/*
Copyright (c) 2017-2019 Timur Gafarov

Boost Software License - Version 1.0 - August 17th, 2003
Permission is hereby granted, free of charge, to any person or organization
obtaining a copy of the software and accompanying documentation covered by
this license (the "Software") to use, reproduce, display, distribute,
execute, and transmit the Software, and to prepare derivative works of the
Software, and to permit third-parties to whom the Software is furnished to
do so, all subject to the following:

The copyright notices in the Software and this entire statement, including
the above license grant, this restriction and the following disclaimer,
must be included in all copies of the Software, in whole or in part, and
all derivative works of the Software, unless such copies or derivative
works are solely in the form of machine-executable object code generated by
a source language processor.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.
*/

module dagon.graphics.light;

import std.stdio;
import std.math;
import std.conv;
import std.random;

import dlib.core.memory;
import dlib.math.vector;
import dlib.math.matrix;
import dlib.math.transformation;
import dlib.math.quaternion;
import dlib.container.array;
import dlib.image.color;

import dagon.core.libs;
import dagon.core.ownership;
import dagon.graphics.view;
import dagon.graphics.rc;
import dagon.graphics.shadow;
import dagon.logics.entity;
import dagon.logics.behaviour;
import dagon.resource.scene;

enum LightType
{
    AreaSphere = 1,
    AreaTube = 2,
    Sun = 3,
    Spot = 4
}

class LightSource: Owner
{
    Vector3f position;
    Quaternionf rotation;
    Vector3f color;
    float radius; // max light attenuation radius
    float areaRadius; // light's own radius
    float tubeLength;
    float energy;
    float spotOuterCutoff;
    float spotInnerCutoff;
    //float spotExponent;
    LightType type;
    bool shadowEnabled;
    ShadowMap shadowMap;

    this(Owner o)
    {
        super(o);
        this.position = Vector3f(0.0f, 0.0f, 0.0f);
        this.rotation = Quaternionf.identity;
        this.tubeLength = 1.0f;
        this.color = Vector3f(1.0f, 1.0f, 1.0f);
        this.radius = 1.0f;
        this.areaRadius = 0.0f;
        this.energy = 1.0f;
        this.type = LightType.AreaSphere;
        this.shadowEnabled = false;
    }

    this(Vector3f pos, Vector3f col, float attRadius, float areaRadius, float energy, Owner o)
    {
        super(o);
        this.position = pos;
        this.rotation = Quaternionf.identity;
        this.tubeLength = 1.0f;
        this.color = col;
        this.radius = attRadius;
        this.areaRadius = areaRadius;
        this.energy = energy;
        this.type = LightType.AreaSphere;
        this.shadowEnabled = false;
    }

    Vector3f direction() @property
    {
        return rotation.rotate(Vector3f(0, 0, 1));
    }

    Vector3f directionEye(Matrix4x4f viewMatrix)
    {
        Vector4f dirHGVector = Vector4f(direction);
        dirHGVector.w = 0.0;
        return (dirHGVector * viewMatrix).xyz;
    }

    void shadow(bool mode) @property
    {
        if (mode)
        {
            if (type == LightType.Sun)
            {
                if (shadowMap is null)
                    shadowMap = New!CascadedShadowMap(this, 1024, 10, 30, 200, -100, 100, this);
            }
        }

        shadowEnabled = mode;
    }

    bool shadow() @property
    {
        return shadowEnabled;
    }

    void updateShadow(Vector3f cameraPosition, Vector3f cameraDirection, RenderingContext* rc, double timeStep)
    {
        if (type == LightType.Sun)
        {
            if (shadowMap && shadowEnabled)
                shadowMap.update(cameraPosition, cameraDirection, rc, timeStep);
        }
    }

    void renderShadow(Scene scene, RenderingContext* rc)
    {
        if (type == LightType.Sun)
        {
            if (shadowMap && shadowEnabled)
                shadowMap.render(scene, rc);
        }
    }
}

class LightManager: Owner
{
    DynamicArray!LightSource lightSources;

	this(Owner o)
    {
		super(o);
	}

    ~this()
    {
        lightSources.free();
    }

    LightSource addPointLight(Vector3f position, Color4f color, float energy, float radius, float areaRadius = 0.0f)
    {
        lightSources.append(New!LightSource(position, color.rgb, radius, areaRadius, energy, this));
        return lightSources.data[$-1];
    }

    LightSource addSunLight(Quaternionf rotation, Color4f color, float energy)
    {
        LightSource light = New!LightSource(this);
        light.rotation = rotation;
        light.color = color.rgb;
        light.energy = energy;
        light.type = LightType.Sun;
        lightSources.append(light);
        return light;
    }

    LightSource addSpotLight(Vector3f position, Color4f color, float energy, Quaternionf rotation, float outerCutoff, float innerCutoff, float volumeRadius)
    {
        LightSource light = New!LightSource(this);
        light.position = position;
        light.rotation = rotation;
        light.color = color.rgb;
        light.energy = energy;
        light.spotOuterCutoff = outerCutoff;
        light.spotInnerCutoff = innerCutoff;
        //light.spotExponent = exponent;
        light.radius = volumeRadius;
        light.type = LightType.Spot;
        lightSources.append(light);
        return light;
    }

    void updateShadows(View view, RenderingContext* rc, double timeStep)
    {
        Vector3f cameraDirection = -view.invViewMatrix.forward;
        cameraDirection.y = 0.0f;
        cameraDirection = cameraDirection.normalized;
        updateShadows(view.cameraPosition, cameraDirection, rc, timeStep);
    }

    void updateShadows(Vector3f cameraPosition, Vector3f cameraDirection, RenderingContext* rc, double timeStep)
    {
        foreach(light; lightSources.data)
            light.updateShadow(cameraPosition, cameraDirection, rc, timeStep);
    }

    void renderShadows(Scene scene, RenderingContext* rc)
    {
        foreach(light; lightSources.data)
            light.renderShadow(scene, rc);
    }
}

// Attach a light to Entity
class LightBehaviour: Behaviour
{
    LightSource light;

    this(Entity e, LightSource light)
    {
        super(e);

        this.light = light;
    }

    override void update(double dt)
    {
        light.position = entity.position;
    }
}