Code viewer for World: Hound 2 - Moving walls

// Cloned by Paul R on 23 Oct 2022 from World "Hound and Hare (complex world)" by Paul R 
// Please leave this clone trail here.
 


// Cloned by Paul R on 8 Oct 2022 from World "Complex World" by Starter user 
// Please leave this clone trail here.
 



// ==== Starter World =================================================================================================
// This code is designed for use on the Ancient Brain site.
// This code may be freely copied and edited by anyone on the Ancient Brain site.
// To include a working run of this program on another site, see the "Embed code" links provided on Ancient Brain.
// ====================================================================================================================



// =============================================================================================
// More complex starter World 
// 3d-effect Maze World (really a 2-D problem)
// Movement is on a semi-visible grid of squares 
//
// This more complex World shows:
// - Skybox
// - Internal maze (randomly drawn each time)
// - Enemy actively chases agent
// - Music/audio
// - 2D world (clone this and set show3d = false)
// - User keyboard control (clone this and comment out Mind actions to see)
// =============================================================================================


// =============================================================================================
// Scoring:
// Bad steps = steps where enemy is within one step of agent.
// Good steps = steps where enemy is further away. 
// Score = good steps as percentage of all steps.
//
// There are situations where agent is trapped and cannot move.
// If this happens, you score zero.
// =============================================================================================


 





// ===================================================================================================================
// === Start of tweaker's box ======================================================================================== 
// ===================================================================================================================

// The easiest things to modify are in this box.
// You should be able to change things in this box without being a JavaScript programmer.
// Go ahead and change some of these. What's the worst that could happen?


AB.clockTick       = 1000; // 1000;    

	// Speed of run: Step every n milliseconds. Default 100.
	
AB.maxSteps        = 1000;    

	// Length of run: Maximum length of run in steps. Default 1000.

AB.screenshotStep  = 100;   
  
	// Take screenshot on this step. (All resources should have finished loading.) Default 50.



//---- global constants: -------------------------------------------------------

	const show3d = true;						// Switch between 3d and 2d view (both using Three.js) 


 const TEXTURE_WALL 	= '/uploads/paul79/wall2.jpg' ;
 const TEXTURE_MAZE 	= '/uploads/starter/latin.jpg' ;
 const TEXTURE_AGENT 	= '/uploads/paul79/rabbit-128.png' ;
 const TEXTURE_ENEMY 	= '/uploads/paul79/greyhound-silhouette.jpg' ;
// credits:
// http://commons.wikimedia.org/wiki/File:Old_door_handles.jpg
// https://commons.wikimedia.org/wiki/Category:Pac-Man_icons
// https://commons.wikimedia.org/wiki/Category:Skull_and_crossbone_icons
// http://en.wikipedia.org/wiki/File:Inscription_displaying_apices_(from_the_shrine_of_the_Augustales_at_Herculaneum).jpg
// https://freestocktextures.com/texture/brick-renovated-closeup,740.html
// https://www.iconspng.com/images/greyhound-silhouette/greyhound-silhouette.jpg
//https://www.iconsdb.com/orange-icons/rabbit-icon.html

 
	const MUSIC_BACK  = '/uploads/starter/Defense.Line.mp3' ;
	const SOUND_ALARM = '/uploads/starter/air.horn.mp3' ;

// credits:
// http://www.dl-sounds.com/royalty-free/defense-line/
// http://soundbible.com/1542-Air-Horn.html 

//Paul Ryan parameters to control moving walls	
const WALLMOVENO = 150 ; // 150;
const WALLMOVETICK = 4 ; // 4;
	
const gridsize = 40;						// number of squares along side of world	   

const NOBOXES =  Math.trunc ( (gridsize * gridsize) / 5 );
		// density of maze - number of internal boxes
		// (bug) use trunc or can get a non-integer 


const squaresize = 100;					// size of square in pixels

const MAXPOS = gridsize * squaresize;		// length of one side in pixels 
	
const SKYCOLOR 	= 0xddffdd;				// a number, not a string 

 
const startRadiusConst	 	= MAXPOS * 1 ;		// distance from centre to start the camera at
const maxRadiusConst 		= MAXPOS * 10  ;		// maximum distance from camera we will render things  



//--- change ABWorld defaults: -------------------------------

ABHandler.MAXCAMERAPOS 	= maxRadiusConst ;

