/*
    * Copyright (c) 2021 Qualcomm Innovation Center, Inc.
    * and other copyright owners as documented in the project's IP log.
    *
    * 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.file;
  
  import java.io.File;
  import java.text.MessageFormat;
  
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.internal.storage.pack.PackExt;
  import org.eclipse.jgit.lib.ObjectId;
  
  /**
   * A pack file (or pack related) File.
   *
   * Example: "pack-0123456789012345678901234567890123456789.idx"
   */
  public class PackFile extends File {
  	private static final long serialVersionUID = 1L;
  
  	private static final String PREFIX = "pack-"; //$NON-NLS-1$
  
  	private final String base; // PREFIX + id i.e.
  								// pack-0123456789012345678901234567890123456789
  
  	private final String id; // i.e. 0123456789012345678901234567890123456789
  
  	private final boolean hasOldPrefix;
  
  	private final PackExt packExt;
  
  	private static String createName(String id, PackExt extension) {
  		return PREFIX + id + '.' + extension.getExtension();
  	}
  
  	/**
  	 * Create a PackFile for a pack or related file.
  	 *
  	 * @param file
  	 *            File pointing to the location of the file.
  	 */
  	public PackFile(File file) {
  		this(file.getParentFile(), file.getName());
  	}
  
  	/**
  	 * Create a PackFile for a pack or related file.
  	 *
  	 * @param directory
  	 *            Directory to create the PackFile in.
  	 * @param id
  	 *            the {@link ObjectId} for this pack
  	 * @param ext
  	 *            the <code>packExt</code> of the name.
  	 */
  	public PackFile(File directory, ObjectId id, PackExt ext) {
  		this(directory, id.name(), ext);
  	}
  
  	/**
  	 * Create a PackFile for a pack or related file.
  	 *
  	 * @param directory
  	 *            Directory to create the PackFile in.
  	 * @param id
  	 *            the <code>id</code> (40 Hex char) section of the pack name.
  	 * @param ext
  	 *            the <code>packExt</code> of the name.
  	 */
  	public PackFile(File directory, String id, PackExt ext) {
  		this(directory, createName(id, ext));
  	}
  
  	/**
  	 * Create a PackFile for a pack or related file.
  	 *
  	 * @param directory
  	 *            Directory to create the PackFile in.
  	 * @param name
  	 *            Filename (last path section) of the PackFile
  	 */
  	public PackFile(File directory, String name) {
  		super(directory, name);
  		int dot = name.lastIndexOf('.');
  
  		if (dot < 0) {
  			base = name;
  			hasOldPrefix = false;
  			packExt = null;
  		} else {
  			base = name.substring(0, dot);
 			String tail = name.substring(dot + 1); // ["old-"] + extension
 			packExt = getPackExt(tail);
 			String old = tail.substring(0,
 					tail.length() - getExtension().length());
 			hasOldPrefix = old.equals(getExtPrefix(true));
 		}
 
 		id = base.startsWith(PREFIX) ? base.substring(PREFIX.length()) : base;
 	}
 
 	/**
 	 * Getter for the field <code>id</code>.
 	 *
 	 * @return the <code>id</code> (40 Hex char) section of the name.
 	 */
 	public String getId() {
 		return id;
 	}
 
 	/**
 	 * Getter for the field <code>packExt</code>.
 	 *
 	 * @return the <code>packExt</code> of the name.
 	 */
 	public PackExt getPackExt() {
 		return packExt;
 	}
 
 	/**
 	 * Create a new similar PackFile with the given extension instead.
 	 *
 	 * @param ext
 	 *            PackExt the extension to use.
 	 * @return a PackFile instance with specified extension
 	 */
 	public PackFile create(PackExt ext) {
 		return new PackFile(getParentFile(), getName(ext));
 	}
 
 	/**
 	 * Create a new similar PackFile in the given directory.
 	 *
 	 * @param directory
 	 *            Directory to create the new PackFile in.
 	 * @return a PackFile in the given directory
 	 */
 	public PackFile createForDirectory(File directory) {
 		return new PackFile(directory, getName(false));
 	}
 
 	/**
 	 * Create a new similar preserved PackFile in the given directory.
 	 *
 	 * @param directory
 	 *            Directory to create the new PackFile in.
 	 * @return a PackFile in the given directory with "old-" prefixing the
 	 *         extension
 	 */
 	public PackFile createPreservedForDirectory(File directory) {
 		return new PackFile(directory, getName(true));
 	}
 
 	private String getName(PackExt ext) {
 		return base + '.' + getExtPrefix(hasOldPrefix) + ext.getExtension();
 	}
 
 	private String getName(boolean isPreserved) {
 		return base + '.' + getExtPrefix(isPreserved) + getExtension();
 	}
 
 	private String getExtension() {
 		return packExt == null ? "" : packExt.getExtension(); //$NON-NLS-1$
 	}
 
 	private static String getExtPrefix(boolean isPreserved) {
 		return isPreserved ? "old-" : ""; //$NON-NLS-1$ //$NON-NLS-2$
 	}
 
 	private static PackExt getPackExt(String endsWithExtension) {
 		for (PackExt ext : PackExt.values()) {
 			if (endsWithExtension.endsWith(ext.getExtension())) {
 				return ext;
 			}
 		}
 		throw new IllegalArgumentException(MessageFormat.format(
 				JGitText.get().unrecognizedPackExtension, endsWithExtension));
 	}
 }