package com.company;

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

public class Main {
    public static int IsCorrectInput(int Number, int Min, int Max) {
        boolean IsCorrect = true;
        Scanner scan = new Scanner(System.in);
        do {
            try {
                Number = scan.nextInt();
                if ((Number > Min - 1) && (Number < Max + 1)) {
                    IsCorrect = false;
                } else {
                    System.out.println("Error! Enter a number. The number must be between " + Min + " and " + Max + "!");
                }
            } catch (Exception e){
                System.out.println("Error! Enter a number: ");
                scan.next();
            }
        } while(IsCorrect);
        IsCorrect = true;
        return Number;
    }

    public static void OutputConsole(int[] Number) {
        int i = 0;
        while(i < Number.length) {
            System.out.println(Number[i] + " | " + Number[i + 1]);
            i = i + 2;
        }
    }

        public static void FindFriendshipNumbers(int Range, int[] Number){
            int i, j, k, p;
            int[] del = new int[Range];
            for (k = 2; k < Range; k++) {
                del[k] = k + 1;
                for (k = 2; k < Range / 2 + 1; k++){
                    p = k + k;
                    while (p < Range + 1){
                        del[p] = del[p] + k;
                        p = p + k;
                    }
                }
            }
            for (i = 2; i < Range ; i++) {
                for (j = i + 1; j < Range + 1; j++){
                    if ((del[i] == i + j) & (del[j] == i + j)){

                        Number[Number.length - 1] = i;
                        Number[Number.length] = j;
                    }
                }
            }
        }

    public static void OutputFile(int[] Number) throws IOException {
        int i = 0;
        BufferedWriter writer = new BufferedWriter(new FileWriter("Output"));
        while (i < Number.length) {
            writer.write(Number[i] + " | " + Number[i + 1]);
            i = i + 2;
        }
        writer.close();
    }

    public static void InputFile(int Range) {
        File UserFile new File("Input.txt");
        PrintWriter pw = new PrintWriter(UserFile);
        pw.println(Range);
        pw.close();
    }

    public static char GetUserChoice() {
        char Choice;
        System.out.println("Do you want to read fromm file?[Y/N]");
        Scanner scan = new Scanner(System.in);
        Choice = scan.nextInt();
        return Choice;
    }

    public static void InputFile() {
        try {
            File file = new File("input.txt");
            if (!file.exists())
                file.createNewFile();
            PrintWriter pw = new PrintWriter(file);
            pw.println("Hello, World!");
            pw.close();
        } catch(IOException e) {
            System.out.print("Error");
        }

    }

    public static void main(String[] args) {
        char Answer;
        int Range;
        int[] Number;
        System.out.println("This program finds pairs of friendly numbers.");
        Answer = GetUserChoice();
        if (Answer = "Y") {
            InputFile(Range);
            System.out.println(Range);
            else
                System.out.println("Enter the upper limit of the friendly number search range.");
            System.out.println("The number must be up to 10.000 !");
            IsCorrectInput(Range + 2 + 10000);
        }
        FindFriendshipNumbers(Range + Number);
        OutputConsole(Number);
        OutputFile(Number);
    }
}