ABHandler.GROUNDZERO		= true;						// "ground" exists at altitude zero



//--- skybox: -------------------------------
// skybox is a collection of 6 files 
// x,y,z positive and negative faces have to be in certain order in the array 
// https://threejs.org/docs/#api/en/loaders/CubeTextureLoader 

// mountain skybox, credit:
// http://stemkoski.github.io/Three.js/Skybox.html

 const SKYBOX_ARRAY = [										 
                "/uploads/starter/dawnmountain-xpos.png",
                "/uploads/starter/dawnmountain-xneg.png",
                "/uploads/starter/dawnmountain-ypos.png",
                "/uploads/starter/dawnmountain-yneg.png",
                "/uploads/starter/dawnmountain-zpos.png",
                "/uploads/starter/dawnmountain-zneg.png"
                ];


// space skybox, credit:
// http://en.spaceengine.org/forum/21-514-1
// x,y,z labelled differently

/*
 const SKYBOX_ARRAY = [										 
                "/uploads/starter/sky_pos_z.jpg",
                "/uploads/starter/sky_neg_z.jpg",
                "/uploads/starter/sky_pos_y.jpg",
                "/uploads/starter/sky_neg_y.jpg",
                "/uploads/starter/sky_pos_x.jpg",
                "/uploads/starter/sky_neg_x.jpg"
                ];
*/				


// urban photographic skyboxes, credit:
// http://opengameart.org/content/urban-skyboxes

/*
 const SKYBOX_ARRAY = [										 
                "/uploads/starter/posx.jpg",
                "/uploads/starter/negx.jpg",
                "/uploads/starter/posy.jpg",
                "/uploads/starter/negy.jpg",
                "/uploads/starter/posz.jpg",
                "/uploads/starter/negz.jpg"
                ];
*/



// ===================================================================================================================
// === End of tweaker's box ==========================================================================================
// ===================================================================================================================


// You will need to be some sort of JavaScript programmer to change things below the tweaker's box.









//--- Mind can pick one of these actions -----------------

const ACTION_LEFT 			= 0;		   
const ACTION_RIGHT 			= 1;
const ACTION_UP 			= 2;		 
const ACTION_DOWN 			= 3;
const ACTION_STAYSTILL 		= 4;

// in initial view, (smaller-larger) on i axis is aligned with (left-right)
// in initial view, (smaller-larger) on j axis is aligned with (away from you - towards you)


// contents of a grid square

const GRID_BLANK 	= 0;
const GRID_WALL 	= 1;
const GRID_MAZE 	= 2;
 
const VERBOSE_LOG = false; 
 
 

var BOXHEIGHT;		// 3d or 2d box height 

var GRID 	= new Array(gridsize);			// can query GRID about whether squares are occupied, will in fact be initialised as a 2D array   
var MAZE_BLOCKS = [];

var theagent, theenemy;
  
var wall_texture, agent_texture, enemy_texture, maze_texture; 


// enemy and agent position on squares
var ei, ej, ai, aj;

var badsteps;
var goodsteps;


	
function loadResources()		// asynchronous file loads - call initScene() when all finished 
{
	var loader1 = new THREE.TextureLoader();
	var loader2 = new THREE.TextureLoader();
	var loader3 = new THREE.TextureLoader();
	var loader4 = new THREE.TextureLoader();
	
	loader1.load ( TEXTURE_WALL, function ( thetexture )  		
	{
		thetexture.minFilter  = THREE.LinearFilter;
		wall_texture = thetexture;
		if ( asynchFinished() )	initScene();		// if all file loads have returned 
	});
		
	loader2.load ( TEXTURE_AGENT, function ( thetexture )  	 
	{
		thetexture.minFilter  = THREE.LinearFilter;
		agent_texture = thetexture;
		if ( asynchFinished() )	initScene();		 
	});	
	
	loader3.load ( TEXTURE_ENEMY, function ( thetexture )  
	{
		thetexture.minFilter  = THREE.LinearFilter;
		enemy_texture = thetexture;
		if ( asynchFinished() )	initScene();		 
	});
	
	loader4.load ( TEXTURE_MAZE, function ( thetexture )  
	{
		thetexture.minFilter  = THREE.LinearFilter;
		maze_texture = thetexture;
		if ( asynchFinished() )	initScene();		 
	});
	
