/*
 * Copyright (C) 2008, Robin Rosenberg <robin.rosenberg@dewire.com>
 * Copyright (C) 2006-2008, Shawn O. Pearce <spearce@spearce.org> 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.lib;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

import org.eclipse.jgit.annotations.Nullable;
import org.eclipse.jgit.errors.InvalidObjectIdException;
import org.eclipse.jgit.util.NB;
import org.eclipse.jgit.util.RawParseUtils;

A SHA-1 abstraction.
/**
 * A SHA-1 abstraction.
 */
public class ObjectId extends AnyObjectId implements Serializable {
	private static final long serialVersionUID = 1L;

	private static final ObjectId ZEROID;

	private static final String ZEROID_STR;

	static {
		ZEROID = new ObjectId(0, 0, 0, 0, 0);
		ZEROID_STR = ZEROID.name();
	}

	
Get the special all-null ObjectId.
Returns:
the all-null ObjectId, often used to stand-in for no object./**
	 * Get the special all-null ObjectId.
	 *
	 * @return the all-null ObjectId, often used to stand-in for no object.
	 */
	public static final ObjectId zeroId() {
		return ZEROID;
	}

	
Test a string of characters to verify it is a hex format.
 If true the string can be parsed with fromString(String). 
Params:
id – 
           the string to test.
Returns:
true if the string can converted into an ObjectId./**
	 * Test a string of characters to verify it is a hex format.
	 * <p>
	 * If true the string can be parsed with {@link #fromString(String)}.
	 *
	 * @param id
	 *            the string to test.
	 * @return true if the string can converted into an ObjectId.
	 */
	public static final boolean isId(@Nullable String id) {
		if (id == null) {
			return false;
		}
		if (id.length() != Constants.OBJECT_ID_STRING_LENGTH)
			return false;
		try {
			for (int i = 0; i < Constants.OBJECT_ID_STRING_LENGTH; i++) {
				RawParseUtils.parseHexInt4((byte) id.charAt(i));
			}
			return true;
		} catch (ArrayIndexOutOfBoundsException e) {
			return false;
		}
	}

	
Convert an ObjectId into a hex string representation.
Params:
i – 
           the id to convert. May be null.
Returns:
the hex string conversion of this id's content./**
	 * Convert an ObjectId into a hex string representation.
	 *
	 * @param i
	 *            the id to convert. May be null.
	 * @return the hex string conversion of this id's content.
	 */
	public static final String toString(ObjectId i) {
		return i != null ? i.name() : ZEROID_STR;
	}

	
Compare two object identifier byte sequences for equality.
Params:
firstBuffer – 
           the first buffer to compare against. Must have at least 20
           bytes from position fi through the end of the buffer.
fi – 
           first offset within firstBuffer to begin testing.
secondBuffer – 
           the second buffer to compare against. Must have at least 20
           bytes from position si through the end of the buffer.
si – 
           first offset within secondBuffer to begin testing.
Returns:
true if the two identifiers are the same./**
	 * Compare two object identifier byte sequences for equality.
	 *
	 * @param firstBuffer
	 *            the first buffer to compare against. Must have at least 20
	 *            bytes from position fi through the end of the buffer.
	 * @param fi
	 *            first offset within firstBuffer to begin testing.
	 * @param secondBuffer
	 *            the second buffer to compare against. Must have at least 20
	 *            bytes from position si through the end of the buffer.
	 * @param si
	 *            first offset within secondBuffer to begin testing.
	 * @return true if the two identifiers are the same.
	 */
	public static boolean equals(final byte[] firstBuffer, final int fi,
			final byte[] secondBuffer, final int si) {
		return firstBuffer[fi] == secondBuffer[si]
				&& firstBuffer[fi + 1] == secondBuffer[si + 1]
				&& firstBuffer[fi + 2] == secondBuffer[si + 2]
				&& firstBuffer[fi + 3] == secondBuffer[si + 3]
				&& firstBuffer[fi + 4] == secondBuffer[si + 4]
				&& firstBuffer[fi + 5] == secondBuffer[si + 5]
				&& firstBuffer[fi + 6] == secondBuffer[si + 6]
				&& firstBuffer[fi + 7] == secondBuffer[si + 7]
				&& firstBuffer[fi + 8] == secondBuffer[si + 8]
				&& firstBuffer[fi + 9] == secondBuffer[si + 9]
				&& firstBuffer[fi + 10] == secondBuffer[si + 10]
				&& firstBuffer[fi + 11] == secondBuffer[si + 11]
				&& firstBuffer[fi + 12] == secondBuffer[si + 12]
				&& firstBuffer[fi + 13] == secondBuffer[si + 13]
				&& firstBuffer[fi + 14] == secondBuffer[si + 14]
				&& firstBuffer[fi + 15] == secondBuffer[si + 15]
				&& firstBuffer[fi + 16] == secondBuffer[si + 16]
				&& firstBuffer[fi + 17] == secondBuffer[si + 17]
				&& firstBuffer[fi + 18] == secondBuffer[si + 18]
				&& firstBuffer[fi + 19] == secondBuffer[si + 19];
	}

