0ad/source/simulation/Stance.h

#ifndef __STANCE_H__
#define __STANCE_H__

#include "EntityHandles.h"
#include "ps/Vector2D.h"

class CEntity;
class CPlayer;

/**
 * A combat stance. This object is given various events by an entity and can choose what the
 * entity will do when it does not have any player orders.
 **/
class CStance
{
protected:
	CEntity* m_Entity;
public:
	CStance(CEntity* ent): m_Entity(ent) {}
	virtual ~CStance() {}

	// Called each tick if the unit is idle.
	virtual void onIdle() = 0;

	// Called when the unit is damaged. Source might be NULL for damage from "acts of Gaia"
	// (but we get notified anyway in case we want to run around in fear). Most stances will
	// probably want to retaliate here.
	virtual void onDamaged(CEntity* source) = 0;

	// Does this stance allow movement at all during AI control?
	virtual bool allowsMovement() = 0;

	// Called when the unit is under AI control and wishes to move to the given position;
	// the stance may choose to cancel if it is too far.
	virtual bool checkMovement(CVector2D proposedPos) = 0;
};

/**
 * Hold Fire stance: Unit never attacks, not even to fight back.
 **/
class CHoldStance : public CStance
{
public:
	CHoldStance(CEntity* ent): CStance(ent) {};
	virtual ~CHoldStance() {};
	virtual void onIdle() {};
	virtual void onDamaged(CEntity* UNUSED(source)) {};
	virtual bool allowsMovement() { return false; };
	virtual bool checkMovement(CVector2D UNUSED(proposedPos)) { return false; }
};

/**
 * Aggressive stance: The unit will attack any enemy it sees and pursue it indefinitely.
 **/
class CAggressStance : public CStance
{
public:
	CAggressStance(CEntity* ent): CStance(ent) {};
	virtual ~CAggressStance() {};
	virtual void onIdle();
	virtual void onDamaged(CEntity* source);
	virtual bool allowsMovement() { return true; };
	virtual bool checkMovement(CVector2D UNUSED(proposedPos)) { return true; }
};

/**
 * Stand Ground stance: The unit will attack enemies in LOS but never move.
 **/
class CStandStance : public CStance
{
public:
	CStandStance(CEntity* ent): CStance(ent) {};
	virtual ~CStandStance() {};
	virtual void onIdle();
	virtual void onDamaged(CEntity* UNUSED(source)) {};	// Empty because onIdle will ensure we're attacking stuff in LOS
	virtual bool allowsMovement() { return false; };
	virtual bool checkMovement(CVector2D UNUSED(proposedPos)) { return false; }
};

/**
 * Defensive stance: The unit will attack enemies but will never pursue them further
 * than its LOS away from its original position (the point where it last became idle).
 **/
class CDefendStance : public CStance
{
	CVector2D idlePos;
public:
	CDefendStance(CEntity* ent): CStance(ent) {};
	virtual ~CDefendStance() {};
	virtual void onIdle();
	virtual void onDamaged(CEntity* source);
	virtual bool allowsMovement() { return true; };
	virtual bool checkMovement(CVector2D proposedPos);
};

/**
 * Utility functions used by the various stances.
 **/
class CStanceUtils
{
private:
	CStanceUtils() {};
public:
	// Attacks the given target using the appropriate attack action (obtained from JavaScript).
	static void attack(CEntity* entity, CEntity* target);

	// Picks a visible entity to attack.
	static CEntity* chooseTarget(CEntity* entity);

	// Picks a visible entity within the given circle to attack
	static CEntity* chooseTarget(float x, float y, float radius, CPlayer* player);
};

#endif