/**
 * Storage class to serve as 'superclass' for concrete financial transactions.
 * It stores and allows access to fields for a 'date', 'amount', 'name', and
 * 'status'. 
 * <p>
 * It defines varoius constants by using the modfier 'final' and defines fields
 * and methods. Fields, as a general rule, are marked as 'private', which means
 * that only objects of the same type as this class can access them directly.
 * Methods are frequently maked as 'public', which means that any class can
 * access them. Occasionally therer may be a need for 'private' methods, if they
 * are useful only from within this class.
 * <p>
 * Finally, this class uses 'javadoc' comments to allow for the automatic creation
 * of some (technical) documentation.
 */
public class Transaction
{
    /** Constant to indicate an active transaction - contributes to a total balance */
    public static final int ACTIVE = 1;
    /** Constant to indicate a deleted transaction - no contribution to balance */
    public static final int DELETED = 2;
    
    /** This field stores a valid date as a String */
    private String date = null;
    /** This field stores the amount as a double type */
    private double amount = 0.0;
    /** This field stores the name for the transaction */
    private String name = null;
    /** This field stores the status of this transaction */
    private int status = ACTIVE;
    /** This field stores the type of transaction */
    private String type = "Transaction";
    
    /**
     * The constructor for a transaction. A 'constructor' is a special method whose
     * name equals the class name and which has no return type. It automatically 
     * executes every time you make a 'new' object from this class (instantiation).
     */
    public Transaction(String date, double amount, String name, String type)
    {
        super();        // calling the superclass constructor
        this.date = date;
        this.amount = amount;
        this.name = name;
        this.status = ACTIVE;
        this.type = type;
    }
    
    /**
     * Method to return the value of the 'date' field
     */
    public String getDate()
    {   return date;
    }
    
    /** 
     * Method to return the value of the 'name' field
     */
    public String getName()
    {   return name;
    }
    
    /**
     * Method to return the value of the 'amount' field. If a transaction is flagged
     * as 'active' returns the actual amount stored, otherwise returns 0.
     */
    public double getAmount()
    {   if (status == ACTIVE)
            return amount;
        else
            return 0.0;
    }
    
    /**
     * Method to return the status of this transaction
     */
    public int getStatus()
    {   return status;
    }
    
    /**
     * Method to set the status of a transaction. The method guarantees that the 
     * status field is always well-defined by 'throwing an exception' so that the 
     * only possible values are ACTIVE or DELETED.
     */
    public void setStatus(int status)
    {
        if (status == ACTIVE)
            this.status = ACTIVE;
        else if (status == DELETED)
            this.status = DELETED;
        else
            throw new IllegalArgumentException("Invliad transaction status");
    }
    
    /**
     * Method to return the value of the 'type' field.
     */
    public String getType()
    {   return type;
    }
    
    /**
     * This method, which every class should have, returns a convenient String
     * representation of the this class. It is automatically called when using the
     * concatenation operation '+' to convert an object to String.
     */
    public String toString()
    {
        String s = type + "\n" + 
                   "\tDate: " + date + "\n" + 
                   "\tName: " + name + "\n" + 
                   "\tAmount: " + amount + "\n";
        if (status == ACTIVE)
            s += "\tACTIVE";
        else if (status == DELETED)
            s += "\tDELETED";
        else
            s += "\tundefined!";
        return s;
    }
}