/*
    * Copyright (C) 2008, 2010 Google Inc.
    * Copyright (C) 2008, Marek Zawirski <marek.zawirski@gmail.com>
    * Copyright (C) 2008, Robin Rosenberg <robin.rosenberg@dewire.com>
    * Copyright (C) 2008, 2020 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.transport;
  
  import static org.eclipse.jgit.transport.GitProtocolConstants.COMMAND_LS_REFS;
  import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_AGENT;
  import static org.eclipse.jgit.transport.GitProtocolConstants.REF_ATTR_PEELED;
  import static org.eclipse.jgit.transport.GitProtocolConstants.REF_ATTR_SYMREF_TARGET;
  import static org.eclipse.jgit.transport.GitProtocolConstants.VERSION_1;
  import static org.eclipse.jgit.transport.GitProtocolConstants.VERSION_2;
  
  import java.io.EOFException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.text.MessageFormat;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Iterator;
  import java.util.LinkedHashMap;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Set;
  
  import org.eclipse.jgit.annotations.NonNull;
  import org.eclipse.jgit.errors.InvalidObjectIdException;
  import org.eclipse.jgit.errors.NoRemoteRepositoryException;
  import org.eclipse.jgit.errors.PackProtocolException;
  import org.eclipse.jgit.errors.RemoteRepositoryException;
  import org.eclipse.jgit.errors.TransportException;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.lib.Constants;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.ObjectIdRef;
  import org.eclipse.jgit.lib.Ref;
  import org.eclipse.jgit.lib.Repository;
  import org.eclipse.jgit.lib.SymbolicRef;
  import org.eclipse.jgit.util.StringUtils;
  import org.eclipse.jgit.util.io.InterruptTimer;
  import org.eclipse.jgit.util.io.TimeoutInputStream;
  import org.eclipse.jgit.util.io.TimeoutOutputStream;
  
  /**
   * Base helper class for pack-based operations implementations. Provides partial
   * implementation of pack-protocol - refs advertising and capabilities support,
   * and some other helper methods.
   *
   * @see BasePackFetchConnection
   * @see BasePackPushConnection
   */
  abstract class BasePackConnection extends BaseConnection {
  
  	protected static final String CAPABILITY_SYMREF_PREFIX = "symref="; //$NON-NLS-1$
  
  	/** The repository this transport fetches into, or pushes out of. */
  	protected final Repository local;
  
  	/** Remote repository location. */
  	protected final URIish uri;
  
  	/** A transport connected to {@link #uri}. */
  	protected final Transport transport;
  
  	/** Low-level input stream, if a timeout was configured. */
  	protected TimeoutInputStream timeoutIn;
  
  	/** Low-level output stream, if a timeout was configured. */
  	protected TimeoutOutputStream timeoutOut;
  
  	/** Timer to manage {@link #timeoutIn} and {@link #timeoutOut}. */
  	private InterruptTimer myTimer;
  
  	/** Input stream reading from the remote. */
  	protected InputStream in;
  
  	/** Output stream sending to the remote. */
  	protected OutputStream out;
  
  	/** Packet line decoder around {@link #in}. */
  	protected PacketLineIn pckIn;
  
  	/** Packet line encoder around {@link #out}. */
  	protected PacketLineOut pckOut;
  
  	/** Send {@link PacketLineOut#end()} before closing {@link #out}? */
 	protected boolean outNeedsEnd;
 
 	/** True if this is a stateless RPC connection. */
 	protected boolean statelessRPC;
 
 	/** Capability tokens advertised by the remote side. */
 	private final Map<String, String> remoteCapabilities = new HashMap<>();
 
 	/** Extra objects the remote has, but which aren't offered as refs. */
 	protected final Set<ObjectId> additionalHaves = new HashSet<>();
 
 	private TransferConfig.ProtocolVersion protocol = TransferConfig.ProtocolVersion.V0;
 
 	BasePackConnection(PackTransport packTransport) {
 		transport = (Transport) packTransport;
 		local = transport.local;
 		uri = transport.uri;
 	}
 
