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/*
 * #%L
 * Image processing operations for SciJava Ops.
 * %%
 * Copyright (C) 2014 - 2024 SciJava developers.
 * %%
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 *    this list of conditions and the following disclaimer.
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package org.scijava.ops.image.geom.geom2d;

import java.util.ArrayList;
import java.util.List;
import java.util.function.BiFunction;

import net.imglib2.Cursor;
import net.imglib2.RandomAccess;
import net.imglib2.RandomAccessibleInterval;
import net.imglib2.RealPoint;
import net.imglib2.roi.geom.real.DefaultWritablePolygon2D;
import net.imglib2.roi.geom.real.Polygon2D;
import net.imglib2.type.BooleanType;
import net.imglib2.type.Type;
import net.imglib2.util.Util;
import net.imglib2.view.Views;
import org.scijava.ops.spi.Nullable;

/**
 * Generic implementation of {@code geom.contour}. This implementation assumes
 * that foreground-pixels are 'true' and background-pixels are 'false'.
 *
 * @author Jonathan Hale (University of Konstanz)
 * @author Daniel Seebacher (University of Konstanz)
 * @author Tim-Oliver Buchholz (University of Konstanz)
 * @implNote op names='geom.contour'
 */
public class DefaultContour> implements
	BiFunction, Boolean, Polygon2D>
{

	// @Parameter(itemIO = ItemIO.INPUT,
	// description = "Set this flag to use refined Jacobs stopping criteria")
	// private boolean useJacobs = true;

	/**
	 * ClockwiseMooreNeighborhoodIterator Iterates clockwise through a 2D Moore
	 * Neighborhood (8 connected Neighborhood). This iterator encourages reuse!
	 * Reset iterator and move underlying random accessible, do not create new
	 * ones. That is more resource efficient and faster.
	 *
	 * @author Jonathan Hale (University of Konstanz)
	 */
	final class ClockwiseMooreNeighborhoodIterator> implements
		java.util.Iterator
	{

		final private RandomAccess m_ra;

		final private int[][] CLOCKWISE_OFFSETS = { { 0, -1 }, { 1, 0 }, { 1, 0 }, {
			0, 1 }, { 0, 1 }, { -1, 0 }, { -1, 0 }, { 0, -1 } };

		final private int[][] CCLOCKWISE_OFFSETS = { { 0, 1 }, { 0, 1 }, { -1, 0 },
			{ -1, 0 }, { 0, -1 }, { 0, -1 }, { 1, 0 }, { 1, 0 } };

		// index of offset to be executed at next next() call.
		private int m_curOffset = 0;

		// startIndex basically tells Cursor when it performed
		// every relative movement in CLOCKWISE_OFFSETS once. After
		// backtrack, this is reset to go through all 8 offsets again.
		private int m_startIndex = 7;

		public ClockwiseMooreNeighborhoodIterator(final RandomAccess ra) {
			m_ra = ra;
		}

		/**
		 * {@inheritDoc}
		 */
		@Override
		public final boolean hasNext() {
			return (m_curOffset != m_startIndex);
		}

		/**
		 * {@inheritDoc}
		 */
		@Override
		public final T next() {
			m_ra.move(CLOCKWISE_OFFSETS[m_curOffset]);
			m_curOffset = (m_curOffset + 1) & 7; // <=> (m_curOffset+1) % 8
			return m_ra.get();
		}

		/**
		 * {@inheritDoc}
		 */
		@Override
		public final void remove() {
			throw new UnsupportedOperationException();
		}

		public final void backtrack() {
			final int[] back = CCLOCKWISE_OFFSETS[m_curOffset];
			m_ra.move(back); // undo last move

			// find out, where to continue:
			if (back[0] == 0) {
				if (back[1] == 1) {
					m_curOffset = 6;
				}
				else {
					m_curOffset = 2;
				}
			}
			else {
				if (back[0] == 1) {
					m_curOffset = 4;
				}
				else {
					m_curOffset = 0;
				}
			}

			m_startIndex = (m_curOffset + 7) & 7; // set Pixel to stop at
		}

		public final int getIndex() {
			return m_curOffset;
		}

		/**
		 * Reset current offset index. This does not influence RandomAccess.
		 */
		public final void reset() {
			m_curOffset = 0;
			m_startIndex = 7;
		}

		/**
		 * backtrack and set only part of neighborhood to be iterated.
		 */
		public void backtrackSpecial() {
			final int[] back = CCLOCKWISE_OFFSETS[m_curOffset];
			m_ra.move(back); // undo last move

			// find out, where to continue:
			if (back[0] == 0) {
				if (back[1] == 1) {
					m_curOffset = 6;
				}
				else {
					m_curOffset = 2;
				}
			}
			else {
				if (back[0] == 1) {
					m_curOffset = 4;
				}
				else {
					m_curOffset = 0;
				}
			}

			m_startIndex = (m_curOffset + 5) & 7; // set Pixel to stop at
		}
	}

	/**
	 * TODO
	 *
	 * @param input the input image
	 * @param useJacobs Set this flag to use refined Jacobs stopping criteria
	 * @return the contour
	 */
	@Override
	public Polygon2D apply(final RandomAccessibleInterval input,
		@Nullable Boolean useJacobs)
	{

		if (useJacobs == null) {
			useJacobs = true;
		}

		// ensure validity of inputs
		if (2 != input.numDimensions()) throw new IllegalArgumentException(
			"Only two-dimensional inputs supported!");

		List p = new ArrayList<>();

		final B var = Util.getTypeFromInterval(input).createVariable();

		final RandomAccess raInput = Views.extendValue(input, var)
			.randomAccess();
		final Cursor cInput = Views.flatIterable(input).cursor();
		final ClockwiseMooreNeighborhoodIterator cNeigh =
			new ClockwiseMooreNeighborhoodIterator<>(raInput);

		double[] position = new double[2];
		double[] startPos = new double[2];

		// find first true pixel
		while (cInput.hasNext()) {
			// we are looking for a true pixel
			if (cInput.next().get()) {
				raInput.setPosition(cInput);
				raInput.localize(startPos);

				// add to polygon
				p.add(new RealPoint(startPos[0], startPos[1]));

				// backtrack:
				raInput.move(-1, 0);

				cNeigh.reset();

				while (cNeigh.hasNext()) {
					if (cNeigh.next().get()) {

						boolean specialBacktrack = false;

						raInput.localize(position);
						if (startPos[0] == position[0] && startPos[1] == position[1]) {
							// startPoint was found.
							if (useJacobs) {
								// Jacobs stopping criteria
								final int index = cNeigh.getIndex();
								if (index == 1 || index == 0) {
									// Jonathans refinement to
									// non-terminating jacobs criteria
									specialBacktrack = true;
								}
								else if (index == 2 || index == 3) {
									// if index is 2 or 3, we entered pixel
									// by moving {1, 0}, refore in same
									// way.
									break;
								} // else criteria not fulfilled, continue.
							}
							else {
								break;
							}
						}
						// add found point to polygon
						p.add(new RealPoint(position[0], position[1]));

						if (specialBacktrack) {
							cNeigh.backtrackSpecial();
						}
						else {
							cNeigh.backtrack();
						}
					}
				}

				break; // we only need to extract one contour.
			}
		}

		return new DefaultWritablePolygon2D(p);
	}

}