	
Convert an ObjectId from raw binary representation.
Params:
bs – 
           the raw byte buffer to read from. At least 20 bytes must be
           available within this byte array.
Returns:
the converted object id./**
	 * Convert an ObjectId from raw binary representation.
	 *
	 * @param bs
	 *            the raw byte buffer to read from. At least 20 bytes must be
	 *            available within this byte array.
	 * @return the converted object id.
	 */
	public static final ObjectId fromRaw(byte[] bs) {
		return fromRaw(bs, 0);
	}

	
Convert an ObjectId from raw binary representation.
Params:
bs – 
           the raw byte buffer to read from. At least 20 bytes after p
           must be available within this byte array.
p – 
           position to read the first byte of data from.
Returns:
the converted object id./**
	 * Convert an ObjectId from raw binary representation.
	 *
	 * @param bs
	 *            the raw byte buffer to read from. At least 20 bytes after p
	 *            must be available within this byte array.
	 * @param p
	 *            position to read the first byte of data from.
	 * @return the converted object id.
	 */
	public static final ObjectId fromRaw(byte[] bs, int p) {
		final int a = NB.decodeInt32(bs, p);
		final int b = NB.decodeInt32(bs, p + 4);
		final int c = NB.decodeInt32(bs, p + 8);
		final int d = NB.decodeInt32(bs, p + 12);
		final int e = NB.decodeInt32(bs, p + 16);
		return new ObjectId(a, b, c, d, e);
	}

	
Convert an ObjectId from raw binary representation.
Params:
is – 
           the raw integers buffer to read from. At least 5 integers must
           be available within this int array.
Returns:
the converted object id./**
	 * Convert an ObjectId from raw binary representation.
	 *
	 * @param is
	 *            the raw integers buffer to read from. At least 5 integers must
	 *            be available within this int array.
	 * @return the converted object id.
	 */
	public static final ObjectId fromRaw(int[] is) {
		return fromRaw(is, 0);
	}

	
Convert an ObjectId from raw binary representation.
Params:
is – 
           the raw integers buffer to read from. At least 5 integers
           after p must be available within this int array.
p – 
           position to read the first integer of data from.
Returns:
the converted object id./**
	 * Convert an ObjectId from raw binary representation.
	 *
	 * @param is
	 *            the raw integers buffer to read from. At least 5 integers
	 *            after p must be available within this int array.
	 * @param p
	 *            position to read the first integer of data from.
	 * @return the converted object id.
	 */
	public static final ObjectId fromRaw(int[] is, int p) {
		return new ObjectId(is[p], is[p + 1], is[p + 2], is[p + 3], is[p + 4]);
	}

