/*
 * Copyright (C) 2010, Garmin International
 * Copyright (C) 2010, Matt Fischer <matt.fischer@garmin.com> 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.revwalk;

import java.io.IOException;

import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.errors.MissingObjectException;
import org.eclipse.jgit.lib.ObjectId;

Only produce commits which are below a specified depth.
See Also:
DepthWalk/**
 * Only produce commits which are below a specified depth.
 *
 * @see DepthWalk
 */
class DepthGenerator extends Generator {
	private final FIFORevQueue pending;

	private final int depth;

	private final int deepenSince;

	private final RevWalk walk;

	
Commits which used to be shallow in the client, but which are
being extended as part of this fetch.  These commits should be
returned to the caller as UNINTERESTING so that their blobs/trees
can be marked appropriately in the pack writer.
/**
	 * Commits which used to be shallow in the client, but which are
	 * being extended as part of this fetch.  These commits should be
	 * returned to the caller as UNINTERESTING so that their blobs/trees
	 * can be marked appropriately in the pack writer.
	 */
	private final RevFlag UNSHALLOW;

	
Commits which the normal framework has marked as UNINTERESTING,
but which we now care about again.  This happens if a client is
extending a shallow checkout to become deeper--the new commits at
the bottom of the graph need to be sent, even though they are
below other commits which the client already has.
/**
	 * Commits which the normal framework has marked as UNINTERESTING,
	 * but which we now care about again.  This happens if a client is
	 * extending a shallow checkout to become deeper--the new commits at
	 * the bottom of the graph need to be sent, even though they are
	 * below other commits which the client already has.
	 */
	private final RevFlag REINTERESTING;

	
Commits reachable from commits that the client specified using --shallow-exclude.
/**
	 * Commits reachable from commits that the client specified using --shallow-exclude.
	 */
	private final RevFlag DEEPEN_NOT;

	
Params:
w – 
s – Parent generator
Throws:
MissingObjectException – 
IncorrectObjectTypeException – 
IOException – /**
	 * @param w
	 * @param s Parent generator
	 * @throws MissingObjectException
	 * @throws IncorrectObjectTypeException
	 * @throws IOException
	 */
	DepthGenerator(DepthWalk w, Generator s) throws MissingObjectException,
			IncorrectObjectTypeException, IOException {
		super(s.firstParent);
		pending = new FIFORevQueue(firstParent);
		walk = (RevWalk)w;

		this.depth = w.getDepth();
		this.deepenSince = w.getDeepenSince();
		this.UNSHALLOW = w.getUnshallowFlag();
		this.REINTERESTING = w.getReinterestingFlag();
		this.DEEPEN_NOT = w.getDeepenNotFlag();

		s.shareFreeList(pending);

		// Begin by sucking out all of the source's commits, and
		// adding them to the pending queue
		FIFORevQueue unshallowCommits = new FIFORevQueue();
		for (;;) {
			RevCommit c = s.next();
			if (c == null)
				break;
			if (c.has(UNSHALLOW)) {
				unshallowCommits.add(c);
			} else if (((DepthWalk.Commit) c).getDepth() == 0) {
				pending.add(c);
			}
		}
		// Move unshallow commits to the front so that the REINTERESTING flag
		// carry over code is executed first.
		for (;;) {
			RevCommit c = unshallowCommits.next();
			if (c == null) {
				break;
			}
			pending.unpop(c);
		}

		// Mark DEEPEN_NOT on all deepen-not commits and their ancestors.
		// TODO(jonathantanmy): This implementation is somewhat
		// inefficient in that any "deepen-not <ref>" in the request
		// results in all commits reachable from that ref being parsed
		// and marked, even if the commit topology is such that it is
		// not necessary.
		for (ObjectId oid : w.getDeepenNots()) {
			RevCommit c;
			try {
				c = walk.parseCommit(oid);
			} catch (IncorrectObjectTypeException notCommit) {
				// The C Git implementation silently tolerates
				// non-commits, so do the same here.
				continue;
			}

			FIFORevQueue queue = new FIFORevQueue();
			queue.add(c);
			while ((c = queue.next()) != null) {
				if (c.has(DEEPEN_NOT)) {
					continue;
				}

				walk.parseHeaders(c);
				c.add(DEEPEN_NOT);
				for (RevCommit p : c.getParents()) {
					queue.add(p);
				}
			}
		}
	}

	@Override
	int outputType() {
		return pending.outputType() | HAS_UNINTERESTING;
	}

	@Override
	void shareFreeList(BlockRevQueue q) {
		pending.shareFreeList(q);
	}

	@Override
	RevCommit next() throws MissingObjectException,
			IncorrectObjectTypeException, IOException {
		// Perform a breadth-first descent into the commit graph,
		// marking depths as we go.  This means that if a commit is
		// reachable by more than one route, we are guaranteed to
		// arrive by the shortest route first.
		for (;;) {
			final DepthWalk.Commit c = (DepthWalk.Commit) pending.next();
			if (c == null)
				return null;

			if ((c.flags & RevWalk.PARSED) == 0)
				c.parseHeaders(walk);

			if (c.getCommitTime() < deepenSince) {
				continue;
			}

			if (c.has(DEEPEN_NOT)) {
				continue;
			}

			int newDepth = c.depth + 1;

			for (int i = 0; i < c.parents.length; i++) {
				if (firstParent && i > 0) {
					break;
				}
				RevCommit p = c.parents[i];
				DepthWalk.Commit dp = (DepthWalk.Commit) p;

				// If no depth has been assigned to this commit, assign
				// it now.  Since we arrive by the shortest route first,
				// this depth is guaranteed to be the smallest value that
				// any path could produce.
				if (dp.depth == -1) {
					boolean failsDeepenSince = false;
					if (deepenSince != 0) {
						if ((p.flags & RevWalk.PARSED) == 0) {
							p.parseHeaders(walk);
						}
						failsDeepenSince =
							p.getCommitTime() < deepenSince;
					}

					dp.depth = newDepth;

					// If the parent is not too deep and was not excluded, add
					// it to the queue so that we can produce it later
					if (newDepth <= depth && !failsDeepenSince &&
							!p.has(DEEPEN_NOT)) {
						pending.add(p);
					} else {
						dp.makesChildBoundary = true;
					}
				}

				if (dp.makesChildBoundary) {
					c.isBoundary = true;
				}

				// If the current commit has become unshallowed, everything
				// below us is new to the client.  Mark its parent as
				// re-interesting, and carry that flag downward to all
				// of its ancestors.
				if(c.has(UNSHALLOW) || c.has(REINTERESTING)) {
					p.add(REINTERESTING);
					p.flags &= ~RevWalk.UNINTERESTING;
				}
			}

			boolean produce = true;

			// Unshallow commits are uninteresting, but still need to be sent
			// up to the PackWriter so that it will exclude objects correctly.
			// All other uninteresting commits should be omitted.
			if ((c.flags & RevWalk.UNINTERESTING) != 0 && !c.has(UNSHALLOW))
				produce = false;

			if (c.getCommitTime() < deepenSince) {
				produce = false;
			}

			if (produce)
				return c;
		}
	}
}