/*
 * Copyright (c) 2010-2011 TMate Software Ltd
 *  
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * For information on how to redistribute this software under
 * the terms of a license other than GNU General Public License
 * contact TMate Software at support@hg4j.com
 */
package org.tmatesoft.hg.repo;

import static org.tmatesoft.hg.repo.HgInternals.wrongLocalRevision;
import static org.tmatesoft.hg.repo.HgRepository.*;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Collection;
import java.util.TreeMap;

import org.tmatesoft.hg.core.HgDataStreamException;
import org.tmatesoft.hg.core.HgException;
import org.tmatesoft.hg.core.Nodeid;
import org.tmatesoft.hg.internal.DataAccess;
import org.tmatesoft.hg.internal.FilterByteChannel;
import org.tmatesoft.hg.internal.RevlogStream;
import org.tmatesoft.hg.util.ByteChannel;
import org.tmatesoft.hg.util.CancelledException;
import org.tmatesoft.hg.util.Path;



/**
 * ? name:HgFileNode?
 *
 * @author Artem Tikhomirov
 * @author TMate Software Ltd.
 */
public class HgDataFile extends Revlog {

	// absolute from repo root?
	// slashes, unix-style?
	// repo location agnostic, just to give info to user, not to access real storage
	private final Path path;
	private Metadata metadata; // get initialized on first access to file content.
	
	/*package-local*/HgDataFile(HgRepository hgRepo, Path filePath, RevlogStream content) {
		super(hgRepo, content);
		path = filePath;
	}

	/*package-local*/HgDataFile(HgRepository hgRepo, Path filePath) {
		super(hgRepo);
		path = filePath;
	}

	// exists is not the best name possible. now it means no file with such name was ever known to the repo.
	// it might be confused with files existed before but lately removed. 
	public boolean exists() {
		return content != null; // XXX need better impl
	}

	// human-readable (i.e. "COPYING", not "store/data/_c_o_p_y_i_n_g.i")
	public Path getPath() {
		return path; // hgRepo.backresolve(this) -> name? In this case, what about hashed long names?
	}

	public int length(Nodeid nodeid) {
		return content.dataLength(getLocalRevision(nodeid));
	}

	public void workingCopy(ByteChannel sink) throws IOException, CancelledException {
		throw HgRepository.notImplemented();
	}
	
//	public void content(int revision, ByteChannel sink, boolean applyFilters) throws HgDataStreamException, IOException, CancelledException {
//		byte[] content = content(revision);
//		final CancelSupport cancelSupport = CancelSupport.Factory.get(sink);
//		final ProgressSupport progressSupport = ProgressSupport.Factory.get(sink);
//		ByteBuffer buf = ByteBuffer.allocate(512);
//		int left = content.length;
//		progressSupport.start(left);
//		int offset = 0;
//		cancelSupport.checkCancelled();
//		ByteChannel _sink = applyFilters ? new FilterByteChannel(sink, getRepo().getFiltersFromRepoToWorkingDir(getPath())) : sink;
//		do {
//			buf.put(content, offset, Math.min(left, buf.remaining()));
//			buf.flip();
//			cancelSupport.checkCancelled();
//			// XXX I may not rely on returned number of bytes but track change in buf position instead.
//			int consumed = _sink.write(buf);
//			buf.compact();
//			offset += consumed;
//			left -= consumed;
//			progressSupport.worked(consumed);
//		} while (left > 0);
//		progressSupport.done(); // XXX shall specify whether #done() is invoked always or only if completed successfully.
//	}
	
	/*XXX not sure distinct method contentWithFilters() is the best way to do, perhaps, callers shall add filters themselves?*/
	public void contentWithFilters(int revision, ByteChannel sink) throws HgDataStreamException, IOException, CancelledException {
		content(revision, new FilterByteChannel(sink, getRepo().getFiltersFromRepoToWorkingDir(getPath())));
	}

	// for data files need to check heading of the file content for possible metadata
	// @see http://mercurial.selenic.com/wiki/FileFormats#data.2BAC8-
	public void content(int revision, ByteChannel sink) throws HgDataStreamException, IOException, CancelledException {
		if (revision == TIP) {
			revision = getLastRevision();
		}
		if (revision == WORKING_COPY) {
			workingCopy(sink);
			return;
		}
		if (wrongLocalRevision(revision) || revision == BAD_REVISION) {
			throw new IllegalArgumentException(String.valueOf(revision));
		}
		if (sink == null) {
			throw new IllegalArgumentException();
		}
		if (metadata == null) {
			metadata = new Metadata();
		}
		ContentPipe insp;
		if (metadata.none(revision)) {
			insp = new ContentPipe(sink, 0);
		} else if (metadata.known(revision)) {
			insp = new ContentPipe(sink, metadata.dataOffset(revision));
		} else {
			// do not know if there's metadata
			insp = new MetadataContentPipe(sink, metadata, getPath());
		}
		insp.checkCancelled();
		super.content.iterate(revision, revision, true, insp);
		try {
			insp.checkFailed();
		} catch (HgDataStreamException ex) {
			throw ex;
		} catch (HgException ex) {
			// shall not happen, unless we changed ContentPipe or its subclass
			throw new HgDataStreamException(getPath(), ex.getClass().getName(), ex);
		}
	}
	
