PackFile.java

/*
 * 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));
    }
}