// Output.java

/**
 * Output gates, a component of a logic circuit simulator.
 * This version is distributed as a solution to Machine Problem 4, Fall 2015.
 * @author Douglas W Jones
 * @version MP4
 */

import java.util.Arrays;
import java.util.List;
import java.util.LinkedList;
import java.util.Scanner;

class Output extends Gate {
	/** Output gates display their inputs on the output display once
	 *  every simulated time unit and perform no useful computation.
	 */
	private Output() {} // prevent outsiders from using the initializer

	// the following strings are used only for formatting textual output
	private static final String [] falseArray
			= {" |   ","  _| "," |-  "," ,=' "," |=  "};
	private static final String [] trueArray
			= {"   | "," |_  ","  -| "," '=, ","  =| "};

	// the following string defines the only name allowed for gate inputs
	private static List <String> inputs = Arrays.asList( "in" );

	// all output gates in the circuit are listed here
	private static List <Output> outputList = new LinkedList <Output> ();

	// outputs count changes to their inputs since the last output event
	private int changeCount = 0; // this and output value determine display

	private static void displayHeaders( float t ) {
		/** Traverse the list of all outputs and display their
		 *  names and then scheduling the first output display event.
		 *  All names are output in a 5-space field.
		 *  Following the headers, display the associated values.
		 */
		for (Output o: outputList) {
			String n = o.name;

			// long names must be truncated
			if (n.length() > 4) {
				n = n.substring( 0, 4 );
			}

			// output leading blank
			System.out.append( ' ' );

			// output edited name
			System.out.append( n );

			// output padding up to next column
			if (n.length() < 4) {
				System.out.append(
					"     ".substring( 0, 4 - n.length() )
				);
			}
		}
		System.out.println();

		// headers preceed first output of values
		displayOutput( t );
	}

	private void outputMe() {
		/** Output the value of one wire.
		 *  All outputs occupy exactly 5 spaces.
		 */
		if (changeCount > 2) changeCount = 4 - (changeCount & 1);
		if (outputValue) {
			System.out.append( trueArray[ changeCount ] );
		} else {
			System.out.append( falseArray[ changeCount ] );
		}
		changeCount = 0;
	}

	private static void displayOutput( float t ) {
		/** Traverse the list of all outputs and display them
		 *  before scheduling the next output display event.
		 */
		for (Output o: outputList) {
			o.outputMe();
		}
		System.out.println();

		if (Simulator.moreEvents()) {
			Simulator.schedule(
				t + 1,
				(float time) -> displayOutput( time )
			);
		}
	}

	public static Gate scan( Scanner sc ) {
		/** This is the public initializer for output gates,
		 *  it reads the gate description using the given scanner
		 *  and returns the handle for the newly initialized gate.
		 */
		// just once, fire up the initial event
		if (outputList.isEmpty()) {
			Simulator.schedule(
				1,
				(float time) -> displayHeaders( time )
			);
		}

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

		// and finally, remember this in the output list
		if (g != null) outputList.add( g );
		return g;
	}

	public void setDriven( Wire w ) {
		/** Override default method to prevent attaching anything
		 *  to the nonexistant output of an output gate.
		 */
		Errors.warn( "Gate output " + name + " cannot drive anything" );
	}

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

	public void inputChange( float t, int i, boolean v ) {
		/** Record the input changes to this gate so that the
		 *  appropriate output can be generated.
		 */
		changeCount = changeCount + 1;
		outputValue = v;
	}
}