	public void history(HgChangelog.Inspector inspector) {
		history(0, getLastRevision(), inspector);
	}

	public void history(int start, int end, HgChangelog.Inspector inspector) {
		if (!exists()) {
			throw new IllegalStateException("Can't get history of invalid repository file node"); 
		}
		final int last = getLastRevision();
		if (start < 0 || start > last) {
			throw new IllegalArgumentException();
		}
		if (end == TIP) {
			end = last;
		} else if (end < start || end > last) {
			throw new IllegalArgumentException();
		}
		final int[] commitRevisions = new int[end - start + 1];
		RevlogStream.Inspector insp = new RevlogStream.Inspector() {
			int count = 0;
			
			public void next(int revisionNumber, int actualLen, int baseRevision, int linkRevision, int parent1Revision, int parent2Revision, byte[] nodeid, DataAccess data) {
				commitRevisions[count++] = linkRevision;
			}
		};
		content.iterate(start, end, false, insp);
		final HgChangelog changelog = getRepo().getChangelog();
//		changelog.range(inspector, commitRevisions); not effective when changes are sparse and far from each other
		//
		final int HistoricallyCloseCommits = 50; // XXX perhaps, shall increase/decrease based on changelog.revisionCount() 
		// (huge changelog => memory mapped files, each file re-read is more expensive than iterating over records in one read?
		//
		// try short sequences on neighboring revisions.
		for (int i = 0; i < commitRevisions.length; ) {
			int x = i;
			i++;
			boolean sequential = true;
			while (i < commitRevisions.length) {
				if (commitRevisions[i] == commitRevisions[i-1] + 1) {
					i++;
				} else if (commitRevisions[i] - commitRevisions[i-1] < HistoricallyCloseCommits) {
					// close enough, but not sequential
					sequential = false;
					i++;
				} else {
					break;
				}
			}
			if (sequential) {
				// commitRevisions[x..i-1] are sequential
				changelog.range(commitRevisions[x], commitRevisions[i-1], inspector);
			} else {
				int[] revs = new int[i-x];
				System.arraycopy(commitRevisions, x, revs, 0, i-x);
				changelog.range(inspector, revs);
			}
		}
	}
	
	// for a given local revision of the file, find out local revision in the changelog
	public int getChangesetLocalRevision(int revision) {
		return content.linkRevision(revision);
	}

	public Nodeid getChangesetRevision(Nodeid nid) {
		int changelogRevision = getChangesetLocalRevision(getLocalRevision(nid));
		return getRepo().getChangelog().getRevision(changelogRevision);
	}

	public boolean isCopy() throws HgDataStreamException {
		if (metadata == null || !metadata.checked(0)) {
			// content() always initializes metadata.
			// FIXME this is expensive way to find out metadata, distinct RevlogStream.Iterator would be better.
			// Alternatively, may parameterize MetadataContentPipe to do prepare only.
			// For reference, when throwing CancelledException, hg status -A --rev 3:80 takes 70 ms
			// however, if we just consume buffer instead (buffer.position(buffer.limit()), same command takes ~320ms
			// (compared to command-line counterpart of 190ms)
			try {
				content(0, new ByteChannel() { // No-op channel
					public int write(ByteBuffer buffer) throws IOException, CancelledException {
						// pretend we consumed whole buffer
//						int rv = buffer.remaining();
//						buffer.position(buffer.limit());
//						return rv;
						throw new CancelledException();
					}
				});
			} catch (CancelledException ex) {
				// it's ok, we did that
			} catch (Exception ex) {
				throw new HgDataStreamException(getPath(), "Can't initialize metadata", ex);
			}
		}
		if (!metadata.known(0)) {
			return false;
		}
		return metadata.find(0, "copy") != null;
	}

	public Path getCopySourceName() throws HgDataStreamException {
		if (isCopy()) {
			return Path.create(metadata.find(0, "copy"));
		}
		throw new UnsupportedOperationException(); // XXX REVISIT, think over if Exception is good (clients would check isCopy() anyway, perhaps null is sufficient?)
	}
	
	public Nodeid getCopySourceRevision() throws HgDataStreamException {
		if (isCopy()) {
			return Nodeid.fromAscii(metadata.find(0, "copyrev")); // XXX reuse/cache Nodeid
		}
		throw new UnsupportedOperationException();
	}
	
