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/* $Id$ */

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/*

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 * This file has the core function for AyStar

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 *  AyStar is a fast pathfinding routine and is used for things like

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 *  AI_pathfinding and Train_pathfinding.

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 *  For more information about AyStar (A* Algorithm), you can look at

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 *    http://en.wikipedia.org/wiki/A-star_search_algorithm

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 */

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/*

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 * Friendly reminder:

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 *  Call (AyStar).free() when you are done with Aystar. It reserves a lot of memory

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 *  And when not free'd, it can cause system-crashes.

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 * Also remember that when you stop an algorithm before it is finished, your

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 * should call clear() yourself!

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 */

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#include "stdafx.h"

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#include "openttd.h"

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#include "aystar.h"

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// This looks in the Hash if a node exists in ClosedList

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//  If so, it returns the PathNode, else NULL

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static PathNode *AyStarMain_ClosedList_IsInList(AyStar *aystar, AyStarNode *node)

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{

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	return (PathNode*)Hash_Get(&aystar->ClosedListHash, node->tile, node->direction);

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}

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// This adds a node to the ClosedList

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//  It makes a copy of the data

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static void AyStarMain_ClosedList_Add(AyStar *aystar, PathNode *node)

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{

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	// Add a node to the ClosedList

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	PathNode *new_node = malloc(sizeof(PathNode));

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	*new_node = *node;

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	Hash_Set(&aystar->ClosedListHash, node->node.tile, node->node.direction, new_node);

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}

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// Checks if a node is in the OpenList

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//   If so, it returns the OpenListNode, else NULL

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static OpenListNode *AyStarMain_OpenList_IsInList(AyStar *aystar, AyStarNode *node)

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{

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	return (OpenListNode*)Hash_Get(&aystar->OpenListHash, node->tile, node->direction);

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}

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// Gets the best node from OpenList

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//  returns the best node, or NULL of none is found

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// Also it deletes the node from the OpenList

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static OpenListNode *AyStarMain_OpenList_Pop(AyStar *aystar)

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{

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	// Return the item the Queue returns.. the best next OpenList item.

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	OpenListNode* res = (OpenListNode*)aystar->OpenListQueue.pop(&aystar->OpenListQueue);

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	if (res != NULL)

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		Hash_Delete(&aystar->OpenListHash, res->path.node.tile, res->path.node.direction);

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	return res;

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}

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// Adds a node to the OpenList

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//  It makes a copy of node, and puts the pointer of parent in the struct

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static void AyStarMain_OpenList_Add(AyStar *aystar, PathNode *parent, AyStarNode *node, int f, int g)

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{

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	// Add a new Node to the OpenList

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	OpenListNode* new_node = malloc(sizeof(OpenListNode));

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	new_node->g = g;

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	new_node->path.parent = parent;

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	new_node->path.node = *node;

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	Hash_Set(&aystar->OpenListHash, node->tile, node->direction, new_node);

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	// Add it to the queue

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	aystar->OpenListQueue.push(&aystar->OpenListQueue, new_node, f);

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}

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/*

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 * Checks one tile and calculate his f-value

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 *  return values:

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 *	AYSTAR_DONE : indicates we are done

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 */

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int AyStarMain_CheckTile(AyStar *aystar, AyStarNode *current, OpenListNode *parent) {

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	int new_f, new_g, new_h;

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	PathNode *closedlist_parent;

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	OpenListNode *check;

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	// Check the new node against the ClosedList

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	if (AyStarMain_ClosedList_IsInList(aystar, current) != NULL) return AYSTAR_DONE;

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	// Calculate the G-value for this node

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	new_g = aystar->CalculateG(aystar, current, parent);

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	// If the value was INVALID_NODE, we don't do anything with this node

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	if (new_g == AYSTAR_INVALID_NODE) return AYSTAR_DONE;

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	// There should not be given any other error-code..

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	assert(new_g >= 0);

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	// Add the parent g-value to the new g-value

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	new_g += parent->g;

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	if (aystar->max_path_cost != 0 && (uint)new_g > aystar->max_path_cost) return AYSTAR_DONE;

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	// Calculate the h-value

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	new_h = aystar->CalculateH(aystar, current, parent);

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	// There should not be given any error-code..

