/*
    * Copyright (C) 2011, 2013 Google Inc., and others. and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
    * SPDX-License-Identifier: BSD-3-Clause
    */
  
  package org.eclipse.jgit.internal.storage.dfs;
  
  import static org.eclipse.jgit.internal.storage.pack.PackExt.PACK;
  import static org.eclipse.jgit.internal.storage.pack.PackExt.REFTABLE;
  
  import java.util.Arrays;
  import java.util.Comparator;
  
  import org.eclipse.jgit.annotations.NonNull;
  import org.eclipse.jgit.internal.storage.dfs.DfsObjDatabase.PackSource;
  import org.eclipse.jgit.internal.storage.pack.PackExt;
  import org.eclipse.jgit.internal.storage.reftable.ReftableWriter;
  import org.eclipse.jgit.storage.pack.PackStatistics;
  
  /**
   * Description of a DFS stored pack/index file.
   * <p>
   * Implementors may extend this class and add additional data members.
   * <p>
   * Instances of this class are cached with the DfsPackFile, and should not be
   * modified once initialized and presented to the JGit DFS library.
   */
  public class DfsPackDescription {
  	/**
  	 * Comparator for packs when looking up objects in indexes.
  	 * <p>
  	 * This comparator tries to position packs in the order readers should examine
  	 * them when looking for objects by SHA-1. The default tries to sort packs
  	 * with more recent modification dates before older packs, and packs with
  	 * fewer objects before packs with more objects.
  	 * <p>
  	 * Uses {@link PackSource#DEFAULT_COMPARATOR} for the portion of comparison
  	 * where packs are sorted by source.
  	 *
  	 * @return comparator.
  	 */
  	public static Comparator<DfsPackDescription> objectLookupComparator() {
  		return objectLookupComparator(PackSource.DEFAULT_COMPARATOR);
  	}
  
  	/**
  	 * Comparator for packs when looking up objects in indexes.
  	 * <p>
  	 * This comparator tries to position packs in the order readers should examine
  	 * them when looking for objects by SHA-1. The default tries to sort packs
  	 * with more recent modification dates before older packs, and packs with
  	 * fewer objects before packs with more objects.
  	 *
  	 * @param packSourceComparator
  	 *            comparator for the {@link PackSource}, used as the first step in
  	 *            comparison.
  	 * @return comparator.
  	 */
  	public static Comparator<DfsPackDescription> objectLookupComparator(
  			Comparator<PackSource> packSourceComparator) {
  		return Comparator.comparing(
  					DfsPackDescription::getPackSource, packSourceComparator)
  			.thenComparing((a, b) -> {
  				PackSource as = a.getPackSource();
  				PackSource bs = b.getPackSource();
  
  				// Tie break GC type packs by smallest first. There should be at most
  				// one of each source, but when multiple exist concurrent GCs may have
  				// run. Preferring the smaller file selects higher quality delta
  				// compression, placing less demand on the DfsBlockCache.
  				if (as == bs && isGC(as)) {
  					int cmp = Long.signum(a.getFileSize(PACK) - b.getFileSize(PACK));
  					if (cmp != 0) {
  						return cmp;
  					}
  				}
  
  				// Newer packs should sort first.
  				int cmp = Long.signum(b.getLastModified() - a.getLastModified());
  				if (cmp != 0) {
  					return cmp;
  				}
  
  				// Break ties on smaller index. Readers may get lucky and find
  				// the object they care about in the smaller index. This also pushes
  				// big historical packs to the end of the list, due to more objects.
  				return Long.signum(a.getObjectCount() - b.getObjectCount());
  			});
  	}
  
  	static Comparator<DfsPackDescription> reftableComparator() {
  		return (a, b) -> {
  				// GC, COMPACT reftables first by reversing default order.
  				int c = PackSource.DEFAULT_COMPARATOR.reversed()
 						.compare(a.getPackSource(), b.getPackSource());
 				if (c != 0) {
 					return c;
 				}
 
 				// Lower maxUpdateIndex first.
 				c = Long.signum(a.getMaxUpdateIndex() - b.getMaxUpdateIndex());
 				if (c != 0) {
 					return c;
 				}
 