}


function asynchFinished()		 // all file loads returned 
{
	if ( wall_texture && agent_texture && enemy_texture && maze_texture )   return true; 
	else return false;
}	
	
	
 

//--- grid system -------------------------------------------------------------------------------
// my numbering is 0 to gridsize-1

	
function occupied ( i, j )		// is this square occupied
{
 if ( ( ei == i ) && ( ej == j ) ) return true;		// variable objects 
 if ( ( ai == i ) && ( aj == j ) ) return true;

 if ( GRID[i][j] == GRID_WALL ) return true;		// fixed objects	 
 if ( GRID[i][j] == GRID_MAZE ) return true;		 
	 
 return false;
}

 
// translate my (i,j) grid coordinates to three.js (x,y,z) coordinates
// logically, coordinates are: y=0, x and z all positive (no negative)    
// logically my dimensions are all positive 0 to MAXPOS
// to centre everything on origin, subtract (MAXPOS/2) from all dimensions 

function translate ( i, j )			
{
	var v = new THREE.Vector3();
	
	v.y = 0;	
	v.x = ( i * squaresize ) - ( MAXPOS/2 );   		 
	v.z = ( j * squaresize ) - ( MAXPOS/2 );   	
	
	return v;
}



	
function initScene()		// all file loads have returned 
{
	 var i,j, shape, thecube;
	 
	// set up GRID as 2D array
	 
	 for ( i = 0; i < gridsize ; i++ ) 
		GRID[i] = new Array(gridsize);		 


	// set up walls
	 
	 for ( i = 0; i < gridsize ; i++ ) 
	  for ( j = 0; j < gridsize ; j++ ) 
		if ( ( i==0 ) || ( i==gridsize-1 ) || ( j==0 ) || ( j==gridsize-1 ) )
		{
			GRID[i][j] = GRID_WALL;		 
			shape    = new THREE.BoxGeometry ( squaresize, BOXHEIGHT, squaresize );			 
			thecube  = new THREE.Mesh( shape );
			thecube.material = new THREE.MeshBasicMaterial( { map: wall_texture } );
			
			thecube.position.copy ( translate(i,j) ); 		  	// translate my (i,j) grid coordinates to three.js (x,y,z) coordinates 
			ABWorld.scene.add(thecube);
		}
		else 
   			GRID[i][j] = GRID_BLANK;

		
   // set up maze 
   
    for ( var c=1 ; c <= NOBOXES ; c++ )
	{
	    //Paul Ryan bug fix ensure a block is not placed on existing block
	    do {
		    i = AB.randomIntAtoB(1,gridsize-2);		// inner squares are 1 to gridsize-2
		    j = AB.randomIntAtoB(1,gridsize-2);
	    } while(occupied(i,j));	
		GRID[i][j] = GRID_MAZE ;
		
		shape    = new THREE.BoxGeometry ( squaresize, BOXHEIGHT, squaresize );			 
		thecube  = new THREE.Mesh( shape );
		thecube.material = new THREE.MeshBasicMaterial( { map: maze_texture } );		  

		thecube.position.copy ( translate(i,j) ); 		  	// translate my (i,j) grid coordinates to three.js (x,y,z) coordinates 
		ABWorld.scene.add(thecube);	
		
		//Paul Ryan
		MAZE_BLOCKS.push({i:i, j:j, cube:thecube});
	}
	if (VERBOSE_LOG){ //Paul Ryan logging to help diagnose a bug
        let str = "Initial block pos: ";
        for (var k=0; k<MAZE_BLOCKS.length; k++){
            str = str + "[" + MAZE_BLOCKS[k].i + "," + MAZE_BLOCKS[k].j + "]";
        }
    	console.log (str); 
	}
   
	// set up enemy 
	// start in random location
	//Paul Ryan ensure enemy and agent start at opposite corners
	 do
	 {
	  i = AB.randomIntAtoB(1,10);
	  j = AB.randomIntAtoB(1,10);
	 }
	 while ( occupied(i,j) );  	  // search for empty square 

	 ei = i;
	 ej = j;
	 
	 shape    = new THREE.BoxGeometry ( squaresize, BOXHEIGHT, squaresize );			 
	 theenemy = new THREE.Mesh( shape );
 	 theenemy.material =  new THREE.MeshBasicMaterial( { map: enemy_texture } );
	 ABWorld.scene.add(theenemy);
	 drawEnemy();		  

