snake.js

var col = 0;
var row = 0;
var pitWidth = 0;
var pitHeight = 0;
var clearID;
var map = [];
var H;
var fillCount = 0;
var direction = -1; // north = 0, east = 1, south = 2, west = 3;
var rotation; // 1 = clockwise, 2 = anti-clockwise
var obstacleCount;

function calcH () {
   var rowData = [];
   H = [];
   for (var r = 0; r < pitHeight; r++) {
      for (var c = 0; c < pitWidth; c++) {
       rowData[c] = movesInRoom(r, c);
	  }
	  H[r] = rowData;
	  rowData = [];
	}
}

function isObstacle(r, c) {
	if (r < 0 || r >= pitHeight-1)
		return false;
	if (c < 0 || c >= pitWidth-1)
		return false;
	if (map[r][c] == -1)
		return true;
	return false;
}

function countAdjObs(r,c) {
	var count = 0;

	//if (isObstacle(r-1,c-1)) count++;
	if (isObstacle(r-1,c)) count++;
	//if (isObstacle(r-1,c+1)) count++;
	if (isObstacle(r,c+1)) count++;
	//if (isObstacle(r+1,c+1)) count++;
	if (isObstacle(r+1,c)) count++;
	//if (isObstacle(r+1,c-1)) count++;
	if (isObstacle(r,c-1)) count++;
	return count;
}

function tweakH() {
	if (rotation = 1 && map[1][1] == -1 && map[1][0] == 0)
		H[1][0] = 1;
	if (rotation = 2 && map[1][1] == -1 && map[0][1] == 0)
		H[0][1] = 1;
	/*
	for (var r = 0; r < pitWidth-1; r++)
		for (var c = 0; c < pitHeight-1; c++)
			if (countAdjObs(r,c) > 1) H[r][c] = 1;
	*/
}

function countMovesAt(move, r, c) {
	var count = 0;
	if (r > 0)
		if (H[r-1][c] == move) count++;
	if (r < pitHeight-1)
		if (H[r+1][c] == move) count++;
	if (c > 0)
		if (H[r][c-1] == move) count++;
	if (c < pitWidth-1)
		if (H[r][c+1] == move) count++;
	return count;
}

function isEdge(r, c) {
	if (r == 0 || r == pitHeight -1 || c == 0 || c == pitWidth -1)
		return true;
	return false;
}

function movesInRoom(r, c) {
   var count = 0;
   
   if (map[r][c] < 0)
      return 0;
   if (r > 0)
      if (map[r-1][c] === 0)
         count++;
   if (r < pitHeight - 1)
      if (map[r+1][c] === 0)
         count++;
   if (c > 0)
       if (map[r][c-1] === 0)
          count++;
   if (c < pitWidth - 1)
       if (map[r][c+1] === 0)
       count++;
   //showMap();
   //console.log("movesInRoom count -- map[" + r + "][" + c + "] = " + count);
   return count;
}

function canMoveTo(r, c) {

   //console.log("canMoveTo @ map[" + r + "][" + c + "]");
   //showMap();
   if (r >= pitHeight || c >= pitWidth || r < 0 || c < 0)
      return false;
   if (map[r][c] === 0) 
      return true;
   return false;
}

function canMoveToDirection(d) {
	switch (d) {
		case 0:
			return (canMoveTo(row-1, col));
		case 1:
			return (canMoveTo(row, col+1));
		case 2:
			return (canMoveTo(row+1, col));
		case 3:
			return (canMoveTo(row, col-1));
	}
}

function updateDirection(d)
{
	console.log("dir = " + direction + " new d = " + d);
	
	direction = d;
	switch (d) {
		case 0:
			console.log("Moving North");
			break;
		case 1:
			console.log("Moving East");
			break;
		case 2:
			console.log("Moving South");
			break;
		case 3:
			console.log("Moving West");
			break;
	}
}

function isDeadEnd(r,c,dir) {
   switch (dir) {
		case 0:
		    if (r === 0) 
			   return false;
			else if (H[r-1][c] < 2)
				return true;
			return false;
			break;
		case 1:
			if (c >= pitWidth-1)
			   return false;
			else if (H[r][c+1] < 2)
				return true;
			return false;
			break;
		case 2:
			if (r >= pitHeight -1)
			   return false;
			else if (H[r+1][c] < 2)
				return true;
			return false;
			break;
		case 3:
			if (c === 0)
			   return false;
			else if (H[r][c-1]< 2)
				return true;
			return false;
			break;
   }
}