 	TransferConfig.ProtocolVersion getProtocolVersion() {
 		return protocol;
 	}
 
 	void setProtocolVersion(@NonNull TransferConfig.ProtocolVersion protocol) {
 		this.protocol = protocol;
 	}
 
 	/**
 	 * Configure this connection with the directional pipes.
 	 *
 	 * @param myIn
 	 *            input stream to receive data from the peer. Caller must ensure
 	 *            the input is buffered, otherwise read performance may suffer.
 	 * @param myOut
 	 *            output stream to transmit data to the peer. Caller must ensure
 	 *            the output is buffered, otherwise write performance may
 	 *            suffer.
 	 */
 	protected final void init(InputStream myIn, OutputStream myOut) {
 		final int timeout = transport.getTimeout();
 		if (timeout > 0) {
 			final Thread caller = Thread.currentThread();
 			if (myTimer == null) {
 				myTimer = new InterruptTimer(caller.getName() + "-Timer"); //$NON-NLS-1$
 			}
 			timeoutIn = new TimeoutInputStream(myIn, myTimer);
 			timeoutOut = new TimeoutOutputStream(myOut, myTimer);
 			timeoutIn.setTimeout(timeout * 1000);
 			timeoutOut.setTimeout(timeout * 1000);
 			myIn = timeoutIn;
 			myOut = timeoutOut;
 		}
 
 		in = myIn;
 		out = myOut;
 
 		pckIn = new PacketLineIn(in);
 		pckOut = new PacketLineOut(out);
 		outNeedsEnd = true;
 	}
 
 	/**
 	 * Reads the advertised references through the initialized stream.
 	 * <p>
 	 * Subclass implementations may call this method only after setting up the
 	 * input and output streams with {@link #init(InputStream, OutputStream)}.
 	 * <p>
 	 * If any errors occur, this connection is automatically closed by invoking
 	 * {@link #close()} and the exception is wrapped (if necessary) and thrown
 	 * as a {@link org.eclipse.jgit.errors.TransportException}.
 	 *
 	 * @return {@code true} if the refs were read; {@code false} otherwise
 	 *         indicating that {@link #lsRefs} must be called
 	 *
 	 * @throws org.eclipse.jgit.errors.TransportException
 	 *             the reference list could not be scanned.
 	 */
 	protected boolean readAdvertisedRefs() throws TransportException {
 		try {
 			return readAdvertisedRefsImpl();
 		} catch (TransportException err) {
 			close();
 			throw err;
 		} catch (IOException | RuntimeException err) {
 			close();
 			throw new TransportException(err.getMessage(), err);
 		}
 	}
 
 	private String readLine() throws IOException {
 		String line = pckIn.readString();
 		if (PacketLineIn.isEnd(line)) {
 			return null;
 		}
 		if (line.startsWith("ERR ")) { //$NON-NLS-1$
 			// This is a customized remote service error.
 			// Users should be informed about it.
 			throw new RemoteRepositoryException(uri, line.substring(4));
 		}
 		return line;
 	}
 
 	private boolean readAdvertisedRefsImpl() throws IOException {
 		final Map<String, Ref> avail = new LinkedHashMap<>();
 		final Map<String, String> symRefs = new LinkedHashMap<>();
 		for (boolean first = true;; first = false) {
 			String line;
 