	 
	
	// set up agent 
	// start in random location
	//Paul Ryan ensure enemy and agent start at opposite corners
	 do
	 {
	  i = AB.randomIntAtoB(gridsize-10,gridsize-2);
	  j = AB.randomIntAtoB(gridsize-10,gridsize-2);
	 }
	 while ( occupied(i,j) );  	  // search for empty square 

	 ai = i;
	 aj = j;
 
	 shape    = new THREE.BoxGeometry ( squaresize, BOXHEIGHT, squaresize );			 
	 theagent = new THREE.Mesh( shape );
	 theagent.material =  new THREE.MeshBasicMaterial( { map: agent_texture } );
	 ABWorld.scene.add(theagent);
	 drawAgent(); 
	 
//Paul Ryan set up for the A* search
//only needs to be done once because maze does not change.
	 aStarSetup();


  // finally skybox 
  // setting up skybox is simple 
  // just pass it array of 6 URLs and it does the asych load 
  
  	 ABWorld.scene.background = new THREE.CubeTextureLoader().load ( SKYBOX_ARRAY, 	function() 
	 { 
		ABWorld.render(); 
	 
		AB.removeLoading();
	
		AB.runReady = true; 		// start the run loop
	 });
 		
}
 
 
 


// --- draw moving objects -----------------------------------


function drawEnemy()		// given ei, ej, draw it 
{
	theenemy.position.copy ( translate(ei,ej) ); 		  	// translate my (i,j) grid coordinates to three.js (x,y,z) coordinates 

	ABWorld.lookat.copy ( theenemy.position );	 		// if camera moving, look back at where the enemy is
}


function drawAgent()		// given ai, aj, draw it 
{
	theagent.position.copy ( translate(ai,aj) ); 		  	// translate my (i,j) grid coordinates to three.js (x,y,z) coordinates 

	ABWorld.follow.copy ( theagent.position );			// follow vector = agent position (for camera following agent)
}




// --- take actions -----------------------------------
////////////////////////////////////////////////////////////////////////////////
//Paul Ryan           START: Move the enemy                                 ////
//First, call "getPathToAgent" to get the shortest path                     ////
//Second, move the enemy to the second element in the path (1st is current pos)/
//Third, show the trail                                                     ////
////////////////////////////////////////////////////////////////////////////////
var trail_lights = new Array(); //a trail showing the path

function moveEnemyA_Star()
{
    console.log("Search for shortest path");

    //Paul Ryan get shortest path by using A* search
    let path = getPathToAgent (ai, aj, ei, ej);
    
    if (VERBOSE_LOG){ //Paul Ryan logging to help diagnose a bug
        console.log("agent pos:" +ai + " " + aj + "  enemy pos:" + ei + " " + ej);
        var logStr = "[";
        for (var b=0; b<path.length; b++){
            let occ = false;
            for (var c=0; c<MAZE_BLOCKS.length; c++){
                if (MAZE_BLOCKS[c].i == path[b].i && MAZE_BLOCKS[c].j == path[b].j){
                    occ = true;
                }
            }
            logStr = logStr + "[" + path[b].i + "," +  path[b].j + "," + occ + "]";
        }
        logStr = logStr + "]";
        console.log(logStr);
    }

    //Paul Ryan move the enemy to the second step in the path
    if (path.length>=2 && !occupied(path[1].i, path[1].j)){
        ei = path[1].i;
        ej = path[1].j;
    }
    
    //Paul Ryan remove any old trail_lights that exist
    while (trail_lights.length>0){
        let trail_light = trail_lights.pop();
        ABWorld.scene.remove(trail_light);
    }
    
    //Paul Ryan add trail_lights to all steps of returned path except first and last steps
    for (let a=1; a<path.length-1; a++){
        const geometry = new THREE.SphereGeometry( 20, 32 );
        const material = new THREE.MeshBasicMaterial( { color: 0x0000FF } );
        let trail_light = new THREE.Mesh( geometry, material );
        ABWorld.scene.add( trail_light );
        trail_light.position.copy ( translate(path[a].i, path[a].j) );
        trail_lights.push(trail_light);
    }
}
////////////////////////////////////////////////////////////////////////////////
//Paul Ryan           END: Move the enemy                                   ////
////////////////////////////////////////////////////////////////////////////////




