// Helene Martin, CSE 143
// Solves a maze using recursive backtracking.

import java.io.*;
import java.util.*;

public class SolveMaze {
   public static void main(String[] args) throws FileNotFoundException {
      String fileText = "";
      Scanner input = new Scanner(new File("maze1.txt"));
      while (input.hasNextLine()) {
         fileText += input.nextLine() + "\n";
      }

      Maze maze = new Maze(fileText);
      maze.setAnimated(true);
      System.out.println(maze);
      System.out.println();

      int startRow = 1;
      int startCol = 6;
      System.out.println("Start from (" + startRow + ", " + startCol + ")");
      solve(maze, startRow, startCol);
   }

   // Finds a pathway out of the given maze from the given start location.
   // Pre: maze != null and startRow/Col are within the maze
   public static void solve(Maze maze, int startRow, int startCol) {
      explore(maze, startRow, startCol);
   }

   // choices: up, down, left, right
   // changing row/col
   // stop:
   // - a wall
   // - already explored
   // - I won!
   private static boolean explore(Maze maze, int row, int col) {
      System.out.println(maze); // for animation

      if (maze.isEscaped()) {
         return true;
      } else if (maze.isWall(row, col) || maze.isExplored(row, col)) {
         return false;
      } else {
         maze.setExplored(row, col);

         if (explore(maze, row - 1, col) || explore(maze, row + 1, col)
               || explore(maze, row, col - 1) || explore(maze, row, col + 1)) {
            maze.mark(row, col);
            System.out.println(maze);
            return true;
         }
         return false;
      }
   }
}