 			if (first) {
 				boolean isV1 = false;
 				try {
 					line = readLine();
 				} catch (EOFException e) {
 					TransportException noRepo = noRepository();
 					noRepo.initCause(e);
 					throw noRepo;
 				}
 				if (line != null && VERSION_1.equals(line)) {
 					// Same as V0, except for this extra line. We shouldn't get
 					// it since we never request V1.
 					setProtocolVersion(TransferConfig.ProtocolVersion.V0);
 					isV1 = true;
 					line = readLine();
 				}
 				if (line == null) {
 					break;
 				}
 				final int nul = line.indexOf('\0');
 				if (nul >= 0) {
 					// Protocol V0: The first line (if any) may contain
 					// "hidden" capability values after a NUL byte.
 					for (String capability : line.substring(nul + 1)
 							.split(" ")) { //$NON-NLS-1$
 						if (capability.startsWith(CAPABILITY_SYMREF_PREFIX)) {
 							String[] parts = capability
 									.substring(
 											CAPABILITY_SYMREF_PREFIX.length())
 									.split(":", 2); //$NON-NLS-1$
 							if (parts.length == 2) {
 								symRefs.put(parts[0], parts[1]);
 							}
 						} else {
 							addCapability(capability);
 						}
 					}
 					line = line.substring(0, nul);
 					setProtocolVersion(TransferConfig.ProtocolVersion.V0);
 				} else if (!isV1 && VERSION_2.equals(line)) {
 					// Protocol V2: remaining lines are capabilities as
 					// key=value pairs
 					setProtocolVersion(TransferConfig.ProtocolVersion.V2);
 					readCapabilitiesV2();
 					// Break out here so that stateless RPC transports get a
 					// chance to set up the output stream.
 					return false;
 				} else {
 					setProtocolVersion(TransferConfig.ProtocolVersion.V0);
 				}
 			} else {
 				line = readLine();
 				if (line == null) {
 					break;
 				}
 			}
 
 			// Expecting to get a line in the form "sha1 refname"
 			if (line.length() < 41 || line.charAt(40) != ' ') {
 				throw invalidRefAdvertisementLine(line);
 			}
 			String name = line.substring(41, line.length());
 			if (first && name.equals("capabilities^{}")) { //$NON-NLS-1$
 				// special line from git-receive-pack (protocol V0) to show
 				// capabilities when there are no refs to advertise
 				continue;
 			}
 
 			final ObjectId id = toId(line, line.substring(0, 40));
 			if (name.equals(".have")) { //$NON-NLS-1$
 				additionalHaves.add(id);
 			} else {
 				processLineV1(name, id, avail);
 			}
 		}
 		updateWithSymRefs(avail, symRefs);
 		available(avail);
 		return true;
 	}
 
 	/**
 	 * Issue a protocol V2 ls-refs command and read its response.
 	 *
 	 * @param refSpecs
 	 *            to produce ref prefixes from if the server supports git
 	 *            protocol V2
 	 * @param additionalPatterns
 	 *            to use for ref prefixes if the server supports git protocol V2
 	 * @throws TransportException
 	 *             if the command could not be run or its output not be read
 	 */
 	protected void lsRefs(Collection<RefSpec> refSpecs,
 			String... additionalPatterns) throws TransportException {
 		try {
 			lsRefsImpl(refSpecs, additionalPatterns);
 		} catch (TransportException err) {
 			close();
 			throw err;
 		} catch (IOException | RuntimeException err) {
 			close();
 			throw new TransportException(err.getMessage(), err);
 		}
 	}
 
 	private void lsRefsImpl(Collection<RefSpec> refSpecs,
 			String... additionalPatterns) throws IOException {
 		pckOut.writeString("command=" + COMMAND_LS_REFS); //$NON-NLS-1$
 		// Add the user-agent
 		String agent = UserAgent.get();
 		if (agent != null && isCapableOf(OPTION_AGENT)) {
 			pckOut.writeString(OPTION_AGENT + '=' + agent);
 		}
 		pckOut.writeDelim();
 		pckOut.writeString("peel"); //$NON-NLS-1$
 		pckOut.writeString("symrefs"); //$NON-NLS-1$
 		for (String refPrefix : getRefPrefixes(refSpecs, additionalPatterns)) {
 			pckOut.writeString("ref-prefix " + refPrefix); //$NON-NLS-1$
 		}
 		pckOut.end();
 		final Map<String, Ref> avail = new LinkedHashMap<>();
 		final Map<String, String> symRefs = new LinkedHashMap<>();
 		for (;;) {
 			String line = readLine();
 			if (line == null) {
 				break;
 			}
 			// Expecting to get a line in the form "sha1 refname"
 			if (line.length() < 41 || line.charAt(40) != ' ') {
 				throw invalidRefAdvertisementLine(line);
 			}
 			String name = line.substring(41, line.length());
 			final ObjectId id = toId(line, line.substring(0, 40));
 			if (name.equals(".have")) { //$NON-NLS-1$
 				additionalHaves.add(id);
 			} else {
 				processLineV2(line, id, name, avail, symRefs);
 			}
 		}
 		updateWithSymRefs(avail, symRefs);
 		available(avail);
 	}
 