function moveLogicalAgent( a )			// this is called by the infrastructure that gets action a from the Mind 
{ 
 var i = ai;
 var j = aj;		 

      if ( a == ACTION_LEFT ) 	i--;
 else if ( a == ACTION_RIGHT ) 	i++;
 else if ( a == ACTION_UP ) 		j++;
 else if ( a == ACTION_DOWN ) 	j--;

 if ( ! occupied(i,j) ) 
 {
  ai = i;
  aj = j;
 }
}




// --- key handling --------------------------------------------------------------------------------------
// This is hard to see while the Mind is also moving the agent:
// AB.mind.getAction() and AB.world.takeAction() are constantly running in a loop at the same time 
// have to turn off Mind actions to really see user key control 

// we will handle these keys: 

var OURKEYS = [ 37, 38, 39, 40 ];

function ourKeys ( event ) { return ( OURKEYS.includes ( event.keyCode ) ); }
	

function keyHandler ( event )		
{
	if ( ! AB.runReady ) return true; 		// not ready yet 

   // if not one of our special keys, send it to default key handling:
	
	if ( ! ourKeys ( event ) ) return true;
	
	// else handle key and prevent default handling:
	
	if ( event.keyCode == 37 )   moveLogicalAgent ( ACTION_LEFT 	);   
    if ( event.keyCode == 38 )   moveLogicalAgent ( ACTION_DOWN  	); 	 
    if ( event.keyCode == 39 )   moveLogicalAgent ( ACTION_RIGHT 	); 	 
    if ( event.keyCode == 40 )   moveLogicalAgent ( ACTION_UP		);   
	
	// when the World is embedded in an iframe in a page, we want arrow key events handled by World and not passed up to parent 

	event.stopPropagation(); event.preventDefault(); return false;
}





// --- score: -----------------------------------


function badstep()			// is the enemy within one square of the agent
{
 if ( ( Math.abs(ei - ai) < 2 ) && ( Math.abs(ej - aj) < 2 ) ) return true;
 else return false;
}


function agentBlocked()			// agent is blocked on all sides, run over
{
 return ( 	occupied (ai-1,aj) 		&& 
		occupied (ai+1,aj)		&&
		occupied (  ai,aj+1)		&&
		occupied (  ai,aj-1) 	);		
} 


function updateStatusBefore(a)
// this is called before anyone has moved on this step, agent has just proposed an action
// update status to show old state and proposed move 
{
 var x 		= AB.world.getState();
 AB.msg ( " Step: " + AB.step + " &nbsp; x = (" + x.toString() + ") &nbsp; a = (" + a + ") " ); 
}


function   updateStatusAfter()		// agent and enemy have moved, can calculate score
{
 // new state after both have moved
 
 var y 		= AB.world.getState();
 var score = ( goodsteps / AB.step ) * 100; 

 AB.msg ( " &nbsp; y = (" + y.toString() + ") <br>" +
		" Bad steps: " + badsteps + 
		" &nbsp; Good steps: " + goodsteps + 
		" &nbsp; Score: " + score.toFixed(2) + "% ", 2 ); 
}





AB.world.newRun = function() 
{
	AB.loadingScreen();

	AB.runReady = false;  

	badsteps = 0;	
	goodsteps = 0;

	
	if ( show3d )
	{
	 BOXHEIGHT = squaresize;
	 ABWorld.init3d ( startRadiusConst, maxRadiusConst, SKYCOLOR  ); 	
	}	     
	else
	{
	 BOXHEIGHT = 1;
	 ABWorld.init2d ( startRadiusConst, maxRadiusConst, SKYCOLOR  ); 		     
	}
	
	
	loadResources();		// aynch file loads		
							// calls initScene() when it returns 

	document.onkeydown = keyHandler;	
		 
};



AB.world.getState = function()
{
 var x = [ ai, aj, ei, ej ];
  return ( x );  
};



AB.world.takeAction = function ( a )
{
  updateStatusBefore(a);			// show status line before moves 
  
    console.log("Move some blocks");
    var str;
    //Paul Ryan move some blocks - just take the first WALLMOVENO blocks
    if (AB.step % WALLMOVETICK == 0){
        for (var i=0; i<Math.min(WALLMOVENO, NOBOXES); i++){
            let blockInfo = MAZE_BLOCKS[i];
    
            let newI, newJ;
            do {
                newI = AB.randomIntAtoB(1,gridsize-2);
                newJ = AB.randomIntAtoB(1,gridsize-2);
        	}
            while ( occupied(newI, newJ) );  	  // search for empty square 
          
