationIn);
  auto scatterAmount = Property(mParticleShader, scatter.mPropAmount);
  anim.AnimateTo(scatterAmount, amount, AlphaFunction::EASE_OUT,
    TimePeriod(0.f, durationOut));
  anim.AnimateTo(scatterAmount, 0.f, AlphaFunction::EASE_IN_OUT_SINE,
    TimePeriod(durationOut, durationIn));
  anim.Play();

  scatter.mAnim = anim;
}

void ParticleView::SetScatterRay(Dali::Vector3 rayDir)
{
  auto& scatter = mScatterProps[mActiveScatter];
  mParticleShader.SetProperty(scatter.mPropRay, rayDir);;
}

void ParticleView::Fade(float duration, float target, AlphaFunction alphaFn,
  std::function<void(Dali::Animation&)> onFinished)
{
  if (mFadeAnim)
  {
    mFadeAnim.Stop();
  }

  Animation anim = Animation::New(duration);
  anim.AnimateTo(Property(mMasterParticles, Actor::Property::COLOR_ALPHA), target, alphaFn);
  if (mSlaveParticles)
  {
    anim.AnimateTo(Property(mSlaveParticles, Actor::Property::COLOR_ALPHA), target, alphaFn);
  }

  if (onFinished)
  {
    anim.FinishedSignal().Connect(this, onFinished);
  }
  anim.Play();

  mFadeAnim = anim;
}

void ParticleView::Fade(float duration, float target, float from, AlphaFunction alphaFn,
  std::function<void(Dali::Animation&)> onFinished)
{
  mMasterParticles.SetProperty(Actor::Property::COLOR_ALPHA, from);
  if (mSlaveParticles)
  {
    mSlaveParticles.SetProperty(Actor::Property::COLOR_ALPHA, from);
  }

  Fade(duration, target, alphaFn, onFinished);
}