 	private Collection<String> getRefPrefixes(Collection<RefSpec> refSpecs,
 			String... additionalPatterns) {
 		if (refSpecs.isEmpty() && (additionalPatterns == null
 				|| additionalPatterns.length == 0)) {
 			return Collections.emptyList();
 		}
 		Set<String> patterns = new HashSet<>();
 		if (additionalPatterns != null) {
 			Arrays.stream(additionalPatterns).filter(Objects::nonNull)
 					.forEach(patterns::add);
 		}
 		for (RefSpec spec : refSpecs) {
 			// TODO: for now we only do protocol V2 for fetch. For push
 			// RefSpecs, the logic would need to be different. (At the
 			// minimum, take spec.getDestination().)
 			String src = spec.getSource();
 			if (ObjectId.isId(src)) {
 				continue;
 			}
 			if (spec.isWildcard()) {
 				patterns.add(src.substring(0, src.indexOf('*')));
 			} else {
 				patterns.add(src);
 				patterns.add(Constants.R_REFS + src);
 				patterns.add(Constants.R_HEADS + src);
 				patterns.add(Constants.R_TAGS + src);
 			}
 		}
 		return patterns;
 	}
 
 	private void readCapabilitiesV2() throws IOException {
 		// In git protocol V2, capabilities are different. If it's a key-value
 		// pair, the key may be a command name, and the value a space-separated
 		// list of capabilities for that command. We still store it in the same
 		// map as for protocol v0/v1. Protocol v2 code has to account for this.
 		for (;;) {
 			String line = readLine();
 			if (line == null) {
 				break;
 			}
 			addCapability(line);
 		}
 	}
 
 	private void addCapability(String capability) {
 		String parts[] = capability.split("=", 2); //$NON-NLS-1$
 		if (parts.length == 2) {
 			remoteCapabilities.put(parts[0], parts[1]);
 		}
 		remoteCapabilities.put(capability, null);
 	}
 
 	private ObjectId toId(String line, String value)
 			throws PackProtocolException {
 		try {
 			return ObjectId.fromString(value);
 		} catch (InvalidObjectIdException e) {
 			PackProtocolException ppe = invalidRefAdvertisementLine(line);
 			ppe.initCause(e);
 			throw ppe;
 		}
 	}
 
 	private void processLineV1(String name, ObjectId id, Map<String, Ref> avail)
 			throws IOException {
 		if (name.endsWith("^{}")) { //$NON-NLS-1$
 			name = name.substring(0, name.length() - 3);
 			final Ref prior = avail.get(name);
 			if (prior == null) {
 				throw new PackProtocolException(uri, MessageFormat.format(
 						JGitText.get().advertisementCameBefore, name, name));
 			}
 			if (prior.getPeeledObjectId() != null) {
 				throw duplicateAdvertisement(name + "^{}"); //$NON-NLS-1$
 			}
 			avail.put(name, new ObjectIdRef.PeeledTag(Ref.Storage.NETWORK, name,
 					prior.getObjectId(), id));
 		} else {
 			final Ref prior = avail.put(name, new ObjectIdRef.PeeledNonTag(
 					Ref.Storage.NETWORK, name, id));
 			if (prior != null) {
 				throw duplicateAdvertisement(name);
 			}
 		}
 	}
 