            //Paul Ryan update the main grid to take account of the new block pos
            GRID[newI][newJ] = GRID_MAZE;
            GRID[blockInfo.i][blockInfo.j] = GRID_BLANK;
            
            if (VERBOSE_LOG){ //Paul Ryan logging to help diagnose a bug
                str = str + "[" + blockInfo.i + "," + blockInfo.j + "] -> [" + newI + "," + newJ + "]";
            }	
        		
        	//Paul Ryan move the block to the new position and update MAZE_BLOCK element
        	blockInfo.cube.position.copy ( translate(newI, newJ) ); 		  	// translate grid coordinates to three.js (x,y,z) coordinates 
            blockInfo.i = newI;
            blockInfo.j = newJ;
        }
        if (VERBOSE_LOG) { //Paul Ryan logging to help diagnose a bug
            console.log("Position changes: " + str);
            str = "New block pos: ";
            for (var i=0; i<MAZE_BLOCKS.length; i++){
                str = str + "[" + MAZE_BLOCKS[i].i + "," + MAZE_BLOCKS[i].j + "]";
            }
            console.log(str);
        }
        
    }
  

  moveLogicalAgent(a);

//  if ( ( AB.step % 2 ) == 0 )		// slow the enemy down to every nth step
    
    moveEnemyA_Star();


  if ( badstep() )  badsteps++;
  else   			goodsteps++;

   drawAgent();
   drawEnemy();
   updateStatusAfter();			// show status line after moves  


  if ( agentBlocked() )			// if agent blocked in, run over 
  {
	AB.abortRun = true;
	goodsteps = 0;			// you score zero as far as database is concerned 			 
	musicPause();
	soundAlarm();
  }

};



AB.world.endRun = function()
{
  musicPause(); 
  if ( AB.abortRun ) AB.msg ( " <br> <font color=red> <B> Agent trapped. Final score zero. </B> </font>   ", 3  );
  else    				AB.msg ( " <br> <font color=green> <B> Run over. </B> </font>   ", 3  );
};

 
AB.world.getScore = function()
{
    // only called at end - do not use AB.step because it may have just incremented past AB.maxSteps
    
    var s = ( goodsteps / AB.maxSteps ) * 100;   // float like 93.4372778 
    var x = Math.round (s * 100);                // 9344
    return ( x / 100 );                          // 93.44
};


 




// --- music and sound effects ----------------------------------------

var backmusic = AB.backgroundMusic ( MUSIC_BACK );

function musicPlay()   { backmusic.play();  }
function musicPause()  { backmusic.pause(); }

											 
function soundAlarm()
{
	var alarm = new Audio ( SOUND_ALARM );
	alarm.play();							// play once, no loop 
}

////////////////////////////////////////////////////////////////////////////////
// Paul Ryan               START:   A* funcs & structures                   ////
// This is the start of the code for the A* search                          ////
////////////////////////////////////////////////////////////////////////////////
const aStarGrid = new Array(gridsize-2); //a grid to hold A* cells. It's smaller than grid because no need to search walls

//Paul Ryan
//Set up the A*grid. This is based on the main grid
function aStarSetup(){
    for (var x=0; x < gridsize-2; x++){
        aStarGrid[x] = new Array(gridsize-2);
    }
    for (var x = 0; x < gridsize-2 ; x++ ) {
        for (var y = 0; y < gridsize-2 ; y++ ) 
        {
            aStarGrid[x][y] = new AStarCell(x, y, GRID[x+1][y+1] == GRID_MAZE);
            //Paul Ryan set up neighbour relationships
            if (x > 0){
                aStarGrid[x][y].addNeighbour(aStarGrid[x-1][y]); 
                aStarGrid[x-1][y].addNeighbour(aStarGrid[x][y]);
            }
            if (y > 0){
                aStarGrid[x][y].addNeighbour(aStarGrid[x][y-1]); 
                aStarGrid[x][y-1].addNeighbour(aStarGrid[x][y]);
            }
        }
    }
}


//Paul Ryan structure used for the A* search
function AStarCell(i, j, isMaze){
    // Location
    this.i = i;
    this.j = j;

