// FILE HANDLING UTILITY CLASS
// Frans Coenen
// University of Liverpool
// 20 April 2013

import java.io.*; 			// File and PrintWriter classes
import javax.swing.*;		// Contains JFileChooser class

class FileHandlingUtility extends JFrame {

	// ------------------- FIELDS ------------------------
	
	/** Instance of PrintWriter class */
    private PrintWriter fileOutput = null;
    /** File instance for output. */
    private File outputFileName = null;
    /** The file name. */
    private String fileName = null;
    /** Array structure for storing file input. */
    private String[] dataArray = null;
    
    // ------------------- CONSTRUCTORS ------------------------
    
    /* ------- Default ------ */
    
    // ------------------- OUTPUT FILE METHODS ------------------------
    
	/** Opens the output file ready to write data to.
    @return true if file succesfully opened, and false otherwise. */

    public boolean openOutputFile() {
		// Display file dialog box
		JFileChooser fileChooser = new JFileChooser();
		fileChooser.setFileSelectionMode(JFileChooser.FILES_ONLY);
		int result = fileChooser.showSaveDialog(this);

		// If cancel button selected return
		if (result == JFileChooser.CANCEL_OPTION) return(false);

		// Obtain selected file
		outputFileName = fileChooser.getSelectedFile();

		// Dispaly error if invalid
		if (outputFileName ==  null || outputFileName.getName().equals("")) {
	    	JOptionPane.showMessageDialog(this,"Invalid File name",
				"Invalid File name.",JOptionPane.ERROR_MESSAGE);
	    	return(false);
	    	}
		else {
   	    	try {
				fileOutput = new PrintWriter(new FileWriter(outputFileName));
	 			fileName   = outputFileName.getName();
	 			return(true);
				}
	    	catch(IOException ioException) {
	    		JOptionPane.showMessageDialog(this,"Error opening File",
			 					"Error",JOptionPane.ERROR_MESSAGE);
      			return(false);
				}
	    	}
		}
	
	// ------------------- INPUT FILE METHODS ------------------------
	
	/** Method to start process of openning a file for input, reading the content, and 
	storing the comtent in the dataArray string array structure.
	@return true if successful, false otherwise. */

    public boolean openInputFile() {
        // Display file dialog so user can select file to open
		JFileChooser fileChooser = new JFileChooser();
		fileChooser.setFileSelectionMode(JFileChooser.FILES_ONLY);
		int result = fileChooser.showOpenDialog(this);

		// If cancel button selected return
		if (result == JFileChooser.CANCEL_OPTION) return(false);

		// Obtain selected file and create File object
		File inputFileName = fileChooser.getSelectedFile();

		// Read file if readabale (i.e. not a directory etc.).
		if (checkFileName(inputFileName)) {
	    	if (readFile(inputFileName)) return(true);
	    	else return(false);
            }
        else return(false);
        }
        
    /** Method to start process of openning a file for input, reading the content, and 
	storing the comtrnt in the dataArray string array structure where the file name is 
	known.
	@param stringFileName the given file name as a string.
	@return true if successful, false otherwise. */

    public boolean openInputFile(String stringFileName) {
		// Create File object
		File inputFileName = new File(stringFileName);

		// Read file if readabale (i.e. not a direcrory etc.).
		if (checkFileName(inputFileName)) {
	    	if (readFile(inputFileName)) return(true);
	    	else return(false);
            }
        else return(false);
        }
        
    /** Checks nature of the selected input file name to make sure it is readable.
    @param fileName the File object to be checked
    @return false if selected file is a directory, access is denied or is
    not a file name; and true otherwise. */

    private boolean checkFileName(File fileName) {
        boolean fileOK = true;

        // Check if file name exist
		if (fileName.exists()) {
	    	// Check if file name is readable
            if (fileName.canRead()) {
                // Check if file name is actually a file
				if (fileName.isFile()) return(fileOK);
				else JOptionPane.showMessageDialog(null,
								"FILE ERROR: File is a directory");
				}
	    	else JOptionPane.showMessageDialog(null,
	    							  "FILE ERROR: Access denied");
	    	}
		else JOptionPane.showMessageDialog(null,
									  "FILE ERROR: No such file!");
		// Return

		return(!fileOK);
		}
		
	/** Reads the designated input file. Need to read it twice, once to dimension the
	dataArray array structure and once to populate that structure.
    @param fileName the File object for the file to be loaded.  
    @return true if successful, false otherwise.		*/

    private boolean readFile(File fileName) {
        boolean success = false;
        
        // Dimension data structure
	    int numLines = getNumberOfLines(fileName);
	    if (numLines>0) {
	    	// Dimension dataArray storage structure 
	    	dataArray = new String[numLines];
	    	// Now read file
	    	if (readInputDataSet(fileName)) success = true;
	    	}
		
		// Return
		return(success);
		}

	
    /** Reads input data from given file and places it in the dataArray array structure.
    @param fileName the File to read.  
    @return true if successful, false otherwise.		*/

    private boolean readInputDataSet(File fileName) {
		boolean success = false;
		
		// Try-catch block
		try {
			FileReader file          = new FileReader(fileName);
	    	BufferedReader fileInput = new BufferedReader(file);
			// Get first row.
			String line = fileInput.readLine();
			// Process rest of file
			int rowIndex=0;
			while (line != null) {
	    		// Process line
	    		dataArray[rowIndex] = line;
	    		// Increment first (row) index in 2-D data array
	    		rowIndex++;
	    		// get next line
        		line = fileInput.readLine();
	    		}
	        success = true;
	        // Close file
        	fileInput.close();
			}
		catch(IOException ioException) {
	        JOptionPane.showMessageDialog(null,"Unknown error reading " +
		               "file: " + fileName + "\n","FILE INPUT ERROR",
                                                  JOptionPane.ERROR_MESSAGE);
	    	}
		
		// Return
		return(success);
		}
		
    /** Method to determined number of lines/records in input file.
    @param fileName the File to read.
    @return the number of rows in the given file (0 if error). */

    private int getNumberOfLines(File fileName) {
        int counter = 0;
        
        // Try-catch block
		try {
			// Open the file
			FileReader file          = new FileReader(fileName);
	    	BufferedReader fileInput = new BufferedReader(file);
			// Loop through file incrementing counter starting with first row.
			String line = fileInput.readLine();
			while (line != null) {
	    		counter++;
            	line = fileInput.readLine();
	    		}
	        // Close file
        	fileInput.close();
        	}
		catch(IOException ioException) {
	        JOptionPane.showMessageDialog(null,"Unknown error reading " +
		               "file: " + fileName + "\n","FILE INPUT ERROR",
                                                  JOptionPane.ERROR_MESSAGE);
	    	}
        	
        // Return counter
		return(counter);
		}
		
	// ------------------- GET METHODS ------------------------
	
	/** Get PrintWriter object if one has been created.
	@return The PrintWriter objet. */
	
	public PrintWriter getfileOutput() {
		return(fileOutput);	
		}
		
	/** Get file name for opened file.
	@return The file name. */
	
	public String getfileName() {
		return(fileName);	
		}
		
	/** Get the dataArray array structure
	@return reference to dataArray. */
	
	public String[] getDataArray() {
		return(dataArray);
		}
		 
	// ------------------- OUTPUT METHODS ------------------------
	
	/** Method to output contents of dataArray storage structure to screen. */
	
	public void outputDataArray() {
		for (int index=0;index<dataArray.length;index++) {
			System.out.println(dataArray[index]);
			}
		}
	}