/*
 * Copyright (c) 2012-2013 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.internal;

import static org.tmatesoft.hg.util.LogFacility.Severity.Warn;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

import org.tmatesoft.hg.core.HgFileRevision;
import org.tmatesoft.hg.core.HgIOException;
import org.tmatesoft.hg.repo.HgDataFile;
import org.tmatesoft.hg.repo.HgManifest;
import org.tmatesoft.hg.repo.HgRuntimeException;
import org.tmatesoft.hg.util.ByteChannel;
import org.tmatesoft.hg.util.CancelledException;
import org.tmatesoft.hg.util.LogFacility.Severity;
import org.tmatesoft.hg.util.Path;

/**
 * 
 * @author Artem Tikhomirov
 * @author TMate Software Ltd.
 */
public class WorkingDirFileWriter implements ByteChannel {

	
	private final Internals hgRepo;
	private final boolean execCap, symlinkCap;
	private final FileSystemHelper fileFlagsHelper;
	private File dest;
	private FileChannel destChannel;
	private int totalBytesWritten;
	private ByteArrayChannel linkChannel;
	private int fmode;

	public WorkingDirFileWriter(Internals internalRepo) {
		hgRepo = internalRepo;
		execCap = Internals.checkSupportsExecutables(internalRepo.getRepo().getWorkingDir());
		symlinkCap = Internals.checkSupportsSymlinks(internalRepo.getRepo().getWorkingDir());
		if (symlinkCap || execCap) {
			fileFlagsHelper = new FileSystemHelper(internalRepo.getSessionContext());
		} else  {
			fileFlagsHelper = null;
		}
	}
	
	/**
	 * Writes content of specified file revision into local filesystem, or create a symlink according to flags. 
	 * Executable bit is set if specified and filesystem supports it. 
	 * @throws HgRuntimeException 
	 */
	public void processFile(final HgDataFile df, final int fileRevIndex, HgManifest.Flags flags) throws HgIOException, HgRuntimeException {
		processFile(df.getPath(), new Fetch() {
			public void readInto(ByteChannel ch) {
				try {
					df.contentWithFilters(fileRevIndex, ch);
				} catch (CancelledException ex) {
					handleUnexpectedCancel(ex);
				}
			}
		}, flags);
	}
	
	public void processFile(final HgFileRevision fr) throws HgIOException, HgRuntimeException {
		processFile(fr.getPath(), new Fetch() {
			
			public void readInto(ByteChannel ch) throws IOException, HgRuntimeException {
				try {
					fr.putContentTo(ch);
				} catch (CancelledException ex) {
					handleUnexpectedCancel(ex);
				}
			}
		}, fr.getFileFlags());
	}
	
	/**
	 * Closes supplied content stream 
	 */
	public void processFile(Path fname, final InputStream content, HgManifest.Flags flags) throws HgIOException, HgRuntimeException {
		processFile(fname, new Fetch() {
			
			public void readInto(ByteChannel ch) throws IOException, HgRuntimeException {
				try {
					 ByteBuffer bb = ByteBuffer.wrap(new byte[8*1024]);
					 int r;
					 while ((r = content.read(bb.array())) != -1) {
						 bb.position(0).limit(r);
						 for (int wrote = 0; wrote < r; ) {
							 r -= wrote; 
							 wrote = ch.write(bb);
							 assert bb.remaining() == r - wrote;
						 }
					 }
				} catch (CancelledException ex) {
					handleUnexpectedCancel(ex);
				}
			}
		}, flags);
	}
	
	private interface Fetch {
		void readInto(ByteChannel ch) throws IOException, HgRuntimeException;
	}

	private void processFile(Path fname, Fetch fetch, HgManifest.Flags flags) throws HgIOException, HgRuntimeException {
		try {
			byte[] symlinkContent = null;
			try {
				prepare(fname, flags);
				fetch.readInto(this);
			} finally {
				symlinkContent = close(fname, flags);
			}
			if (flags == HgManifest.Flags.Link && symlinkCap) {
				assert symlinkContent != null;
				fileFlagsHelper.createSymlink(dest.getParentFile(), dest.getName(), symlinkContent);
			} else if (flags == HgManifest.Flags.Exec && execCap) {
				fileFlagsHelper.setExecutableBit(dest.getParentFile(), dest.getName());
			}
			// Although HgWCStatusCollector treats 644 (`hg manifest -v`) and 664 (my fs) the same, it's better
			// to detect actual flags here
			fmode = flags.fsMode(); // default to one from manifest
			if (fileFlagsHelper != null) {
				// if neither execBit nor link is supported by fs, it's unlikely file mode is supported, too.
				try {
					fmode = fileFlagsHelper.getFileMode(dest, fmode);
				} catch (IOException ex) {
					// Warn, we've got default value and can live with it
					hgRepo.getSessionContext().getLog().dump(getClass(), Warn, ex, "Failed get file access rights");
				}
			}
		} catch (IOException ex) {
			String msg = String.format("Failed to write file %s to the working directory", fname);
			throw new HgIOException(msg, ex, dest);
		}
	}

	private void prepare(Path fname, HgManifest.Flags flags) throws IOException {
		String fpath = fname.toString();
		dest = new File(hgRepo.getRepo().getWorkingDir(), fpath);
		if (fpath.indexOf('/') != -1) {
			dest.getParentFile().mkdirs();
		}
		destChannel = null;
		linkChannel = null;
		totalBytesWritten = 0;
		fmode = 0;
		if (flags != HgManifest.Flags.Link) {
			destChannel = new FileOutputStream(dest).getChannel();
		} else {
			linkChannel = new ByteArrayChannel();
		}
	}
	
	private byte[] close(Path fname, HgManifest.Flags flags) throws IOException {
		if (flags != HgManifest.Flags.Link) {
			destChannel.close();
			destChannel = null;
			// leave dest in case anyone enquires with #getDestinationFile
		}
		if (linkChannel != null) {
			final byte[] rv = linkChannel.toArray();
			linkChannel = null;
			return rv;
		}
		return null;
	}

	public int write(ByteBuffer buffer) throws IOException, CancelledException {
		final int written;
		if (linkChannel != null) {
			written = linkChannel.write(buffer);
		} else {
			written = destChannel.write(buffer);
		}
		totalBytesWritten += written;
		return written;
	}

	/**
	 * Information purposes only, to find out trouble location if {@link #processFile(HgDataFile, int)} fails
	 */
	public File getDestinationFile() {
		return dest;
	}
	
	public int bytesWritten() {
		return totalBytesWritten;
	}

	public int fmode() {
		return fmode;
	}

	public int mtime() {
		return (int) (dest.lastModified() / 1000);
	}

	private void handleUnexpectedCancel(CancelledException ex) {
		hgRepo.getLog().dump(WorkingDirFileWriter.class, Severity.Error, ex, "Our impl doesn't throw cancellation");
	}
}