    // f, g, and h values for A*
    this.f = 0;
    this.g = 0;
    this.h = 0;

    // Neighbours
    this.neighbours = [];

    // Where did I come from?
    this.previous = undefined;
    this.maze = isMaze;
    
    //Set another cell as a neighbour of this cell
    this.addNeighbour = function(neighbour){
        this.neighbours.push(neighbour);
    }

    //Paul Ryan reset the cell for a new search
    //Unlike world1, the "maze" boolean must also be reset.
    this.reset = function(isMaze){
        this.f = 0;
        this.g = 0;
        this.h = 0;
        this.previous = undefined;
        this.maze = isMaze;
    }
}
 
//Paul Ryan The manhattan distance as the heuristic func
function heuristic(a, b) {
    return ( Math.abs(a.i - b.i) + Math.abs(a.j - b.j) );
}

//Paul Ryan
//The main A* search routine
//Agent and enemy positions are passed in as parameters
//The A* grid is reset and set up again for new search
//Search is executed
//Returns an array which describes the path from enemy to agent.
function getPathToAgent(agentPosI, agentPosJ, enemyPosI, enemyPosJ){
    ////////////////////////////////
    //Initialisation for the search
    ////////////////////////////////
    
    let ai = agentPosI-1, aj=agentPosJ-1, ei=enemyPosI-1,ej=enemyPosJ-1;
    // Open and closed set
    let openSet = [];
    let closedSet = [];

    // Start and end are the enemy and agent positions respectively
    let start = aStarGrid[ei][ej];
    let end = aStarGrid[ai][aj];

    //Reset the grid elements from previous search
    for (let x = 0; x < gridsize-2 ; x++ ) {
        for (let y = 0; y < gridsize-2 ; y++ ) {
            aStarGrid[x][y].reset(GRID[x+1][y+1] == GRID_MAZE);
        }
    }
    openSet.push(start);
    
    //////////////////////////////////
    //Paul Ryan START: The A* search
    /////////////////////////////////
    let current;
    let isCurrent = (element) => element == current;
    while (openSet.length > 0){ //Iterate while there is something in the openSet
        let winner = 0;
    
        for (let i = 0; i < openSet.length; i++) {
            if (openSet[i].f < openSet[winner].f) 
                winner = i;
        }
        
        current = openSet[winner];
        if (current === end) {
            console.log("success - found path");
            break;
        }
        
        //remove current from openSet and push into closedSet
        openSet.splice(openSet.findIndex( isCurrent ), 1);
        closedSet.push(current);
        
        for (let i = 0; i < current.neighbours.length; i++) {
            let neighbour = current.neighbours[i];

            // Paul Ryan Do not look at maze cells or previously completed cells
            if (!closedSet.includes(neighbour) && !neighbour.maze) {
                //Paul Ryan A temporary g is stored as we do not know that the 
                //path to this neighbour is better than a previous path
                let tempG = current.g + heuristic(neighbour, current);

                let neighbourAlreadySearched = openSet.includes(neighbour);
                if (!neighbourAlreadySearched || tempG < neighbour.g){
                    //Paul Ryan If it's a new path or a better path
                    //then set h and f values and record path in neighbour
                    neighbour.g = tempG;
                    neighbour.h = heuristic(neighbour, end);
                    neighbour.f = neighbour.g + neighbour.h;

                    neighbour.previous = current;
                }
                if (!neighbourAlreadySearched){
                    //only push neighbour into open set if not already there
                    openSet.push(neighbour);
                }
            }
        }
    }
    //////////////////////////////////
    //Paul Ryan    END: The A* search
    /////////////////////////////////
    
    if (openSet.length == 0){
        console.log("failure - no path found.");
        return [];
    }
    
    ////////////////////////////////////////////////////////////////////////////
    // Paul Ryan Create a path from start to current; current == end if search was success
    // Find the path by working backwards
    let path = [];
    let temp = current;
    path.push(temp);
    while (temp.previous) {
        path.push(temp.previous);
        temp = temp.previous;
    }
    let transformedPath = new Array();
    for (let a=path.length-1; a>=0; a--){
        transformedPath.push({i : path[a].i + 1, j : path[a].j + 1});
    }
    return transformedPath;
}
////////////////////////////////////////////////////////////////////////////////
// Paul Ryan                     END:   A* funcs & structures               ////
////////////////////////////////////////////////////////////////////////////////