package Advent2018;

import util.AdventOfCode;
import util.Direction;
import util.Node;

import java.util.*;

public class Day13 extends AdventOfCode {

    static final int GRID_SIZE = 150;
    static final String CART_DIR = "^>v<";

    String[][] grid;
    List<Cart> carts;
    String first = "";
    String lastCart = "";


    enum Turn {
        LEFT, STRAIGHT, RIGHT
    }

    class Cart {
        int num;
        Node position;
        Direction dir;
        Turn last = Turn.RIGHT;
        boolean collided;
        int getY() { return position.getY(); }
        int getX() { return position.getX(); }

        void move() {

            position = dir.move(position);
            for (Cart each :carts) {
                if (!each.equals(this)) {
                    if (!each.collided) {
                        if (each.position.equals(this.position)) {
                            if (first.length() == 0) first = getX() + "," + getY();
                            System.out.println("Collision at " + getX() + "," + getY());
                            System.out.println("Between " + this.num + " and " + each.num);
                            this.collided = true;
                            each.collided = true;
                            return;
                        }
                    }

                }
            }

            String next = grid[position.getY()][position.getX()];
            switch (next) {
                case "/":
                    switch (dir) {
                        case NORTH:
                        case SOUTH:
                            dir = dir.getRight();
                            break;
                        case EAST:
                        case WEST:
                            dir = dir.getLeft();
                            break;
                    }
                    break;
                case "\\":
                    switch (dir) {
                        case NORTH:
                        case SOUTH:
                            dir = dir.getLeft();
                            break;
                        case EAST:
                        case WEST:
                            dir = dir.getRight();
                            break;
                    }
                    break;
                case "+":
                    switch (last) {
                        case RIGHT:
                            last = Turn.LEFT;
                            dir = dir.getLeft();
                            break;
                        case STRAIGHT:
                            last = Turn.RIGHT;
                            dir = dir.getRight();
                            break;
                        case LEFT:
                            last = Turn.STRAIGHT;
                            break;
                    }
            }
        }
    }

    public Day13(List<String> input) {
        super(input);
    }


    @Override
    public Object part1() {

        int count = carts.size();

        while (count > 1) {
            carts.sort(Comparator.comparing(Cart::getY).thenComparing(Cart::getX));
            count = (int) carts.stream().filter(x -> !x.collided).count();
            for (Cart each : carts) {
                if (!each.collided) each.move();
            }
        }
        Cart last = carts.stream().filter(x -> !x.collided).findFirst().get();
        lastCart = last.position.getX() + "," + last.position.getY();

        return first;
    }

    @Override
    public Object part2() {
        return lastCart;
    }

    @Override
    public void parse() {

        carts = new ArrayList<>();
        grid = new String[GRID_SIZE][GRID_SIZE];
        int count = 0;
        for (int i = 0; i < input.size(); i++) {
            String line = input.get(i);
            for (int j = 0; j < line.length(); j++) {
                String cell = Character.toString(line.charAt(j));
                grid [i][j] = cell;
                if (CART_DIR.contains(cell)) {
                    Cart c = new Cart();
                    c.num = count++;
                    c.position = new Node(j, i);
                    c.dir = Direction.getByNum(CART_DIR.indexOf(cell));
                    carts.add(c);
                }
            }
        }

    }

}