/*
    * Copyright (C) 2019, Google Inc. 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.internal.storage.reftable;
  
  import org.eclipse.jgit.annotations.Nullable;
  import org.eclipse.jgit.errors.MissingObjectException;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.lib.AnyObjectId;
  import org.eclipse.jgit.lib.BatchRefUpdate;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.ObjectIdRef;
  import org.eclipse.jgit.lib.PersonIdent;
  import org.eclipse.jgit.lib.ProgressMonitor;
  import org.eclipse.jgit.lib.Ref;
  import org.eclipse.jgit.lib.RefDatabase;
  import org.eclipse.jgit.lib.ReflogEntry;
  import org.eclipse.jgit.lib.Repository;
  import org.eclipse.jgit.lib.SymbolicRef;
  import org.eclipse.jgit.revwalk.RevObject;
  import org.eclipse.jgit.revwalk.RevTag;
  import org.eclipse.jgit.revwalk.RevWalk;
  import org.eclipse.jgit.transport.ReceiveCommand;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.TreeSet;
  import java.util.concurrent.locks.Lock;
  import java.util.stream.Collectors;
  
  import static org.eclipse.jgit.lib.Ref.Storage.NEW;
  import static org.eclipse.jgit.lib.Ref.Storage.PACKED;
  
  import static org.eclipse.jgit.transport.ReceiveCommand.Result.LOCK_FAILURE;
  import static org.eclipse.jgit.transport.ReceiveCommand.Result.NOT_ATTEMPTED;
  import static org.eclipse.jgit.transport.ReceiveCommand.Result.OK;
  import static org.eclipse.jgit.transport.ReceiveCommand.Result.REJECTED_MISSING_OBJECT;
  import static org.eclipse.jgit.transport.ReceiveCommand.Result.REJECTED_NONFASTFORWARD;
  import static org.eclipse.jgit.transport.ReceiveCommand.Type.DELETE;
  import static org.eclipse.jgit.transport.ReceiveCommand.Type.UPDATE_NONFASTFORWARD;
  
  /**
   * {@link org.eclipse.jgit.lib.BatchRefUpdate} for Reftable based RefDatabase.
   */
  public abstract class ReftableBatchRefUpdate extends BatchRefUpdate {
  	private final Lock lock;
  
  	private final ReftableDatabase refDb;
  
  	private final Repository repository;
  
  	/**
  	 * Initialize.
  	 *
  	 * @param refdb
  	 *            The RefDatabase
  	 * @param reftableDb
  	 *            The ReftableDatabase
  	 * @param lock
  	 *            A lock protecting the refdatabase's state
  	 * @param repository
  	 *            The repository on which this update will run
  	 */
  	protected ReftableBatchRefUpdate(RefDatabase refdb, ReftableDatabase reftableDb, Lock lock,
  			Repository repository) {
  		super(refdb);
  		this.refDb = reftableDb;
  		this.lock = lock;
  		this.repository = repository;
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public void execute(RevWalk rw, ProgressMonitor pm, List<String> options) {
  		List<ReceiveCommand> pending = getPending();
  		if (pending.isEmpty()) {
  			return;
  		}
  		if (options != null) {
  			setPushOptions(options);
  		}
  		try {
  			if (!checkObjectExistence(rw, pending)) {
  				return;
  			}
  			// if we are here, checkObjectExistence might have flagged some problems
  			// but the transaction is not atomic, so we should proceed with the other
 			// pending commands.
 			pending = getPending();
 			if (!checkNonFastForwards(rw, pending)) {
 				return;
 			}
 			pending = getPending();
 
 			lock.lock();
 			try {
 				if (!checkExpected(pending)) {
 					return;
 				}
 				pending = getPending();
 				if (!checkConflicting(pending)) {
 					return;
 				}
 				pending = getPending();
 				if (!blockUntilTimestamps(MAX_WAIT)) {
 					return;
 				}
 
 				List<Ref> newRefs = toNewRefs(rw, pending);
 				applyUpdates(newRefs, pending);
 				for (ReceiveCommand cmd : pending) {
 					if (cmd.getResult() == NOT_ATTEMPTED) {
 						// XXX this is a bug in DFS ?
 						cmd.setResult(OK);
 					}
 				}
 			} finally {
 				lock.unlock();
 			}
 		} catch (IOException e) {
 			pending.get(0).setResult(LOCK_FAILURE, "io error"); //$NON-NLS-1$
 			ReceiveCommand.abort(pending);
 		}
 	}
 
