Create a PackFile class for Pack filenames

The PackFile class is intended to be a central place to do all
common pack filename manipulation and parsing to help reduce repeated
code and bugs. Use the PackFile class in the Pack class and in many
tests to ensure it works well in a variety of situations. Later changes
will expand use of PackFiles to even more areas.

Change-Id: I921b30f865759162bae46ddd2c6d669de06add4a
Signed-off-by: Nasser Grainawi <quic_nasserg@quicinc.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

3 files changed, 170 insertions, 30 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
index 9d215ca455..95265feb4e 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
@@ -771,6 +771,7 @@ public class JGitText extends TranslationBundle {
 	/***/ public String unmergedPaths;
 	/***/ public String unpackException;
 	/***/ public String unreadablePackIndex;
+	/***/ public String unrecognizedPackExtension;
 	/***/ public String unrecognizedRef;
 	/***/ public String unsetMark;
 	/***/ public String unsupportedAlternates;
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/Pack.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/Pack.java
index d928633a73..fa938b3111 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/Pack.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/Pack.java
@@ -78,13 +78,11 @@ public class Pack implements Iterable<PackIndex.MutableEntry> {
 	public static final Comparator<Pack> SORT = (a, b) -> b.packLastModified
 			.compareTo(a.packLastModified);
 
-	private final File packFile;
+	private final PackFile packFile;
 
 	private final int extensions;
 
-	private File keepFile;
-
-	private volatile String packName;
+	private PackFile keepFile;
 
 	final int hash;
 
@@ -137,7 +135,7 @@ public class Pack implements Iterable<PackIndex.MutableEntry> {
 	 *            additional pack file extensions with the same base as the pack
 	 */
 	public Pack(File packFile, int extensions) {
-		this.packFile = packFile;
+		this.packFile = new PackFile(packFile);
 		this.fileSnapshot = PackFileSnapshot.save(packFile);
 		this.packLastModified = fileSnapshot.lastModifiedInstant();
 		this.extensions = extensions;
@@ -156,16 +154,18 @@ public class Pack implements Iterable<PackIndex.MutableEntry> {
 				idx = loadedIdx;
 				if (idx == null) {
 					if (invalid) {
-						throw new PackInvalidException(packFile, invalidatingCause);
+						throw new PackInvalidException(packFile,
+								invalidatingCause);
 					}
 					try {
 						long start = System.currentTimeMillis();
-						idx = PackIndex.open(extFile(INDEX));
+						PackFile idxFile = packFile.create(INDEX);
+						idx = PackIndex.open(idxFile);
 						if (LOG.isDebugEnabled()) {
 							LOG.debug(String.format(
 									"Opening pack index %s, size %.3f MB took %d ms", //$NON-NLS-1$
-									extFile(INDEX).getAbsolutePath(),
-									Float.valueOf(extFile(INDEX).length()
+									idxFile.getAbsolutePath(),
+									Float.valueOf(idxFile.length()
 											/ (1024f * 1024)),
 									Long.valueOf(System.currentTimeMillis()
 											- start)));
@@ -205,7 +205,7 @@ public class Pack implements Iterable<PackIndex.MutableEntry> {
 	 *
 	 * @return the File object which locates this pack on disk.
 	 */
-	public File getPackFile() {
+	public PackFile getPackFile() {
 		return packFile;
 	}
 
@@ -225,16 +225,7 @@ public class Pack implements Iterable<PackIndex.MutableEntry> {
 	 * @return name extracted from {@code pack-*.pack} pattern.
 	 */
 	public String getPackName() {
-		String name = packName;
-		if (name == null) {
-			name = getPackFile().getName();
-			if (name.startsWith("pack-")) //$NON-NLS-1$
-				name = name.substring("pack-".length()); //$NON-NLS-1$
-			if (name.endsWith(".pack")) //$NON-NLS-1$
-				name = name.substring(0, name.length() - ".pack".length()); //$NON-NLS-1$
-			packName = name;
-		}
-		return name;
+		return packFile.getId();
 	}
 
 	/**
@@ -261,8 +252,9 @@ public class Pack implements Iterable<PackIndex.MutableEntry> {
 	 * @return true if a .keep file exist.
 	 */
 	public boolean shouldBeKept() {
-		if (keepFile == null)
-			keepFile = extFile(KEEP);
+		if (keepFile == null) {
+			keepFile = packFile.create(KEEP);
+		}
 		return keepFile.exists();
 	}
 
@@ -1137,7 +1129,7 @@ public class Pack implements Iterable<PackIndex.MutableEntry> {
 		if (bitmapIdx == null && hasExt(BITMAP_INDEX)) {
 			final PackBitmapIndex idx;
 			try {
-				idx = PackBitmapIndex.open(extFile(BITMAP_INDEX), idx(),
+				idx = PackBitmapIndex.open(packFile.create(BITMAP_INDEX), idx(),
 						getReverseIdx());
 			} catch (FileNotFoundException e) {
 				// Once upon a time this bitmap file existed. Now it
@@ -1187,13 +1179,6 @@ public class Pack implements Iterable<PackIndex.MutableEntry> {
 		}
 	}
 
-	private File extFile(PackExt ext) {
-		String p = packFile.getName();
-		int dot = p.lastIndexOf('.');
-		String b = (dot < 0) ? p : p.substring(0, dot);
-		return new File(packFile.getParentFile(), b + '.' + ext.getExtension());
-	}
-
 	private boolean hasExt(PackExt ext) {
 		return (extensions & ext.getBit()) != 0;
 	}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/PackFile.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/PackFile.java
new file mode 100644
index 0000000000..c2e6f324d1
--- /dev/null
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/PackFile.java
@@ -0,0 +1,154 @@
+/*
+ * 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;
+
+/**
+ * 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;
+
+	/**
+	 * 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 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));
+	}
+}