// Copyright (C) 2007 Id Software, Inc.
//

#ifndef __MATH_EXTRAPOLATE_H__
#define __MATH_EXTRAPOLATE_H__

/*
==============================================================================================

	Extrapolation

==============================================================================================
*/

enum extrapolation_t {
	EXTRAPOLATION_NONE			= 0x01,	// no extrapolation, covered distance = duration * 0.001 * ( baseSpeed )
	EXTRAPOLATION_LINEAR		= 0x02,	// linear extrapolation, covered distance = duration * 0.001 * ( baseSpeed + speed )
	EXTRAPOLATION_ACCELLINEAR	= 0x04,	// linear acceleration, covered distance = duration * 0.001 * ( baseSpeed + 0.5 * speed )
	EXTRAPOLATION_DECELLINEAR	= 0x08,	// linear deceleration, covered distance = duration * 0.001 * ( baseSpeed + 0.5 * speed )
	EXTRAPOLATION_ACCELSINE		= 0x10,	// sinusoidal acceleration, covered distance = duration * 0.001 * ( baseSpeed + sqrt( 0.5 ) * speed )
	EXTRAPOLATION_DECELSINE		= 0x20,	// sinusoidal deceleration, covered distance = duration * 0.001 * ( baseSpeed + sqrt( 0.5 ) * speed )
	EXTRAPOLATION_NOSTOP		= 0x40	// do not stop at startTime + duration
};

template< class type >
class idExtrapolate {
	
public:
						idExtrapolate();

	void				Init( const float startTime, const float duration, const type &startValue, const type &baseSpeed, const type &speed, const extrapolation_t extrapolationType );
	type				GetCurrentValue( float time ) const;
	type				GetCurrentSpeed( float time ) const;
	bool				IsDone( float time ) const { return ( !( extrapolationType & EXTRAPOLATION_NOSTOP ) && time >= startTime + duration ); }
	void				SetStartTime( float time ) { startTime = time; currentTime = -1; }
	float				GetStartTime( void ) const { return startTime; }
	float				GetEndTime( void ) const { return ( !( extrapolationType & EXTRAPOLATION_NOSTOP ) && duration > 0 ) ? startTime + duration : 0; }
	float				GetDuration( void ) const { return duration; }
	void				SetStartValue( const type &value ) { startValue = value; currentTime = -1; }
	const type &		GetStartValue( void ) const { return startValue; }
	const type &		GetBaseSpeed( void ) const { return baseSpeed; }
	const type &		GetSpeed( void ) const { return speed; }
	extrapolation_t		GetExtrapolationType( void ) const { return extrapolationType; }

private:
	extrapolation_t		extrapolationType;
	float				startTime;
	float				duration;
	type				startValue;
	type				baseSpeed;
	type				speed;
	mutable float		currentTime;
	mutable type		currentValue;
};

/*
====================
idExtrapolate::idExtrapolate
====================
*/
template< class type >
ID_INLINE idExtrapolate<type>::idExtrapolate() {
	extrapolationType = EXTRAPOLATION_NONE;
	startTime = duration = 0.0f;
	memset( &startValue, 0, sizeof( startValue ) );
	memset( &baseSpeed, 0, sizeof( baseSpeed ) );
	memset( &speed, 0, sizeof( speed ) );
	currentTime = -1;
	currentValue = startValue;
}

/*
====================
idExtrapolate::Init
====================
*/
template< class type >
ID_INLINE void idExtrapolate<type>::Init( const float startTime, const float duration, const type &startValue, const type &baseSpeed, const type &speed, const extrapolation_t extrapolationType ) {
	this->extrapolationType = extrapolationType;
	this->startTime = startTime;
	this->duration = duration;
	this->startValue = startValue;
	this->baseSpeed = baseSpeed;
	this->speed = speed;
	currentTime = -1;
	currentValue = startValue;
}

