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

/**
 * Grouping symbols checking program / Homework 2
 *
 * @author Jose Ed. Dieck
 * @version 1/30/2015
 *
 */
public class Homework2 {

    private Homework2() {
    }

    /**
     * First spot on args data
     */
    public static final int FILEPATH = 0;

    /**
     * Default value for an empty args length
     */
    public static final int EMPTY_ARGS = 0;

    /**
     * Default count start variable
     */
    public static final int COUNT_START = 0;

    /**
     * String variable containing opening grouping symbols for comparison
     */
    public static final String OPENING = "({[";

    /**
     * String variable containing closing grouping symbols for comparison
     */
    public static final String CLOSING = ")}]";

    /**
     * Main method for the program, taking in a file path as argument
     *
     * @param args
     *            filepath for the file to be checked
     * @throws FileNotFoundException
     *             exception thrown if the file could not be found
     */
    public static void main(String[] args) throws FileNotFoundException {

        if (args.length == EMPTY_ARGS) {
            System.out.println("Usage: java Homework2 (file path)");
            return;
        }

        File toRead = new File(args[FILEPATH]);
        boolean checked = checkBraces(toRead);

        if (checked) {
            System.out.println("The file is valid.");
        } else {
            System.out.println("The file is not valid.");
        }

    }

    public static boolean checkBraces(File file) throws FileNotFoundException {

        Scanner read = new Scanner(file);
        Stack<String> openChar = new Stack<String>();
        String line = "";
        String toCheck = "";

        while (read.hasNextLine()) {

            line = read.nextLine();

            for (int i = COUNT_START; i < line.length(); i++) {
                toCheck = Character.toString(line.charAt(i));
                if (OPENING.contains(toCheck)) {
                    openChar.push(toCheck);
                } else if (CLOSING.contains(toCheck)) {
                    if (openChar.isEmpty()) {
                        read.close();
                        return false;
                    } else if (toCheck.equals(")")) {
                        if (openChar.peek().equals("(")) {
                            openChar.pop();
                        } else {
                            read.close();
                            return false;
                        }

                    } else if (toCheck.equals("}")) {
                        if (openChar.peek().equals("{")) {
                            openChar.pop();
                        } else {
                            read.close();
                            return false;
                        }
                    } else {
                        if (openChar.peek().equals("[")) {
                            openChar.pop();
                        } else {
                            read.close();
                            return false;
                        }
                    }
                }
            }
        }

        read.close();
        return true;
    }
}