function isDeadEndAtDir(dir) {
	return isDeadEnd(row, col, dir);
}

function deadEndCount(r, c) {
   var count = 0;
   
   if (isDeadEnd(r,c,0)) count++;
   if (isDeadEnd(r,c,1)) count++;
   if (isDeadEnd(r,c,2)) count++;
   if (isDeadEnd(r,c,3)) count++;
   return count;
}

function moveSnake(dir) {
	switch (dir) {
		case 0:
			if (canMoveTo(row-1, col) && !isDeadEndAtDir(0)) {
				row--;
				updateDirection(0);
				return true;
			}
			return false;
		case 1:
			if (canMoveTo(row, col+1) && !isDeadEndAtDir(1)) {
				col++;
				updateDirection(1);
				return true;
			}
			return false;
		case 2:
			if (canMoveTo(row+1, col) && !isDeadEndAtDir(2)) {
				row++;
				updateDirection(2);
				return true;
			}
			return false;
		case 3:
			if (canMoveTo(row, col-1) && !isDeadEndAtDir(3)) {
				col--;
				updateDirection(3);
				return true;
			}
			return false;
	}
}

function moveOneDirection() {

    console.log("moveOneDirection");
	if (canMoveTo(row-1, col)) {
		row--;
		updateDirection(0);
		return true;
	}
	if (canMoveTo(row, col+1)) {
		col++;
		updateDirection(1);
		return true;
	}
	if (canMoveTo(row+1, col)) {
		row++;
		updateDirection(2);
		return true;
	}
	if (canMoveTo(row, col-1)) {
		col--;
		updateDirection(3);
		return true;
	}
}   

function carryOnMyWaywardSnake() {
	
    console.log("carryOnMyWaywardSnake");
	if (rotation == 1) {
		switch (direction) {
			case 0:
				if (moveSnake(3)) break;
				if (moveSnake(0)) break;
				if (moveSnake(1)) break;
				if (moveSnake(2)) break;
				console.log("====PANIC!!!");
				lastMove();
				break;
			case 1:
				if (moveSnake(0)) break;
				if (moveSnake(1)) break;
				if (moveSnake(2)) break;
				if (moveSnake(3)) break;
				console.log("====PANIC!!!");
				lastMove();
				break;
			case 2:
				if (moveSnake(1)) break;
				if (moveSnake(2)) break;
				if (moveSnake(3)) break;
				if (moveSnake(0)) break;
				console.log("====PANIC!!!");
				lastMove();
				break;
			case 3:
				if (moveSnake(2)) break;
				if (moveSnake(3)) break;
				if (moveSnake(0)) break;
				if (moveSnake(1)) break;
				console.log("====PANIC!!!");
				lastMove();
				break;
		}
	} else {
		switch (direction) {
			case 0:
				if (moveSnake(1)) break;
				if (moveSnake(0)) break;
				if (moveSnake(3)) break;
				if (moveSnake(2)) break;
				console.log("====PANIC!!!");
				lastMove();
				break;
			case 1:
				if (moveSnake(2)) break;
				if (moveSnake(1)) break;
				if (moveSnake(0)) break;
				if (moveSnake(3)) break;
				console.log("====PANIC!!!");
				lastMove();
				break;
			case 2:
				if (moveSnake(3)) break;
				if (moveSnake(2)) break;
				if (moveSnake(1)) break;
				if (moveSnake(0)) break;
				console.log("====PANIC!!!");
				lastMove();
				break;
			case 3:
				if (moveSnake(0)) break;
				if (moveSnake(3)) break;
				if (moveSnake(2)) break;
				if (moveSnake(1)) break;
				console.log("====PANIC!!!");
				lastMove();
				break;
		}
	}
}   

function startEast() {
   var sumSouth = 0;
   var sumEast = 0;
   
   var highSouth = 0;
   var highEast = 0;
   
   for (var row = 0; row < pitHeight; row++) {
      for (var col = 0; col < pitWidth; col++)
	     sumEast = sumEast + H[row][col];
	  if (sumEast > highEast)
	     highEast = sumEast;
	  sumEast = 0;
	}
	
	for (var col = 0; col < pitWidth; col++) {
	   for (var row = 0; row < pitHeight; row++) 
	      sumSouth = sumSouth + H[row][col];
	    if (sumSouth > highSouth) 
		   highSouth = sumSouth;
		sumSouth = 0;
	}
	if (highSouth > highEast)
	   return false;
	else
	   return true;
}

