citylimits/core/position.h

/* position.h
 *
 * Micropolis, Unix Version.  This game was released for the Unix platform
 * in or about 1990 and has been modified for inclusion in the One Laptop
 * Per Child program.  Copyright (C) 1989 - 2007 Electronic Arts Inc.  If
 * you need assistance with this program, you may contact:
 *   http://wiki.laptop.org/go/Micropolis  or email  micropolis@laptop.org.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or (at
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.  You should have received a
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 */

/** 
 * @file position.h
 * @brief Defines position handling and direction enumeration for the
 * Micropolis game engine.
 *
 * This header file provides classes and functions for handling
 * positions and directions within the Micropolis game world. It
 * includes the 'Position' class for representing X/Y coordinates and
 * 'Direction2' enumeration for defining 8 cardinal directions.
 * Functions for manipulating and querying these positions and
 * directions are also provided, which are essential for navigating
 * and interacting with the game world's grid.
 */


#ifndef H_POSITION
#define H_POSITION


/** Another direction enumeration class, with 8 possible directions.
 * @todo Eliminate #Direction.
 * @todo After eliminating #Direction, rename this enum to Direction.
 */
enum Direction2 {
    DIR2_INVALID,    ///< Invalid direction.
    DIR2_NORTH,      ///< Direction pointing north.
    DIR2_NORTH_EAST, ///< Direction pointing north-east.
    DIR2_EAST,       ///< Direction pointing east.
    DIR2_SOUTH_EAST, ///< Direction pointing south-east.
    DIR2_SOUTH,      ///< Direction pointing south.
    DIR2_SOUTH_WEST, ///< Direction pointing south-west.
    DIR2_WEST,       ///< Direction pointing west.
    DIR2_NORTH_WEST, ///< Direction pointing north-west.

    DIR2_BEGIN = DIR2_NORTH,        ///< First valid direction.
    DIR2_END = DIR2_NORTH_WEST + 1, ///< End-condition for directions
};

/**
 * Increment the direction by 45 degrees.
 * @param dir Direction to rotate.
 * @return Rotated direction, possibly >= DIR2_END.
 */
static inline Direction2 increment45(Direction2 dir, int count = 1)
{
    return (Direction2)(dir + count);
}


/**
 * Increment the direction by 90 degrees.
 * @param dir Direction to rotate.
 * @return Rotated direction, possibly >= DIR2_END.
 */
static inline Direction2 increment90(Direction2 dir)
{
    return increment45(dir, 2);
}

/**
 * Increment the direction by 45 degrees.
 * @param dir Direction to rotate.
 * @return Rotated direction.
 */
static inline Direction2 rotate45(Direction2 dir, int count = 1)
{
    return (Direction2)(((dir - DIR2_NORTH + count) & 7) + DIR2_NORTH);
}

/**
 * Rotate the direction by 90 degrees.
 * @param dir Direction to rotate.
 * @return Rotated direction.
 */
static inline Direction2 rotate90(Direction2 dir)
{
    return rotate45(dir, 2);
}

/**
 * Rotate the direction by 180 degrees.
 * @param dir Direction to rotate.
 * @return Rotated direction.
 */
static inline Direction2 rotate180(Direction2 dir)
{
    return rotate45(dir, 4);
}


/** X/Y position. */
class Position {

public:

    Position();
    Position(int x, int y);
    Position(const Position &pos);
    Position(const Position &pos, Direction2 dir);
    Position(const Position &pos, int dx, int dy);
    Position &operator=(const Position &pos);

    bool move(Direction2 dir);
    inline bool testBounds();

    int posX; ///< Horizontal coordinate of the position.
    int posY; ///< Vertical coordnate of the position.
};


/**
 * Test whether the position is on-map.
 * @return Position is on-map.
 */
inline bool Position::testBounds()
{
    return (this->posX >= 0 && this->posX < WORLD_W
                && this->posY >= 0 && this->posY < WORLD_H);
}

/**
 * Less-than comparison on positions (needed for map since Position is used as
 * key value).
 * @param pos1 First position.
 * @param pos2 Second position.
 * @return First position is smaller than second position.
 */
inline bool operator<(const Position &pos1, const Position &pos2)
{
    if (pos1.posX != pos2.posX) return pos1.posX < pos2.posX;
    return pos1.posY < pos2.posY;
}


#endif