// Name: Jonathan Turner
// Class: CS 4306/01
// Term: Spring 2024
// Instructor: Dr. Haddad
// Assignment: 2
// IDE Name: IntelliJ
/*
Algorithm Design Block
    Algorithm title: Finding Substrings

    Logical steps:
        Step 1: Gather input for the text and store them in a string.
        Step 2: Create a counter that tracks how many substrings are in the text.
        Step 3: Iterate through a for loop (i) that goes from 1->n.
        Step 4: If the ith letter in the text is equal to A, then move to Step 5. Otherwise, continue loop.
        Step 5: Iterate through a for loop (j) which is inside loop (i) and goes from i+1->n.
        Step 6: If the jth letter in the text is equal to B, increment counter.
        Step 7: At the end of the loop (i), return the counter to show the number of substrings.

    Pseudocode Syntax:
        text <- input
        counter <- 0
        comps <- 0

        for i <- 1 to n
            if text[i] = A
                for j <- i+1 to n
                    if text[j] = B
                        counter + 1
                    comps + 1
            comps + 1

        return counter, comps

    Big-O Analysis: (Based on Implementation)
*/
package Assignments.A2;

import java.util.Scanner;

/**
 * Performs a brute force/exhaustive search for
 * how many substrings start with A and end with B.
 *
 * @author Jonathan Turner
 * @version Spring 2024
 */
public class Substrings {

    public static void main(String[] args) {
        Substrings program = new Substrings();
        program.start();
    }

    private String text;
    private int subStringCount;
    private int comparisons;

    /**
     * Used as the main sentential loop and loops until the exit option is selected.
     *
     * @precondition none
     * @postcondition none
     */
    public void start() {
        int option = this.getOption();
        while (option != 3) {
            this.executeOption(option);
            option = this.getOption();
        }
    }

    /**
     * Performs the action related to the option that was chosen.
     *
     * @precondition none
     * @postcondition the action was performed.
     *
     * @param option the option that was chosen.
     */
    private void executeOption(int option) {
        if (option == 1) {
            this.text = this.getString();
        } else {
            if (this.text == null) {
                System.out.println("Please specify a text to perform the algorithm.");
                return;
            }
            this.performAlgorithm();
            System.out.println("Input string:       " + this.text);
            System.out.println("# of substrings:    " + this.subStringCount);
            System.out.println("# of comparisons:   " + this.comparisons);
        }
        System.out.println();
    }

    /**
     * Uses private fields to generate the number of subsets and comparisons.
     *
     * @precondition text != null && text != empty
     * @postcondition the results are generated.
     */
    private void performAlgorithm() {
        this.subStringCount = 0;
        this.comparisons = 0;
        char[] values = this.text.toLowerCase().toCharArray();

        for (int i = 0; i < this.text.length(); i++) {
            if (values[i] == 'a') {
                for (int j = i+1; j < this.text.length(); j++) {
                    if (values[j] == 'b') {
                        subStringCount++;
                    }
                    comparisons++;
                }
            }
            comparisons++;
        }
    }

    /**
     * Prints out the menu of options, asks for an input, and if that input is invalid it prints an error and
     * prompts the user again for the input.
     *
     * @precondition none
     * @postcondition none
     *
     * @return the option selected
     */
    private int getOption() {
        this.displayMenu(); // Prints out the menu

        // Asks for the option and begins the loop until a valid option is gathered.
        System.out.print("Enter option number: ");
        int input = getIntegerInput();
        while (input < 1 || input > 3) { // Compares it to the valid options available.
            System.out.println("\nPlease enter a valid input.");
            System.out.print("Enter option number: ");
            input = getIntegerInput();
        }
        System.out.println();
        return input;
    }

    /**
     * Displays the menu options.
     *
     * @precondition none
     * @postcondition the menu is displayed.
     */
    private void displayMenu() {
        System.out.println("-----------------MAIN MENU--------------");
        System.out.println("1. Read input string");
        System.out.println("2. Run algorithm and display outputs");
        System.out.println("3. Exit program");
        System.out.println();
    }

    /**
     * Gets a string and returns it. If the input is not valid it loops until valid.
     *
     * @precondition none
     * @postcondition none
     * @return a user-input text string.
     */
    private String getString() {
        System.out.println("Specify a text to check number of substrings.");
        System.out.print("Text: ");
        Scanner sc = new Scanner(System.in);
        String input = sc.nextLine();

        while (input == null || input.isEmpty()) {
            System.out.println("Please specify a valid text to check substrings.");
            System.out.print("Text: ");
            input = sc.nextLine();
        }

        return input;
    }

    /**
     * Gets user input to a number. A prompt must be provided prior to running this method.
     * If the input was not an integer/(unable to be autoboxed), returns -1.
     *
     * @precondition none
     * @postcondition none
     *
     * @return the integer input, if invalid -1.
     */
    private int getIntegerInput() {
        Scanner sc = new Scanner(System.in);
        try {
            String textInput = sc.nextLine();
            return Integer.parseInt(textInput);
        } catch (Exception e) {
            return -1;
        }
    }
}