Copyright (c) 2012 Contributors.
All rights reserved.
This program and the accompanying materials are made available
under the terms of the Eclipse Public License v1.0
which accompanies this distribution and is available at
http://eclipse.org/legal/epl-v10.html
Contributors:
  John Kew (vmware)         	initial implementation
  Lyor Goldstein (vmware)	add support for weaved class being re-defined
/*******************************************************************************
 * Copyright (c) 2012 Contributors.
 * All rights reserved.
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution and is available at
 * http://eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *   John Kew (vmware)         	initial implementation
 *   Lyor Goldstein (vmware)	add support for weaved class being re-defined
 *******************************************************************************/

package org.aspectj.weaver.tools.cache;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FilenameFilter;
import java.io.OutputStream;
import java.util.Map;

import org.aspectj.bridge.MessageUtil;
import org.aspectj.util.FileUtil;
import org.aspectj.util.LangUtil;


Naive File-Backed Class Cache with no expiry or application
centric invalidation.

Enabled with the system property, "aj.weaving.cache.dir"
If this system property is not set, no caching will be
performed.

A CRC checksum is stored alongside the class file to verify
the bytes on read. If for some reason there is an error
reading either the class or crc file, or if the crc does not
match the class data the cache entry is deleted.

An alternate implementation of this could store the class file
as a jar/zip directly, which would have the required crc; as
a first pass however it is somewhat useful to view these files
in expanded form for debugging.
/**
 * Naive File-Backed Class Cache with no expiry or application
 * centric invalidation.
 * <p/>
 * Enabled with the system property, "aj.weaving.cache.dir"
 * If this system property is not set, no caching will be
 * performed.
 * <p/>
 * A CRC checksum is stored alongside the class file to verify
 * the bytes on read. If for some reason there is an error
 * reading either the class or crc file, or if the crc does not
 * match the class data the cache entry is deleted.
 * <p/>
 * An alternate implementation of this could store the class file
 * as a jar/zip directly, which would have the required crc; as
 * a first pass however it is somewhat useful to view these files
 * in expanded form for debugging.
 */
public class DefaultFileCacheBacking extends AbstractIndexedFileCacheBacking {
	private final Map<String, IndexEntry> index;

	private static final Object LOCK = new Object();

	protected DefaultFileCacheBacking(File cacheDir) {
		super(cacheDir);
		index = readIndex();
	}

	public static final DefaultFileCacheBacking createBacking(File cacheDir) {
		if (!cacheDir.exists()) {
			if (!cacheDir.mkdirs()) {
				MessageUtil.error("Unable to create cache directory at " + cacheDir.getName());
				return null;
			}
		} else if (!cacheDir.isDirectory()) {
			MessageUtil.error("Not a cache directory at " + cacheDir.getName());
			return null;
		}

		if (!cacheDir.canWrite()) {
			MessageUtil.error("Cache directory is not writable at " + cacheDir.getName());
			return null;
		}
		return new DefaultFileCacheBacking(cacheDir);
	}

    @Override
	protected Map<String, IndexEntry> getIndex() {
		return index;
	}

	@Override
    protected IndexEntry resolveIndexMapEntry (File cacheDir, IndexEntry ie) {
        File cacheEntry = new File(cacheDir, ie.key);
        if (ie.ignored || cacheEntry.canRead()) {
            return ie;
        } else {
            return null;
        }
    }

	private void removeIndexEntry(String key) {
		synchronized (LOCK) {
			index.remove(key);
			writeIndex();
		}
	}

	private void addIndexEntry(IndexEntry ie) {
		synchronized (LOCK) {
			index.put(ie.key, ie);
			writeIndex();
		}
	}

    @Override
	protected Map<String, IndexEntry> readIndex() {
		synchronized (LOCK) {
			return super.readIndex();
		}
	}

	@Override
	protected void writeIndex() {
		synchronized (LOCK) {
			super.writeIndex();
		}
	}

	public void clear() {
		File	cacheDir=getCacheDirectory();
		int		numDeleted=0;
		synchronized (LOCK) {
			numDeleted = FileUtil.deleteContents(cacheDir);
		}

		if ((numDeleted > 0) && (logger != null) && logger.isTraceEnabled()) {
			logger.info("clear(" + cacheDir + ") deleted");
		}
	}

	public static CacheBacking createBacking(String scope) {
		String cache = System.getProperty(WEAVED_CLASS_CACHE_DIR);
		if (cache == null) {
			return null;
		}

