/**
 * @file llstatemachine.h
 * @brief LLStateMachine class header file.
 *
 * $LicenseInfo:firstyear=2001&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2010, Linden Research, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#ifndef LL_LLSTATEMACHINE_H
#define LL_LLSTATEMACHINE_H

#include <string>

#include "llerror.h"
#include <map>

class LLUniqueID
{
    friend bool operator==(const LLUniqueID &a, const LLUniqueID &b);
    friend bool operator!=(const LLUniqueID &a, const LLUniqueID &b);
protected:
    static U32  sNextID;
    U32         mId;
public:
    LLUniqueID(){mId = sNextID++;}
    virtual ~LLUniqueID(){}
    U32     getID() {return mId;}
};

class LLFSMTransition : public LLUniqueID
{
public:
    LLFSMTransition() : LLUniqueID(){};
    virtual std::string getName()const { return "unnamed"; }
};

class LLFSMState : public LLUniqueID
{
public:
    LLFSMState() : LLUniqueID(){};
    virtual void onEntry(void *){};
    virtual void onExit(void *){};
    virtual void execute(void *){};
    virtual std::string getName() const { return "unnamed"; }
};

class LLStateDiagram
{
typedef std::map<LLFSMTransition*, LLFSMState*> Transitions;

friend std::ostream& operator<<(std::ostream &s, LLStateDiagram &FSM);
friend class LLStateMachine;

protected:
    typedef std::map<LLFSMState*, Transitions> StateMap;
    StateMap            mStates;
    Transitions         mDefaultTransitions;
    LLFSMState*         mDefaultState;
    bool                mUseDefaultState;

public:
    LLStateDiagram();
    virtual ~LLStateDiagram();

protected:
    // add a state to the state graph, executed implicitly when adding transitions
    bool addState(LLFSMState *state);

    // add a directed transition between 2 states
    bool addTransition(LLFSMState& start_state, LLFSMState& end_state, LLFSMTransition& transition);

    // add an undirected transition between 2 states
    bool addUndirectedTransition(LLFSMState& start_state, LLFSMState& end_state, LLFSMTransition& transition);

    // add a transition that is taken if none other exist
    void addDefaultTransition(LLFSMState& end_state, LLFSMTransition& transition);

    // process a possible transition, and get the resulting state
    LLFSMState* processTransition(LLFSMState& start_state, LLFSMTransition& transition);

    // add a transition that exists for every state
    void setDefaultState(LLFSMState& default_state);

    // return total number of states with no outgoing transitions
    S32 numDeadendStates();

    // does this state exist in the state diagram?
    bool stateIsValid(LLFSMState& state);

    // get a state pointer by ID
    LLFSMState* getState(U32 state_id);

public:
    // save the graph in a DOT file for rendering and visualization
    bool saveDotFile(const std::string& filename);
};

class LLStateMachine
{
protected:
    LLFSMState*         mCurrentState;
    LLFSMState*         mLastState;
    LLFSMTransition*    mLastTransition;
    LLStateDiagram*     mStateDiagram;

public:
    LLStateMachine();
    virtual ~LLStateMachine();

    // set state diagram
    void setStateDiagram(LLStateDiagram* diagram);

    // process this transition
    void processTransition(LLFSMTransition &transition, void* user_data);

    // returns current state
    LLFSMState* getCurrentState() const;

    // execute current state
    void runCurrentState(void *data);

    // set state by state pointer
    bool setCurrentState(LLFSMState *initial_state, void* user_data, bool skip_entry = true);

    // set state by unique ID
    bool setCurrentState(U32 state_id, void* user_data, bool skip_entry = true);
};

#endif //_LL_LLSTATEMACHINE_H