import java.io.FileReader;
import java.io.BufferedReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;
import javax.swing.JFileChooser;

public class Message {
    // Displays a dialog box for selecting a file, returning a ByteScanner
    // corresponding to the selected file. Canceling the dialog terminates
    // the program.
    public static BufferedReader promptUser(String prompt) {
        JFileChooser chooser = new JFileChooser();
        chooser.setDialogTitle(prompt);
        int result = chooser.showDialog(null, prompt);
        if(result != JFileChooser.APPROVE_OPTION) { // dialog canceled
            System.err.println("File selection canceled; program complete");
            System.exit(0);
            return null; // should never happen
        }
        try {
            return new BufferedReader(new FileReader(chooser.getSelectedFile()));
        } catch(IOException e) {
            System.err.println("Error opening file; program complete");
            System.exit(0);
            return null; // should never happen
        }
    }

    // Reads the next message from the indicated source, returning a
    // Message object encapsulating its important information.
    // If the end of file has been reached, the method returns null.
    public static Message readNext(BufferedReader in) {
        try {
            List<String> words = new ArrayList<String>();
            while(true) {
                String line = in.readLine();
                if(line == null) return null;

                Scanner sc = new Scanner(line);
                if(line.startsWith("ID:")) {
                    sc.next(); // skip past "ID:"
                    int id = sc.nextInt();
                    boolean isSpam = sc.next().equals("spam");
                    return new Message(id, words, isSpam);
                } else {
                    while(sc.hasNext()) {
                        words.add(sc.next());
                    }
                }
            }
        } catch(IOException e) {
            return null;
        }
    }

    private int id;
    private List<String> words;
    private boolean isSpam;

    // Constructs a Message including the indicated information
    private Message(int id, List<String> words, boolean isSpam) {
        this.id = id;
        this.words = Collections.unmodifiableList(words);
        this.isSpam = isSpam;
    }

    // Returns the identifying number for this message.
    public int getId() {
        return id;
    }

    // Returns a list of all words found in this message.
    public List<String> getWords() {
        return words;
    }

    // Returns true if this message has been marked as spam.
    public boolean isSpam() {
        return isSpam;
    }
}