package cz.cuni.amis.pathfinding.alg.floydwarshall;
   
   import java.lang.ref.SoftReference;
   import java.util.ArrayList;
   import java.util.Collection;
   import java.util.HashMap;
   import java.util.Iterator;
   import java.util.List;
   import java.util.Map;
  import java.util.logging.Level;
  import java.util.logging.Logger;
  
  import cz.cuni.amis.pathfinding.map.IPFKnownMap;
  import cz.cuni.amis.pathfinding.map.IPFKnownMapView;
  import cz.cuni.amis.pathfinding.map.IPFMap;
  import cz.cuni.amis.pathfinding.map.IPFMapView;
  import cz.cuni.amis.pathfinding.map.IPFMapView.DefaultView;
  import cz.cuni.amis.utils.Iterators;
  import cz.cuni.amis.utils.NullCheck;
  
  /**
   * Floyd-Warshall algorithm for precomputing all-possible paths within the {@link IPFKnownMap}.
   * <p><p>
   * It precomputes all the paths inside the environment using Floyd-Warshall
   * algorithm (time: O(n^3)) in the form of matrix.
   * <p><p> 
   * Use {@link FloydWarshall#isReachable(Object, Object)}, {@link FloydWarshall#getPathCost(Object, Object)}
   * and {@link FloydWarshall#getPath(Object, Object)} to obtain information about computed paths.
   * the info about the path.
   * <p><p>
   * {@link FloydWarshall#getPath(Object, Object)} is caching retrieved paths using {@link SoftReference}s.
   * <p><p>
   * If needed you may call {@link FloydWarshall#compute()} to recompute paths, this call is needed if you set new map / agent view
   * using {@link FloydWarshall#setMap(IPFKnownMap)} or {@link FloydWarshall#setMapView(IPFMapView)}.
   * <p><p>
   * Based upon the implementation from Martin Krulis with his kind consent, thank you! Even though it was heavily recreated by now ;-)
   * <p><p>
   * NOTE: requires O(map.nodes.size^2) of memory! So be careful.
   * <p><p>
   * NOTE: you should read javadocs for {@link IPFMap}, {@link IPFKnownMap} and {@link IPFMapView} to understand how you can separate 
   * your map representation from various agent "views on the map" (i.e., how to provide customized path finding 
   * for different agents, e.g., fish vs. human)
   * 
   * @author Jimmy
   */
  public class FloydWarshall<NODE>  {
  	
  	/**
  	 * Class describing cell inside the FloydWarshall matrix holding additional informations relating to the path between two
  	 * nodes.
  	 * <p><p>
  	 * These nodes are stored under "indices" inside {@link FloydWarshall#pathMatrix}.
  	 * 
  	 * @author Jimmy
  	 *
  	 * @param <N>
  	 */
  	public static class PathMatrixNode<N> {
  
  		private int cost = Integer.MAX_VALUE;
  		private Integer viaNode = null;
  		private SoftReference<List<N>> path = null;
  
  		/**
  		 * Doesn't leading anywhere
  		 */
  		public PathMatrixNode() {
  		}
  
  		public PathMatrixNode(int cost) {
  			this.cost = cost;
  		}
  		
  		/**
  		 * Returns aprox. number of bytes used by this class (for 32-bit Java, might be as twice as much for 64-bit!) including
  		 * currently cached path.
  		 * @return
  		 */
  		public int getBytesAprox() {
  			List<N> path = (this.path != null ? this.path.get() : null);
  			return 4 + 8 + (path == null ? 4 : 4 + path.size() * 4); 
  		}
  		
  		/**
  		 * Returns aprox. number of bytes used by this class (for 32-bit Java, might be as twice as much for 64-bit!) EXCLUDING
  		 * currently cached path.
  		 * 
  		 * @return
  		 */
  		public int getBytesAproxWithoutPath() {
  			List<N> path = (this.path != null ? this.path.get() : null);
  			return 4 + 8 + 4; 
  		}
  
