/*
 * Copyright (C) 2008, 2014 Shawn O. Pearce <spearce@spearce.org> and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package org.eclipse.jgit.revplot;

import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.revwalk.RevFlag;

/**
 * Basic commit graph renderer for graphical user interfaces.
 * <p>
 * Lanes are drawn as columns left-to-right in the graph, and the commit short
 * message is drawn to the right of the lane lines for this cell. It is assumed
 * that the commits are being drawn as rows of some sort of table.
 * <p>
 * Client applications can subclass this implementation to provide the necessary
 * drawing primitives required to display a commit graph. Most of the graph
 * layout is handled by this class, allowing applications to implement only a
 * handful of primitive stubs.
 * <p>
 * This class is suitable for us within an AWT TableCellRenderer or within a SWT
 * PaintListener registered on a Table instance. It is meant to rubber stamp the
 * graphics necessary for one row of a plotted commit list.
 * <p>
 * Subclasses should call {@link #paintCommit(PlotCommit, int)} after they have
 * otherwise configured their instance to draw one commit into the current
 * location.
 * <p>
 * All drawing methods assume the coordinate space for the current commit's cell
 * starts at (upper left corner is) 0,0. If this is not true (like say in SWT)
 * the implementation must perform the cell offset computations within the
 * various draw methods.
 *
 * @param <TLane>
 *            type of lane being used by the application.
 * @param <TColor>
 *            type of color object used by the graphics library.
 */
public abstract class AbstractPlotRenderer<TLane extends PlotLane, TColor> {
	private static final int LANE_WIDTH = 14;

	private static final int LINE_WIDTH = 2;

	private static final int LEFT_PAD = 2;

	/**
	 * Paint one commit using the underlying graphics library.
	 *
	 * @param commit
	 *            the commit to render in this cell. Must not be null.
	 * @param h
	 *            total height (in pixels) of this cell.
	 */
	@SuppressWarnings("unchecked")
	protected void paintCommit(PlotCommit<TLane> commit, int h) {
		final int dotSize = computeDotSize(h);
		final TLane myLane = commit.getLane();
		final int myLaneX = laneC(myLane);
		final TColor myColor = laneColor(myLane);

		int maxCenter = myLaneX;
		for (TLane passingLane : (TLane[]) commit.passingLanes) {
			final int cx = laneC(passingLane);
			final TColor c = laneColor(passingLane);
			drawLine(c, cx, 0, cx, h, LINE_WIDTH);
			maxCenter = Math.max(maxCenter, cx);
		}

		final int dotX = myLaneX - dotSize / 2 - 1;
		final int dotY = (h - dotSize) / 2;

		final int nParent = commit.getParentCount();
		if (nParent > 0) {
			drawLine(myColor, myLaneX, h, myLaneX, (h + dotSize) / 2,
					LINE_WIDTH);

			for (PlotLane mergingLane : commit.mergingLanes) {
				final TLane pLane = (TLane) mergingLane;
				final TColor pColor = laneColor(pLane);
				final int cx = laneC(pLane);
				if (Math.abs(myLaneX - cx) > LANE_WIDTH) {
					final int ix;
					if (myLaneX < cx) {
						ix = cx - LANE_WIDTH / 2;
					} else {
						ix = cx + LANE_WIDTH / 2;
					}

					drawLine(pColor, myLaneX, h / 2, ix, h / 2, LINE_WIDTH);
					drawLine(pColor, ix, h / 2, cx, h, LINE_WIDTH);
				} else
					drawLine(pColor, myLaneX, h / 2, cx, h, LINE_WIDTH);
				maxCenter = Math.max(maxCenter, cx);
			}
		}


		if (commit.getChildCount() > 0) {
			for (PlotLane forkingOffLane : commit.forkingOffLanes) {
				final TLane childLane = (TLane) forkingOffLane;
				final TColor cColor = laneColor(childLane);
				final int cx = laneC(childLane);
				if (Math.abs(myLaneX - cx) > LANE_WIDTH) {
					final int ix;
					if (myLaneX < cx) {
						ix = cx - LANE_WIDTH / 2;
					} else {
						ix = cx + LANE_WIDTH / 2;
					}

					drawLine(cColor, myLaneX, h / 2, ix, h / 2, LINE_WIDTH);
					drawLine(cColor, ix, h / 2, cx, 0, LINE_WIDTH);
				} else {
					drawLine(cColor, myLaneX, h / 2, cx, 0, LINE_WIDTH);
				}
				maxCenter = Math.max(maxCenter, cx);
			}

