package visualizationElements;

import java.awt.Graphics;
import java.util.Stack;
import java.util.Vector;

/**
 * Represents a maze to visualize.
 * @author MSchaefer
 *
 */
public class Maze extends VisualizationElement{

	private static final int CELL_WIDTH = 30;
	private static final int CELL_HEIGTH = 30;
	private static final int START_X_POS = 20;
	private static final int START_Y_POS = 20;
	private Cell[][] maze;
	private Cell currentCell;
	private int heigth;
	private int width;
	private int xpos;
	private int ypos;
	private Stack<Cell> cellStack;
 
	
	/**
	 * Creates a new Maze.
	 * @param heigth Height of the Maze.
	 * @param width Width of the Maze.
	 */
	public Maze(int heigth, int width){
		super();
		
		this.setHeigth(heigth);
		this.setWidth(width);
		
		this.cellStack = new Stack<Cell>();
		this.maze = new Cell[width][heigth];
		
		initMaze();
	}
	


	@Override
	public void draw(Graphics g) {
		xpos = START_X_POS;
		ypos = START_Y_POS;
		for(int column = 0; column < width; column++){
			for(int row = 0; row < heigth; row++){
				Cell currentCell = maze[column][row];
				
				if(currentCell.hasNorthWall()){
					g.drawLine(xpos, ypos, xpos + CELL_WIDTH, ypos);					
				}
				if(currentCell.hasSouthWall()){
					g.drawLine(xpos, ypos + CELL_HEIGTH, xpos + CELL_WIDTH, ypos + CELL_HEIGTH);
				}
				if(currentCell.hasWestWall()){
					g.drawLine(xpos, ypos, xpos, ypos + CELL_HEIGTH);
				}
				if(currentCell.hasEastWall()){
					g.drawLine(xpos + CELL_WIDTH, ypos, xpos + CELL_WIDTH, ypos + CELL_HEIGTH);
				}
				ypos = ypos + CELL_HEIGTH;
			}
			ypos = START_Y_POS;
			xpos = xpos + CELL_WIDTH;
		}
	}
	

	
	/**
	 * @param maze the maze to set
	 */
	public void setMaze(Cell[][] maze) {
		this.maze = maze;
	}

	/**
	 * @return the maze
	 */
	public Cell[][] getMaze() {
		return maze;
	}

	/**
	 * @param heigth the heigth to set
	 */
	public void setHeigth(int heigth) {
		this.heigth = heigth;
	}

	/**
	 * @return the heigth
	 */
	public int getHeigth() {
		return heigth;
	}

	/**
	 * @param width the width to set
	 */
	public void setWidth(int width) {
		this.width = width;
	}

	/**
	 * @return the width
	 */
	public int getWidth() {
		return width;
	}
	/**
	 * Initializes the maze.
	 */
	private void initMaze() {
		initMazeWithAllWalls();
		generateWays();
	}
	
	
	/**
	 * Initializes a Maze full of walls. 
	 */
	private void initMazeWithAllWalls() {
		
		xpos = START_X_POS;
		ypos = START_Y_POS;
		for(int column = 0; column < width; column++){
			for(int row = 0; row < heigth; row++){
				maze[column][row] = new Cell(column, row);
				ypos = ypos + CELL_HEIGTH;
			}
			xpos = xpos + CELL_WIDTH;
		}		
	}

	
	/**
	 * Generates ways through a maze full of walls.
	 */
	private void generateWays(){		
		/*
		-Pick a room randomly, and push it onto the stack. This is the starting room.
		-Pick a room adjacent to the first room, and open a door between them. This room is the current room.
		-Push the starting room onto the stack.
		-While there's at least one room left on the stack, repeat the following steps:
			-If there are any unconnected rooms next to the current room,
				-Pick one randomly, and open a door between it and the current room.
				-Push the current room onto the stack; the new room becomes the current room.
				-Go back to the top of the loop.
			-If there are no unconnected rooms next to the current room,
				-Pop a room off of the stack; it becomes the current room.
				-Go back to the top of the loop.
		-When the stack is empty, the maze is complete.*/
		
		boolean goalMarked = false;
		currentCell = maze[0][0];
		currentCell.setAsStart();
		currentCell.removeNorthWall();
		cellStack.push(currentCell);
		
		while(cellStack.size() > 0){
			currentCell.markAsVisited();
			
			if(!goalMarked){
				if(currentCell.getRow() == maze.length - 1){
					currentCell.setAsGoal();
					currentCell.removeSouthWall();
					goalMarked = true;
				}
				else if(currentCell.getColumn() == maze[0].length - 1){
					currentCell.setAsGoal();
					currentCell.removeEastWall();
					goalMarked = true;
				}			
			}
			