function lastMove() {
	clearInterval(clearID);
    alert("Filled " + fillCount + " of " + (pitWidth * pitHeight) + " tiles with " + obstacleCount + " obstacles");	 
}

function calcNextMove() {
    
	var moves = movesInRoom(row, col);
	
	console.log("=====================");
	console.log("calcNextMove Moves = " + moves);
	console.log("Snake at [" + row + "][" + col + " dir = " + direction);
	//showMap();
	
	
	switch (moves) {
	    case 0: // no moves left - done
		    lastMove();
		    break;
		case 1: // only 1 move - find it and take it.
		    moveOneDirection();
		    break;
		default: // 2-3 moves left
		    // if 1st time moving -- figure out a flow and go
			
			if (direction == -1) {
			    if (startEast()) {
				    console.log("Starting out -- Go East!");
					rotation = 1;
					if (canMoveTo(row, col+1)) {
						updateDirection(1);
						col++;
					} else {
						updateDirection(2);
						row++;
					}
				} else {
					rotation = 2;
				    console.log("Starting out -- Go South!");
					if (canMoveTo(row+1, col)) {
						direction = 2;
					    updateDirection(2);
						row++;
					} else {
					    updateDirection(1);
						col++;
					}
				}
			} else { // try to continue on current direction or divert beware of deadends.
			     carryOnMyWaywardSnake();
			} 
			
	}
}

function draw() {
    var canvas = document.getElementById('snakePit')
    var ctx = canvas.getContext('2d');

    ctx.fillStyle = "green";
	ctx.fillRect(col*10,row*10, 10,10);
    ctx.fillStyle = "white";
    ctx.strokeRect(col*10,row*10, 10,10);
	map[row][col] = 1;
	fillCount++;
	// calcH();
	calcNextMove();
}

// for debugging

function showMap() {
    var output = "";
	console.log("Map");
	console.log("-----");
	for (var y = 0; y < pitHeight; y++) {
	   for (var x =  0; x < pitWidth; x++)
	      output = output + map[y][x] + " ";
		console.log(output);
		output = "";
	}
}

function showH() {
    var output = "";
	console.log("H");
	console.log("-----");
	for (var y = 0; y < pitHeight; y++) {
	   for (var x =  0; x < pitWidth; x++)
	      output = output + H[y][x] + " ";
		console.log(output);
		output = "";
	}
}

$(document).ready( function() {
    var canvas = document.getElementById('snakePit');
	var ctx = canvas.getContext("2d");
    var size = [];
	var coordinates;
	var rowData = [];
	var inputError;
	
	// get size of map and initialize map array
	
	
	size = prompt("Enter size of Snake Pit (width and height) example: 10 10").split(" ");
	canvas.width = size[0] * 10;
	canvas.height = size[1] * 10;
	pitWidth = size[0];
	pitHeight = size[1];
	
	for (var y = 0; y < pitHeight; y++) {
	   for (var x = 0; x < pitWidth; x++)
	      rowData[x] = 0;
	   map[y] = rowData;
	   rowData = [];
    }
	
	obstacleCount = prompt("How many obstacles?");
	obstacleCount = parseInt(obstacleCount,10);
	console.log(obstacleCount);
	
	
	for (var i = 1; i <= obstacleCount; i++) {
		coordinates = prompt("Enter coordinates Row Column of obstacle " + i + " of " + obstacleCount).split(" ");
		coordinates[0] = parseInt(coordinates[0],10);
		coordinates[1] = parseInt(coordinates[1],10);
		map[coordinates[1]][coordinates[0]] = -1; // obstacles are -1
		ctx.fillStyle = "red";
		ctx.fillRect(coordinates[0]*10, coordinates[1]*10, 10,10);
		ctx.fillStyle = "white";
		ctx.strokeRect(coordinates[0]*10, coordinates[1]*10, 10,10);
		inputError = false;		
	}
	
	showMap();
	
	if (map[0][0] == -1) {
		alert("Filled " + fillCount + " of " + (pitWidth * pitHeight) + " tiles with " + obstacleCount + " obstacles");	 
	} else {
		calcH();
		//showH();
		tweakH();
		//showH();
		console.log("Start Up the drawing");
		clearID = setInterval(draw,100); 
	}
});