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package com.Laba2_3;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;

public class Main {
    public static Scanner in = new Scanner(System.in);

    static double[][] inputArrFromFile() {
        boolean isInvalidInput;
        double[][] matrice = new double[0][0];

        do {
            isInvalidInput = false;
            System.out.println("Enter the path to the file, for example 'C:\\Users\\Think\\Desktop\\Input.txt' ");
            String fileName = in.nextLine();
            try {
                BufferedReader input = new BufferedReader(new FileReader(fileName));
                String text = input.readLine();
                int number = Integer.parseInt(text);
                matrice = new double[number + 1][number + 1];
                for (int i = 0; i < number; i++) {
                    text = input.readLine();
                    String[] arrFilling = text.split(" ");
                    for (int j = 0; j < number + 1; j++) {
                        matrice[i][j] = Double.parseDouble(arrFilling[j]);
                    }
                }
                for (int i = 0; i < number; i++) {
                    for (int j = 0; j < number + 1; j++) {
                        System.out.printf(" " + matrice[i][j]);
                    }
                    System.out.println();
                }
                input.close();
            } catch (FileNotFoundException e) {
                System.out.println("A file with the same name was not found, try again");
                isInvalidInput = true;
            } catch (IOException e) {
                System.out.println("This file cannot be opened, try again");
            } catch (NumberFormatException e) {
                System.out.println("Error! The file contains invalid data. Please check the file and ad text.");
                isInvalidInput = true;
            }
        } while (isInvalidInput);
        return matrice;
    }

    static double[][] gauss(double matrice[][], int length) {
        for (int i = 0; i < length + 1; i++) {
            matrice[1][i] = (matrice[0][i] * 1.5) + matrice[1][i];
            matrice[2][i] = (matrice[0][i] + matrice[2][i]);
            matrice[2][i] = (matrice[2][i] - matrice[1][i] * 4);
            matrice[1][i] = matrice[1][i] * 2;
        }
        return matrice;
    }

    static void output(double[][] matrice, int length) {
        System.out.println("The result is");
        for (int i = 0; i < length - 1; i++) {
            for (int j = 0; j < length; j++) {
                System.out.print(" " + matrice[i][j]);
            }
            System.out.println();

        }
    }

    public static void saveToFile(double[][] matrice, int length) {
        System.out.println("Enter the path to the output file, for example 'C:\\Users\\Think\\Desktop\\Output.txt' ");
        String fileName = in.nextLine();
        try (FileWriter writer = new FileWriter(fileName, false)) {
            writer.write("The result is ");
            int i, j;
            for (i = 0; i < length - 1; i++) {
                writer.append("\n");
                for (j = 0; j < length; j++) {
                    String str = Double.toString(matrice[i][j]);
                    writer.write(" " + str);
                }
            }
        } catch (IOException e) {
            System.out.println("File couldn`t be opened");
        }
    }


    public static void main(String[] args) {
        System.out.println("This program performs a direct move by the Gauss method for a system of linear equations");
        double[][] arrA = inputArrFromFile();
        double[][] arrB = gauss(arrA, arrA.length - 1);
        saveToFile(arrB, arrB.length);
        output(arrB, arrB.length);
    }
}