/*
 * 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 static org.tmatesoft.hg.repo.HgRepository.TIP;
import static org.tmatesoft.hg.repo.HgRepository.WORKING_COPY;

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.Nodeid;
import org.tmatesoft.hg.internal.FilterByteChannel;
import org.tmatesoft.hg.internal.RevlogStream;
import org.tmatesoft.hg.util.ByteChannel;
import org.tmatesoft.hg.util.CancelSupport;
import org.tmatesoft.hg.util.CancelledException;
import org.tmatesoft.hg.util.Path;
import org.tmatesoft.hg.util.ProgressSupport;



/**
 * ? 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?
	}

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

	public byte[] content() {
		return content(TIP);
	}
	
	/*XXX not sure applyFilters is the best way to do, perhaps, callers shall add filters themselves?*/
	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.
	}

	// for data files need to check heading of the file content for possible metadata
	// @see http://mercurial.selenic.com/wiki/FileFormats#data.2BAC8-
	@Override
	public byte[] content(int revision) {
		if (revision == TIP) {
			revision = getLastRevision();
		}
		if (wrongLocalRevision(revision) || revision == BAD_REVISION || revision == WORKING_COPY) {
			throw new IllegalArgumentException(String.valueOf(revision));
		}
		byte[] data = super.content(revision);
		if (metadata == null) {
			metadata = new Metadata();
		}
		if (metadata.none(revision)) {
			// although not very reasonable when data is byte array, this check might
			// get handy when there's a stream/channel to avoid useless reads and rewinds.
			return data;
		}
		int toSkip = 0;
		if (!metadata.known(revision)) {
			if (data.length < 4 || (data[0] != 1 && data[1] != 10)) {
				metadata.recordNone(revision);
				return data;
			}
			int lastEntryStart = 2;
			int lastColon = -1;
			ArrayList<MetadataEntry> _metadata = new ArrayList<MetadataEntry>();
			String key = null, value = null;
			for (int i = 2; i < data.length; i++) {
				if (data[i] == (int) ':') {
					key = new String(data, lastEntryStart, i - lastEntryStart);
					lastColon = i;
				} else if (data[i] == '\n') {
					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(data, lastColon + 1, i - lastColon - 1).trim();
					_metadata.add(new MetadataEntry(key, value));
					key = value = null;
					lastColon = -1;
					lastEntryStart = i+1;
				} else if (data[i] == 1 && i + 1 < data.length && data[i+1] == 10) {
					if (key != null && lastColon != -1 && i > lastColon) {
						// just in case last entry didn't end with newline
						value = new String(data, lastColon + 1, i - lastColon - 1);
						_metadata.add(new MetadataEntry(key, value));
					}
					lastEntryStart = i+1;
					break;
				}
			}
			_metadata.trimToSize();
			metadata.add(revision, lastEntryStart, _metadata);
			toSkip = lastEntryStart;
		} else {
			toSkip = metadata.dataOffset(revision);
		}
		// XXX copy of an array may be memory-hostile, a wrapper with baseOffsetShift(lastEntryStart) would be more convenient
		byte[] rv = new byte[data.length - toSkip];
		System.arraycopy(data, toSkip, rv, 0, rv.length);
		return rv;
	}

	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, byte[] data) {
				commitRevisions[count++] = linkRevision;
			}
		};
		content.iterate(start, end, false, insp);
		getRepo().getChangelog().range(inspector, commitRevisions);
	}
	
	// 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() {
		if (metadata == null || !metadata.checked(0)) {
			// content() always initializes metadata.
			content(0); // FIXME expensive way to find out metadata, distinct RevlogStream.Iterator would be better.
		}
		if (!metadata.known(0)) {
			return false;
		}
		return metadata.find(0, "copy") != null;
	}

	public Path getCopySourceName() {
		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() {
		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;
		}
	}
}