package org.aion.db.utils.slices;

import static java.nio.ByteOrder.LITTLE_ENDIAN;
import static org.aion.db.utils.slices.SizeOf.SIZE_OF_BYTE;
import static org.aion.db.utils.slices.SizeOf.SIZE_OF_INT;
import static org.aion.db.utils.slices.SizeOf.SIZE_OF_LONG;
import static org.aion.db.utils.slices.SizeOf.SIZE_OF_SHORT;

import com.google.common.base.Preconditions;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.FileChannel;
import java.nio.channels.GatheringByteChannel;
import java.nio.channels.ScatteringByteChannel;
import java.nio.charset.Charset;
import java.util.Arrays;

/** Little Endian slice of a byte array. */
public final class Slice implements Comparable<Slice> {
    private final byte[] data;
    private final int offset;
    private final int length;

    private int hash;

    public Slice(int length) {
        data = new byte[length];
        this.offset = 0;
        this.length = length;
    }

    public Slice(byte[] data) {
        Preconditions.checkNotNull(data, "array is null");
        this.data = data;
        this.offset = 0;
        this.length = data.length;
    }

    public Slice(byte[] data, int offset, int length) {
        Preconditions.checkNotNull(data, "array is null");
        this.data = data;
        this.offset = offset;
        this.length = length;
    }

    /** Length of this slice. */
    public int length() {
        return length;
    }

    /** Gets the array underlying this slice. */
    public byte[] getRawArray() {
        return data;
    }

    /** Gets the offset of this slice in the underlying array. */
    public int getRawOffset() {
        return offset;
    }

    /**
     * Gets a byte at the specified absolute {@code index} in this buffer.
     *
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0} or
     *     {@code index + 1} is greater than {@code this.capacity}
     */
    public byte getByte(int index) {
        Preconditions.checkPositionIndexes(index, index + SIZE_OF_BYTE, this.length);
        index += offset;
        return data[index];
    }

    /**
     * Gets an unsigned byte at the specified absolute {@code index} in this buffer.
     *
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0} or
     *     {@code index + 1} is greater than {@code this.capacity}
     */
    public short getUnsignedByte(int index) {
        return (short) (getByte(index) & 0xFF);
    }

    /**
     * Gets a 16-bit short integer at the specified absolute {@code index} in this slice.
     *
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0} or
     *     {@code index + 2} is greater than {@code this.capacity}
     */
    public short getShort(int index) {
        Preconditions.checkPositionIndexes(index, index + SIZE_OF_SHORT, this.length);
        index += offset;
        return (short) (data[index] & 0xFF | data[index + 1] << 8);
    }

    /**
     * Gets a 32-bit integer at the specified absolute {@code index} in this buffer.
     *
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0} or
     *     {@code index + 4} is greater than {@code this.capacity}
     */
    public int getInt(int index) {
        Preconditions.checkPositionIndexes(index, index + SIZE_OF_INT, this.length);
        index += offset;
        return (data[index] & 0xff)
                | (data[index + 1] & 0xff) << 8
                | (data[index + 2] & 0xff) << 16
                | (data[index + 3] & 0xff) << 24;
    }

    /**
     * Gets a 64-bit long integer at the specified absolute {@code index} in this buffer.
     *
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0} or
     *     {@code index + 8} is greater than {@code this.capacity}
     */
    public long getLong(int index) {
        Preconditions.checkPositionIndexes(index, index + SIZE_OF_LONG, this.length);
        index += offset;
        return ((long) data[index] & 0xff)
                | ((long) data[index + 1] & 0xff) << 8
                | ((long) data[index + 2] & 0xff) << 16
                | ((long) data[index + 3] & 0xff) << 24
                | ((long) data[index + 4] & 0xff) << 32
                | ((long) data[index + 5] & 0xff) << 40
                | ((long) data[index + 6] & 0xff) << 48
                | ((long) data[index + 7] & 0xff) << 56;
    }

    /**
     * Transfers this buffer's data to the specified destination starting at the specified absolute
     * {@code index}.
     *
     * @param dstIndex the first index of the destination
     * @param length the number of bytes to transfer
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0}, if
     *     the specified {@code dstIndex} is less than {@code 0}, if {@code index + length} is
     *     greater than {@code this.capacity}, or if {@code dstIndex + length} is greater than
     *     {@code dst.capacity}
     */
    public void getBytes(int index, Slice dst, int dstIndex, int length) {
        getBytes(index, dst.data, dstIndex, length);
    }

