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    use crate::codec::decoder::Decoder;
    use crate::codec::encoder::Encoder;

    use bytes::{Buf, BufMut, Bytes, BytesMut};
    use std::{cmp, fmt, io, str, usize};

    const DEFAULT_SEEK_DELIMITERS: &[u8] = b",;\n\r";
    const DEFAULT_SEQUENCE_WRITER: &[u8] = b",";
    /// A simple [`Decoder`] and [`Encoder`] implementation that splits up data into chunks based on any character in the given delimiter string.
    ///
    /// [`Decoder`]: crate::codec::Decoder
    /// [`Encoder`]: crate::codec::Encoder
    ///
    /// # Example
    /// Decode string of bytes containing various different delimiters.
    ///
    /// [`BytesMut`]: bytes::BytesMut
    /// [`Error`]: std::io::Error
    ///
    /// ```
    /// use tokio_util::codec::{AnyDelimiterCodec, Decoder};
    /// use bytes::{BufMut, BytesMut};
    ///
    /// #
    /// # #[tokio::main(flavor = "current_thread")]
    /// # async fn main() -> Result<(), std::io::Error> {
    /// let mut codec = AnyDelimiterCodec::new(b",;\r\n".to_vec(),b";".to_vec());
    /// let buf = &mut BytesMut::new();
    /// buf.reserve(200);
    /// buf.put_slice(b"chunk 1,chunk 2;chunk 3\n\r");
    /// assert_eq!("chunk 1", codec.decode(buf).unwrap().unwrap());
    /// assert_eq!("chunk 2", codec.decode(buf).unwrap().unwrap());
    /// assert_eq!("chunk 3", codec.decode(buf).unwrap().unwrap());
    /// assert_eq!("", codec.decode(buf).unwrap().unwrap());
    /// assert_eq!(None, codec.decode(buf).unwrap());
    /// # Ok(())
    /// # }
    /// ```
    ///
    #[derive(Clone, Debug, Eq, PartialEq, Ord, PartialOrd, Hash)]
    pub struct AnyDelimiterCodec {
        // Stored index of the next index to examine for the delimiter character.
        // This is used to optimize searching.
        // For example, if `decode` was called with `abc` and the delimiter is '{}', it would hold `3`,
        // because that is the next index to examine.
        // The next time `decode` is called with `abcde}`, the method will
        // only look at `de}` before returning.
        next_index: usize,

        /// The maximum length for a given chunk. If `usize::MAX`, chunks will be
        /// read until a delimiter character is reached.
        max_length: usize,

        /// Are we currently discarding the remainder of a chunk which was over
        /// the length limit?
        is_discarding: bool,

        /// The bytes that are using for search during decode
        seek_delimiters: Vec<u8>,

        /// The bytes that are using for encoding
        sequence_writer: Vec<u8>,
    }

    impl AnyDelimiterCodec {
        /// Returns a `AnyDelimiterCodec` for splitting up data into chunks.
        ///
        /// # Note
        ///
        /// The returned `AnyDelimiterCodec` will not have an upper bound on the length
        /// of a buffered chunk. See the documentation for [`new_with_max_length`]
        /// for information on why this could be a potential security risk.
        ///
        /// [`new_with_max_length`]: crate::codec::AnyDelimiterCodec::new_with_max_length()
        pub fn new(seek_delimiters: Vec<u8>, sequence_writer: Vec<u8>) -> AnyDelimiterCodec {
            AnyDelimiterCodec {
                next_index: 0,
                max_length: usize::MAX,
                is_discarding: false,
                seek_delimiters,
                sequence_writer,
            }
        }

        /// Returns a `AnyDelimiterCodec` with a maximum chunk length limit.
        ///
        /// If this is set, calls to `AnyDelimiterCodec::decode` will return a
        /// [`AnyDelimiterCodecError`] when a chunk exceeds the length limit. Subsequent calls
        /// will discard up to `limit` bytes from that chunk until a delimiter
        /// character is reached, returning `None` until the delimiter over the limit
        /// has been fully discarded. After that point, calls to `decode` will
        /// function as normal.
        ///
        /// # Note
        ///
        /// Setting a length limit is highly recommended for any `AnyDelimiterCodec` which
        /// will be exposed to untrusted input. Otherwise, the size of the buffer
        /// that holds the chunk currently being read is unbounded. An attacker could
        /// exploit this unbounded buffer by sending an unbounded amount of input
        /// without any delimiter characters, causing unbounded memory consumption.
        ///
        /// [`AnyDelimiterCodecError`]: crate::codec::AnyDelimiterCodecError
        pub fn new_with_max_length(
            seek_delimiters: Vec<u8>,
            sequence_writer: Vec<u8>,
            max_length: usize,
        ) -> Self {
            AnyDelimiterCodec {
                max_length,
                ..AnyDelimiterCodec::new(seek_delimiters, sequence_writer)
            }
        }

