CustomerRating

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

public class CustomerRating {

    private static final String FILE_NAME = "rating.txt";
    /**
     * Small size on purpose to trigger ArrayIndexOutOfBoundsException when
     * full.
     */
    private static final int MAX_SIZE = 5;

    private static final Customer[] records = new Customer[MAX_SIZE];
    private static int count = 0;

    /**
     * Main intentionally declares 'throws IOException' to follow the spec.
     */
    public static void main(String[] args) throws IOException {
        // 1) Read data file (must exist or the program terminates with an IOException)
        loadFromFile(FILE_NAME);

        // Display what we have after loading
        printListHeader();
        printListBody();
        System.out.println();

        // 2) Input loop
        try (Scanner sc = new Scanner(System.in)) {
            while (true) {
                System.out.print(
                        "Enter age[integer], followed by <TAB> key, then rating[decimal number] "
                        + "(or type \"!\" to exit): "
                );
                String line = sc.nextLine().trim();
                if (line.equals("!")) {
                    break;
                }

                // Must be exactly two fields separated by a TAB
                String[] parts = line.split("\\t");
                if (parts.length != 2) {
                    System.out.println("Invalid input format. Please enter: age<TAB>rating");
                    continue;
                }

                try {
                    int age = Integer.parseInt(parts[0].trim());
                    double rating = Double.parseDouble(parts[1].trim());

                    // Intentionally rely on real array bounds to raise the exception
                    // so we can catch it and show the required message.
                    try {
                        records[count] = new Customer(age, rating);
                        count++; // increment only if the write succeeded
                        System.out.printf("Customer added: Age=%d  Rating=%.2f%n", age, rating);
                    } catch (ArrayIndexOutOfBoundsException ex) {
                        System.out.println("Array out of bound... New record will not be recorded.");
                    }
                } catch (NumberFormatException nfe) {
                    System.out.println("Invalid number... Record skipped.");
                }
            }
        }

        // 3) Before exit: show the most updated list and averages
        System.out.println();
        printListHeader();
        printListBody();
        System.out.println();
        printAverages();

        // 4) Save back to file (if this throws, program terminates automatically per spec)
        saveToFile(FILE_NAME);
    }

    /**
     * Read all existing records from the data file.
     */
    private static void loadFromFile(String fileName) throws IOException {
        try (BufferedReader br = new BufferedReader(new FileReader(fileName))) {
            String line;
            while ((line = br.readLine()) != null) {
                // Each line: age<TAB>rating
                String[] parts = line.split("\\t");
                if (parts.length != 2) {
                    continue; // skip malformed lines silently

                }
                int age = Integer.parseInt(parts[0].trim());
                double rating = Double.parseDouble(parts[1].trim());

                // If file has more than MAX_SIZE, extra lines will trigger the exception
                // and be ignored with a message, while the program continues.
                try {
                    records[count] = new Customer(age, rating);
                    count++;
                } catch (ArrayIndexOutOfBoundsException ex) {
                    System.out.println("Array out of bound while loading file... Extra file records skipped.");
                    break; // no more room; stop loading
                }
            }
        }
    }

    /**
     * Write all (non-average) records back to the file.
     */
    private static void saveToFile(String fileName) throws IOException {
        try (PrintWriter pw = new PrintWriter(new FileWriter(fileName))) {
            for (int i = 0; i < count; i++) {
                pw.println(records[i].getAge() + "\t" + String.format("%.2f", records[i].getRating()));
            }
        }
    }

    private static void printListHeader() {
        System.out.println("Most updated list of customer ratings");
        System.out.println("-------------------------------------");
        System.out.printf("%-10s %-10s%n", "Age", "Rating");
    }

    private static void printListBody() {
        for (int i = 0; i < count; i++) {
            System.out.println(records[i]);
        }
    }

    private static void printAverages() {
        double sumAge = 0.0, sumRating = 0.0;
        for (int i = 0; i < count; i++) {
            sumAge += records[i].getAge();
            sumRating += records[i].getRating();
        }
        double avgAge = (count == 0) ? 0.0 : sumAge / count;
        double avgRating = (count == 0) ? 0.0 : sumRating / count;

        System.out.printf("Average(Age)=%.2f%n", avgAge);
        System.out.printf("Average(Rating)=%.2f%n", avgRating);
        System.out.println();
    }
}