/*
 * Copyright (c) 2003, 2021, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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/*
 *******************************************************************************
 * Copyright (C) 1996-2014, International Business Machines Corporation and
 * others. All Rights Reserved.
 *******************************************************************************
 */

package jdk_internal.icu.impl;

import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.UncheckedIOException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.Arrays;

import jdk_internal.icu.util.VersionInfo;
import net.lax1dude.eaglercraft.v1_8.EagRuntime;

public final class ICUBinary {

	/**
	 * Special interface for data authentication
	 */
	public static interface Authenticate {
		/**
		 * Method used in ICUBinary.readHeader() to provide data format authentication.
		 *
		 * @param version version of the current data
		 * @return true if dataformat is an acceptable version, false otherwise
		 */
		public boolean isDataVersionAcceptable(byte version[]);
	}

	// public inner interface ------------------------------------------------

	private static final class IsAcceptable implements Authenticate {
		@Override
		public boolean isDataVersionAcceptable(byte version[]) {
			return version[0] == 1;
		}
	}

	// public methods --------------------------------------------------------

	private static final byte BIG_ENDIAN_ = 1;

	/**
	 * Magic numbers to authenticate the data file
	 */
	private static final byte MAGIC1 = (byte) 0xda;

	private static final byte MAGIC2 = (byte) 0x27;

	/**
	 * File format authentication values
	 */
	private static final byte CHAR_SET_ = 0;

	private static final byte CHAR_SIZE_ = 2;

	/**
	 * Error messages
	 */
	private static final String MAGIC_NUMBER_AUTHENTICATION_FAILED_ = "ICUBinary data file error: Magic number authentication failed";

	private static final String HEADER_AUTHENTICATION_FAILED_ = "ICUBinary data file error: Header authentication failed";

	public static byte[] getBytes(ByteBuffer bytes, int length, int additionalSkipLength) {
		byte[] dest = new byte[length];
		bytes.get(dest);
		if (additionalSkipLength > 0) {
			skipBytes(bytes, additionalSkipLength);
		}
		return dest;
	}

	public static char[] getChars(ByteBuffer bytes, int length, int additionalSkipLength) {
		char[] dest = new char[length];
		bytes.asCharBuffer().get(dest);
		skipBytes(bytes, length * 2 + additionalSkipLength);
		return dest;
	}

	public static int[] getInts(ByteBuffer bytes, int length, int additionalSkipLength) {
		int[] dest = new int[length];
		bytes.asIntBuffer().get(dest);
		skipBytes(bytes, length * 4 + additionalSkipLength);
		return dest;
	}

	/**
	 * Loads an ICU binary data file and returns it as a ByteBuffer. The buffer
	 * contents is normally read-only, but its position etc. can be modified.
	 *
	 * @param itemPath Relative ICU data item path, for example "root.res" or
	 *                 "coll/ucadata.icu".
	 * @return The data as a read-only ByteBuffer.
	 */
	public static ByteBuffer getRequiredData(String itemPath) {
		try (InputStream is = EagRuntime.getRequiredResourceStream(itemPath)) {

			// is.available() may return 0, or 1, or the total number of bytes in the
			// stream,
			// or some other number.
			// Do not try to use is.available() == 0 to find the end of the stream!
			byte[] bytes;
			int avail = is.available();
			if (avail > 32) {
				// There are more bytes available than just the ICU data header length.
				// With luck, it is the total number of bytes.
				bytes = new byte[avail];
			} else {
				bytes = new byte[128]; // empty .res files are even smaller
			}
			// Call is.read(...) until one returns a negative value.
			int length = 0;
			for (;;) {
				if (length < bytes.length) {
					int numRead = is.read(bytes, length, bytes.length - length);
					if (numRead < 0) {
						break; // end of stream
					}
					length += numRead;
				} else {
					// See if we are at the end of the stream before we grow the array.
					int nextByte = is.read();
					if (nextByte < 0) {
						break;
					}
					int capacity = 2 * bytes.length;
					if (capacity < 128) {
						capacity = 128;
					} else if (capacity < 0x4000) {
						capacity *= 2; // Grow faster until we reach 16kB.
					}
					bytes = Arrays.copyOf(bytes, capacity);
					bytes[length++] = (byte) nextByte;
				}
			}
			return ByteBuffer.wrap(bytes, 0, length);
		} catch (IOException e) {
			throw new UncheckedIOException(e);
		}
	}

	// private variables -------------------------------------------------

	public static String getString(ByteBuffer bytes, int length, int additionalSkipLength) {
		CharSequence cs = bytes.asCharBuffer();
		String s = cs.subSequence(0, length).toString();
		skipBytes(bytes, length * 2 + additionalSkipLength);
		return s;
	}

	/**
	 * Returns a VersionInfo for the bytes in the compact version integer.
	 */
	public static VersionInfo getVersionInfoFromCompactInt(int version) {
		return VersionInfo.getInstance(version >>> 24, (version >> 16) & 0xff, (version >> 8) & 0xff, version & 0xff);
	}

