/**
* Copyright (c) 2006-2009 LOVE Development Team
* 
* This software is provided 'as-is', without any express or implied
* warranty.  In no event will the authors be held liable for any damages
* arising from the use of this software.
* 
* Permission is granted to anyone to use this software for any purpose,
* including commercial applications, and to alter it and redistribute it
* freely, subject to the following restrictions:
* 
* 1. The origin of this software must not be misrepresented; you must not
*    claim that you wrote the original software. If you use this software
*    in a product, an acknowledgment in the product documentation would be
*    appreciated but is not required.
* 2. Altered source versions must be plainly marked as such, and must not be
*    misrepresented as being the original software.
* 3. This notice may not be removed or altered from any source distribution.
**/

#ifndef LOVE_GRAPHICS_OPENGL_PARTICLE_SYSTEM_H
#define LOVE_GRAPHICS_OPENGL_PARTICLE_SYSTEM_H

// LOVE

#include <common/math.h>
#include <common/Vector.h>
#include <graphics/Drawable.h>
#include "Image.h"

namespace love
{
namespace graphics
{
namespace opengl
{

	// Represents a single particle.
	struct particle
	{
		float lifetime;
		float life;

		float position[2];
		float direction;

		love::Vector speed;
		float gravity;
		float radialAcceleration;
		float tangentialAcceleration;

		float size;
		float sizeStart;
		float sizeEnd;

		float rotation;
		float spinStart;
		float spinEnd;

		float color[4];
	};

	/**
	* A class for creating, moving and drawing particles.
	* A big thanks to bobthebloke.org
	**/
	class ParticleSystem : public Drawable
	{
	protected:

		// The max amount of particles.
		unsigned int bufferSize;

		// Pointer to the first particle.
		particle * pStart;

		// Pointer to the next available free space.
		particle * pLast;

		// Pointer to the end of the memory allocation.
		particle * pEnd;

		// The sprite to be drawn.
		Image * sprite;

		// Whether the particle emitter is active.
		bool active;

		// The emission rate (particles/sec).
		int emissionRate;

		// Used to determine when a particle should be emitted.
		float emitCounter;

		// The relative position of the particle emitter.
		love::Vector position;

		// The lifetime of the particle emitter (-1 means infinite) and the life it has left.
		float lifetime;
		float life;

		// The particle life.
		float particleLifeMin;
		float particleLifeMax;

		// The direction (and spread) the particles will be emitted in. Measured in radians.
		float direction;
		float spread;

		// Whether the direction should be relative to the emitter's movement.
		bool relative;

		// The speed.
		float speedMin;
		float speedMax;

		// Acceleration towards the bottom of the screen
		float gravityMin;
		float gravityMax;

		// Acceleration towards the emitter's center
		float radialAccelerationMin;
		float radialAccelerationMax;

		// Acceleration perpendicular to the particle's direction.
		float tangentialAccelerationMin;
		float tangentialAccelerationMax;

		// Size.
		float sizeStart;
		float sizeEnd;
		float sizeVariation;

		// Rotation
		float rotationMin;
		float rotationMax;

		// Spin.
		float spinStart;
		float spinEnd;
		float spinVariation;

		// Color.
		unsigned char colorStart[4];
		unsigned char colorEnd[4];

		void add();
		void remove(particle * p);

	public:

		/**
		* Creates a particle system with the specified buffersize and sprite.
		**/
		ParticleSystem(Image * sprite, unsigned int buffer);

		/**
		* Deletes any allocated memory.
		**/
		virtual ~ParticleSystem();

		/**
		* Sets the sprite used in the particle system.
		* @param sprite The new sprite.
		**/
		void setSprite(Image * image);

		/**
		* Clears the current buffer and allocates the appropriate amount of space for the buffer.
		* @param size The new buffer size.
		**/
		void setBufferSize(unsigned int size);

		/**
		* Sets the emission rate.
		* @param rate The amount of particles per second.
		**/
		void setEmissionRate(int rate);

		/**
		* Sets the lifetime of the particle emitter (-1 means eternal)
		* @param life The lifetime (in seconds).
		**/
		void setLifetime(float life);

		/**
		* Sets the life range of the particles.
		* @param lifeMin The minimum life.
		* @param lifeMax The maximum life (if 0, then becomes the same as minimum life).
		**/
		void setParticleLife(float min, float max = 0);

		/**
		* Sets the position of the center of the emitter and the direction (if set to relative).
		* Used to move the emitter without changing the position of already existing particles.
		* @param x The x-coordinate.
		* @param y The y-coordinate.
		**/
		void setPosition(float x, float y);

		/**
		* Sets the direction and the spread of the particle emitter.
		* @param direction The direction (in degrees).
		**/
		void setDirection(float direction);

		/**
		* Sets the spread of the particle emitter.
		* @param spread The spread (in degrees).
		**/
		void setSpread(float spread);

		/**
		* Sets whether the direction should be relative to the particle emitters movement. Used in conjunction with setPosition.
		* @param relative Whether to have relative direction.
		**/
		void setRelativeDirection(bool relative);

		/**
		* Sets the speed of the particles.
		* @param speed The speed.
		**/
		void setSpeed(float speed);