			Vector<Cell> unvisitedNeighbours = getUnvisitedCellNeighbors(currentCell);
			
			if(unvisitedNeighbours.size() != 0){
				int randomUnvisitedNeighbourIndex = (int) (Math.random() * unvisitedNeighbours.size());		
				
				Cell randomUnvisitedNeighbour = unvisitedNeighbours.get(randomUnvisitedNeighbourIndex);
				
				removeWallBetweenCurrentCellAndNeighbour(currentCell, randomUnvisitedNeighbour);
				cellStack.push(currentCell);
				currentCell = randomUnvisitedNeighbour;
			}
			else{
				currentCell = cellStack.pop();
			}
		}		
	}	

	
	/**
	 * Removes a cell's south wall.
	 * @param column Column of the cell.
	 * @param row Row of the cell.
	 */
	private void removeCellsSouthWall(int column, int row){
		maze[column][row].removeSouthWall();
		
		// removes WestWall of neighbor
		if(row < maze[column].length && maze[column][row + 1].hasNorthWall()){
			removeCellsNorthWall(column, row + 1);
		}
	}
	
	
	/**
	 * Removes a cell's north wall.
	 * @param column Column of the cell.
	 * @param row Row of the cell.
	 */
	private void removeCellsNorthWall(int column, int row){
		maze[column][row].removeNorthWall();
		
		// removes WestWall of neighbor
		if(row < maze[column].length && maze[column][row - 1].hasSouthWall()){
			removeCellsSouthWall(column, row - 1);
		}
	}

	
	/**
	 * Removes a cell's east wall.
	 * @param column Column of the cell.
	 * @param row Row of the cell.
	 */
	private void removeCellsEastWall(int column, int row) {
		maze[column][row].removeEastWall();
		
		// removes WestWall of neighbor
		if(column < maze.length - 1 && maze[column + 1][row].hasWestWall()){
			removeCellsWestWall(column + 1, row);
		}
	}
	
	
	/**
	 * Removes a cell's west wall.
	 * @param column Column of the cell.
	 * @param row Row of the cell.
	 */
	private void removeCellsWestWall(int column, int row){
		maze[column][row].removeWestWall();
		
		// removes WestWall of neighbor
		if(column < maze.length - 1 && maze[column - 1][row].hasEastWall()){
			removeCellsEastWall(column - 1, row);
		}
	}

	
	/**
	 * Removes the wall between two cells.
	 * @param cell Cell to remove a wall.
	 * @param neighbor The Cell's neighbour to remove the corresponding wall.
	 */
	private void removeWallBetweenCurrentCellAndNeighbour(Cell cell, Cell neighbor) {
		if(neighbor.getRow() == cell.getRow()){
			if(neighbor.getColumn() < cell.getColumn()){
				removeCellsWestWall(cell.getColumn(), cell.getRow());
			}
			else{
				removeCellsEastWall(cell.getColumn(), cell.getRow());
			}
		}
		else if(neighbor.getRow() < cell.getRow()){
			removeCellsNorthWall(cell.getColumn(), cell.getRow());
		}
		else{
			removeCellsSouthWall(cell.getColumn(), cell.getRow());
		}		
	}

	
	/**
	 * Gets all unvisited neighbors of a cell.
	 * @param currentCell The cell to get the neighbors.
	 * @return The cell's unvisited neighbors.
	 */
	private Vector<Cell> getUnvisitedCellNeighbors(Cell currentCell) {
		Vector<Cell> neighbours = getAllCellNeighbours(currentCell);
		Vector<Cell> unvisitedNeighbours = new Vector<Cell>();
		
		for(Cell neighbour : neighbours){
			if(!neighbour.isVisited()){
				unvisitedNeighbours.add(neighbour);
			}
		}
		return unvisitedNeighbours;
	}

	
	/**
	 * Gets all neighbors of a cell.
	 * @param currentCell The cell to get the neighbors.
	 * @return The cell's neighbors.
	 */
	private Vector<Cell> getAllCellNeighbours(Cell currentCell) {
		Vector<Cell> neighbours = new Vector<Cell>();
		
		int currentCellRow = currentCell.getRow();
		int currentCellColumn = currentCell.getColumn();
		
		if(currentCellRow < heigth-1){
			neighbours.add(maze[currentCellColumn][currentCellRow+1]);
		}
		if(currentCellRow != 0){
			neighbours.add(maze[currentCellColumn][currentCellRow-1]);
		}
		if(currentCellColumn < width-1){
			neighbours.add(maze[currentCellColumn+1][currentCellRow]);
		}
		if(currentCellColumn != 0){		
			neighbours.add(maze[currentCellColumn-1][currentCellRow]);
		}
		
		return neighbours;
	}
}