 	/**
 	 * Implements the storage-specific part of the update.
 	 *
 	 * @param newRefs
 	 *            the new refs to create
 	 * @param pending
 	 *            the pending receive commands to be executed
 	 * @throws IOException
 	 *             if any of the writes fail.
 	 */
 	protected abstract void applyUpdates(List<Ref> newRefs,
 			List<ReceiveCommand> pending) throws IOException;
 
 	private List<ReceiveCommand> getPending() {
 		return ReceiveCommand.filter(getCommands(), NOT_ATTEMPTED);
 	}
 
 	private boolean checkObjectExistence(RevWalk rw,
 			List<ReceiveCommand> pending) throws IOException {
 		for (ReceiveCommand cmd : pending) {
 			try {
 				if (!cmd.getNewId().equals(ObjectId.zeroId())) {
 					rw.parseAny(cmd.getNewId());
 				}
 			} catch (MissingObjectException e) {
 				// ReceiveCommand#setResult(Result) converts REJECTED to
 				// REJECTED_NONFASTFORWARD, even though that result is also
 				// used for a missing object. Eagerly handle this case so we
 				// can set the right result.
 				cmd.setResult(REJECTED_MISSING_OBJECT);
 				if (isAtomic()) {
 					ReceiveCommand.abort(pending);
 					return false;
 				}
 			}
 		}
 		return true;
 	}
 
 	private boolean checkNonFastForwards(RevWalk rw,
 			List<ReceiveCommand> pending) throws IOException {
 		if (isAllowNonFastForwards()) {
 			return true;
 		}
 		for (ReceiveCommand cmd : pending) {
 			cmd.updateType(rw);
 			if (cmd.getType() == UPDATE_NONFASTFORWARD) {
 				cmd.setResult(REJECTED_NONFASTFORWARD);
 				if (isAtomic()) {
 					ReceiveCommand.abort(pending);
 					return false;
 				}
 			}
 		}
 		return true;
 	}
 
 	private boolean checkConflicting(List<ReceiveCommand> pending)
 			throws IOException {
 		TreeSet<String> added = new TreeSet<>();
 		Set<String> deleted =
 				pending.stream()
 						.filter(cmd -> cmd.getType() == DELETE)
 						.map(c -> c.getRefName())
 						.collect(Collectors.toSet());
 
 		boolean ok = true;
 		for (ReceiveCommand cmd : pending) {
 			if (cmd.getType() == DELETE) {
 				continue;
 			}
 
 			String name = cmd.getRefName();
 			if (refDb.isNameConflicting(name, added, deleted)) {
 				if (isAtomic()) {
 					cmd.setResult(
 							ReceiveCommand.Result.REJECTED_OTHER_REASON, JGitText.get().transactionAborted);
 				} else {
 					cmd.setResult(LOCK_FAILURE);
 				}
 
 				ok = false;
 			}
 			added.add(name);
 		}
 
 		if (isAtomic()) {
 			if (!ok) {
 				pending.stream()
 						.filter(cmd -> cmd.getResult() == NOT_ATTEMPTED)
 						.forEach(cmd -> cmd.setResult(LOCK_FAILURE));
 			}
 			return ok;
 		}
 
 		for (ReceiveCommand cmd : pending) {
 			if (cmd.getResult() == NOT_ATTEMPTED) {
 				return true;
 			}
 		}
 
 		return false;
 	}
 
 	private boolean checkExpected(List<ReceiveCommand> pending)
 			throws IOException {
 		for (ReceiveCommand cmd : pending) {
 			if (!matchOld(cmd, refDb.exactRef(cmd.getRefName()))) {
 				cmd.setResult(LOCK_FAILURE);
 				if (isAtomic()) {
 					ReceiveCommand.abort(pending);
 					return false;
 				}
 			}
 		}
 		return true;
 	}
 
 	private static boolean matchOld(ReceiveCommand cmd, @Nullable Ref ref) {
 		if (ref == null) {
 			return AnyObjectId.isEqual(ObjectId.zeroId(), cmd.getOldId())
 				&& cmd.getOldSymref() == null;
 		} else if (ref.isSymbolic()) {
 			return ref.getTarget().getName().equals(cmd.getOldSymref());
 		}
 		ObjectId id = ref.getObjectId();
 		if (id == null) {
 			id = ObjectId.zeroId();
 		}
 		return cmd.getOldId().equals(id);
 	}
 