    /**
     * Transfers this buffer's data to the specified destination starting at the specified absolute
     * {@code index}.
     *
     * @param destinationIndex the first index of the destination
     * @param length the number of bytes to transfer
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0}, if
     *     the specified {@code dstIndex} is less than {@code 0}, if {@code index + length} is
     *     greater than {@code this.capacity}, or if {@code dstIndex + length} is greater than
     *     {@code dst.length}
     */
    public void getBytes(int index, byte[] destination, int destinationIndex, int length) {
        Preconditions.checkPositionIndexes(index, index + length, this.length);
        Preconditions.checkPositionIndexes(
                destinationIndex, destinationIndex + length, destination.length);
        index += offset;
        System.arraycopy(data, index, destination, destinationIndex, length);
    }

    public byte[] getBytes() {
        return getBytes(0, length);
    }

    public byte[] getBytes(int index, int length) {
        index += offset;
        if (index == 0) {
            return Arrays.copyOf(data, length);
        } else {
            byte[] value = new byte[length];
            System.arraycopy(data, index, value, 0, length);
            return value;
        }
    }

    /**
     * Transfers this buffer's data to the specified destination starting at the specified absolute
     * {@code index} until the destination's position reaches its limit.
     *
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0} or if
     *     {@code index + dst.remaining()} is greater than {@code this.capacity}
     */
    public void getBytes(int index, ByteBuffer destination) {
        Preconditions.checkPositionIndex(index, this.length);
        index += offset;
        destination.put(data, index, Math.min(length, destination.remaining()));
    }

    /**
     * Transfers this buffer's data to the specified stream starting at the specified absolute
     * {@code index}.
     *
     * @param length the number of bytes to transfer
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0} or if
     *     {@code index + length} is greater than {@code this.capacity}
     * @throws java.io.IOException if the specified stream threw an exception during I/O
     */
    public void getBytes(int index, OutputStream out, int length) throws IOException {
        Preconditions.checkPositionIndexes(index, index + length, this.length);
        index += offset;
        out.write(data, index, length);
    }

    /**
     * Transfers this buffer's data to the specified channel starting at the specified absolute
     * {@code index}.
     *
     * @param length the maximum number of bytes to transfer
     * @return the actual number of bytes written out to the specified channel
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0} or if
     *     {@code index + length} is greater than {@code this.capacity}
     * @throws java.io.IOException if the specified channel threw an exception during I/O
     */
    public int getBytes(int index, GatheringByteChannel out, int length) throws IOException {
        Preconditions.checkPositionIndexes(index, index + length, this.length);
        index += offset;
        return out.write(ByteBuffer.wrap(data, index, length));
    }

    /**
     * Sets the specified 16-bit short integer at the specified absolute {@code index} in this
     * buffer. The 16 high-order bits of the specified value are ignored.
     *
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0} or
     *     {@code index + 2} is greater than {@code this.capacity}
     */
    public void setShort(int index, int value) {
        Preconditions.checkPositionIndexes(index, index + SIZE_OF_SHORT, this.length);
        index += offset;
        data[index] = (byte) (value);
        data[index + 1] = (byte) (value >>> 8);
    }

    /**
     * Sets the specified 32-bit integer at the specified absolute {@code index} in this buffer.
     *
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0} or
     *     {@code index + 4} is greater than {@code this.capacity}
     */
    public void setInt(int index, int value) {
        Preconditions.checkPositionIndexes(index, index + SIZE_OF_INT, this.length);
        index += offset;
        data[index] = (byte) (value);
        data[index + 1] = (byte) (value >>> 8);
        data[index + 2] = (byte) (value >>> 16);
        data[index + 3] = (byte) (value >>> 24);
    }

    /**
     * Sets the specified 64-bit long integer at the specified absolute {@code index} in this
     * buffer.
     *
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0} or
     *     {@code index + 8} is greater than {@code this.capacity}
     */
    public void setLong(int index, long value) {
        Preconditions.checkPositionIndexes(index, index + SIZE_OF_LONG, this.length);
        index += offset;
        data[index] = (byte) (value);
        data[index + 1] = (byte) (value >>> 8);
        data[index + 2] = (byte) (value >>> 16);
        data[index + 3] = (byte) (value >>> 24);
        data[index + 4] = (byte) (value >>> 32);
        data[index + 5] = (byte) (value >>> 40);
        data[index + 6] = (byte) (value >>> 48);
        data[index + 7] = (byte) (value >>> 56);
    }

