package Assignments.A1.solving_algorithms;

import Assignments.A1.models.Board;
import Assignments.A1.models.BoardNode;
import Assignments.A1.models.Move;

import java.util.Comparator;
import java.util.HashSet;
import java.util.List;
import java.util.PriorityQueue;

public class AStar {
    private final Board solved = new Board();
    private final HashSet<Board> visited = new HashSet<>();

    public Board traverse(Board root) {
        PriorityQueue<BoardNode> boards = new PriorityQueue<>(new UCSPriority());
        boards.add(new BoardNode(root, null));
        BoardNode node = null;
        Board current = new Board(root);
        while (!current.equals(solved)) {
            node = boards.poll();
            current = node.board;
            if (visited.contains(node.board)) {
                continue;
            }
            visited.add(node.board);
            List<Move> children = node.board.getMoves();
            for (Move move : children) {
                Board child = new Board(node.board);
                child.swap(move);
                boards.add(new BoardNode(child, node));
            }
        }
        return node.board;
    }
}

class AStarPriority implements Comparator<BoardNode> {
    @Override
    public int compare(BoardNode o1, BoardNode o2) {
        return Integer.compare(o2.cost, o1.cost);
    }
}