package am.aua.npuzzle;

import java.util.LinkedHashSet;
import java.util.Set;

import am.aua.search.Action;
import am.aua.search.State;

public class Tiles implements State {
	public static final int EMPTY_TILE = 0;
	
	protected final int width;
	protected final int[] tiles;
	protected final int emptyTileRow;
	protected final int emptyTileColumn;

	private StringBuilder stringBuilder = new StringBuilder();
	
	public Tiles(int[][] tiles) {
		width = tiles.length;
		this.tiles = new int[width * width];
		int emptyRow = -1;
		int emptyColumn = -1;
		int index=0;
		for (int row = 0; row < width; row++)
			for (int column = 0; column < width; column++) {
				int tile = tiles[row][column];
				if (tile == EMPTY_TILE) {
					emptyRow = row;
					emptyColumn = column;
				}
				this.tiles[index++] = tile;
			}
		emptyTileRow = emptyRow;
		emptyTileColumn = emptyColumn;
	}
	protected Tiles(int width, int[] tiles, int emptyTileRow, int emptyTileColumn) {
		this.width = width;
		this.tiles = tiles;
		this.emptyTileRow = emptyTileRow;
		this.emptyTileColumn = emptyTileColumn;
	}
	public int getWidth() {
		return width;
	}
	public int getEmptyTileRow() {
		return emptyTileRow;
	}
	public int getEmptyTileColumn() {
		return emptyTileColumn;
	}
	public int getTile(int row, int column) {
		return tiles[row * width + column];
	}
	public Set<Action> getApplicableActions() {
		Set<Action> actions = new LinkedHashSet<Action>();
		for (Movement movement : Movement.values()) {
			int newEmptyTileRow = emptyTileRow + movement.deltaRow;
			int newEmptyTileColumn = emptyTileColumn + movement.deltaColumn;
			if (0 <= newEmptyTileRow && newEmptyTileRow < width &&
			    0 <= newEmptyTileColumn && newEmptyTileColumn < width)
				actions.add(movement);
		}
		return actions;
	}
	public State getActionResult(Action action) {
		Movement movement=(Movement)action;
		int newEmptyTileRow = emptyTileRow + movement.deltaRow;
		int newEmptyTileColumn = emptyTileColumn + movement.deltaColumn;
		int[] newTiles = tiles.clone();
		newTiles[emptyTileRow * width + emptyTileColumn] = getTile(newEmptyTileRow, newEmptyTileColumn);
		newTiles[newEmptyTileRow * width + newEmptyTileColumn] = EMPTY_TILE;
		return new Tiles(width, newTiles, newEmptyTileRow, newEmptyTileColumn);
	}

	@Override
	public int hashCode() {
		stringBuilder.setLength(0);
		for (int row = 0; row < width; row++) {
			for (int col = 0; col < width; col++) {
				stringBuilder.append(getTile(row, col));
			}
		}
		return stringBuilder.toString().hashCode();
	}

	@Override
	public boolean equals(Object that) {
		if (!(that instanceof Tiles)) {
			return false;
		}

		Tiles otherState = (Tiles) that;
		for (int i = 0; i < width * width; i++) {
			if (tiles[i] != otherState.tiles[i]) {
				return false;
			}
		}
		return true;
	}
}