 	/**
 	 * Writes the refs to the writer, and calls finish.
 	 *
 	 * @param writer
 	 *            the writer on which we should write.
 	 * @param newRefs
 	 *            the ref data to write..
 	 * @param pending
 	 *            the log data to write.
 	 * @throws IOException
 	 *            in case of problems.
 	 */
 	protected void write(ReftableWriter writer, List<Ref> newRefs,
 			List<ReceiveCommand> pending) throws IOException {
 		long updateIndex = refDb.nextUpdateIndex();
 		writer.setMinUpdateIndex(updateIndex).setMaxUpdateIndex(updateIndex)
 				.begin().sortAndWriteRefs(newRefs);
 		if (!isRefLogDisabled()) {
 			writeLog(writer, updateIndex, pending);
 		}
 	}
 
 	private void writeLog(ReftableWriter writer, long updateIndex,
 			List<ReceiveCommand> pending) throws IOException {
 		Map<String, ReceiveCommand> cmds = new HashMap<>();
 		List<String> byName = new ArrayList<>(pending.size());
 		for (ReceiveCommand cmd : pending) {
 			cmds.put(cmd.getRefName(), cmd);
 			byName.add(cmd.getRefName());
 		}
 		Collections.sort(byName);
 
 		PersonIdent ident = getRefLogIdent();
 		if (ident == null) {
 			ident = new PersonIdent(repository);
 		}
 		for (String name : byName) {
 			ReceiveCommand cmd = cmds.get(name);
 			if (isRefLogDisabled(cmd)) {
 				continue;
 			}
 			String msg = getRefLogMessage(cmd);
 			if (isRefLogIncludingResult(cmd)) {
 				String strResult = toResultString(cmd);
 				if (strResult != null) {
 					msg = msg.isEmpty() ? strResult : msg + ": " + strResult; //$NON-NLS-1$
 				}
 			}
 			writer.writeLog(name, updateIndex, ident, cmd.getOldId(),
 					cmd.getNewId(), msg);
 		}
 	}
 
 	private String toResultString(ReceiveCommand cmd) {
 		switch (cmd.getType()) {
 		case CREATE:
 			return ReflogEntry.PREFIX_CREATED;
 		case UPDATE:
 			// Match the behavior of a single RefUpdate. In that case, setting
 			// the force bit completely bypasses the potentially expensive
 			// isMergedInto check, by design, so the reflog message may be
 			// inaccurate.
 			//
 			// Similarly, this class bypasses the isMergedInto checks when the
 			// force bit is set, meaning we can't actually distinguish between
 			// UPDATE and UPDATE_NONFASTFORWARD when isAllowNonFastForwards()
 			// returns true.
 			return isAllowNonFastForwards() ? ReflogEntry.PREFIX_FORCED_UPDATE
 					: ReflogEntry.PREFIX_FAST_FORWARD;
 		case UPDATE_NONFASTFORWARD:
 			return ReflogEntry.PREFIX_FORCED_UPDATE;
 		default:
 			return null;
 		}
 	}
 
 	// Extracts and peels the refs out of the ReceiveCommands
 	private static List<Ref> toNewRefs(RevWalk rw, List<ReceiveCommand> pending)
 		throws IOException {
 		List<Ref> refs = new ArrayList<>(pending.size());
 		for (ReceiveCommand cmd : pending) {
 			if (cmd.getResult() != NOT_ATTEMPTED) {
 				continue;
 			}
 
 			String name = cmd.getRefName();
 			ObjectId newId = cmd.getNewId();
 			String newSymref = cmd.getNewSymref();
 			if (AnyObjectId.isEqual(ObjectId.zeroId(), newId)
 				&& newSymref == null) {
 				refs.add(new ObjectIdRef.Unpeeled(NEW, name, null));
 				continue;
 			} else if (newSymref != null) {
 				refs.add(new SymbolicRef(name,
 					new ObjectIdRef.Unpeeled(NEW, newSymref, null)));
 				continue;
 			}
 
 			RevObject obj = rw.parseAny(newId);
 			RevObject peel = null;
 			if (obj instanceof RevTag) {
 				peel = rw.peel(obj);
 			}
 			if (peel != null) {
 				refs.add(new ObjectIdRef.PeeledTag(PACKED, name, newId,
 					peel.copy()));
 			} else {
 				refs.add(new ObjectIdRef.PeeledNonTag(PACKED, name, newId));
 			}
 		}
 		return refs;
 	}
 }