Database.java

import com.mashape.unirest.http.exceptions.UnirestException; // UnirestException may be thrown while trying to update
// Movie Database
import java.io.*;
import java.util.ArrayList;
/*
 *   This class stores all of the data needed for the application to run, namely:
 *          * the movies now showing (present in the local movie database)
 *          * the languages available (English and Hindi only)
 *          * the seats which are already booked ( present in the local seats database)
 *          * the receipt for the tickets booked by the current user (initialized after booking is finalized)
 *  It has methods for loading the data from the local database into memory
 *  and method for updating the local database from online database
 */
class Database{
	private String[] movies, lang,seats; // The data from the database
	private File movies_f, seats_f;  // The local files of the database
	private static String[] receipt; // Receipt data
	static boolean update = true; // Whether to update the local database or not
	/*
	 *   Constructor :
	 *       Parameters: none
	 *       Description: It runs when a Database object is initialized, it performs initial loading tasks.
	 */
	Database() throws IOException {
		// if there is internet connection,
		// then update the local movie database from the internet
		try {
			if(!update) throw new AssertionError(); 
			updateMovies(); // May throw Unirest Exception if unable to connect to internet
		}
		catch (FileNotFoundException fe){ // If no internet, then don't update
			System.out.println("APIKEY file not found,\nUsing Local Database");
		}
		catch (UnirestException ue){ // If no internet, then don't update
			System.out.println("Couldn't Update Database,\nUsing Local Database");
		}
		catch (AssertionError ae){ // If mentioned to run locally, then run locally
			System.out.println("Executing locally");
		}
		receipt = new String[7];    // initializing the receipt array with 7 fields
		// (movie, language, date, time, Username, seats, price)
		loadMovies();               // loading the movies local database into memory
		loadSeats();                // loading the seats local database into memory
		lang = new String[]{"English","Hindi"}; // initializing language database
	}
	/*
	 *   Method: updateMovies()
	 *   Parameters: none
	 *   Returns: void
	 *   Description: This method tries to update the local movies database by calling the getMovies() method from
	 *               class GetMoviesOnline. It creates a new movies.txt file and stores the fetched results in the file
	 */
	private void updateMovies() throws UnirestException , IOException , FileNotFoundException{
		System.out.println("Updating Local Database");
		movies = GetMoviesOnline.getMovies();   // try to fetch latest movies from internet and store it in a variable
		// may throw Unirest exception if unable to connect to API
		movies_f = new File("data/movies.txt");
		if(movies_f.exists()){    // If movie file already exists, delete it, as updated version of file will be created
			if(!movies_f.delete()) throw new IOException("Local Database could not be deleted");// If unable to delete
		}
		// Create a new file to store data
		if(!movies_f.createNewFile()) throw new IOException("Local Database could not be created");//If unable to create
		RandomAccessFile raf = new RandomAccessFile(movies_f,"rw");
		for(String movie:movies){
			raf.writeBytes(movie+"\n"); // Write each movie in database in a new line
		}
	}
	/*
	 *   Method: loadMovies()
	 *   Parameters: none
	 *   Returns: void
	 *   Description: This method tries to load the local movies database and store its value in memory.
	 */
	private void loadMovies() throws IOException{
		movies_f = new File("data/movies.txt");
		if(!movies_f.exists()){ // If database doesn't exist, terminate
			System.err.println("Movie File Does Not Exist");
			System.exit(1);
		}
		else{
			System.out.println("Movie File Exist at : "+ movies_f.getAbsolutePath());
		}
		int k=0;
		movies = new String[countLines(movies_f.getAbsolutePath())]; // create local variable to store data of file
		// (size of local array = no. of lines in data)
		RandomAccessFile raf = new RandomAccessFile(movies_f,"r");
		while(raf.getFilePointer()!= raf.length()){
			movies[k++] = raf.readLine(); // store each line present in database in array
		}
		System.out.println("Movie Database loaded!");
	}
	/*
	 *   Method: loadSeats()
	 *   Parameters: none
	 *   Returns: void
	 *   Description: This method tries to load the local seats database and store its value in memory.
	 */
	private void loadSeats()  throws IOException {

		seats_f = new File("data/seats.txt");
		if(!seats_f.exists()){ // If database file doesn't exist, create it.
