/*
    * Copyright (C) 2011, Google Inc. 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.lib.ConfigConstants.CONFIG_CORE_SECTION;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_DFS_SECTION;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_DELTA_BASE_CACHE_LIMIT;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_STREAM_BUFFER;
  import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_STREAM_FILE_TRESHOLD;
  
  import org.eclipse.jgit.lib.Config;
  import org.eclipse.jgit.storage.pack.PackConfig;
  
  /**
   * Options controlling how objects are read from a DFS stored repository.
   */
  public class DfsReaderOptions {
  	/** 1024 (number of bytes in one kibibyte/kilobyte) */
  	public static final int KiB = 1024;
  
  	/** 1024 {@link #KiB} (number of bytes in one mebibyte/megabyte) */
  	public static final int MiB = 1024 * KiB;
  
  	private int deltaBaseCacheLimit;
  	private int streamFileThreshold;
  
  	private int streamPackBufferSize;
  
  	/**
  	 * Create a default reader configuration.
  	 */
  	public DfsReaderOptions() {
  		setDeltaBaseCacheLimit(10 * MiB);
  		setStreamFileThreshold(PackConfig.DEFAULT_BIG_FILE_THRESHOLD);
  	}
  
  	/**
  	 * Get maximum number of bytes to hold in per-reader DeltaBaseCache.
  	 *
  	 * @return maximum number of bytes to hold in per-reader DeltaBaseCache.
  	 */
  	public int getDeltaBaseCacheLimit() {
  		return deltaBaseCacheLimit;
  	}
  
  	/**
  	 * Set the maximum number of bytes in the DeltaBaseCache.
  	 *
  	 * @param maxBytes
  	 *            the new limit.
  	 * @return {@code this}
  	 */
  	public DfsReaderOptions setDeltaBaseCacheLimit(int maxBytes) {
  		deltaBaseCacheLimit = Math.max(0, maxBytes);
  		return this;
  	}
  
  	/**
  	 * Get the size threshold beyond which objects must be streamed.
  	 *
  	 * @return the size threshold beyond which objects must be streamed.
  	 */
  	public int getStreamFileThreshold() {
  		return streamFileThreshold;
  	}
  
  	/**
  	 * Set new byte limit for objects that must be streamed.
  	 *
  	 * @param newLimit
  	 *            new byte limit for objects that must be streamed. Objects
  	 *            smaller than this size can be obtained as a contiguous byte
  	 *            array, while objects bigger than this size require using an
  	 *            {@link org.eclipse.jgit.lib.ObjectStream}.
  	 * @return {@code this}
  	 */
  	public DfsReaderOptions setStreamFileThreshold(int newLimit) {
  		streamFileThreshold = Math.max(0, newLimit);
  		return this;
  	}
  
  	/**
  	 * Get number of bytes to use for buffering when streaming a pack file
  	 * during copying.
  	 *
  	 * @return number of bytes to use for buffering when streaming a pack file
  	 *         during copying. If 0 the block size of the pack is used.
  	 */
  	public int getStreamPackBufferSize() {
  		return streamPackBufferSize;
  	}
 
 	/**
 	 * Set new buffer size in bytes for buffers used when streaming pack files
 	 * during copying.
 	 *
 	 * @param bufsz
 	 *            new buffer size in bytes for buffers used when streaming pack
 	 *            files during copying.
 	 * @return {@code this}
 	 */
 	public DfsReaderOptions setStreamPackBufferSize(int bufsz) {
 		streamPackBufferSize = Math.max(0, bufsz);
 		return this;
 	}
 
 	/**
 	 * Update properties by setting fields from the configuration.
 	 * <p>
 	 * If a property is not defined in the configuration, then it is left
 	 * unmodified.
 	 *
 	 * @param rc
 	 *            configuration to read properties from.
 	 * @return {@code this}
 	 */
 	public DfsReaderOptions fromConfig(Config rc) {
 		setDeltaBaseCacheLimit(rc.getInt(
 				CONFIG_CORE_SECTION,
 				CONFIG_DFS_SECTION,
 				CONFIG_KEY_DELTA_BASE_CACHE_LIMIT,
 				getDeltaBaseCacheLimit()));
 
 		long maxMem = Runtime.getRuntime().maxMemory();
 		long sft = rc.getLong(
 				CONFIG_CORE_SECTION,
 				CONFIG_DFS_SECTION,
 				CONFIG_KEY_STREAM_FILE_TRESHOLD,
 				getStreamFileThreshold());
 		sft = Math.min(sft, maxMem / 4); // don't use more than 1/4 of the heap
 		sft = Math.min(sft, Integer.MAX_VALUE); // cannot exceed array length
 		setStreamFileThreshold((int) sft);
 
 		setStreamPackBufferSize(rc.getInt(
 				CONFIG_CORE_SECTION,
 				CONFIG_DFS_SECTION,
 				CONFIG_KEY_STREAM_BUFFER,
 				getStreamPackBufferSize()));
 		return this;
 	}
 }