	
Convert an ObjectId from hex characters (US-ASCII).
Params:
buf – 
           the US-ASCII buffer to read from. At least 40 bytes after
           offset must be available within this byte array.
offset – 
           position to read the first character from.
Returns:
the converted object id./**
	 * Convert an ObjectId from hex characters (US-ASCII).
	 *
	 * @param buf
	 *            the US-ASCII buffer to read from. At least 40 bytes after
	 *            offset must be available within this byte array.
	 * @param offset
	 *            position to read the first character from.
	 * @return the converted object id.
	 */
	public static final ObjectId fromString(byte[] buf, int offset) {
		return fromHexString(buf, offset);
	}

	
Convert an ObjectId from hex characters.
Params:
str – 
           the string to read from. Must be 40 characters long.
Returns:
the converted object id./**
	 * Convert an ObjectId from hex characters.
	 *
	 * @param str
	 *            the string to read from. Must be 40 characters long.
	 * @return the converted object id.
	 */
	public static ObjectId fromString(String str) {
		if (str.length() != Constants.OBJECT_ID_STRING_LENGTH) {
			throw new InvalidObjectIdException(str);
		}
		return fromHexString(Constants.encodeASCII(str), 0);
	}

	private static final ObjectId fromHexString(byte[] bs, int p) {
		try {
			final int a = RawParseUtils.parseHexInt32(bs, p);
			final int b = RawParseUtils.parseHexInt32(bs, p + 8);
			final int c = RawParseUtils.parseHexInt32(bs, p + 16);
			final int d = RawParseUtils.parseHexInt32(bs, p + 24);
			final int e = RawParseUtils.parseHexInt32(bs, p + 32);
			return new ObjectId(a, b, c, d, e);
		} catch (ArrayIndexOutOfBoundsException e) {
			InvalidObjectIdException e1 = new InvalidObjectIdException(bs, p,
					Constants.OBJECT_ID_STRING_LENGTH);
			e1.initCause(e);
			throw e1;
		}
	}

	
Construct an ObjectId from 160 bits provided in 5 words.
Params:
new_1 – 
           an int
new_2 – 
           an int
new_3 – 
           an int
new_4 – 
           an int
new_5 – 
           an int
Since:
4.7/**
	 * Construct an ObjectId from 160 bits provided in 5 words.
	 *
	 * @param new_1
	 *            an int
	 * @param new_2
	 *            an int
	 * @param new_3
	 *            an int
	 * @param new_4
	 *            an int
	 * @param new_5
	 *            an int
	 * @since 4.7
	 */
	public ObjectId(int new_1, int new_2, int new_3, int new_4, int new_5) {
		w1 = new_1;
		w2 = new_2;
		w3 = new_3;
		w4 = new_4;
		w5 = new_5;
	}

	
Initialize this instance by copying another existing ObjectId.

This constructor is mostly useful for subclasses who want to extend an
ObjectId with more properties, but initialize from an existing ObjectId
instance acquired by other means.
Params:
src – 
           another already parsed ObjectId to copy the value out of./**
	 * Initialize this instance by copying another existing ObjectId.
	 * <p>
	 * This constructor is mostly useful for subclasses who want to extend an
	 * ObjectId with more properties, but initialize from an existing ObjectId
	 * instance acquired by other means.
	 *
	 * @param src
	 *            another already parsed ObjectId to copy the value out of.
	 */
	protected ObjectId(AnyObjectId src) {
		w1 = src.w1;
		w2 = src.w2;
		w3 = src.w3;
		w4 = src.w4;
		w5 = src.w5;
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public ObjectId toObjectId() {
		return this;
	}

	private void writeObject(ObjectOutputStream os) throws IOException {
		os.writeInt(w1);
		os.writeInt(w2);
		os.writeInt(w3);
		os.writeInt(w4);
		os.writeInt(w5);
	}

	private void readObject(ObjectInputStream ois) throws IOException {
		w1 = ois.readInt();
		w2 = ois.readInt();
		w3 = ois.readInt();
		w4 = ois.readInt();
		w5 = ois.readInt();
	}
}