 				// Older reftable first.
 				return Long.signum(a.getLastModified() - b.getLastModified());
 			};
 	}
 
 	static Comparator<DfsPackDescription> reuseComparator() {
 		return (a, b) -> {
 			PackSource as = a.getPackSource();
 			PackSource bs = b.getPackSource();
 
 			if (as == bs && DfsPackDescription.isGC(as)) {
 				// Push smaller GC files last; these likely have higher quality
 				// delta compression and the contained representation should be
 				// favored over other files.
 				return Long.signum(b.getFileSize(PACK) - a.getFileSize(PACK));
 			}
 
 			// DfsPackDescription.compareTo already did a reasonable sort.
 			// Rely on Arrays.sort being stable, leaving equal elements.
 			return 0;
 		};
 	}
 
 	private final DfsRepositoryDescription repoDesc;
 	private final String packName;
 	private PackSource packSource;
 	private long lastModified;
 	private long[] sizeMap;
 	private int[] blockSizeMap;
 	private long objectCount;
 	private long deltaCount;
 	private long minUpdateIndex;
 	private long maxUpdateIndex;
 
 	private PackStatistics packStats;
 	private ReftableWriter.Stats refStats;
 	private int extensions;
 	private int indexVersion;
 	private long estimatedPackSize;
 
 	/**
 	 * Initialize a description by pack name and repository.
 	 * <p>
 	 * The corresponding index file is assumed to exist. If this is not true
 	 * implementors must extend the class and override
 	 * {@link #getFileName(PackExt)}.
 	 * <p>
 	 * Callers should also try to fill in other fields if they are reasonably
 	 * free to access at the time this instance is being initialized.
 	 *
 	 * @param name
 	 *            name of the pack file. Must end with ".pack".
 	 * @param repoDesc
 	 *            description of the repo containing the pack file.
 	 * @param packSource
 	 *            the source of the pack.
 	 */
 	public DfsPackDescription(DfsRepositoryDescription repoDesc, String name,
 			@NonNull PackSource packSource) {
 		this.repoDesc = repoDesc;
 		int dot = name.lastIndexOf('.');
 		this.packName = (dot < 0) ? name : name.substring(0, dot);
 		this.packSource = packSource;
 
 		int extCnt = PackExt.values().length;
 		sizeMap = new long[extCnt];
 		blockSizeMap = new int[extCnt];
 	}
 
 	/**
 	 * Get description of the repository.
 	 *
 	 * @return description of the repository.
 	 */
 	public DfsRepositoryDescription getRepositoryDescription() {
 		return repoDesc;
 	}
 
 	/**
 	 * Adds the pack file extension to the known list.
 	 *
 	 * @param ext
 	 *            the file extension
 	 */
 	public void addFileExt(PackExt ext) {
 		extensions |= ext.getBit();
 	}
 
 	/**
 	 * Whether the pack file extension is known to exist.
 	 *
 	 * @param ext
 	 *            the file extension
 	 * @return whether the pack file extension is known to exist.
 	 */
 	public boolean hasFileExt(PackExt ext) {
 		return (extensions & ext.getBit()) != 0;
 	}
 
 	/**
 	 * Get file name
 	 *
 	 * @param ext
 	 *            the file extension
 	 * @return name of the file.
 	 */
 	public String getFileName(PackExt ext) {
 		return packName + '.' + ext.getExtension();
 	}
 
 	/**
 	 * Get cache key for use by the block cache.
 	 *
 	 * @param ext
 	 *            the file extension.
 	 * @return cache key for use by the block cache.
 	 */
 	public DfsStreamKey getStreamKey(PackExt ext) {
 		return DfsStreamKey.of(getRepositoryDescription(), getFileName(ext),
 				ext);
 	}
 
 	/**
 	 * Get the source of the pack.
 	 *
 	 * @return the source of the pack.
 	 */
 	@NonNull
 	public PackSource getPackSource() {
 		return packSource;
 	}
 
 	/**
 	 * Set the source of the pack.
 	 *
 	 * @param source
 	 *            the source of the pack.
 	 * @return {@code this}
 	 */
 	public DfsPackDescription setPackSource(@NonNull PackSource source) {
 		packSource = source;
 		return this;
 	}
 