 	private void processLineV2(String line, ObjectId id, String rest,
 			Map<String, Ref> avail, Map<String, String> symRefs)
 			throws IOException {
 		String[] parts = rest.split(" "); //$NON-NLS-1$
 		String name = parts[0];
 		// Two attributes possible, symref-target or peeled
 		String symRefTarget = null;
 		String peeled = null;
 		for (int i = 1; i < parts.length; i++) {
 			if (parts[i].startsWith(REF_ATTR_SYMREF_TARGET)) {
 				if (symRefTarget != null) {
 					throw new PackProtocolException(uri, MessageFormat.format(
 							JGitText.get().duplicateRefAttribute, line));
 				}
 				symRefTarget = parts[i]
 						.substring(REF_ATTR_SYMREF_TARGET.length());
 			} else if (parts[i].startsWith(REF_ATTR_PEELED)) {
 				if (peeled != null) {
 					throw new PackProtocolException(uri, MessageFormat.format(
 							JGitText.get().duplicateRefAttribute, line));
 				}
 				peeled = parts[i].substring(REF_ATTR_PEELED.length());
 			}
 			if (peeled != null && symRefTarget != null) {
 				break;
 			}
 		}
 		Ref idRef;
 		if (peeled != null) {
 			idRef = new ObjectIdRef.PeeledTag(Ref.Storage.NETWORK, name, id,
 					toId(line, peeled));
 		} else {
 			idRef = new ObjectIdRef.PeeledNonTag(Ref.Storage.NETWORK, name, id);
 		}
 		Ref prior = avail.put(name, idRef);
 		if (prior != null) {
 			throw duplicateAdvertisement(name);
 		}
 		if (!StringUtils.isEmptyOrNull(symRefTarget)) {
 			symRefs.put(name, symRefTarget);
 		}
 	}
 
 	/**
 	 * Updates the given refMap with {@link SymbolicRef}s defined by the given
 	 * symRefs.
 	 * <p>
 	 * For each entry, symRef, in symRefs, whose value is a key in refMap, adds
 	 * a new entry to refMap with that same key and value of a new
 	 * {@link SymbolicRef} with source=symRef.key and
 	 * target=refMap.get(symRef.value), then removes that entry from symRefs.
 	 * <p>
 	 * If refMap already contains an entry for symRef.key, it is replaced.
 	 * </p>
 	 * </p>
 	 * <p>
 	 * For example, given:
 	 * </p>
 	 *
 	 * <pre>
 	 * refMap.put("refs/heads/main", ref);
 	 * symRefs.put("HEAD", "refs/heads/main");
 	 * </pre>
 	 *
 	 * then:
 	 *
 	 * <pre>
 	 * updateWithSymRefs(refMap, symRefs);
 	 * </pre>
 	 *
 	 * has the <em>effect</em> of:
 	 *
 	 * <pre>
 	 * refMap.put("HEAD",
 	 * 		new SymbolicRef("HEAD", refMap.get(symRefs.remove("HEAD"))))
 	 * </pre>
 	 * <p>
 	 * Any entry in symRefs whose value is not a key in refMap is ignored. Any
 	 * circular symRefs are ignored.
 	 * </p>
 	 * <p>
 	 * Upon completion, symRefs will contain only any unresolvable entries.
 	 * </p>
 	 *
 	 * @param refMap
 	 *            a non-null, modifiable, Map to update, and the provider of
 	 *            symref targets.
 	 * @param symRefs
 	 *            a non-null, modifiable, Map of symrefs.
 	 * @throws NullPointerException
 	 *             if refMap or symRefs is null
 	 */
 	static void updateWithSymRefs(Map<String, Ref> refMap, Map<String, String> symRefs) {
 		boolean haveNewRefMapEntries = !refMap.isEmpty();
 		while (!symRefs.isEmpty() && haveNewRefMapEntries) {
 			haveNewRefMapEntries = false;
 			final Iterator<Map.Entry<String, String>> iterator = symRefs.entrySet().iterator();
 			while (iterator.hasNext()) {
 				final Map.Entry<String, String> symRef = iterator.next();
 				if (!symRefs.containsKey(symRef.getValue())) { // defer forward reference
 					final Ref r = refMap.get(symRef.getValue());
 					if (r != null) {
 						refMap.put(symRef.getKey(), new SymbolicRef(symRef.getKey(), r));
 						haveNewRefMapEntries = true;
 						iterator.remove();
 					}
 				}
 			}
 		}
 		// If HEAD is still in the symRefs map here, the real ref was not
 		// reported, but we know it must point to the object reported for HEAD.
 		// So fill it in in the refMap.
 		String headRefName = symRefs.get(Constants.HEAD);
 		if (headRefName != null && !refMap.containsKey(headRefName)) {
 			Ref headRef = refMap.get(Constants.HEAD);
 			if (headRef != null) {
 				ObjectId headObj = headRef.getObjectId();
 				headRef = new ObjectIdRef.PeeledNonTag(Ref.Storage.NETWORK,
 						headRefName, headObj);
 				refMap.put(headRefName, headRef);
 				headRef = new SymbolicRef(Constants.HEAD, headRef);
 				refMap.put(Constants.HEAD, headRef);
 				symRefs.remove(Constants.HEAD);
 			}
 		}
 	}
 
