package edu.wit.cs.comp1050;

import java.util.ArrayList;

public class Shifter {

	/**
	 * Number of letters in the English alphabet
	 */
	public static final int NUM_LETTERS = ('z' - 'a') + 1;

	private String s;

	/**
	 * Initializes the shifter
	 *
	 * @param s encrypted string
	 */
	public Shifter(String s) {
		this.s = s;
	}

	/**
	 * Returns the result of shifting by a supplied amount
	 *
	 * @param n number of places to shift
	 * @return shifted string
	 */
	public String shift(int n) {

		StringBuilder newString = new StringBuilder();

		char[] letters = s.toCharArray();

		if (s.isEmpty()) {
			return "";
		}

		else if (s == " ") {
			return " ";
		}

		if (n > 26 || n < -26) {
			n = n % 26;
		}

		for (int i = 0; i < letters.length; i++) {
			if (letters[i] >= 'a' && letters[i] <= 'z') {

				if (letters[i] + n < 'a') {
					letters[i] = (char) ((letters[i] + n) + 26);
				} else if (letters[i] + n > 'z') {
					letters[i] = (char) ((letters[i] + n) - 26);
				}

				else {
					letters[i] = (char) (letters[i] + n);
				}

			}

			if (letters[i] >= 'A' && letters[i] <= 'Z') {
				if (letters[i] + n < 'A') {
					letters[i] = (char) ((letters[i] + n) + 26);
				} else if (letters[i] + n > 'Z') {
					letters[i] = (char) ((letters[i] + n) - 26);
				} else {
					letters[i] = ((char) (letters[i] + n));
				}
			}
		}
		for (int i = 0; i < letters.length; i++) {
			newString.append(letters[i]);
		}
		return newString.toString();
	}

	/**
	 * Finds all shifts that contain the supplied substring
	 *
	 * @param sub substring to find
	 * @return array of shifts (0-25) that contain the substring (in order)
	 */
	public int[] findShift(String sub) {

		String method;
		ArrayList<Integer> shifts = new ArrayList<>();

		int count = 0;
		for (int i = 0; i <= 25; i++) {

			method = shift(count);

			if (method.contains(sub)) {

				shifts.add(i);

			}
			count++;
		}

		int[] numShifts = new int[shifts.size()];

		for (int i = 0; i < numShifts.length; i++) {

			numShifts[i] = shifts.get(i);

		}
		return numShifts;
	}

}