 	/**
 	 * Get time the pack was created, in milliseconds.
 	 *
 	 * @return time the pack was created, in milliseconds.
 	 */
 	public long getLastModified() {
 		return lastModified;
 	}
 
 	/**
 	 * Set time the pack was created, in milliseconds.
 	 *
 	 * @param timeMillis
 	 *            time the pack was created, in milliseconds. 0 if not known.
 	 * @return {@code this}
 	 */
 	public DfsPackDescription setLastModified(long timeMillis) {
 		lastModified = timeMillis;
 		return this;
 	}
 
 	/**
 	 * Get minUpdateIndex for the reftable, if present.
 	 *
 	 * @return minUpdateIndex for the reftable, if present.
 	 */
 	public long getMinUpdateIndex() {
 		return minUpdateIndex;
 	}
 
 	/**
 	 * Set minUpdateIndex for the reftable.
 	 *
 	 * @param min
 	 *            minUpdateIndex for the reftable.
 	 * @return {@code this}
 	 */
 	public DfsPackDescription setMinUpdateIndex(long min) {
 		minUpdateIndex = min;
 		return this;
 	}
 
 	/**
 	 * Get maxUpdateIndex for the reftable, if present.
 	 *
 	 * @return maxUpdateIndex for the reftable, if present.
 	 */
 	public long getMaxUpdateIndex() {
 		return maxUpdateIndex;
 	}
 
 	/**
 	 * Set maxUpdateIndex for the reftable.
 	 *
 	 * @param max
 	 *            maxUpdateIndex for the reftable.
 	 * @return {@code this}
 	 */
 	public DfsPackDescription setMaxUpdateIndex(long max) {
 		maxUpdateIndex = max;
 		return this;
 	}
 
 	/**
 	 * Set size of the file in bytes.
 	 *
 	 * @param ext
 	 *            the file extension.
 	 * @param bytes
 	 *            size of the file in bytes. If 0 the file is not known and will
 	 *            be determined on first read.
 	 * @return {@code this}
 	 */
 	public DfsPackDescription setFileSize(PackExt ext, long bytes) {
 		int i = ext.getPosition();
 		if (i >= sizeMap.length) {
 			sizeMap = Arrays.copyOf(sizeMap, i + 1);
 		}
 		sizeMap[i] = Math.max(0, bytes);
 		return this;
 	}
 
 	/**
 	 * Get size of the file, in bytes.
 	 *
 	 * @param ext
 	 *            the file extension.
 	 * @return size of the file, in bytes. If 0 the file size is not yet known.
 	 */
 	public long getFileSize(PackExt ext) {
 		int i = ext.getPosition();
 		return i < sizeMap.length ? sizeMap[i] : 0;
 	}
 
 	/**
 	 * Get blockSize of the file, in bytes.
 	 *
 	 * @param ext
 	 *            the file extension.
 	 * @return blockSize of the file, in bytes. If 0 the blockSize size is not
 	 *         yet known and may be discovered when opening the file.
 	 */
 	public int getBlockSize(PackExt ext) {
 		int i = ext.getPosition();
 		return i < blockSizeMap.length ? blockSizeMap[i] : 0;
 	}
 
 	/**
 	 * Set blockSize of the file, in bytes.
 	 *
 	 * @param ext
 	 *            the file extension.
 	 * @param blockSize
 	 *            blockSize of the file, in bytes. If 0 the blockSize is not
 	 *            known and will be determined on first read.
 	 * @return {@code this}
 	 */
 	public DfsPackDescription setBlockSize(PackExt ext, int blockSize) {
 		int i = ext.getPosition();
 		if (i >= blockSizeMap.length) {
 			blockSizeMap = Arrays.copyOf(blockSizeMap, i + 1);
 		}
 		blockSizeMap[i] = Math.max(0, blockSize);
 		return this;
 	}
 
 	/**
 	 * Set estimated size of the .pack file in bytes.
 	 *
 	 * @param estimatedPackSize
 	 *            estimated size of the .pack file in bytes. If 0 the pack file
 	 *            size is unknown.
 	 * @return {@code this}
 	 */
 	public DfsPackDescription setEstimatedPackSize(long estimatedPackSize) {
 		this.estimatedPackSize = Math.max(0, estimatedPackSize);
 		return this;
 	}
 