  		/**
  		 * Returns the cost of the path between nodes, if the path does not exist, returns {@link Integer#MAX_VALUE}.
  		 * @return
  		 */
  		public int getPathCost() {
 			return cost;
 		}
 
 		/**
 		 * Sets the cost of the path between nodes.
 		 * @param cost
 		 */
 		public void setPathCost(int cost) {
 			this.cost = cost;
 		}
 
 		/**
 		 * Returns the node you have to travel through.
 		 * @return
 		 */
 		public Integer getViaNode() {
 			return viaNode;
 		}
 
 		/**
 		 * Sets the node you have to travel through.
 		 * @param indice
 		 */
 		public void setViaNode(Integer indice) {
 			this.viaNode = indice;
 		}
 
 		/**
 		 * Returns the full path between nodes.
 		 * <p><p>
 		 * WARNING: this is cached path! Might return null even though such path exists! Use {@link FloydWarshall#getPath(Object, Object)}
 		 * to obtain the result in every case.
 		 * @return
 		 */
 		public List<N> getPath() {
 			return path == null ? null : path.get();
 		}
 
 		/**
 		 * Sets the full path between nodes, computed as the last step of {@link FloydWarshall#performFloydWarshall(List)}. Such path
 		 * is going to be stored using {@link SoftReference} (cached) and might be freed by GC if heap runs dry.
 		 * @param path
 		 */
 		public void setPath(List<N> path) {
 			this.path = new SoftReference<List<N>>(path);
 		}
 
 	}
 	
 	/**
 	 * Map used for the computation of paths.
 	 */
 	private IPFKnownMap<NODE> map;
 
 	/**
 	 * Agent's custom view of the map.
 	 */
 	private IPFKnownMapView<NODE> view;
 
 	/**
 	 * Logger used by this object.
 	 */
 	private Logger log = null;
 	
 	/**
 	 * Map converting nodes to their corresponding indices inside {@link FloydWarshall#pathMatrix}.
 	 */
 	private Map<NODE, Integer> nodesIndices;
 
 	/**
 	 * Mapping indices (inside {@link FloydWarshall#pathMatrix}) to nodes.
 	 */
 	private Map<Integer, NODE> indicesNodes;
 
 	/**
 	 * FloydWarshall's matrix of distances & paths.
 	 */
 	private PathMatrixNode<NODE>[][] pathMatrix;
 	
 	// ===========
 	// CONSTRUCTOR
 	// ===========
 
 	/**
 	 * FloydWarshall configured with "map" with no agent-specific view on the map, {@link DefaultView} is used.
 	 * <p><p>
 	 * {@link FloydWarshall#compute()} method is immediately called from within this constructor.
 	 *  
 	 * @param map
 	 */
 	public FloydWarshall(IPFKnownMap<NODE> map) {
 		this.map = map;
 		this.view = new IPFKnownMapView.DefaultView();
 		NullCheck.check(this.map, "map");
 		compute();
 	}
 	
 	/**
 	 * FloydWarshall configured with "map" and agent-specific view on the map, if "view" is null, {@link DefaultView} is going to be used.
 	 * <p><p>
 	 * {@link FloydWarshall#compute()} method is immediately called from within this constructor.
 	 *  
 	 * @param map
 	 * @param view may be null
 	 */
 	public FloydWarshall(IPFKnownMap<NODE> map, IPFKnownMapView<NODE> view) {
 		this.map = map;
 		this.view = view;
 		NullCheck.check(this.map, "map");
 		if (this.view == null) {
 			this.view = new IPFKnownMapView.DefaultView();
 		}
 		compute();
 	}
 	
 	/**
 	 * FloydWarshall configured with "map" with no agent-specific view on the map, {@link DefaultView} is used.
 	 * <p><p>
 	 * {@link FloydWarshall#compute()} method is immediately called from within this constructor.
 	 *  
 	 * @param map
 	 * @param log may be null
 	 */
 	public FloydWarshall(IPFKnownMap<NODE> map, Logger log) {
 		this.map = map;
 		this.view = new IPFKnownMapView.DefaultView();
 		NullCheck.check(this.map, "map");
 		this.log = log;
 		compute();
 	}
 	
