/*
 * Copyright (c) 2016, 2019, 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package jdk.jfr.internal.consumer;

import java.io.DataInput;
import java.io.EOFException;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.file.Path;

public final class RecordingInput implements DataInput, AutoCloseable {

    private final static int DEFAULT_BLOCK_SIZE = 64_000;

    private static final class Block {
        private byte[] bytes = new byte[0];
        private long blockPosition;
        private long blockPositionEnd;

        boolean contains(long position) {
            return position >= blockPosition && position < blockPositionEnd;
        }

        public void read(RandomAccessFile file, int amount) throws IOException {
            blockPosition = file.getFilePointer();
            // reuse byte array, if possible
            if (amount > bytes.length) {
                bytes = new byte[amount];
            }
            this.blockPositionEnd = blockPosition + amount;
            file.readFully(bytes, 0, amount);
        }

        public byte get(long position) {
            return bytes[(int) (position - blockPosition)];
        }

        public void reset() {
            blockPosition = 0;
            blockPositionEnd = 0;
        }
    }
    private final int blockSize;
    private final FileAccess fileAccess;
    private RandomAccessFile file;
    private String filename;
    private Block currentBlock = new Block();
    private Block previousBlock = new Block();
    private long position;
    private long size = -1; // Fail fast if setSize(...) has not been called
                            // before parsing

    RecordingInput(File f, FileAccess fileAccess, int blockSize) throws IOException {
        this.blockSize = blockSize;
        this.fileAccess = fileAccess;
        initialize(f);
    }

    private void initialize(File f) throws IOException {
        this.filename = fileAccess.getAbsolutePath(f);
        this.file = fileAccess.openRAF(f, "r");
        this.position = 0;
        this.size = -1;
        this.currentBlock.reset();
        previousBlock.reset();
        if (fileAccess.length(f) < 8) {
            throw new IOException("Not a valid Flight Recorder file. File length is only " + fileAccess.length(f) + " bytes.");
        }
    }

    public RecordingInput(File f, FileAccess fileAccess) throws IOException {
        this(f, fileAccess, DEFAULT_BLOCK_SIZE);
    }

    void positionPhysical(long position) throws IOException {
        file.seek(position);
    }

    byte readPhysicalByte() throws IOException {
        return file.readByte();
    }

    long readPhysicalLong() throws IOException {
        return file.readLong();
    }

    @Override
    public final byte readByte() throws IOException {
        if (!currentBlock.contains(position)) {
            position(position);
        }
        return currentBlock.get(position++);
    }

    @Override
    public final void readFully(byte[] dest, int offset, int length) throws IOException {
        // TODO: Optimize, use Arrays.copy if all bytes are in current block
        // array
        for (int i = 0; i < length; i++) {
            dest[i + offset] = readByte();
        }
    }

    @Override
    public final void readFully(byte[] dst) throws IOException {
        readFully(dst, 0, dst.length);
    }

    short readRawShort() throws IOException {
        // copied from java.io.Bits
        byte b0 = readByte();
        byte b1 = readByte();
        return (short) ((b1 & 0xFF) + (b0 << 8));
    }

    @Override
    public double readDouble() throws IOException {
        // copied from java.io.Bits
        return Double.longBitsToDouble(readRawLong());
    }

    @Override
    public float readFloat() throws IOException {
        // copied from java.io.Bits
        return Float.intBitsToFloat(readRawInt());
    }

    int readRawInt() throws IOException {
        // copied from java.io.Bits
        byte b0 = readByte();
        byte b1 = readByte();
        byte b2 = readByte();
        byte b3 = readByte();
        return ((b3 & 0xFF)) + ((b2 & 0xFF) << 8) + ((b1 & 0xFF) << 16) + ((b0) << 24);
    }

    long readRawLong() throws IOException {
        // copied from java.io.Bits
        byte b0 = readByte();
        byte b1 = readByte();
        byte b2 = readByte();
        byte b3 = readByte();
        byte b4 = readByte();
        byte b5 = readByte();
        byte b6 = readByte();
        byte b7 = readByte();
        return ((b7 & 0xFFL)) + ((b6 & 0xFFL) << 8) + ((b5 & 0xFFL) << 16) + ((b4 & 0xFFL) << 24) + ((b3 & 0xFFL) << 32) + ((b2 & 0xFFL) << 40) + ((b1 & 0xFFL) << 48) + (((long) b0) << 56);
    }

    public final long position() {
        return position;
    }

    public final void position(long newPosition) throws IOException {
        if (!currentBlock.contains(newPosition)) {
            if (!previousBlock.contains(newPosition)) {
                if (newPosition > size) {
                    throw new EOFException("Trying to read at " + newPosition + ", but file is only " + size + " bytes.");
                }
                long blockStart = trimToFileSize(calculateBlockStart(newPosition));
                file.seek(blockStart);
                // trim amount to file size
                long amount = Math.min(size - blockStart, blockSize);
                previousBlock.read(file, (int) amount);
            }
            // swap previous and current
            Block tmp = currentBlock;
            currentBlock = previousBlock;
            previousBlock = tmp;
        }
        position = newPosition;
    }

    private final long trimToFileSize(long position) throws IOException {
        return Math.min(size(), Math.max(0, position));
    }

    private final long calculateBlockStart(long newPosition) {
        // align to end of current block
        if (currentBlock.contains(newPosition - blockSize)) {
            return currentBlock.blockPosition + currentBlock.bytes.length;
        }
        // align before current block
        if (currentBlock.contains(newPosition + blockSize)) {
            return currentBlock.blockPosition - blockSize;
        }
        // not near current block, pick middle
        return newPosition - blockSize / 2;
    }

    long size() {
        return size;
    }

    @Override
    public void close() throws IOException {
        file.close();
    }

