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engines/twp/graph.h

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+/* 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