		File cacheDir = new File(cache, scope);
		return createBacking(cacheDir);
	}

	@Override
	public String[] getKeys(final String regex) {
		File	cacheDirectory = getCacheDirectory();
		File[] files = cacheDirectory.listFiles(new FilenameFilter() {
				public boolean accept(File file, String s) {
					if (s.matches(regex)) {
						return true;
					}
					return false;
				}
			});
		if (LangUtil.isEmpty(files)) {
			return EMPTY_KEYS;
		}
		String[] keys = new String[files.length];
		for (int i = 0; i < files.length; i++) {
			keys[i] = files[i].getName();
		}
		return keys;
	}

	public CachedClassEntry get(CachedClassReference ref, byte[] originalBytes) {
		File cacheDirectory = getCacheDirectory();
		String	refKey=ref.getKey();
		File cacheFile = new File(cacheDirectory, refKey);
		IndexEntry ie = index.get(refKey);
		if (ie == null) {
			// no index, delete
			delete(cacheFile);
			return null;
		}

		// check if original file changed
		if (crc(originalBytes) != ie.crcClass) {
			delete(cacheFile);
			return null;
		}
		
		if (ie.ignored) {
			return new CachedClassEntry(ref, WeavedClassCache.ZERO_BYTES, CachedClassEntry.EntryType.IGNORED);
		}

		if (cacheFile.canRead()) {
			byte[] bytes = read(cacheFile, ie.crcWeaved);
			if (bytes != null) {
				if (!ie.generated) {
					return new CachedClassEntry(ref, bytes, CachedClassEntry.EntryType.WEAVED);
				} else {
					return new CachedClassEntry(ref, bytes, CachedClassEntry.EntryType.GENERATED);
				}
			}
		}

		return null;
	}

	public void put(CachedClassEntry entry, byte[] originalBytes) {
		File	cacheDirectory = getCacheDirectory();
		String	refKey = entry.getKey();
		IndexEntry ie = index.get(refKey);
		File 	cacheFile = new File(cacheDirectory, refKey);
		final boolean	writeEntryBytes;
		// check if original bytes changed or the ignored/generated flags
		if ((ie != null)
		 && ((ie.ignored != entry.isIgnored()) || (ie.generated != entry.isGenerated()) || (crc(originalBytes) != ie.crcClass))) {
			delete(cacheFile);
			writeEntryBytes = true;
		} else {
			writeEntryBytes = !cacheFile.exists();
		}

		if (writeEntryBytes) {
			ie = createIndexEntry(entry, originalBytes);
			if (!entry.isIgnored()) {
				ie.crcWeaved = write(cacheFile, entry.getBytes());
			}
			addIndexEntry(ie);
		}
	}

	public void remove(CachedClassReference ref) {
		File	cacheDirectory = getCacheDirectory();
		String	refKey = ref.getKey();
		File	cacheFile = new File(cacheDirectory, refKey);
		synchronized (LOCK) {
			removeIndexEntry(refKey);
			delete(cacheFile);
		}
	}

	@Override
	protected void delete(File file) {
		synchronized (LOCK) {
			super.delete(file);
		}
	}

	protected byte[] read(File file, long expectedCRC) {
		byte[]	bytes=null;
		synchronized (LOCK) {
			FileInputStream fis = null;
			try {
				fis = new FileInputStream(file);
				bytes = FileUtil.readAsByteArray(fis);
			} catch (Exception e) {
				if ((logger != null) && logger.isTraceEnabled()) {
					logger.warn("read(" + file.getAbsolutePath() + ")"
							+ " failed (" + e.getClass().getSimpleName() + ")"
							+ " to read contents: " + e.getMessage(), e);
				}
			} finally {
				close(fis, file);
			}

			// delete the file if there was an exception reading it or mismatched crc
			if ((bytes == null) || (crc(bytes) != expectedCRC)) {
				delete(file);
				return null;
			}
		}

		return bytes;
	}

	protected long write(File file, byte[] bytes) {
		synchronized (LOCK) {
			if (file.exists()) {
				return -1L;
			}
			OutputStream out = null;
			try {
				out = new FileOutputStream(file);
				out.write(bytes);
			} catch (Exception e) {
				if ((logger != null) && logger.isTraceEnabled()) {
					logger.warn("write(" + file.getAbsolutePath() + ")"
							+ " failed (" + e.getClass().getSimpleName() + ")"
							+ " to write contents: " + e.getMessage(), e);
				}
				// delete the file if there was an exception writing it
				delete(file);
				return -1L;
			} finally {
				close(out, file);
			}

			return crc(bytes);
		}
	}

}