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	assert(new_h >= 0);

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	// The f-value if g + h

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	new_f = new_g + new_h;

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	// Get the pointer to the parent in the ClosedList (the currentone is to a copy of the one in the OpenList)

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	closedlist_parent = AyStarMain_ClosedList_IsInList(aystar, &parent->path.node);

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	// Check if this item is already in the OpenList

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	if ((check = AyStarMain_OpenList_IsInList(aystar, current)) != NULL) {

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		uint i;

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		// Yes, check if this g value is lower..

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		if (new_g > check->g) return AYSTAR_DONE;

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		aystar->OpenListQueue.del(&aystar->OpenListQueue, check, 0);

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		// It is lower, so change it to this item

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		check->g = new_g;

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		check->path.parent = closedlist_parent;

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		/* Copy user data, will probably have changed */

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		for (i=0;i<lengthof(current->user_data);i++)

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			check->path.node.user_data[i] = current->user_data[i];

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		// Readd him in the OpenListQueue

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		aystar->OpenListQueue.push(&aystar->OpenListQueue, check, new_f);

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	} else {

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		// A new node, add him to the OpenList

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		AyStarMain_OpenList_Add(aystar, closedlist_parent, current, new_f, new_g);

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	}

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	return AYSTAR_DONE;

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}

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/*

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 * This function is the core of AyStar. It handles one item and checks

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 *  his neighbour items. If they are valid, they are added to be checked too.

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 *  return values:

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 *	AYSTAR_EMPTY_OPENLIST : indicates all items are tested, and no path

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 *	has been found.

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 *	AYSTAR_LIMIT_REACHED : Indicates that the max_nodes limit has been

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 *	reached.

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 *	AYSTAR_FOUND_END_NODE : indicates we found the end. Path_found now is true, and in path is the path found.

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 *	AYSTAR_STILL_BUSY : indicates we have done this tile, did not found the path yet, and have items left to try.

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 */

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int AyStarMain_Loop(AyStar *aystar) {

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	int i, r;

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	// Get the best node from OpenList

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	OpenListNode *current = AyStarMain_OpenList_Pop(aystar);

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	// If empty, drop an error

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	if (current == NULL) return AYSTAR_EMPTY_OPENLIST;

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	// Check for end node and if found, return that code

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	if (aystar->EndNodeCheck(aystar, current) == AYSTAR_FOUND_END_NODE) {

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		if (aystar->FoundEndNode != NULL)

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			aystar->FoundEndNode(aystar, current);

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		free(current);

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		return AYSTAR_FOUND_END_NODE;

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	}

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	// Add the node to the ClosedList

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	AyStarMain_ClosedList_Add(aystar, &current->path);

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	// Load the neighbours

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	aystar->GetNeighbours(aystar, current);

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	// Go through all neighbours

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	for (i=0;i<aystar->num_neighbours;i++) {

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		// Check and add them to the OpenList if needed

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		r = aystar->checktile(aystar, &aystar->neighbours[i], current);

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	}

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	// Free the node

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	free(current);

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	if (aystar->max_search_nodes != 0 && Hash_Size(&aystar->ClosedListHash) >= aystar->max_search_nodes)

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		/* We've expanded enough nodes */

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		return AYSTAR_LIMIT_REACHED;

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	else

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		// Return that we are still busy

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		return AYSTAR_STILL_BUSY;

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}

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/*

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 * This function frees the memory it allocated

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 */

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void AyStarMain_Free(AyStar *aystar) {

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	aystar->OpenListQueue.free(&aystar->OpenListQueue, false);

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	/* 2nd argument above is false, below is true, to free the values only

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	 * once */

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	delete_Hash(&aystar->OpenListHash, true);

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	delete_Hash(&aystar->ClosedListHash, true);

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#ifdef AYSTAR_DEBUG

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	printf("[AyStar] Memory free'd\n");

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#endif

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}

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/*

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 * This function make the memory go back to zero

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 *  This function should be called when you are using the same instance again.

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 */

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void AyStarMain_Clear(AyStar *aystar) {

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	// Clean the Queue, but not the elements within. That will be done by

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	// the hash.