    /**
     * Sets the specified byte at the specified absolute {@code index} in this buffer. The 24
     * high-order bits of the specified value are ignored.
     *
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0} or
     *     {@code index + 1} is greater than {@code this.capacity}
     */
    public void setByte(int index, int value) {
        Preconditions.checkPositionIndexes(index, index + SIZE_OF_BYTE, this.length);
        index += offset;
        data[index] = (byte) value;
    }

    /**
     * Transfers the specified source buffer's data to this buffer starting at the specified
     * absolute {@code index}.
     *
     * @param srcIndex the first index of the source
     * @param length the number of bytes to transfer
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0}, if
     *     the specified {@code srcIndex} is less than {@code 0}, if {@code index + length} is
     *     greater than {@code this.capacity}, or if {@code srcIndex + length} is greater than
     *     {@code src.capacity}
     */
    public void setBytes(int index, Slice src, int srcIndex, int length) {
        setBytes(index, src.data, src.offset + srcIndex, length);
    }

    /**
     * Transfers the specified source array's data to this buffer starting at the specified absolute
     * {@code index}.
     *
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0}, if
     *     the specified {@code srcIndex} is less than {@code 0}, if {@code index + length} is
     *     greater than {@code this.capacity}, or if {@code srcIndex + length} is greater than
     *     {@code src.length}
     */
    public void setBytes(int index, byte[] source, int sourceIndex, int length) {
        Preconditions.checkPositionIndexes(index, index + length, this.length);
        Preconditions.checkPositionIndexes(sourceIndex, sourceIndex + length, source.length);
        index += offset;
        System.arraycopy(source, sourceIndex, data, index, length);
    }

    /**
     * Transfers the specified source buffer's data to this buffer starting at the specified
     * absolute {@code index} until the source buffer's position reaches its limit.
     *
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0} or if
     *     {@code index + src.remaining()} is greater than {@code this.capacity}
     */
    public void setBytes(int index, ByteBuffer source) {
        Preconditions.checkPositionIndexes(index, index + source.remaining(), this.length);
        index += offset;
        source.get(data, index, source.remaining());
    }

    /**
     * Transfers the content of the specified source stream to this buffer starting at the specified
     * absolute {@code index}.
     *
     * @param length the number of bytes to transfer
     * @return the actual number of bytes read in from the specified channel. {@code -1} if the
     *     specified channel is closed.
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0} or if
     *     {@code index + length} is greater than {@code this.capacity}
     * @throws java.io.IOException if the specified stream threw an exception during I/O
     */
    public int setBytes(int index, InputStream in, int length) throws IOException {
        Preconditions.checkPositionIndexes(index, index + length, this.length);
        index += offset;
        int readBytes = 0;
        do {
            int localReadBytes = in.read(data, index, length);
            if (localReadBytes < 0) {
                if (readBytes == 0) {
                    return -1;
                } else {
                    break;
                }
            }
            readBytes += localReadBytes;
            index += localReadBytes;
            length -= localReadBytes;
        } while (length > 0);

        return readBytes;
    }

    /**
     * Transfers the content of the specified source channel to this buffer starting at the
     * specified absolute {@code index}.
     *
     * @param length the maximum number of bytes to transfer
     * @return the actual number of bytes read in from the specified channel. {@code -1} if the
     *     specified channel is closed.
     * @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0} or if
     *     {@code index + length} is greater than {@code this.capacity}
     * @throws java.io.IOException if the specified channel threw an exception during I/O
     */
    public int setBytes(int index, ScatteringByteChannel in, int length) throws IOException {
        Preconditions.checkPositionIndexes(index, index + length, this.length);
        index += offset;
        ByteBuffer buf = ByteBuffer.wrap(data, index, length);
        int readBytes = 0;

        do {
            int localReadBytes;
            try {
                localReadBytes = in.read(buf);
            } catch (ClosedChannelException e) {
                localReadBytes = -1;
            }
            if (localReadBytes < 0) {
                if (readBytes == 0) {
                    return -1;
                } else {
                    break;
                }
            } else if (localReadBytes == 0) {
                break;
            }
            readBytes += localReadBytes;
        } while (readBytes < length);

        return readBytes;
    }

    public int setBytes(int index, FileChannel in, int position, int length) throws IOException {
        Preconditions.checkPositionIndexes(index, index + length, this.length);
        index += offset;
        ByteBuffer buf = ByteBuffer.wrap(data, index, length);
        int readBytes = 0;

        do {
            int localReadBytes;
            try {
                localReadBytes = in.read(buf, position + readBytes);
            } catch (ClosedChannelException e) {
                localReadBytes = -1;
            }
            if (localReadBytes < 0) {
                if (readBytes == 0) {
                    return -1;
                } else {
                    break;
                }
            } else if (localReadBytes == 0) {
                break;
            }
            readBytes += localReadBytes;
        } while (readBytes < length);