	/**
	 * Reads an ICU data header, checks the data format, and returns the data
	 * version.
	 *
	 * <p>
	 * Assumes that the ByteBuffer position is 0 on input. The buffer byte order is
	 * set according to the data. The buffer position is advanced past the header
	 * (including UDataInfo and comment).
	 *
	 * <p>
	 * See C++ ucmndata.h and unicode/udata.h.
	 *
	 * @return dataVersion
	 * @throws IOException if this is not a valid ICU data item of the expected
	 *                     dataFormat
	 */
	public static int readHeader(ByteBuffer bytes, int dataFormat, Authenticate authenticate) throws IOException {
		assert bytes.position() == 0;
		byte magic1 = bytes.get(2);
		byte magic2 = bytes.get(3);
		if (magic1 != MAGIC1 || magic2 != MAGIC2) {
			throw new IOException(MAGIC_NUMBER_AUTHENTICATION_FAILED_);
		}

		byte isBigEndian = bytes.get(8);
		byte charsetFamily = bytes.get(9);
		byte sizeofUChar = bytes.get(10);
		if (isBigEndian < 0 || 1 < isBigEndian || charsetFamily != CHAR_SET_ || sizeofUChar != CHAR_SIZE_) {
			throw new IOException(HEADER_AUTHENTICATION_FAILED_);
		}
		bytes.order(isBigEndian != 0 ? ByteOrder.BIG_ENDIAN : ByteOrder.LITTLE_ENDIAN);

		int headerSize = bytes.getChar(0);
		int sizeofUDataInfo = bytes.getChar(4);
		if (sizeofUDataInfo < 20 || headerSize < (sizeofUDataInfo + 4)) {
			throw new IOException("Internal Error: Header size error");
		}
		// TODO: Change Authenticate to take int major, int minor, int milli, int micro
		// to avoid array allocation.
		byte[] formatVersion = new byte[] { bytes.get(16), bytes.get(17), bytes.get(18), bytes.get(19) };
		if (bytes.get(12) != (byte) (dataFormat >> 24) || bytes.get(13) != (byte) (dataFormat >> 16)
				|| bytes.get(14) != (byte) (dataFormat >> 8) || bytes.get(15) != (byte) dataFormat
				|| (authenticate != null && !authenticate.isDataVersionAcceptable(formatVersion))) {
			throw new IOException(HEADER_AUTHENTICATION_FAILED_
					+ String.format("; data format %02x%02x%02x%02x, format version %d.%d.%d.%d", bytes.get(12),
							bytes.get(13), bytes.get(14), bytes.get(15), formatVersion[0] & 0xff,
							formatVersion[1] & 0xff, formatVersion[2] & 0xff, formatVersion[3] & 0xff));
		}

		bytes.position(headerSize);
		return // dataVersion
		((int) bytes.get(20) << 24) | ((bytes.get(21) & 0xff) << 16) | ((bytes.get(22) & 0xff) << 8)
				| (bytes.get(23) & 0xff);
	}

	public static final byte[] readHeader(InputStream inputStream, byte dataFormatIDExpected[],
			Authenticate authenticate) throws IOException {
		DataInputStream input = new DataInputStream(inputStream);
		char headersize = input.readChar();
		int readcount = 2;
		// reading the header format
		byte magic1 = input.readByte();
		readcount++;
		byte magic2 = input.readByte();
		readcount++;
		if (magic1 != MAGIC1 || magic2 != MAGIC2) {
			throw new IOException(MAGIC_NUMBER_AUTHENTICATION_FAILED_);
		}

		input.readChar(); // reading size
		readcount += 2;
		input.readChar(); // reading reserved word
		readcount += 2;
		byte bigendian = input.readByte();
		readcount++;
		byte charset = input.readByte();
		readcount++;
		byte charsize = input.readByte();
		readcount++;
		input.readByte(); // reading reserved byte
		readcount++;

		byte dataFormatID[] = new byte[4];
		input.readFully(dataFormatID);
		readcount += 4;
		byte dataVersion[] = new byte[4];
		input.readFully(dataVersion);
		readcount += 4;
		byte unicodeVersion[] = new byte[4];
		input.readFully(unicodeVersion);
		readcount += 4;
		if (headersize < readcount) {
			throw new IOException("Internal Error: Header size error");
		}
		input.skipBytes(headersize - readcount);

		if (bigendian != BIG_ENDIAN_ || charset != CHAR_SET_ || charsize != CHAR_SIZE_
				|| !Arrays.equals(dataFormatIDExpected, dataFormatID)
				|| (authenticate != null && !authenticate.isDataVersionAcceptable(dataVersion))) {
			throw new IOException(HEADER_AUTHENTICATION_FAILED_);
		}
		return unicodeVersion;
	}

	/**
	 * Same as readHeader(), but returns a VersionInfo rather than a compact int.
	 */
	public static VersionInfo readHeaderAndDataVersion(ByteBuffer bytes, int dataFormat, Authenticate authenticate)
			throws IOException {
		return getVersionInfoFromCompactInt(readHeader(bytes, dataFormat, authenticate));
	}

	public static void skipBytes(ByteBuffer bytes, int skipLength) {
		if (skipLength > 0) {
			bytes.position(bytes.position() + skipLength);
		}
	}
}
