/* Copyright (c) 2010, Carl Burch. License information is located in the
 * com.cburch.logisim.Main source code and at www.cburch.com/logisim/. */

package com.cburch.gray;

import com.cburch.logisim.data.BitWidth;
import com.cburch.logisim.data.Value;
import com.cburch.logisim.instance.InstanceData;
import com.cburch.logisim.instance.InstanceState;

/** Represents the state of a counter. */
class CounterData implements InstanceData, Cloneable {
	/** Retrieves the state associated with this counter in the circuit state,
	 * generating the state if necessary.
	 */
	public static CounterData get(InstanceState state, BitWidth width) {
		CounterData ret = (CounterData) state.getData();
		if (ret == null) {
			// If it doesn't yet exist, then we'll set it up with our default
			// values and put it into the circuit state so it can be retrieved
			// in future propagations.
			ret = new CounterData(null, Value.createKnown(width, 0));
			state.setData(ret);
		} else if (!ret.value.getBitWidth().equals(width)) {
			ret.value = ret.value.extendWidth(width.getWidth(), Value.FALSE);
		}
		return ret;
	}

	/** The last clock input value observed. */
	private Value lastClock;
	
	/** The current value emitted by the counter. */
	private Value value;

	/** Constructs a state with the given values. */
	public CounterData(Value lastClock, Value value) {
		this.lastClock = lastClock;
		this.value = value;
	}

	/** Returns a copy of this object. */
	@Override
	public Object clone() {
		// We can just use what super.clone() returns: The only instance variables are
		// Value objects, which are immutable, so we don't care that both the copy
		// and the copied refer to the same Value objects. If we had mutable instance
		// variables, then of course we would need to clone them.
		try { return super.clone(); }
		catch (CloneNotSupportedException e) { return null; }
	}
	
	/** Updates the last clock observed, returning true if triggered. */
	public boolean updateClock(Value value) {
		Value old = lastClock;
		lastClock = value;
		return old == Value.FALSE && value == Value.TRUE;
	}
	
	/** Returns the current value emitted by the counter. */
	public Value getValue() {
		return value;
	}
	
	/** Updates the current value emitted by the counter. */
	public void setValue(Value value) {
		this.value = value;
	}
}

