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 int div(int number) {
        int sum = 0;
        for (int i = 1; i < number; i++) sum += (number % i) == 0 ? i : 0;
        return sum;
    }

    public static int [] FindFriendshipNumbers(int Range) {
        int[] array = new int[Range];
        int a = 0;
        int[] Result = new int[a];
        for (int i = 1; i < Range + 1; i++) {
            int div = div(i);
            if (div < Range + 1 && array[div] == i)
            Result[a] = div;
            a = a + 1;
            Result[a] = i;
            array[i] = div;
        }
        return Result;
    }


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

    public static int InputFile() {
        boolean isInvalidInput;
        int number = 0;
        do {
            isInvalidInput = false;
            try {
                BufferedReader input = new BufferedReader(new FileReader("C:\\Users\\Eugene\\Desktop\\java\\Input.txt"));
                String text;
                while ((text = input.readLine()) != null) {
                    number = Integer.parseInt(text);
                }
                if (number < 2) {
                    System.out.println("Ошибка! Число, находящееся в файле, не является натуральным. Пожалуйста, проверьте файл и повторите попытку.");
                    isInvalidInput = true;
                }
                input.close();
            } catch (FileNotFoundException e) {
                System.out.println(" l");
                isInvalidInput = true;
            } catch (IOException e) {
                System.out.println(" 2");
                isInvalidInput = true;
            } catch (NumberFormatException e) {
                System.out.println("Ошибка! Файл содержит неверные данные. Пожалуйста, проверьте файл и повторите попытку.");
                isInvalidInput = true;
            }
        } while (isInvalidInput);
        return number;
    }

    public static char GetUserChoice() {
        System.out.println("Do you want to read fromm file?[Y/N]");
        Scanner sc = new Scanner(System.in);
        char Choice = sc.next().charAt(0);
        return Choice;
    }

    public static void main(String[] args) throws IOException {
        char Answer;
        int Range = 0;
        int [] Result = new int[0];
        System.out.println("This program finds pairs of friendly numbers.");
        Answer = GetUserChoice();
        if (Answer == 'Y') {
            Range = InputFile();
            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 !");
            Range = IsCorrectInput(Range, 2, 10000);
        }
        Result = FindFriendshipNumbers(Range);
        OutputConsole(Result);
        OutputFile(Result);
    }
}