	@Override
	public String toString() {
		StringBuilder sb = new StringBuilder(getClass().getSimpleName());
		sb.append('(');
		sb.append(getPath());
		sb.append(')');
		return sb.toString();
	}

	private static final class MetadataEntry {
		private final String entry;
		private final int valueStart;
		/*package-local*/MetadataEntry(String key, String value) {
			entry = key + value;
			valueStart = key.length();
		}
		/*package-local*/boolean matchKey(String key) {
			return key.length() == valueStart && entry.startsWith(key);
		}
//		uncomment once/if needed
//		public String key() {
//			return entry.substring(0, valueStart);
//		}
		public String value() {
			return entry.substring(valueStart);
		}
	}

	private static class Metadata {
		// XXX sparse array needed
		private final TreeMap<Integer, Integer> offsets = new TreeMap<Integer, Integer>();
		private final TreeMap<Integer, MetadataEntry[]> entries = new TreeMap<Integer, MetadataEntry[]>();
		
		private final Integer NONE = new Integer(-1); // do not duplicate -1 integers at least within single file (don't want statics)

		// true when there's metadata for given revision
		boolean known(int revision) {
			Integer i = offsets.get(revision);
			return i != null && NONE != i;
		}

		// true when revision has been checked for metadata presence.
		public boolean checked(int revision) {
			return offsets.containsKey(revision);
		}

		// true when revision has been checked and found not having any metadata
		boolean none(int revision) {
			Integer i = offsets.get(revision);
			return i == NONE;
		}

		// mark revision as having no metadata.
		void recordNone(int revision) {
			Integer i = offsets.get(revision);
			if (i == NONE) {
				return; // already there
			} 
			if (i != null) {
				throw new IllegalStateException(String.format("Trying to override Metadata state for revision %d (known offset: %d)", revision, i));
			}
			offsets.put(revision, NONE);
		}

		// since this is internal class, callers are supposed to ensure arg correctness (i.e. ask known() before)
		int dataOffset(int revision) {
			return offsets.get(revision);
		}
		void add(int revision, int dataOffset, Collection<MetadataEntry> e) {
			assert !offsets.containsKey(revision);
			offsets.put(revision, dataOffset);
			entries.put(revision, e.toArray(new MetadataEntry[e.size()]));
		}
		String find(int revision, String key) {
			for (MetadataEntry me : entries.get(revision)) {
				if (me.matchKey(key)) {
					return me.value();
				}
			}
			return null;
		}
	}

	private static class MetadataContentPipe extends ContentPipe {

		private final Metadata metadata;
		private final Path fname; // need this only for error reporting

		public MetadataContentPipe(ByteChannel sink, Metadata _metadata, Path file) {
			super(sink, 0);
			metadata = _metadata;
			fname = file;
		}

		@Override
		protected void prepare(int revisionNumber, DataAccess da) throws HgException, IOException {
			final int daLength = da.length();
			if (daLength < 4 || da.readByte() != 1 || da.readByte() != 10) {
				metadata.recordNone(revisionNumber);
				da.reset();
				return;
			}
			int lastEntryStart = 2;
			int lastColon = -1;
			ArrayList<MetadataEntry> _metadata = new ArrayList<MetadataEntry>();
			// XXX in fact, need smth like ByteArrayBuilder, similar to StringBuilder,
			// which can't be used here because we can't convert bytes to chars as we read them
			// (there might be multi-byte encoding), and we need to collect all bytes before converting to string 
			ByteArrayOutputStream bos = new ByteArrayOutputStream();
			String key = null, value = null;
			boolean byteOne = false;
			for (int i = 2; i < daLength; i++) {
				byte b = da.readByte();
				if (b == '\n') {
					if (byteOne) { // i.e. \n follows 1
						lastEntryStart = i+1;
						// XXX is it possible to have here incomplete key/value (i.e. if last pair didn't end with \n)
						break;
					}
					if (key == null || lastColon == -1 || i <= lastColon) {
						throw new IllegalStateException(); // FIXME log instead and record null key in the metadata. Ex just to fail fast during dev
					}
					value = new String(bos.toByteArray()).trim();
					bos.reset();
					_metadata.add(new MetadataEntry(key, value));
					key = value = null;
					lastColon = -1;
					lastEntryStart = i+1;
					continue;
				} 
				// byteOne has to be consumed up to this line, if not jet, consume it
				if (byteOne) {
					// insert 1 we've read on previous step into the byte builder
					bos.write(1);
					// fall-through to consume current byte
					byteOne = false;
				}
				if (b == (int) ':') {
					assert value == null;
					key = new String(bos.toByteArray());
					bos.reset();
					lastColon = i;
				} else if (b == 1) {
					byteOne = true;
				} else {
					bos.write(b);
				}
			}
			_metadata.trimToSize();
			metadata.add(revisionNumber, lastEntryStart, _metadata);
			if (da.isEmpty() || !byteOne) {
				throw new HgDataStreamException(fname, String.format("Metadata for revision %d is not closed properly", revisionNumber), null);
			}
			// da is in prepared state (i.e. we consumed all bytes up to metadata end).
		}
	}
}