			int nonForkingChildren = commit.getChildCount()
					- commit.forkingOffLanes.length;
			if (nonForkingChildren > 0)
						drawLine(myColor, myLaneX, 0, myLaneX, dotY, LINE_WIDTH);
		}

		if (commit.has(RevFlag.UNINTERESTING))
			drawBoundaryDot(dotX, dotY, dotSize, dotSize);
		else
			drawCommitDot(dotX, dotY, dotSize, dotSize);

		int textx = Math.max(maxCenter + LANE_WIDTH / 2, dotX + dotSize) + 8;
		int n = commit.refs.length;
		for (int i = 0; i < n; ++i) {
			textx += drawLabel(textx + dotSize, h/2, commit.refs[i]);
		}

		final String msg = commit.getShortMessage();
		drawText(msg, textx + dotSize, h);
	}

	/**
	 * Draw a decoration for the Ref ref at x,y
	 *
	 * @param x
	 *            left
	 * @param y
	 *            top
	 * @param ref
	 *            A peeled ref
	 * @return width of label in pixels
	 */
	protected abstract int drawLabel(int x, int y, Ref ref);

	private static int computeDotSize(int h) {
		int d = (int) (Math.min(h, LANE_WIDTH) * 0.50f);
		d += (d & 1);
		return d;
	}

	/**
	 * Obtain the color reference used to paint this lane.
	 * <p>
	 * Colors returned by this method will be passed to the other drawing
	 * primitives, so the color returned should be application specific.
	 * <p>
	 * If a null lane is supplied the return value must still be acceptable to a
	 * drawing method. Usually this means the implementation should return a
	 * default color.
	 *
	 * @param myLane
	 *            the current lane. May be null.
	 * @return graphics specific color reference. Must be a valid color.
	 */
	protected abstract TColor laneColor(TLane myLane);

	/**
	 * Draw a single line within this cell.
	 *
	 * @param color
	 *            the color to use while drawing the line.
	 * @param x1
	 *            starting X coordinate, 0 based.
	 * @param y1
	 *            starting Y coordinate, 0 based.
	 * @param x2
	 *            ending X coordinate, 0 based.
	 * @param y2
	 *            ending Y coordinate, 0 based.
	 * @param width
	 *            number of pixels wide for the line. Always at least 1.
	 */
	protected abstract void drawLine(TColor color, int x1, int y1, int x2,
			int y2, int width);

	/**
	 * Draw a single commit dot.
	 * <p>
	 * Usually the commit dot is a filled oval in blue, then a drawn oval in
	 * black, using the same coordinates for both operations.
	 *
	 * @param x
	 *            upper left of the oval's bounding box.
	 * @param y
	 *            upper left of the oval's bounding box.
	 * @param w
	 *            width of the oval's bounding box.
	 * @param h
	 *            height of the oval's bounding box.
	 */
	protected abstract void drawCommitDot(int x, int y, int w, int h);

	/**
	 * Draw a single boundary commit (aka uninteresting commit) dot.
	 * <p>
	 * Usually a boundary commit dot is a light gray oval with a white center.
	 *
	 * @param x
	 *            upper left of the oval's bounding box.
	 * @param y
	 *            upper left of the oval's bounding box.
	 * @param w
	 *            width of the oval's bounding box.
	 * @param h
	 *            height of the oval's bounding box.
	 */
	protected abstract void drawBoundaryDot(int x, int y, int w, int h);

	/**
	 * Draw a single line of text.
	 * <p>
	 * The font and colors used to render the text are left up to the
	 * implementation.
	 *
	 * @param msg
	 *            the text to draw. Does not contain LFs.
	 * @param x
	 *            first pixel from the left that the text can be drawn at.
	 *            Character data must not appear before this position.
	 * @param y
	 *            pixel coordinate of the baseline of the text. Implementations
	 *            must adjust this coordinate to account for the way their
	 *            implementation handles font rendering.
	 */
	protected abstract void drawText(String msg, int x, int y);

	private static int laneX(PlotLane myLane) {
		final int p = myLane != null ? myLane.getPosition() : 0;
		return LEFT_PAD + LANE_WIDTH * p;
	}

	private static int laneC(PlotLane myLane) {
		return laneX(myLane) + LANE_WIDTH / 2;
	}
}