 	/**
 	 * FloydWarshall configured with "map" and agent-specific view on the map, if "view" is null, {@link DefaultView} is going to be used.
 	 * <p><p>
 	 * {@link FloydWarshall#compute()} method is immediately called from within this constructor.
 	 *  
 	 * @param map
 	 * @param view may be null
 	 * @param log may be null
 	 */
 	public FloydWarshall(IPFKnownMap<NODE> map, IPFKnownMapView<NODE> view, Logger log) {
 		this.map = map;
 		this.view = view;
 		NullCheck.check(this.map, "map");
 		this.log = log;
 		if (this.view == null) {
 			if (log != null && log.isLoggable(Level.WARNING)) log.warning("No view specified! IPFKnownMapView.DefaultView is going to be used.");
 			this.view = new IPFKnownMapView.DefaultView();
 		}		
 		compute();
 	}
 	
 	/**
 	 * Returns logger used by this object.
 	 * @return
 	 */
 	public Logger getLog() {
 		return log;
 	}
 
 	/**
 	 * Sets logger used by this object.
 	 * @param log
 	 */
 	public void setLog(Logger log) {
 		this.log = log;
 	}
 
 	/**
 	 * Map abstraction the FloydWarshall is working with.
 	 * @return
 	 */
 	public IPFKnownMap<NODE> getMap() {
 		return map;
 	}
 
 	/**
 	 * Sets map abstraction into the FloydWarshall.
 	 * @param map
 	 */
 	public synchronized void setMap(IPFKnownMap<NODE> map) {
 		this.map = map;
 	}
 
 	/**
 	 * Returns agent-specific map view for the map.
 	 * @return
 	 */
 	public IPFKnownMapView<NODE> getMapView() {
 		return view;
 	}
 
 	/**
 	 * Sets agent-specific map view for the map. 
 	 * @param mapView
 	 */
 	public synchronized void setMapView(IPFKnownMapView<NODE> mapView) {
 		this.view = mapView;
 	}
 	
 	/**
 	 * Force FloydWarshall to refresh its path matrix, useful if you modify the map or view using {@link FloydWarshall#setMap(IPFKnownMap)}
 	 * or {@link FloydWarshall#setMapView(IPFKnownMapView)}.
 	 * <p><p>
 	 * Called automatically from constructors!
 	 */
 	public synchronized void compute() {
 		if (log != null && log.isLoggable(Level.FINE)) log.fine(this + ": Computing paths...");
 		
 		List<NODE> nodes = new ArrayList<NODE>();
 		
 		Collection<NODE> mapNodes = map.getNodes();
 		if (mapNodes != null) {
 			Iterator<NODE> iter = mapNodes.iterator();
 			while (iter.hasNext()) {
 				NODE node = iter.next();
 				if (view.isNodeOpened(node)) {
 					// we can use it
 					nodes.add(node);
 				}
 			}
 		}
 		
 		Collection<NODE> extraNodes = view.getExtraNodes(mapNodes);
 		if (extraNodes != null) {
 			Iterator<NODE> iter = extraNodes.iterator();
 			while (iter.hasNext()) {
 				NODE node = iter.next();
 				if (view.isNodeOpened(node)) {
 					// we can use it
 					nodes.add(node);
 				}
 			}
 		}
 		
 		performFloydWarshall(nodes);
 		if (log != null && log.isLoggable(Level.FINE)) log.fine(this + ": Paths computed!");
 	}
 	
 	public synchronized void cacheAllPaths() {
 		int size = pathMatrix.length;
 		// Construct paths + log unreachable paths.		
 		if (log != null && log.isLoggable(Level.FINE)) log.fine(this + ": Caching all paths O(" + size + "^3)...");
 		long time = System.currentTimeMillis();
 		int count = 0;
 		for (int i = 0; i < size; i++) {
 			for (int j = 0; j < size; j++) {
 				if (pathMatrix[i][j].getPathCost() == Integer.MAX_VALUE) {
 					// WE'RE PURPOSEFULLY TESTING "FINER" LEVEL HERE!
 					if (log != null && log.isLoggable(Level.FINER)) log.warning("Unreachable path from " + indicesNodes.get(i) + " -> " + indicesNodes.get(j));
 					count++;
 				} else {
 					// path exists ... retrieve it
 					pathMatrix[i][j].setPath(retrievePath(i, j));
 				}
 			}
 		}
 		if (log != null && log.isLoggable(Level.FINE)) log.fine(this + ": Paths cached (" + (System.currentTimeMillis() - time) + " ms).");
 	}
 	
