path: root/src/game-server/map.cpp

/*
 *  The Mana World
 *  Copyright 2004 The Mana World Development Team
 *
 *  This file is part of The Mana World.
 *
 *  The Mana World 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 2 of the License, or
 *  any later version.
 *
 *  The Mana World 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with The Mana World; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *  $Id$
 */

#include <queue>

#include "game-server/map.hpp"

MetaTile::MetaTile():
    whichList(0)
{
}


Location::Location(int x, int y, MetaTile *tile):
    x(x), y(y), tile(tile)
{
}

bool Location::operator< (const Location &loc) const
{
   return tile->Fcost > loc.tile->Fcost;
}


Map::Map():
    width(0), height(0),
    tileWidth(32), tileHeight(32),
    onClosedList(1), onOpenList(2)
{
    metaTiles = new MetaTile[width * height];
}

Map::Map(int width, int height):
    width(width), height(height),
    tileWidth(32), tileHeight(32),
    onClosedList(1), onOpenList(2)
{
    metaTiles = new MetaTile[width * height];
}

Map::~Map()
{
    delete[] metaTiles;
}

void
Map::setSize(int width, int height)
{
    this->width = width;
    this->height = height;
    delete[] metaTiles;
    metaTiles = new MetaTile[width * height];
}

void
Map::setWalk(int x, int y, bool walkable)
{
    metaTiles[x + y * width].walkable = walkable;
}

bool
Map::getWalk(int x, int y)
{
    // If walkable, check for colliding into a being
    if (!tileCollides(x, y))
    {
        /*
        std::list<Being*>::iterator i = beings.begin();
        while (i != beings.end()) {
            Being *being = (*i);
            // Collision when non-portal being is found at this location
            if (being->x == x && being->y == y && being->job != 45) {
                return false;
            }
            i++;
        }
        */
        return true;
    }
    else {
        return false;
    }
}

bool
Map::tileCollides(int x, int y)
{
    // You can't walk outside of the map
    if (x < 0 || y < 0 || x >= width || y >= height) {
        return true;
    }

    // Check if the tile is walkable
    return !metaTiles[x + y * width].walkable;
}

MetaTile*
Map::getMetaTile(int x, int y)
{
    return &metaTiles[x + y * width];
}

static int const basicCost = 100;

std::list<PATH_NODE>
Map::findPath(int startX, int startY, int destX, int destY)
{
    // Path to be built up (empty by default)
    std::list<PATH_NODE> path;

    // Declare open list, a list with open tiles sorted on F cost
    std::priority_queue<Location> openList;

    // Return when destination not walkable
    if (!getWalk(destX, destY)) return path;

    // Reset starting tile's G cost to 0
    MetaTile *startTile = getMetaTile(startX, startY);
    startTile->Gcost = 0;

    // Add the start point to the open list
    openList.push(Location(startX, startY, startTile));

    bool foundPath = false;

    // Keep trying new open tiles until no more tiles to try or target found
    while (!openList.empty() && !foundPath)
    {
        // Take the location with the lowest F cost from the open list, and
        // add it to the closed list.
        Location curr = openList.top();
        openList.pop();

        // If the tile is already on the closed list, this means it has already
        // been processed with a shorter path to the start point (lower G cost)
        if (curr.tile->whichList == onClosedList)
        {
            continue;
        }

        // Put the current tile on the closed list
        curr.tile->whichList = onClosedList;

        // Check the adjacent tiles
        for (int dy = -1; dy <= 1; dy++)
        {
            for (int dx = -1; dx <= 1; dx++)
            {
                // Calculate location of tile to check
                int x = curr.x + dx;
                int y = curr.y + dy;

                // Skip if if we're checking the same tile we're leaving from,
                // or if the new location falls outside of the map boundaries
                if ((dx == 0 && dy == 0) ||
                        (x < 0 || y < 0 || x >= width || y >= height))
                {
                    continue;
                }

                MetaTile *newTile = getMetaTile(x, y);

                // Skip if the tile is on the closed list or is not walkable
                if (newTile->whichList == onClosedList || !getWalk(x, y))
                {
                    continue;
                }

                // When taking a diagonal step, verify that we can skip the
                // corner. We allow skipping past beings but not past non-
                // walkable tiles.
                if (dx != 0 && dy != 0)
                {
                    MetaTile *t1 = getMetaTile(curr.x, curr.y + dy);
                    MetaTile *t2 = getMetaTile(curr.x + dx, curr.y);

                    if (!(t1->walkable && t2->walkable))
                    {
                        continue;
                    }
                }

                // Calculate G cost for this route, ~sqrt(2) for moving diagonal
                int Gcost = curr.tile->Gcost +
                    (dx == 0 || dy == 0 ? basicCost : basicCost * 362 / 256);

                /* Demote an arbitrary direction to speed pathfinding by
                   adding a defect (TODO: change depending on the desired
                   visual effect, e.g. a cross-product defect toward
                   destination).
                   Important: as long as the total defect along any path is
                   less than the basicCost, the pathfinder will still find one
                   of the shortest paths! */
                if (dx == 0 || dy == 0)
                {
                    // Demote horizontal and vertical directions, so that two
                    // consecutive directions cannot have the same Fcost.
                    ++Gcost;
                }

                // Skip if Gcost becomes too much
                // Warning: probably not entirely accurate
                if (Gcost > 20 * basicCost)
                {
                    continue;
                }

                if (newTile->whichList != onOpenList)
                {
                    // Found a new tile (not on open nor on closed list)

                    /* Update Hcost of the new tile. The pathfinder does not
                       work reliably if the heuristic cost is higher than the
                       real cost. In particular, using Manhattan distance is
                       forbidden here. */
                    int dx = std::abs(x - destX), dy = std::abs(y - destY);
                    newTile->Hcost = std::abs(dx - dy) * basicCost +
                        std::min(dx, dy) * (basicCost * 362 / 256);

                    // Set the current tile as the parent of the new tile
                    newTile->parentX = curr.x;
                    newTile->parentY = curr.y;

                    // Update Gcost and Fcost of new tile
                    newTile->Gcost = Gcost;
                    newTile->Fcost = newTile->Gcost + newTile->Hcost;

                    if (x != destX || y != destY) {
                        // Add this tile to the open list
                        newTile->whichList = onOpenList;
                        openList.push(Location(x, y, newTile));
                    }
                    else {
                        // Target location was found
                        foundPath = true;
                    }
                }
                else if (Gcost < newTile->Gcost)
                {
                    // Found a shorter route.
                    // Update Gcost and Fcost of the new tile
                    newTile->Gcost = Gcost;
                    newTile->Fcost = newTile->Gcost + newTile->Hcost;

                    // Set the current tile as the parent of the new tile
                    newTile->parentX = curr.x;
                    newTile->parentY = curr.y;

                    // Add this tile to the open list (it's already
                    // there, but this instance has a lower F score)
                    openList.push(Location(x, y, newTile));
                }
            }
        }
    }

    // Two new values to indicate whether a tile is on the open or closed list,
    // this way we don't have to clear all the values between each pathfinding.
    onClosedList += 2;
    onOpenList += 2;

    // If a path has been found, iterate backwards using the parent locations
    // to extract it.
    if (foundPath)
    {
        int pathX = destX;
        int pathY = destY;

        while (pathX != startX || pathY != startY)
        {
            // Add the new path node to the start of the path list
            path.push_front(PATH_NODE(pathX, pathY));

            // Find out the next parent
            MetaTile *tile = getMetaTile(pathX, pathY);
            pathX = tile->parentX;
            pathY = tile->parentY;
        }
    }

    return path;
}