package randomAccess;

import java.io.EOFException;
import java.io.IOException;
import java.io.RandomAccessFile;

/**
*   Class to print out a management hierarchy, given an employee ID.
*
*   @author Bryan J. Higgs, 31 January, 2001.
*/
public class EmployeeTree
{
    /**
    *   Main entry point.
    *
    *   @param args command line arguments.
    *               args[0] is the name of the file to read.
    *               args[1] is the employee ID.
    */
    public static void main(String[] args)
    {
        if (args.length < 2)
        {
            System.err.println(
                "Usage: java randomAccess.EmployeeTree <file-to-read> <empID>");
            return;
        }
        // Extract the filename
        String fileName = args[0];
        // Extract the employee ID
        int empID = Integer.parseInt(args[1]);

        RandomAccessFile file = null;
        try
        {
            // Create random access file object for reading
            file = new RandomAccessFile(fileName, "r");
            // Print the management hierarchy
            printTree(file, empID);
            // end it with a fresh newline
            System.out.println();
        }
        catch (IOException ex)
        {
            ex.printStackTrace();
        }
        finally
        {
            if (file != null)
            {
                try
                {
                    file.close();
                }
                catch (IOException ex)
                {
                    // Ignore
                }
            }
        }
    }

    /**
    *   Prints out a management hierarchy, given an employee ID
    */
    private static int printTree(RandomAccessFile file, int empID)
        throws IOException
    {
        // Calculate position of employee record in file.
        long position = (empID-1) * Employee.RECORD_SIZE;
        // Seek to it.
        file.seek(position);
        // Read employee data
        Employee emp = new Employee();
        emp.read(file);
        // Perform a sanity check
        if (emp.getID() != empID)
        {
            throw new IllegalStateException(
                            "Employee IDs don't match:" + empID + ", " + emp.getID());
        }

        int level = 0;  // Used for indentation
        if (emp.getManagedBy() != Employee.NO_MANAGER)
        {
            // If employee has a manager, recurse
            level = printTree(file, emp.getManagedBy());
            // Indent to level
            for (int i = 0; i < level; i++)
                System.out.print(' ');
            System.out.print("manages ");
        }
        // Print out employee name
        System.out.println(emp.getName());

        return ++level;
    }
}