// Input.java

/** 
 * Input gates, a component of a logic circuit simulator.
 * This version is distributed as a solution to Machine Problem 5, Fall 2015.
 * @author Douglas W. Jones
 * @version MP5
 */
import java.util.Arrays;
import java.util.List;
import java.util.LinkedList;
import java.util.Scanner;

class Input extends Gate {
	/** Input gates consume input from the outside world and present
	 *  it to the logic circuit.
	 */
	private Input() {} // prevent outsiders from using the initializer

	// the following empty list prevents any inputs from being connected
	private static List <String> inputs = new LinkedList <String> ();

	// the scanner from which input changes will be read
	private static Scanner sc = null;

	// does the first input event need to be scheduled?
	private static boolean needToSchedule = true;

	public static Gate scan( Scanner sc ) {
		/** This is the public initializer for input gates,
		 *  it reads the gate description using the given scanner
		 *  and it returns the handle for the newly initialized gate.
		 */
		// just once, setup to read inputs later
		if (Input.sc == null) {
			Input.sc = sc; // remember the scanner to use
		}

		// now do the scan as for any other gate
		Input g = new Input();
		g.scan( sc, inputs );
		if (g.name == null) g = null;

		return g;
	}

	public void checkInputs() {
		/** Override default CheckInputs method.  Input gates have
		 *  no inputs from the logic circuit itself, so we use this
		 *  to finish the initialization, scheduling the first
		 *  input change event.
		 */
		// just once, no matter how many input gates.
		if (needToSchedule) {
			needToSchedule = false;
			if (sc.hasNextFloat()) {
				// there is a next input event
				Simulator.schedule(
					sc.nextFloat(),
					(float time) -> scanInput( time )
				);
			}
		}
	}

	public String toString() {
		/** Convert an input gate back to its textual description.
		 */
		return "gate input " + name + ' ' + delay;
	}

	public void inputChange( float t, int i, boolean v ) {
		/** Input gates have no inputs, so should never be called.
		 */
	}

	private static void scanInput( float t ) {
		/** Event service routine, scheduled each time an input change
		 *  should occur.  Scan the name of the input gate and the
		 *  new input value, make those changes and then skip to the
		 *  next line of input and scan the time of the next input
		 *  change (if any).
		 */
		if (!sc.hasNext()) {
                        Errors.warn(
                                "" + t + " " + "?"
                                + "-- input or stop not specified"
                        );
		} else {
			String name = sc.next();
			Input i = null;          // the named input
			boolean inputValue = false; // new value of the input
			
			if ("stop".equals(name)) {
				// not very graceful, but it does stop.
				System.exit( 0 );
			}

			// make sure the name identifies an input gate
			Gate g = LogicCircuit.findGate( name );
			if ((g == null)
			||  !(g instanceof Input)) {
				Errors.warn(
					"" + t + " " + name + "?"
					+ "-- not an input"
				);
				i = null;
			} else {
				i = (Input) g;
			}

			// deal with the value of the input
			if (!sc.hasNextBoolean()) {
				Errors.warn(
					"" + t + " " + name + "?"
					+ "-- input value not specified"
				);
			} else {
				inputValue = sc.nextBoolean();
			}

			if ((i != null) && (i.outputValue != inputValue)) {
				// something actually changes!
				i.outputValue = inputValue;
				i.outputChange( t, inputValue );
			}

			// deal with end of input line
			final boolean iv = inputValue; // kluge
			SyntaxCheck.lineEnd(
				sc, () -> "" + t + " " + name + iv
			);

			// see if there is a next input event to schedule
			if (sc.hasNextFloat()) {
				Simulator.schedule(
					sc.nextFloat(),
					(float time) -> scanInput( time )
				);
			}
		}
	}
}