        return readBytes;
    }

    public Slice copySlice() {
        return copySlice(0, length);
    }

    /**
     * Returns a copy of this buffer's sub-region. Modifying the content of the returned buffer or
     * this buffer does not affect each other at all.
     */
    public Slice copySlice(int index, int length) {
        Preconditions.checkPositionIndexes(index, index + length, this.length);

        index += offset;
        byte[] copiedArray = new byte[length];
        System.arraycopy(data, index, copiedArray, 0, length);
        return new Slice(copiedArray);
    }

    public byte[] copyBytes() {
        return copyBytes(0, length);
    }

    public byte[] copyBytes(int index, int length) {
        Preconditions.checkPositionIndexes(index, index + length, this.length);
        index += offset;
        if (index == 0) {
            return Arrays.copyOf(data, length);
        } else {
            byte[] value = new byte[length];
            System.arraycopy(data, index, value, 0, length);
            return value;
        }
    }

    /**
     * Returns a slice of this buffer's readable bytes. Modifying the content of the returned buffer
     * or this buffer affects each other's content while they maintain separate indexes and marks.
     */
    public Slice slice() {
        return slice(0, length);
    }

    /**
     * Returns a slice of this buffer's sub-region. Modifying the content of the returned buffer or
     * this buffer affects each other's content while they maintain separate indexes and marks.
     */
    public Slice slice(int index, int length) {
        if (index == 0 && length == this.length) {
            return this;
        }

        Preconditions.checkPositionIndexes(index, index + length, this.length);
        if (index >= 0 && length == 0) {
            return Slices.EMPTY_SLICE;
        }
        return new Slice(data, offset + index, length);
    }

    /** Creates an input stream over this slice. */
    public SliceInput input() {
        return new SliceInput(this);
    }

    /** Creates an output stream over this slice. */
    public SliceOutput output() {
        return new BasicSliceOutput(this);
    }

    /**
     * Converts this buffer's readable bytes into a NIO buffer. The returned buffer shares the
     * content with this buffer.
     */
    public ByteBuffer toByteBuffer() {
        return toByteBuffer(0, length);
    }

    /**
     * Converts this buffer's sub-region into a NIO buffer. The returned buffer shares the content
     * with this buffer.
     */
    public ByteBuffer toByteBuffer(int index, int length) {
        Preconditions.checkPositionIndexes(index, index + length, this.length);
        index += offset;
        return ByteBuffer.wrap(data, index, length).order(LITTLE_ENDIAN);
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        Slice slice = (Slice) o;

        // do lengths match
        if (length != slice.length) {
            return false;
        }

        // if arrays have same base offset, some optimizations can be taken...
        if (offset == slice.offset && data == slice.data) {
            return true;
        }
        for (int i = 0; i < length; i++) {
            if (data[offset + i] != slice.data[slice.offset + i]) {
                return false;
            }
        }
        return true;
    }

    @Override
    public int hashCode() {
        if (hash != 0) {
            return hash;
        }

        int result = length;
        for (int i = offset; i < offset + length; i++) {
            result = 31 * result + data[i];
        }
        if (result == 0) {
            result = 1;
        }
        hash = result;
        return hash;
    }

    /**
     * Compares the content of the specified buffer to the content of this buffer. This comparison
     * is performed byte by byte using an unsigned comparison.
     */
    public int compareTo(Slice that) {
        if (this == that) {
            return 0;
        }
        if (this.data == that.data && length == that.length && offset == that.offset) {
            return 0;
        }

        int minLength = Math.min(this.length, that.length);
        for (int i = 0; i < minLength; i++) {
            int thisByte = 0xFF & this.data[this.offset + i];
            int thatByte = 0xFF & that.data[that.offset + i];
            if (thisByte != thatByte) {
                return (thisByte) - (thatByte);
            }
        }
        return this.length - that.length;
    }

    /** Decodes this buffer's readable bytes into a string with the specified character set name. */
    public String toString(Charset charset) {
        return toString(0, length, charset);
    }

    /** Decodes this buffer's sub-region into a string with the specified character set. */
    public String toString(int index, int length, Charset charset) {
        if (length == 0) {
            return "";
        }

        return Slices.decodeString(toByteBuffer(index, length), charset);
    }

    public String toString() {
        return getClass().getSimpleName() + '(' + "length=" + length() + ')';
    }
}