 	//////////////////////////////////////
 	// FloydWarshall algorithms & variable 
 	//////////////////////////////////////
 
 	
 	/**
 	 * Perform FloydWarshall over the list of nodes initializing {@link FloydWarshall#nodesIndices}, {@link FloydWarshall#pathMatrix}.
 	 * @param nodes
 	 */
 	@SuppressWarnings("unchecked")
 	private void performFloydWarshall(List<NODE> nodes) {
 		if (log != null && log.isLoggable(Level.FINE)) log.fine(this + ": Running Floyd-Warshall algorithm...");
 		long start = System.currentTimeMillis();
 
 		// prepares data structures
 		int size = nodes.size();
 		nodesIndices = new HashMap<NODE, Integer>(size);
 		indicesNodes = new HashMap<Integer, NODE>(size);
 		pathMatrix = new PathMatrixNode[size][size];
 
 		// Initialize navPoint indices mapping.
 		for (int i = 0; i < nodes.size(); ++i) {
 			nodesIndices.put(nodes.get(i), i);
 			indicesNodes.put(i, nodes.get(i));
 		}
 
 		// Initialize distance matrix.
 		if (log != null && log.isLoggable(Level.FINE)) log.fine(this + ": Initializing matrix...");
 		for (int i = 0; i < size; i++) {
 			for (int j = 0; j < size; j++) {
 				pathMatrix[i][j] = new PathMatrixNode<NODE>((i == j) ? 0 : Integer.MAX_VALUE);
 			}
 		}
 
 		// Set initial arc costs into distance matrix.
 		if (log != null && log.isLoggable(Level.FINE)) log.fine(this + ": Setting initial arc costs...");
 		for (int i = 0; i < size; i++) {
 			NODE node1 = nodes.get(i);
 			if (!view.isNodeOpened(node1)) continue; // forbidden node
 			
 			Collection<NODE> neighbors = map.getNeighbors(node1);
 			Collection<NODE> extraNeighbors = view.getExtraNeighbors(node1, neighbors);
 			Iterator<NODE> iterator = 
 				new Iterators<NODE>(
 					neighbors == null ? null : neighbors.iterator(), 
 					extraNeighbors == null ? null : extraNeighbors.iterator()
 				);
 			
 			while(iterator.hasNext()) {
 				NODE node2 = iterator.next();
 				if (!view.isNodeOpened(node2)) continue;       // forbidden node
 				if (!view.isArcOpened(node1, node2)) continue; // forbidden arc
 				int j = nodesIndices.get(node2);
 				
 				int arcCost = map.getArcCost(node1, node2);
 				arcCost += view.getArcExtraCost(node1, node2, arcCost);
 				int nodeCost = map.getNodeCost(node2);
 				nodeCost += view.getNodeExtraCost(node2, nodeCost);
 				
 				pathMatrix[i][j].setPathCost(arcCost+nodeCost);
 			}
 		}
 
 		// Perform Floyd-Warshall.
 		if (log != null && log.isLoggable(Level.FINE)) log.fine(this + ": Computing path-matrix O(" + size + "^3)...");
 		for (int k = 0; k < size; k++) {
 			for (int i = 0; i < size; i++) {
 				NODE node1 = nodes.get(i);
 				NODE node2 = nodes.get(k);
 				for (int j = 0; j < size; j++) {
 					NODE node3 = nodes.get(j);
 					int newLen =
 						pathMatrix[i][k].getPathCost() == Integer.MAX_VALUE ?
 								Integer.MAX_VALUE
 							:	(pathMatrix[k][j].getPathCost() == Integer.MAX_VALUE) ? 
 									Integer.MAX_VALUE
 								:	pathMatrix[i][k].getPathCost() + pathMatrix[k][j].getPathCost();
 					if (pathMatrix[i][j].getPathCost() > newLen) {
 						pathMatrix[i][j].setPathCost(newLen);
 						pathMatrix[i][j].setViaNode(k);
 					}
 				}
 			}
 		}
 