			System.err.println("Seats File Does Not Exist, Creating.");
			if(seats_f.createNewFile()) System.out.println("Seats File Created at : "+ seats_f.getAbsolutePath());
			else{
				System.err.print("Could not create seats file.");   // If cannot make file, exit.
			}
		}
		else{
			System.out.println("Seats File Exist at : "+ seats_f.getAbsolutePath());
		}
		int k=0;
		seats = new String[countLines(seats_f.getAbsolutePath())];  // create local variable to store data of file
		// (size of local array = no. of lines in data)
		RandomAccessFile raf = new RandomAccessFile(seats_f,"r");
		while(raf.getFilePointer()!= raf.length()){
			seats[k++] = raf.readLine(); // store each line present in database in array
		}
		System.out.println("Seats Database Loaded!");
	}
	/*
	 *   Method: countLines()
	 *   Parameters: String filename - the file name of the document
	 *   Returns: int - the number of lines in the document
	 *   Description: This counts the number of lines in a given document (by counting the number of '\n' characters
	 *               present in it.
	 */
	static int countLines(String filename) throws IOException {
		try (InputStream is = new BufferedInputStream(new FileInputStream(filename))) { // tries to access given file
			byte[] c = new byte[1024];  // local buffer of 1KB
			int count = 0;
			int readChars;
			boolean endsWithoutNewLine = false;
			while ((readChars = is.read(c)) != -1) {  // while EOF is not encountered
				for (int i = 0; i < readChars; ++i) {//read the characters stored in buffer
					if (c[i] == '\n') // if '/n' is present, increase counter
						++count;
				}
				endsWithoutNewLine = (c[readChars - 1] != '\n'); // Stores weather the last character of current buffer
				// was a newline or not.
			}
			if (endsWithoutNewLine) { // if the last character of the file wasn't a newline, then increase counter by 1
				++count;
			}
			return count;
		}
	}
	String[] getLang() {
		return lang;
	}
	String[] getMovies(){
		return movies;
	}
	String[] getSeats() {
		return seats;
	}
	public static String[] getReceipt() {
		return receipt;
	}
	/*
	 *   Method: setSeats()
	 *   Parameters: none
	 *   Returns: void
	 *   Description: This methods stores the current user's booking details in the database and in the receipt variable
	 */
	void setSeats(String movie, String lang, String date, String time, String name , ArrayList<String> seats)
			throws IOException  {
			/*  Store the data in receipt variable    */
			receipt[0] = movie;
			receipt[1] = lang;
			receipt[2] = date;
			receipt[3] = time;
			receipt[4] = name;
			receipt[5] = "";
			receipt[6] = "0";   // set price initially to 0
			if(name.equals("")){        // If no name is entered, store it as anonymous.
				name = "<Anonymous>";
			}
			if(!seats_f.exists()){  // If seats database doesn't exist, terminate
				System.err.println("Seat File Does Not Exist");
				System.exit(1);
			}
			RandomAccessFile raf = new RandomAccessFile(seats_f,"rw");
			raf.seek(raf.length());     // Append to the end of the file
			raf.writeBytes(movie+"\t"+lang+"\t"+date+"\t"+time+"\t"+name);  // Deliminate tokens using tabs in database
			for(String seat:seats){
				receipt[5] += seat+" ";     // Store seats in receipt
				receipt[6] = Integer.parseInt(receipt[6]) + price(seat) + "";    // Calculate price of seats and store in receipt
				raf.writeBytes("\t"+seat);  // Store seats in database
			}
			receipt[5] = receipt[5].trim();
			receipt[6] = "Rs. " + receipt[6];
			raf.writeBytes("\n");
			raf.close();
	}
	/*
	 *   Method: price()
	 *   Parameters: String seat - the seat code whose price is to be evaluated
	 *   Returns: int - the price of booking the seat
	 *   Description: Calculates the price of booking a particular seat and returns it
	 */
	static int price(String seat){
		int row = seat.charAt(0) - 65 ; // get the row number of the seat
		int d = row/2;                  // divide the rows in three categories, front, middle, and back, having
		d+=1;                           // different prices.
		return d*120;
	}
}