IT-PF02

package case1;

import java.io.*;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Scanner;
import java.text.DecimalFormat;

/**
 * A simple currency converter program that allows users to convert between USD
 * and PHP.
 * The program supports two roles: admin and user.
 * - Admin can set the exchange rate between USD and PHP.
 * - User can perform currency conversions and view the conversion history.
 */
public class Case1 {

    public static void main(String[] args) {
        // File paths for storing exchange rate and conversion history
        final String RATE_PATH = "rates.txt";
        final String HISTORY_PATH = "currency.txt";

        // Scanner for user input
        try (Scanner scanner = new Scanner(System.in)) {
            while (true) {
                // Display the main menu
                System.out.println("\n============= Currency Converter =======admin======");
                System.out.print("Are you an 'admin', 'user', or do you want to 'exit'?\n> ");
                String role = scanner.nextLine().trim().toLowerCase();

                // Exit the program if the user chooses "exit"
                if (role.equals("exit")) {
                    System.out.println("Exiting program. Goodbye!");
                    break;
                }

                // Handle operations based on the user's role
                switch (role) {
                    case "admin":
                        handleAdmin(scanner, RATE_PATH); // Admin functionality
                        break;
                    case "user":
                        handleUser(scanner, RATE_PATH, HISTORY_PATH); // User functionality
                        break;
                    default:
                        System.out.println("Invalid role. Please type 'admin', 'user', or 'exit'.");
                        break;
                }
            }
        }
    }

    /**
     * Handles admin functionality for setting a new exchange rate.
     * 
     * @param scanner   Scanner object for user input
     * @param RATE_PATH Path to the file where the exchange rate is stored
     */
    private static void handleAdmin(Scanner scanner, String RATE_PATH) {
        try {
            System.out.println("\n==============================================\n");
            System.out.print("Enter new Dollar to Peso rate: ");
            String input = scanner.nextLine();
            double newRate = Double.parseDouble(input); // Parse the new exchange rate

            // Validate the new rate
            if (newRate <= 0) {
                System.out.println("Invalid rate. Please enter a positive number.");
                return;
            }

            // Get the current date and time
            LocalDateTime now = LocalDateTime.now();
            DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
            String timestamp = now.format(formatter);

            // Save the new rate and timestamp to the file
            try (BufferedWriter rateWriter = new BufferedWriter(new FileWriter(RATE_PATH, true))) {
                rateWriter.write(newRate + "\n" + timestamp + "\n");
            }

            System.out.println("Rate updated to " + newRate + " on " + timestamp);
        } catch (NumberFormatException e) {
            System.out.println("Invalid numeric input. Please enter a valid number.");
        } catch (IOException e) {
            System.out.println("Error writing to rate file: " + e.getMessage());
        }
    }

    /**
     * Handles user functionality for converting USD to PHP or vice versa.
     * 
     * @param scanner      Scanner object for user input
     * @param RATE_PATH    Path to the file where the exchange rate is stored
     * @param HISTORY_PATH Path to the file where conversion history is stored
     */
    private static void handleUser(Scanner scanner, String RATE_PATH, String HISTORY_PATH) {
        File rateFile = new File(RATE_PATH);

        // Check if the rate file exists
        if (!rateFile.exists()) {
            System.out.println("Rate file not found. Ask admin to set the rate first.");
            return;
        }

        try {
            // Retrieve the exchange rate from the file
            double rate = getExchangeRate(RATE_PATH);
            String lastUpdated;

            // Read the last updated timestamp from the file
            try (BufferedReader rateReader = new BufferedReader(new FileReader(RATE_PATH))) {
                rateReader.readLine(); // Skip the rate line
                lastUpdated = rateReader.readLine();
            }

            if (lastUpdated == null) {
                System.out.println("Rate file is corrupted. Ask admin to reset the rate.");
                return;
            }

            // Display the current exchange rate and last updated timestamp
            System.out.println("\n==============================================\n");
            System.out.println("Last rate update: " + lastUpdated);
            System.out.println("Current rate: 1 USD = " + rate + " PHP\n");

            // Prompt the user to choose the input type (USD or PHP)
            System.out.print("Do you want to enter amount in 'USD' or 'PHP'? ");
            String choice = scanner.nextLine().trim().toLowerCase();

            double usd = 0, php = 0;
            DecimalFormat df = new DecimalFormat("#,##0.00");

            if (choice.equals("usd")) {
                // Prompt the user for the amount in USD
                System.out.print("Enter amount in USD: ");
                while (!scanner.hasNextDouble()) {
                    System.out.println("Invalid input. Please enter a valid number.");
                    scanner.next(); // Clear invalid input
                }
                usd = scanner.nextDouble();
                scanner.nextLine(); // Consume newline

                // Validate the amount
                if (usd <= 0) {
                    System.out.println("Invalid amount. Please enter a positive number.");
                    return;
                }

                php = usd * rate; // Convert USD to PHP
                System.out.printf("PHP %s = $%s%n", df.format(php), df.format(usd));
            } else if (choice.equals("php")) {
                // Prompt the user for the amount in PHP
                System.out.print("Enter amount in PHP: ");
                while (!scanner.hasNextDouble()) {
                    System.out.println("Invalid input. Please enter a valid number.");
                    scanner.next(); // Clear invalid input
                }
                php = scanner.nextDouble();
                scanner.nextLine(); // Consume newline

                // Validate the amount
                if (php <= 0) {
                    System.out.println("Invalid amount. Please enter a positive number.");
                    return;
                }

                usd = php / rate; // Convert PHP to USD
                System.out.printf("PHP %s = $%s%n", df.format(php), df.format(usd));
            } else {
                System.out.println("Invalid choice. Please restart and choose 'USD' or 'PHP'.");
                return;
            }

            // Save the conversion history to the file
            try (BufferedWriter historyWriter = new BufferedWriter(new FileWriter(HISTORY_PATH, true))) {
                String log = lastUpdated + " | $" + df.format(usd) + " = PHP " + df.format(php) + " @ rate: " + rate
                        + "\n";
                historyWriter.write(log);
            }

            System.out.println("\nConversion saved to currency.txt");

        } catch (NumberFormatException e) {
            System.out.println("Rate file contains invalid data. Ask admin to reset the rate.");
        } catch (IOException e) {
            System.out.println(
                    "Error: Unable to read the rate file. Please ensure the file exists and is not corrupted.");
        }
    }

    /**
     * Retrieves the exchange rate from the specified file.
     * 
     * @param ratePath Path to the file where the exchange rate is stored
     * @return The exchange rate as a double
     * @throws IOException           If an error occurs while reading the file
     * @throws NumberFormatException If the file contains invalid data
     */
    private static double getExchangeRate(String ratePath) throws IOException, NumberFormatException {
        try (BufferedReader rateReader = new BufferedReader(new FileReader(ratePath))) {
            return Double.parseDouble(rateReader.readLine());
        }
    }
}