 		// Check reachability...
 		if (log != null && log.isLoggable(Level.FINE)) log.fine(this + ": Checking reachability...");
 		int count = 0;
 		for (int i = 0; i < size; i++) {
 			for (int j = 0; j < size; j++) {
 				if (pathMatrix[i][j].getPathCost() == Integer.MAX_VALUE) {
 					// WE'RE PURPOSEFULLY TESTING "FINER" LEVEL HERE!
 					if (log != null && log.isLoggable(Level.FINER)) log.warning("Unreachable path from " + nodes.get(i) + " -> " + nodes.get(j));
 					count++;
 				}
 			}
 		}
 
 		if (count > 0) {
 			if (log != null && log.isLoggable(Level.WARNING)) log.warning(this + ": There are " + count + " unreachable nodes pairs (if you wish to see their list, set logging to Level.FINER).");
 		} else {
 			if (log != null && log.isLoggable(Level.INFO)) log.info(this + ": All nodes are connected, there are NO unreachable pairs of nodes.");
 		}
 
 		if (log != null && log.isLoggable(Level.INFO)) log.info(this + ": Computation for " + size + " navpoints took " + (System.currentTimeMillis() - start) + " millis.");
 		
 		if (log != null && log.isLoggable(Level.INFO)) {		
 			log.info(this + ": Memory consumption (no paths cached) is aprox. " + getAproxMemory() + " bytes, might be as twice as much for 64-bit system.");
 		}
 				
 		if (log != null && log.isLoggable(Level.FINE)) log.fine(this + ": Floyd-Warshall algorithm finished!");
 	}
 
 	/**
 	 * Returns approximation of memory consumption of this object in bytes for 32-bit JVM, might be as twice for 64-bit JVM!
 	 * @return
 	 */
 	public long getAproxMemory() {
 		long bytes = 0;
 		for (int i = 0; i < pathMatrix.length; ++i) {
 			for (int j = 0; j < pathMatrix.length; ++j) {
 				bytes += pathMatrix[i][j].getBytesAprox();
 			}
 		}
 		bytes += pathMatrix.length * 8 * 2; 
 		return bytes;
 	}
 
 	/**
 	 * Sub-routine of {@link FloydWarshall#retrievePath(Integer, Integer)} - do not use! ... Well you may, it returns
 	 * path without 'from', 'to' or null if such path dosn't exist.
 	 * <p><p>
 	 * DO NOT USE OUTSIDE {@link FloydWarshall#performFloydWarshall(List)} (relies on indicesNavPoints).
 	 * <p><p>
 	 * Uses recursion.
 	 * 
 	 * @param from
 	 * @param to
 	 * @return
 	 */
 	private List<NODE> retrievePathInner(Integer from, Integer to) {
 		PathMatrixNode node = pathMatrix[from][to];
 		if (node.getPathCost() == Integer.MAX_VALUE)
 			return null;
 		if (node.getViaNode() == null) {
 			return new ArrayList<NODE>(0);
 		}
 		if (node.getViaNode() == null)
 			return new ArrayList<NODE>(0);
 
 		List<NODE> path = new ArrayList<NODE>();
 		path.addAll(retrievePathInner(from, node.getViaNode()));
 		path.add(indicesNodes.get(node.getViaNode()));
 		path.addAll(retrievePathInner(node.getViaNode(), to));
 
 		return path;
 	}
 
 	/**
 	 * Returns path between from-to or null if path doesn't exist. Path begins
 	 * with 'from' and ends with 'to'.
 	 * <p><p>
 	 * DO NOT USE OUTSIDE CONSTRUCTOR (relies on indicesNavPoints).
 	 * 
 	 * @param from
 	 * @param to
 	 * @return
 	 */
 	private List<NODE> retrievePath(Integer from, Integer to) {
 		List<NODE> path = new ArrayList<NODE>();
 		path.add(indicesNodes.get(from));
 		path.addAll(retrievePathInner(from, to));
 		path.add(indicesNodes.get(to));
 		return path;
 	}
 