/*
====================
idExtrapolate::GetCurrentValue
====================
*/
template< class type >
ID_INLINE type idExtrapolate<type>::GetCurrentValue( float time ) const {
	float deltaTime, s;

	if ( time == currentTime ) {
		return currentValue;
	}

	currentTime = time;

	if ( time < startTime ) {
		return startValue;
	}

	if ( !( extrapolationType &	EXTRAPOLATION_NOSTOP ) && ( time > startTime + duration ) ) {
		time = startTime + duration;
	}

	switch( extrapolationType & ~EXTRAPOLATION_NOSTOP ) {
		case EXTRAPOLATION_NONE: {
			deltaTime = ( time - startTime ) * 0.001f;
			currentValue = startValue + deltaTime * baseSpeed;
			break;
		}
		case EXTRAPOLATION_LINEAR: {
			deltaTime = ( time - startTime ) * 0.001f;
			currentValue = startValue + deltaTime * ( baseSpeed + speed );
			break;
		}
		case EXTRAPOLATION_ACCELLINEAR: {
			if ( !duration ) {
				currentValue = startValue;
			} else {
				deltaTime = ( time - startTime ) / duration;
				s = ( 0.5f * deltaTime * deltaTime ) * ( duration * 0.001f );
				currentValue = startValue + deltaTime * baseSpeed + s * speed;
			}
			break;
		}
		case EXTRAPOLATION_DECELLINEAR: {
			if ( !duration ) {
				currentValue = startValue;
			} else {
				deltaTime = ( time - startTime ) / duration;
				s = ( deltaTime - ( 0.5f * deltaTime * deltaTime ) ) * ( duration * 0.001f );
				currentValue = startValue + deltaTime * baseSpeed + s * speed;
			}
			break;
		}
		case EXTRAPOLATION_ACCELSINE: {
			if ( !duration ) {
				currentValue = startValue;
			} else {
				deltaTime = ( time - startTime ) / duration;
				s = ( 1.0f - idMath::Cos( deltaTime * idMath::HALF_PI ) ) * duration * 0.001f * idMath::SQRT_1OVER2;
				currentValue = startValue + deltaTime * baseSpeed + s * speed;
			}
			break;
		}
		case EXTRAPOLATION_DECELSINE: {
			if ( !duration ) {
				currentValue = startValue;
			} else {
				deltaTime = ( time - startTime ) / duration;
				s = idMath::Sin( deltaTime * idMath::HALF_PI ) * duration * 0.001f * idMath::SQRT_1OVER2;
				currentValue = startValue + deltaTime * baseSpeed + s * speed;
			}
			break;
		}
	}
	return currentValue;
}

/*
====================
idExtrapolate::GetCurrentSpeed
====================
*/
template< class type >
ID_INLINE type idExtrapolate<type>::GetCurrentSpeed( float time ) const {
	float deltaTime, s;

	if ( time < startTime || !duration ) {
		return ( startValue - startValue );
	}

	if ( !( extrapolationType &	EXTRAPOLATION_NOSTOP ) && ( time > startTime + duration ) ) {
		return ( startValue - startValue );
	}

	switch( extrapolationType & ~EXTRAPOLATION_NOSTOP ) {
		case EXTRAPOLATION_NONE: {
			return baseSpeed;
		}
		case EXTRAPOLATION_LINEAR: {
			return baseSpeed + speed;
		}
		case EXTRAPOLATION_ACCELLINEAR: {
			deltaTime = ( time - startTime ) / duration;
			s = deltaTime;
			return baseSpeed + s * speed;
		}
		case EXTRAPOLATION_DECELLINEAR: {
			deltaTime = ( time - startTime ) / duration;
			s = 1.0f - deltaTime;
			return baseSpeed + s * speed;
		}
		case EXTRAPOLATION_ACCELSINE: {
			deltaTime = ( time - startTime ) / duration;
			s = idMath::Sin( deltaTime * idMath::HALF_PI );
			return baseSpeed + s * speed;
		}
		case EXTRAPOLATION_DECELSINE: {
			deltaTime = ( time - startTime ) / duration;
			s = idMath::Cos( deltaTime * idMath::HALF_PI );
			return baseSpeed + s * speed;
		}
		default: {
			return baseSpeed;
		}
	}
}

#endif /* !__MATH_EXTRAPOLATE_H__ */