graph.h

/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * 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 your option) any later version.
 *
 * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#ifndef TWP_GRAPH_H
#define TWP_GRAPH_H

#include "common/array.h"
#include "math/vector2d.h"
#include "twp/util.h"

namespace Twp {

class IndexedPriorityQueue {
public:
    explicit IndexedPriorityQueue(Common::Array<float> &keys);

    void insert(int index);
    int pop();

    void reorderUp();
    void reorderDown();

    bool isEmpty();

private:
    Common::Array<float> &_keys;
    Common::Array<int> _data;
};

// An edge is a part of a walkable area, it is used by a Graph.
// See also:
//  - PathFinder
//  - Graph
struct GraphEdge {
    GraphEdge(int start, int to, float cost);

    int start;  // Index of the node in the graph representing the start of the edge.
    int to;     // Index of the node in the graph representing the end of the edge.
    float cost; // Cost of the edge in the graph.
};

// A graph helps to find a path between two points.
// This class has been ported from http://www.groebelsloot.com/2016/03/13/pathfinding-part-2/
// and modified
class Graph {
public:
    Graph();
    void addNode(const Math::Vector2d &node);
    void addEdge(const GraphEdge &edge);
    // Gets the edge from 'from' index to 'to' index.
    GraphEdge *edge(int start, int to);
    Common::Array<int> getPath(int source, int target);

    Common::Array<Math::Vector2d> _nodes;
    Common::Array<Common::Array<GraphEdge> > _edges;
    Common::Array<Math::Vector2d> _concaveVertices;
};

class AStar {
public:
    AStar(Graph *graph);
    void search(int source, int target);

    Graph *_graph = nullptr;
    Common::Array<GraphEdge *> _spt; // The Shortest Path Tree
    Common::Array<float> _gCost;     // This array will store the G cost of each node
    Common::Array<float> _fCost;     // This array will store the F cost of each node
    Common::Array<GraphEdge *> _sf;  // The Search Frontier
};

// Represents an area where an actor can or cannot walk
class Walkbox {
public:
    Walkbox(const Common::Array<Vector2i> &polygon, bool visible = true);

    // Indicates whether or not the specified position is inside this walkbox.
    bool contains(const Math::Vector2d &position, bool toleranceOnOutside = true) const;
    bool concave(int vertex) const;
    void setVisible(bool visible) { _visible = visible; }
    bool isVisible() const { return _visible; }
    const Common::Array<Vector2i> &getPoints() const { return _polygon; }
    Math::Vector2d getClosestPointOnEdge(const Math::Vector2d &p) const;

public:
    Common::String _name;

private:
    Common::Array<Vector2i> _polygon;
    bool _visible;
};

// A PathFinder is used to find a walkable path within one or several walkboxes.
class PathFinder {
public:
    void setWalkboxes(const Common::Array<Walkbox> &walkboxes);
    Common::Array<Walkbox> getWalkboxes() const { return _walkboxes; }
    Common::Array<Math::Vector2d> calculatePath(const Math::Vector2d &start, const Math::Vector2d &to);
    void setDirty(bool dirty) { _isDirty = dirty; }
    bool isDirty() const { return _isDirty; }
    const Graph &getGraph() const { return _walkgraph; }

private:
    Common::SharedPtr<Graph> createGraph();
    bool inLineOfSight(const Math::Vector2d &start, const Math::Vector2d &to);

private:
    Common::Array<Walkbox> _walkboxes;
    Common::SharedPtr<Graph> _graph;
    Graph _walkgraph;
    bool _isDirty = true;
};

} // namespace Twp

#endif