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	aystar->OpenListQueue.clear(&aystar->OpenListQueue, false);

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	// Clean the hashes

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	clear_Hash(&aystar->OpenListHash, true);

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	clear_Hash(&aystar->ClosedListHash, true);

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#ifdef AYSTAR_DEBUG

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	printf("[AyStar] Cleared AyStar\n");

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#endif

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}

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/*

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 * This is the function you call to run AyStar.

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 *  return values:

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 *	AYSTAR_FOUND_END_NODE : indicates we found an end node.

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 *	AYSTAR_NO_PATH : indicates that there was no path found.

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 *	AYSTAR_STILL_BUSY : indicates we have done some checked, that we did not found the path yet, and that we still have items left to try.

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 * When the algorithm is done (when the return value is not AYSTAR_STILL_BUSY)

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 * aystar->clear() is called. Note that when you stop the algorithm halfway,

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 * you should still call clear() yourself!

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 */

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int AyStarMain_Main(AyStar *aystar) {

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	int r, i = 0;

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	// Loop through the OpenList

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	//  Quit if result is no AYSTAR_STILL_BUSY or is more than loops_per_tick

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	while ((r = aystar->loop(aystar)) == AYSTAR_STILL_BUSY && (aystar->loops_per_tick == 0 || ++i < aystar->loops_per_tick)) { }

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#ifdef AYSTAR_DEBUG

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	if (r == AYSTAR_FOUND_END_NODE)

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		printf("[AyStar] Found path!\n");

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	else if (r == AYSTAR_EMPTY_OPENLIST)

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		printf("[AyStar] OpenList run dry, no path found\n");

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	else if (r == AYSTAR_LIMIT_REACHED)

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		printf("[AyStar] Exceeded search_nodes, no path found\n");

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#endif

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	if (aystar->BeforeExit != NULL)

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		aystar->BeforeExit(aystar);

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	if (r != AYSTAR_STILL_BUSY)

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		/* We're done, clean up */

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		aystar->clear(aystar);

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	// Check result-value

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	if (r == AYSTAR_FOUND_END_NODE) return AYSTAR_FOUND_END_NODE;

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	// Check if we have some left in the OpenList

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	if (r == AYSTAR_EMPTY_OPENLIST || r == AYSTAR_LIMIT_REACHED) return AYSTAR_NO_PATH;

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	// Return we are still busy

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	return AYSTAR_STILL_BUSY;

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}

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/*

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 * Adds a node from where to start an algorithm. Multiple nodes can be added

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 * if wanted. You should make sure that clear() is called before adding nodes

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 * if the AyStar has been used before (though the normal main loop calls

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 * clear() automatically when the algorithm finishes

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 * g is the cost for starting with this node.

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 */

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void AyStarMain_AddStartNode(AyStar *aystar, AyStarNode *start_node, uint g) {

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#ifdef AYSTAR_DEBUG

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	printf("[AyStar] Starting A* Algorithm from node (%d, %d, %d)\n",

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		TileX(start_node->tile), TileY(start_node->tile), start_node->direction);

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#endif

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	AyStarMain_OpenList_Add(aystar, NULL, start_node, 0, g);

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}

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void init_AyStar(AyStar* aystar, Hash_HashProc hash, uint num_buckets) {

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	// Allocated the Hash for the OpenList and ClosedList

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	init_Hash(&aystar->OpenListHash, hash, num_buckets);

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	init_Hash(&aystar->ClosedListHash, hash, num_buckets);

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	// Set up our sorting queue

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	//  BinaryHeap allocates a block of 1024 nodes

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	//  When thatone gets full it reserves an otherone, till this number

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	//  That is why it can stay this high

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	init_BinaryHeap(&aystar->OpenListQueue, 102400);

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	aystar->addstart	= AyStarMain_AddStartNode;

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	aystar->main		= AyStarMain_Main;

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	aystar->loop		= AyStarMain_Loop;

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	aystar->free		= AyStarMain_Free;

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	aystar->clear		= AyStarMain_Clear;

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	aystar->checktile	= AyStarMain_CheckTile;

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}