    @Override
    public final int skipBytes(int n) throws IOException {
        long position = position();
        position(position + n);
        return (int) (position() - position);
    }

    @Override
    public final boolean readBoolean() throws IOException {
        return readByte() != 0;
    }

    @Override
    public int readUnsignedByte() throws IOException {
        return readByte() & 0x00FF;
    }

    @Override
    public int readUnsignedShort() throws IOException {
        return readShort() & 0xFFFF;
    }

    @Override
    public final String readLine() throws IOException {
        throw new UnsupportedOperationException();
    }

    // NOTE, this method should really be called readString
    // but can't be renamed without making RecordingInput a
    // public class.
    //
    // This method DOES Not read as expected (s2 + utf8 encoded character)
    // instead it read:
    // byte encoding
    // int size
    // data (byte or char)
    //
    // where encoding
    //
    // 0, means null
    // 1, means UTF8 encoded byte array
    // 2, means char array
    // 3, means latin-1 (ISO-8859-1) encoded byte array
    // 4, means ""
    @Override
    public String readUTF() throws IOException {
        throw new UnsupportedOperationException("Use StringParser");
    }

    @Override
    public char readChar() throws IOException {
        return (char) readLong();
    }

    @Override
    public short readShort() throws IOException {
        return (short) readLong();
    }

    @Override
    public int readInt() throws IOException {
        return (int) readLong();
    }

    @Override
    public long readLong() throws IOException {
        final byte[] bytes = currentBlock.bytes;
        final int index = (int) (position - currentBlock.blockPosition);

        if (index + 8 < bytes.length && index >= 0) {
            byte b0 = bytes[index];
            long ret = (b0 & 0x7FL);
            if (b0 >= 0) {
                position += 1;
                return ret;
            }
            int b1 = bytes[index + 1];
            ret += (b1 & 0x7FL) << 7;
            if (b1 >= 0) {
                position += 2;
                return ret;
            }
            int b2 = bytes[index + 2];
            ret += (b2 & 0x7FL) << 14;
            if (b2 >= 0) {
                position += 3;
                return ret;
            }
            int b3 = bytes[index + 3];
            ret += (b3 & 0x7FL) << 21;
            if (b3 >= 0) {
                position += 4;
                return ret;
            }
            int b4 = bytes[index + 4];
            ret += (b4 & 0x7FL) << 28;
            if (b4 >= 0) {
                position += 5;
                return ret;
            }
            int b5 = bytes[index + 5];
            ret += (b5 & 0x7FL) << 35;
            if (b5 >= 0) {
                position += 6;
                return ret;
            }
            int b6 = bytes[index + 6];
            ret += (b6 & 0x7FL) << 42;
            if (b6 >= 0) {
                position += 7;
                return ret;
            }
            int b7 = bytes[index + 7];
            ret += (b7 & 0x7FL) << 49;
            if (b7 >= 0) {
                position += 8;
                return ret;
            }
            int b8 = bytes[index + 8];// read last byte raw
            position += 9;
            return ret + (((long) (b8 & 0XFF)) << 56);
        } else {
            return readLongSlow();
        }
    }

    private long readLongSlow() throws IOException {
        byte b0 = readByte();
        long ret = (b0 & 0x7FL);
        if (b0 >= 0) {
            return ret;
        }

        int b1 = readByte();
        ret += (b1 & 0x7FL) << 7;
        if (b1 >= 0) {
            return ret;
        }

        int b2 = readByte();
        ret += (b2 & 0x7FL) << 14;
        if (b2 >= 0) {
            return ret;
        }

        int b3 = readByte();
        ret += (b3 & 0x7FL) << 21;
        if (b3 >= 0) {
            return ret;
        }

        int b4 = readByte();
        ret += (b4 & 0x7FL) << 28;
        if (b4 >= 0) {
            return ret;
        }

        int b5 = readByte();
        ret += (b5 & 0x7FL) << 35;
        if (b5 >= 0) {
            return ret;
        }

        int b6 = readByte();
        ret += (b6 & 0x7FL) << 42;
        if (b6 >= 0) {
            return ret;
        }

        int b7 = readByte();
        ret += (b7 & 0x7FL) << 49;
        if (b7 >= 0) {
            return ret;

        }

        int b8 = readByte(); // read last byte raw
        return ret + (((long) (b8 & 0XFF)) << 56);
    }

    public void setValidSize(long size) {
        if (size > this.size) {
            this.size = size;
        }
    }

    public long getFileSize() throws IOException {
        return file.length();
    }

    public String getFilename() {
        return filename;
    }

    // Purpose of this method is to reuse block cache from a
    // previous RecordingInput
    public void setFile(Path path) throws IOException {
        try {
            file.close();
        } catch (IOException e) {
            // perhaps deleted
        }
        file = null;
        initialize(path.toFile());
    }
/*


 *
 *
 */
}