 	/**
 	 * Get estimated size of the .pack file in bytes.
 	 *
 	 * @return estimated size of the .pack file in bytes. If 0 the pack file
 	 *         size is unknown.
 	 */
 	public long getEstimatedPackSize() {
 		return estimatedPackSize;
 	}
 
 	/**
 	 * Get number of objects in the pack.
 	 *
 	 * @return number of objects in the pack.
 	 */
 	public long getObjectCount() {
 		return objectCount;
 	}
 
 	/**
 	 * Set number of objects in the pack.
 	 *
 	 * @param cnt
 	 *            number of objects in the pack.
 	 * @return {@code this}
 	 */
 	public DfsPackDescription setObjectCount(long cnt) {
 		objectCount = Math.max(0, cnt);
 		return this;
 	}
 
 	/**
 	 * Get number of delta compressed objects in the pack.
 	 *
 	 * @return number of delta compressed objects in the pack.
 	 */
 	public long getDeltaCount() {
 		return deltaCount;
 	}
 
 	/**
 	 * Set number of delta compressed objects in the pack.
 	 *
 	 * @param cnt
 	 *            number of delta compressed objects in the pack.
 	 * @return {@code this}
 	 */
 	public DfsPackDescription setDeltaCount(long cnt) {
 		deltaCount = Math.max(0, cnt);
 		return this;
 	}
 
 	/**
 	 * Get statistics from PackWriter, if the pack was built with it.
 	 *
 	 * @return statistics from PackWriter, if the pack was built with it.
 	 *         Generally this is only available for packs created by
 	 *         DfsGarbageCollector or DfsPackCompactor, and only when the pack
 	 *         is being committed to the repository.
 	 */
 	public PackStatistics getPackStats() {
 		return packStats;
 	}
 
 	DfsPackDescription setPackStats(PackStatistics stats) {
 		this.packStats = stats;
 		setFileSize(PACK, stats.getTotalBytes());
 		setObjectCount(stats.getTotalObjects());
 		setDeltaCount(stats.getTotalDeltas());
 		return this;
 	}
 
 	/**
 	 * Get stats from the sibling reftable, if created.
 	 *
 	 * @return stats from the sibling reftable, if created.
 	 */
 	public ReftableWriter.Stats getReftableStats() {
 		return refStats;
 	}
 
 	void setReftableStats(ReftableWriter.Stats stats) {
 		this.refStats = stats;
 		setMinUpdateIndex(stats.minUpdateIndex());
 		setMaxUpdateIndex(stats.maxUpdateIndex());
 		setFileSize(REFTABLE, stats.totalBytes());
 		setBlockSize(REFTABLE, stats.refBlockSize());
 	}
 
 	/**
 	 * Discard the pack statistics, if it was populated.
 	 *
 	 * @return {@code this}
 	 */
 	public DfsPackDescription clearPackStats() {
 		packStats = null;
 		refStats = null;
 		return this;
 	}
 
 	/**
 	 * Get the version of the index file written.
 	 *
 	 * @return the version of the index file written.
 	 */
 	public int getIndexVersion() {
 		return indexVersion;
 	}
 
 	/**
 	 * Set the version of the index file written.
 	 *
 	 * @param version
 	 *            the version of the index file written.
 	 * @return {@code this}
 	 */
 	public DfsPackDescription setIndexVersion(int version) {
 		indexVersion = version;
 		return this;
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public int hashCode() {
 		return packName.hashCode();
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public boolean equals(Object b) {
 		if (b instanceof DfsPackDescription) {
 			DfsPackDescription desc = (DfsPackDescription) b;
 			return packName.equals(desc.packName) &&
 					getRepositoryDescription().equals(desc.getRepositoryDescription());
 		}
 		return false;
 	}
 
 	static boolean isGC(PackSource s) {
 		switch (s) {
 		case GC:
 		case GC_REST:
 		case GC_TXN:
 			return true;
 		default:
 			return false;
 		}
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public String toString() {
 		return getFileName(PackExt.PACK);
 	}
 }