		/**
		* Sets the speed of the particles.
		* @param min The minimum speed.
		* @param max The maximum speed.
		**/
		void setSpeed(float min, float max);

		/**
		* Sets the gravity of the particles (the acceleration along the y-axis).
		* @param gravity The amount of gravity.
		**/
		void setGravity(float gravity);

		/**
		* Sets the gravity of the particles (the acceleration along the y-axis).
		* @param min The minimum gravity.
		* @param max The maximum gravity.
		**/
		void setGravity(float min, float max);

		/**
		* Sets the radial acceleration (the acceleration towards the particle emitter).
		* @param acceleration The amount of acceleration.
		**/
		void setRadialAcceleration(float acceleration);

		/**
		* Sets the radial acceleration (the acceleration towards the particle emitter).
		* @param min The minimum acceleration.
		* @param max The maximum acceleration.
		**/
		void setRadialAcceleration(float min, float max);

		/**
		* Sets the tangential acceleration (the acceleration perpendicular to the particle's direction).
		* @param acceleration The amount of acceleration.
		**/
		void setTangentialAcceleration(float acceleration);

		/**
		* Sets the tangential acceleration (the acceleration perpendicular to the particle's direction).
		* @param min The minimum acceleration.
		* @param max The maximum acceleration.
		**/
		void setTangentialAcceleration(float min, float max);

		/**
		* Sets the size of the sprite (1.0 being the default size).
		* @param size The size of the sprite.
		**/
		void setSize(float size);

		/**
		* Sets the size of the sprite upon creation and upon death (1.0 being the default size).
		* @param start The size of the sprite upon creation
		* @param end The size of the sprite upon death.
		**/
		void setSize(float start, float end);

		/**
		* Sets the size of the sprite upon creation and upon death (1.0 being the default size) and any variation.
		* @param start The size of the sprite upon creation
		* @param end The size of the sprite upon death.
		* @param variation The amount of variation on the starting size (0 being no variation and 1.0 a random size between start and end).
		**/
		void setSize(float start, float end, float variation);

		/**
		* Sets the amount of variation to the sprite's beginning size (0 being no variation and 1.0 a random size between start and end).
		* @param variation The amount of variation.
		**/
		void setSizeVariation(float variation);

		/**
		* Sets the amount of rotation a sprite starts out with.
		* @param rotation The amount of rotation.
		**/
		void setRotation(float rotation);

		/**
		* Sets the amount of rotation a sprite starts out with (a random value between min and max).
		* @param min The minimum amount of rotation.
		* @param max The maximum amount of rotation.
		**/
		void setRotation(float min, float max);

		/**
		* Sets the spin of the sprite.
		* @param spin The spin of the sprite (in degrees).
		**/
		void setSpin(float spin);

		/**
		* Sets the spin of the sprite upon particle creation and death.
		* @param start The spin of the sprite upon creation (in degrees).
		* @param end The spin of the sprite upon death (in degrees).
		**/
		void setSpin(float start, float end);

		/**
		* Sets the spin of the sprite upon particle creation and death and the variation.
		* @param start The spin of the sprite upon creation (in degrees).
		* @param end The spin of the sprite upon death (in degrees).
		* @param variation The variation of the start spin (0 being no variation and 1 beign a random spin between start and end).
		**/
		void setSpin(float start, float end, float variation);

		/**
		* Sets the variation of the start spin (0 being no variation and 1 beign a random spin between start and end).
		* @param variation The variation in degrees.
		**/
		void setSpinVariation(float variation);

		/**
		* Sets the color of the particles.
		* @param color The color.
		**/
		void setColor(unsigned char * color);

		/**
		* Sets the color of the particles.
		* @param start The color of the particle when created.
		* @param end The color of the particle upon death.
		**/
		void setColor(unsigned char * start, unsigned char * end);

		/**
		* Returns the x-coordinate of the emitter's position.
		**/
		float getX() const;

		/**
		* Returns the y-coordinate of the emitter's position.
		**/
		float getY() const;

		/**
		* Returns the direction of the emitter (in degrees).
		**/
		float getDirection() const;

		/**
		* Returns the directional spread of the emitter (in degrees).
		**/
		float getSpread() const;

		/**
		* Returns the amount of particles that are currently active in the system.
		**/
		int count() const;

		/**
		* Starts/resumes the particle emitter.
		**/
		void start();

		/**
		* Stops the particle emitter and resets.
		**/
		void stop();

		/**
		* Pauses the particle emitter.
		**/
		void pause();

		/**
		* Resets the particle emitter.
		**/
		void reset();

		/**
		* Returns whether the particle emitter is active.
		**/
		bool isActive() const;

		/**
		* Returns whether the particle system is empty of particles or not.
		**/
		bool isEmpty() const;

		/**
		* Returns whether the amount of particles has reached the buffer limit or not.
		**/
		bool isFull() const;

		/**
		* Draws the particle emitter at the specified position.
		* @param x The x-coordinate.
		* @param y The y-coordinate.
		**/
		virtual void draw(float x, float y, float angle, float sx, float sy, float ox, float oy) const;

		/**
		* Updates the particle system.
		* @param dt Time since last update.
		**/
		void update(float dt);
	};

} // opengl
} // graphics
} // love

#endif // LOVE_GRAPHICS_OPENGL_PARTICLE_SYSTEM_H