        /// Returns the maximum chunk length when decoding.
        ///
        /// ```
        /// use std::usize;
        /// use tokio_util::codec::AnyDelimiterCodec;
        ///
        /// let codec = AnyDelimiterCodec::new(b",;\n".to_vec(), b";".to_vec());
        /// assert_eq!(codec.max_length(), usize::MAX);
        /// ```
        /// ```
        /// use tokio_util::codec::AnyDelimiterCodec;
        ///
        /// let codec = AnyDelimiterCodec::new_with_max_length(b",;\n".to_vec(), b";".to_vec(), 256);
        /// assert_eq!(codec.max_length(), 256);
        /// ```
        pub fn max_length(&self) -> usize {
            self.max_length
        }
    }

    impl Decoder for AnyDelimiterCodec {
        type Item = Bytes;
        type Error = AnyDelimiterCodecError;

        fn decode(&mut self, buf: &mut BytesMut) -> Result<Option<Bytes>, AnyDelimiterCodecError> {
            loop {
                // Determine how far into the buffer we'll search for a delimiter. If
                // there's no max_length set, we'll read to the end of the buffer.
                let read_to = cmp::min(self.max_length.saturating_add(1), buf.len());

                let new_chunk_offset = buf[self.next_index..read_to].iter().position(|b| {
                    self.seek_delimiters
                        .iter()
                        .any(|delimiter| *b == *delimiter)
                });

                match (self.is_discarding, new_chunk_offset) {
                    (true, Some(offset)) => {
                        // If we found a new chunk, discard up to that offset and
                        // then stop discarding. On the next iteration, we'll try
                        // to read a chunk normally.
                        buf.advance(offset + self.next_index + 1);
                        self.is_discarding = false;
                        self.next_index = 0;
                    }
                    (true, None) => {
                        // Otherwise, we didn't find a new chunk, so we'll discard
                        // everything we read. On the next iteration, we'll continue
                        // discarding up to max_len bytes unless we find a new chunk.
                        buf.advance(read_to);
                        self.next_index = 0;
                        if buf.is_empty() {
                            return Ok(None);
                        }
                    }
                    (false, Some(offset)) => {
                        // Found a chunk!
                        let new_chunk_index = offset + self.next_index;
                        self.next_index = 0;
                        let mut chunk = buf.split_to(new_chunk_index + 1);
                        chunk.truncate(chunk.len() - 1);
                        let chunk = chunk.freeze();
                        return Ok(Some(chunk));
                    }
                    (false, None) if buf.len() > self.max_length => {
                        // Reached the maximum length without finding a
                        // new chunk, return an error and start discarding on the
                        // next call.
                        self.is_discarding = true;
                        return Err(AnyDelimiterCodecError::MaxChunkLengthExceeded);
                    }
                    (false, None) => {
                        // We didn't find a chunk or reach the length limit, so the next
                        // call will resume searching at the current offset.
                        self.next_index = read_to;
                        return Ok(None);
                    }
                }
            }
        }

        fn decode_eof(&mut self, buf: &mut BytesMut) -> Result<Option<Bytes>, AnyDelimiterCodecError> {
            Ok(match self.decode(buf)? {
                Some(frame) => Some(frame),
                None => {
                    // return remaining data, if any
                    if buf.is_empty() {
                        None
                    } else {
                        let chunk = buf.split_to(buf.len());
                        self.next_index = 0;
                        Some(chunk.freeze())
                    }
                }
            })
        }
    }

    impl<T> Encoder<T> for AnyDelimiterCodec
    where
        T: AsRef<str>,
    {
        type Error = AnyDelimiterCodecError;

        fn encode(&mut self, chunk: T, buf: &mut BytesMut) -> Result<(), AnyDelimiterCodecError> {
            let chunk = chunk.as_ref();
            buf.reserve(chunk.len() + 1);
            buf.put(chunk.as_bytes());
            buf.put(self.sequence_writer.as_ref());

            Ok(())
        }
    }

    impl Default for AnyDelimiterCodec {
        fn default() -> Self {
            Self::new(
                DEFAULT_SEEK_DELIMITERS.to_vec(),
                DEFAULT_SEQUENCE_WRITER.to_vec(),
            )
        }
    }

    /// An error occured while encoding or decoding a chunk.
    #[derive(Debug)]
    pub enum AnyDelimiterCodecError {
        /// The maximum chunk length was exceeded.
        MaxChunkLengthExceeded,
        /// An IO error occurred.
        Io(io::Error),
    }

    impl fmt::Display for AnyDelimiterCodecError {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            match self {
                AnyDelimiterCodecError::MaxChunkLengthExceeded => {
                    write!(f, "max chunk length exceeded")
                }
                AnyDelimiterCodecError::Io(e) => write!(f, "{}", e),
            }
        }
    }

    impl From<io::Error> for AnyDelimiterCodecError {
        fn from(e: io::Error) -> AnyDelimiterCodecError {
            AnyDelimiterCodecError::Io(e)
        }
    }

    impl std::error::Error for AnyDelimiterCodecError {}