/*
 * Copyright (c) 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 java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

import org.tmatesoft.hg.core.HgBadStateException;
import org.tmatesoft.hg.core.HgFileRevision;
import org.tmatesoft.hg.core.Nodeid;
import org.tmatesoft.hg.internal.ManifestRevision;
import org.tmatesoft.hg.internal.Pool;
import org.tmatesoft.hg.util.Path;
import org.tmatesoft.hg.util.PathPool;
import org.tmatesoft.hg.util.PathRewrite;

/**
 *
 * @author Artem Tikhomirov
 * @author TMate Software Ltd.
 */
public class HgMergeState {
	private Nodeid wcp1, wcp2;
	
	public enum Kind {
		Resolved, Unresolved;
	}
	
	public static class Entry {
		private final Kind state;
		private final HgFileRevision parent1;
		private final HgFileRevision parent2;
		private final HgFileRevision ancestor;
		private final Path wcFile;

		/*package-local*/Entry(Kind s, Path actualCopy, HgFileRevision p1, HgFileRevision p2, HgFileRevision ca) {
			if (p1 == null || p2 == null || ca == null || actualCopy == null) {
				throw new IllegalArgumentException();
			}
			state = s;
			wcFile = actualCopy;
			parent1 = p1;
			parent2 = p2;
			ancestor = ca;
		}
		
		public Kind getState() {
			return state;
		}
		public Path getActualFile() {
			return wcFile;
		}
		public HgFileRevision getFirstParent() {
			return parent1;
		}
		public HgFileRevision getSecondParent() {
			return parent2;
		}
		public HgFileRevision getCommonAncestor() {
			return ancestor;
		}
	}

	private final HgRepository repo;
	private Entry[] entries;

	HgMergeState(HgRepository hgRepo) {
		repo = hgRepo;
	}

	public void refresh() throws IOException/*XXX it's unlikely caller can do anything reasonable about IOException */ {
		entries = null;
		final File f = new File(repo.getRepositoryRoot(), "merge/state");
		if (!f.canRead()) {
			// empty state
			return;
		}
		Nodeid[] wcParents = repo.loadDirstate().parents();
		wcp1 = wcParents[0]; wcp2 = wcParents[1];
		ArrayList<Entry> result = new ArrayList<Entry>();
		PathPool pathPool = new PathPool(new PathRewrite.Empty());
		Pool<Nodeid> nodeidPool = new Pool<Nodeid>();
		Pool<String> fnamePool = new Pool<String>();
		final ManifestRevision m1 = new ManifestRevision(nodeidPool, fnamePool);
		final ManifestRevision m2 = new ManifestRevision(nodeidPool, fnamePool);
		final int rp1 = repo.getChangelog().getLocalRevision(wcp1);
		final int rp2 = repo.getChangelog().getLocalRevision(wcp2);
		repo.getManifest().walk(rp1, rp1, m1);
		repo.getManifest().walk(rp2, rp2, m2);
		BufferedReader br = new BufferedReader(new FileReader(f));
		String s = br.readLine();
		Nodeid n = Nodeid.fromAscii(s);
		if (!wcp1.equals(n)) {
			throw new AssertionError("I assume merge/state records revision of the wc we merge into");
		}
		while ((s = br.readLine()) != null) {
			String[] r = s.split("\\00");
			HgFileRevision p1 = new HgFileRevision(repo, m1.nodeid(r[3]), pathPool.path(r[3]));
			HgFileRevision ca = new HgFileRevision(repo, Nodeid.fromAscii(r[5]), pathPool.path(r[4]));
			HgFileRevision p2 = new HgFileRevision(repo, m2.nodeid(r[6]), pathPool.path(r[6]));
			final Kind k;
			if ("u".equals(r[1])) {
				k = Kind.Unresolved;
			} else if ("r".equals(r[1])) {
				k = Kind.Resolved;
			} else {
				throw new HgBadStateException(r[1]);
			}
			Entry e = new Entry(k, pathPool.path(r[0]), p1, p2, ca);
			result.add(e);
		}
		entries = result.toArray(new Entry[result.size()]);
		br.close();
		pathPool.clear();
	}
	
	public Nodeid getFirstParent() {
		if (wcp1 == null) {
			throw new HgBadStateException("Call #refresh() first");
		}
		return wcp1;
	}
	
	public Nodeid getSecondParent() {
		if (wcp2 == null) {
			throw new HgBadStateException("Call #refresh() first");
		}
		return wcp2;
	}
	
	public List<Entry> getConflicts() {
		return entries == null ? Collections.<Entry>emptyList() : Arrays.asList(entries);
	}
}