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package practicalrefactorings.floodfill;

import java.awt.Color;
import java.util.ArrayList;
import static java.util.Arrays.asList;
import java.util.Collection;
import java.util.LinkedList;
import java.util.Queue;

public class Floodfill {
	private Position start;
	private Grid<Color> original;
	private Grid<Color> floodedGrid;
	private Color color;

	public Grid<Color> fillAt(Grid<Color> original, int startX, int startY, Color color) {
		start = new Position(startX, startY);
		this.original = original;
		this.floodedGrid = new ArrayBackedGrid<>(original.width(), original.height());
		this.color = color;
		getFloodedGrid();
		return floodedGrid;
	}

	private void getFloodedGrid() {
		if (start.x() >= 0 && start.x() < original.width() && start.y() >= 0 && start.y() < original.height()) {
			copyOriginalToFlooded();
			colorReplacement();
		} else {
			throw new IndexOutOfBoundsException("Got " + new Position(start.x(), start.y()) + " but grid is only " + original.width() + "x" + original.height());
		}
	}

	private void copyOriginalToFlooded() {
		for (int x = 0; x < original.width(); x++) {
			for (int y = 0; y < original.height(); y++) {
				floodedGrid.set(original.get(x, y), x, y);
			}
		}
	}

	private void colorReplacement() {
		Queue<Position> left = new LinkedList<>();
		left.add(new Position(start.x(), start.y()));
		Color replacingColor = original.get(start.x(), start.y());
		if (!replacingColor.equals(color)) {
			while (!left.isEmpty()) {
				Position at = left.poll();
				if (at.x() >= 0 && at.x() < floodedGrid.width() && at.y() >= 0 && at.y() < floodedGrid.height()) {
					Collection<Position> uncoloredNeighbors = getUncoloredPositions(replacingColor, at);
					left.addAll(uncoloredNeighbors);
				}
			}
		}
	}

	private Collection<Position> getUncoloredPositions(Color replacingColor, Position at) {
		floodedGrid.set(color, at.x(), at.y());
		Collection<Position> neighbors = asList(
				new Position(at.x() + 1, at.y()),
				new Position(at.x(), at.y() + 1),
				new Position(at.x() - 1, at.y()),
				new Position(at.x(), at.y() - 1)
		);
		Collection<Position> uncoloredNeighbors = new ArrayList<>();
		getPositionForColoring(replacingColor, neighbors, uncoloredNeighbors);
		return uncoloredNeighbors;
	}

	private void getPositionForColoring(Color replacingColor, Collection<Position> neighbors, Collection<Position> uncoloredNeighbors) {
		for (Position position : neighbors) {
			if (position.x() >= 0 && position.x() < floodedGrid.width() && position.y() >= 0 && position.y() < floodedGrid.height()) {
				Color colorAtPosition = floodedGrid.get(position.x(), position.y());
				if (colorAtPosition.equals(replacingColor)) {
					uncoloredNeighbors.add(position);
				}
			}
		}
	}
}