 	/**
 	 * Create an exception to indicate problems finding a remote repository. The
 	 * caller is expected to throw the returned exception.
 	 *
 	 * Subclasses may override this method to provide better diagnostics.
 	 *
 	 * @return a TransportException saying a repository cannot be found and
 	 *         possibly why.
 	 */
 	protected TransportException noRepository() {
 		return new NoRemoteRepositoryException(uri, JGitText.get().notFound);
 	}
 
 	/**
 	 * Whether this option is supported
 	 *
 	 * @param option
 	 *            option string
 	 * @return whether this option is supported
 	 */
 	protected boolean isCapableOf(String option) {
 		return remoteCapabilities.containsKey(option);
 	}
 
 	/**
 	 * Request capability
 	 *
 	 * @param b
 	 *            buffer
 	 * @param option
 	 *            option we want
 	 * @return {@code true} if the requested option is supported
 	 */
 	protected boolean wantCapability(StringBuilder b, String option) {
 		if (!isCapableOf(option))
 			return false;
 		b.append(' ');
 		b.append(option);
 		return true;
 	}
 
 	/**
 	 * Return a capability value.
 	 *
 	 * @param option
 	 *            to get
 	 * @return the value stored, if any.
 	 */
 	protected String getCapability(String option) {
 		return remoteCapabilities.get(option);
 	}
 
 	/**
 	 * Add user agent capability
 	 *
 	 * @param b
 	 *            a {@link java.lang.StringBuilder} object.
 	 */
 	protected void addUserAgentCapability(StringBuilder b) {
 		String a = UserAgent.get();
 		if (a != null && remoteCapabilities.get(OPTION_AGENT) != null) {
 			b.append(' ').append(OPTION_AGENT).append('=').append(a);
 		}
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public String getPeerUserAgent() {
 		String agent = remoteCapabilities.get(OPTION_AGENT);
 		return agent != null ? agent : super.getPeerUserAgent();
 	}
 
 	private PackProtocolException duplicateAdvertisement(String name) {
 		return new PackProtocolException(uri, MessageFormat.format(JGitText.get().duplicateAdvertisementsOf, name));
 	}
 
 	private PackProtocolException invalidRefAdvertisementLine(String line) {
 		return new PackProtocolException(uri, MessageFormat.format(JGitText.get().invalidRefAdvertisementLine, line));
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public void close() {
 		if (out != null) {
 			try {
 				if (outNeedsEnd) {
 					outNeedsEnd = false;
 					pckOut.end();
 				}
 				out.close();
 			} catch (IOException err) {
 				// Ignore any close errors.
 			} finally {
 				out = null;
 				pckOut = null;
 			}
 		}
 
 		if (in != null) {
 			try {
 				in.close();
 			} catch (IOException err) {
 				// Ignore any close errors.
 			} finally {
 				in = null;
 				pckIn = null;
 			}
 		}
 
 		if (myTimer != null) {
 			try {
 				myTimer.terminate();
 			} finally {
 				myTimer = null;
 				timeoutIn = null;
 				timeoutOut = null;
 			}
 		}
 	}
 
 	/**
 	 * Tell the peer we are disconnecting, if it cares to know.
 	 */
 	protected void endOut() {
 		if (outNeedsEnd && out != null) {
 			try {
 				outNeedsEnd = false;
 				pckOut.end();
 			} catch (IOException e) {
 				try {
 					out.close();
 				} catch (IOException err) {
 					// Ignore any close errors.
 				} finally {
 					out = null;
 					pckOut = null;
 				}
 			}
 		}
 	}
 }