 	/**
 	 * Returns {@link PathMatrixNode<NODE>} describing path from "nodeFrom" to "nodeTo". 
 	 * @param nodeFrom
 	 * @param nodeTo
 	 * @return
 	 */
 	public PathMatrixNode<NODE> getPathMatrixNode(NODE nodeFrom, NODE nodeTo) {
 		Integer from = nodesIndices.get(nodeFrom);
 		Integer to = nodesIndices.get(nodeTo);
 		if (from == null || to == null) return null;
 		return pathMatrix[from][to];
 	}
 
 	/**
 	 * Whether node 'to' is reachable (path exists) from the node 'from'.
 	 * 
 	 * @param from
 	 * @param to
 	 * @return
 	 */
 	public boolean isReachable(NODE from, NODE to) {
 		if ((from == null) || (to == null)) return false;
 		PathMatrixNode matrixNode = getPathMatrixNode(from, to);
 		if (matrixNode == null) return false;
 		return matrixNode.getPathCost() != Integer.MAX_VALUE;
 	}
 
 	/**
 	 * Calculate's distance between two nav points (using pathfinding).
 	 * <p><p>
 	 * Throws exception if object is disabled, see {@link FloydWarshallMap#setEnabled(boolean)}. Note that the object
 	 * is enabled by default.
 	 * 
 	 * @return Distance or {@link Integer#MAX_VALUE} if there's no path.
 	 */
 	public int getPathCost(NODE from, NODE to) {
 		if ((from == null) || (to == null))
 			return Integer.MAX_VALUE;
 		PathMatrixNode matrixNode = getPathMatrixNode(from, to);
 		if (matrixNode == null) return Integer.MAX_VALUE;
 		return matrixNode.getPathCost();
 	}
 
 	/**
 	 * Returns path between navpoints 'from' -> 'to'. The path begins with
 	 * 'from' and ends with 'to'. If such path doesn't exist, returns null.
 	 * <p><p>
 	 * Path is automatically cached using {@link SoftReference}.
 	 * 
 	 * @param from
 	 * @param to
 	 * @return
 	 */
 	public List<NODE> getPath(NODE from, NODE to) {
 		if ((from == null) || (to == null))
 			return null;
 		if (log != null && log.isLoggable(Level.FINE)) log.fine("Retrieving path: " + from + " -> " + to);
 		PathMatrixNode matrixNode = getPathMatrixNode(from, to);
 		if (matrixNode == null) return null;
 		if (matrixNode.getPathCost() == Integer.MAX_VALUE) return null;
 		List<NODE> path = matrixNode.getPath();
 		if (path == null) {
 			// was not cached or JVM has GC()ed it
 			path = retrievePathInner(nodesIndices.get(from), nodesIndices.get(to));
 			// cache the path
 			matrixNode.setPath(path);
 		}
 		if (log != null && log.isLoggable(Level.FINE)) log.fine("Path " + from + " -> " + to + " exists, " + path.size() + " nodes long.");
 		return path;
 	}
 	
 	/**
 	 * Returns matrix of nodes as computed by FloydWarshall algorithm. You should not alter it by hand!
 	 * @return
 	 */
 	public PathMatrixNode<NODE>[][] getMatrix() {
 		return pathMatrix;
 	}
 	
 	/**
 	 * Returns index of the node inside {@link FloydWarshall#getMatrix()}. Note that if node that is not inside the matrix is passed,
 	 * this will return null! 
 	 * @param node
 	 * @return
 	 */
 	public Integer getNodeIndex(NODE node) {
 		return nodesIndices.get(node);
 	}
 
 	@Override
 	public String toString() {
 		return "FloydWarshall";
 	}
 
 }