use std::io;

use std::io::prelude::*;

use std::mem;

use crate::zio;

use crate::{Compress, Decompress};

/// A ZLIB encoder, or compressor.

///

/// This structure implements a [`Read`] interface. When read from, it reads

/// uncompressed data from the underlying [`BufRead`] and provides the compressed data.

///

/// [`Read`]: https://doc.rust-lang.org/std/io/trait.Read.html

/// [`BufRead`]: https://doc.rust-lang.org/std/io/trait.BufRead.html

///

/// # Examples

///

/// ```

/// use std::io::prelude::*;

/// use flate2::Compression;

/// use flate2::bufread::ZlibEncoder;

/// use std::fs::File;

/// use std::io::BufReader;

///

/// // Use a buffered file to compress contents into a Vec<u8>

///

/// # fn open_hello_world() -> std::io::Result<Vec<u8>> {

/// let f = File::open("examples/hello_world.txt")?;

/// let b = BufReader::new(f);

/// let mut z = ZlibEncoder::new(b, Compression::fast());

/// let mut buffer = Vec::new();

/// z.read_to_end(&mut buffer)?;

/// # Ok(buffer)

/// # }

/// ```

#[derive(Debug)]

pub struct ZlibEncoder<R> {

    obj: R,

    data: Compress,

}

impl<R: BufRead> ZlibEncoder<R> {

    /// Creates a new encoder which will read uncompressed data from the given

    /// stream and emit the compressed stream.

    pub fn new(r: R, level: crate::Compression) -> ZlibEncoder<R> {

        ZlibEncoder {

            obj: r,

            data: Compress::new(level, true),

        }

    }

    /// Creates a new encoder with the given `compression` settings which will

    /// read uncompressed data from the given stream `r` and emit the compressed stream.

    pub fn new_with_compress(r: R, compression: Compress) -> ZlibEncoder<R> {

        ZlibEncoder {

            obj: r,

            data: compression,

        }

    }

}

pub fn reset_encoder_data<R>(zlib: &mut ZlibEncoder<R>) {

    zlib.data.reset()

}

impl<R> ZlibEncoder<R> {

    /// Resets the state of this encoder entirely, swapping out the input

    /// stream for another.

    ///

    /// This function will reset the internal state of this encoder and replace

    /// the input stream with the one provided, returning the previous input

    /// stream. Future data read from this encoder will be the compressed

    /// version of `r`'s data.

    pub fn reset(&mut self, r: R) -> R {

        reset_encoder_data(self);

        mem::replace(&mut self.obj, r)

    }

    /// Acquires a reference to the underlying reader

    pub fn get_ref(&self) -> &R {

        &self.obj

    }

    /// Acquires a mutable reference to the underlying stream

    ///

    /// Note that mutation of the stream may result in surprising results if

    /// this encoder is continued to be used.

    pub fn get_mut(&mut self) -> &mut R {

        &mut self.obj

    }

    /// Consumes this encoder, returning the underlying reader.

    pub fn into_inner(self) -> R {

        self.obj

    }

    /// Returns the number of bytes that have been read into this compressor.

    ///

    /// Note that not all bytes read from the underlying object may be accounted

    /// for, there may still be some active buffering.

    pub fn total_in(&self) -> u64 {

        self.data.total_in()

    }

    /// Returns the number of bytes that the compressor has produced.

    ///

    /// Note that not all bytes may have been read yet, some may still be

    /// buffered.

    pub fn total_out(&self) -> u64 {

        self.data.total_out()

    }

}

impl<R: BufRead> Read for ZlibEncoder<R> {

    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {

        zio::read(&mut self.obj, &mut self.data, buf)

    }

}

impl<R: BufRead + Write> Write for ZlibEncoder<R> {

    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {

        self.get_mut().write(buf)

    }

    fn flush(&mut self) -> io::Result<()> {

        self.get_mut().flush()

    }

}

/// A ZLIB decoder, or decompressor.

///

/// This structure implements a [`Read`] interface. When read from, it reads

/// compressed data from the underlying [`BufRead`] and provides the uncompressed data.

///

/// After reading a single member of the ZLIB data this reader will return

/// Ok(0) even if there are more bytes available in the underlying reader.

/// If you need the following bytes, call `into_inner()` after Ok(0) to

/// recover the underlying reader.

///

/// [`Read`]: https://doc.rust-lang.org/std/io/trait.Read.html

/// [`BufRead`]: https://doc.rust-lang.org/std/io/trait.BufRead.html

///

/// # Examples

///

/// ```

/// use std::io::prelude::*;

/// use std::io;

/// # use flate2::Compression;

/// # use flate2::write::ZlibEncoder;

/// use flate2::bufread::ZlibDecoder;

///

/// # fn main() {

/// # let mut e = ZlibEncoder::new(Vec::new(), Compression::default());

/// # e.write_all(b"Hello World").unwrap();

/// # let bytes = e.finish().unwrap();

/// # println!("{}", decode_bufreader(bytes).unwrap());

/// # }

/// #

/// // Uncompresses a Zlib Encoded vector of bytes and returns a string or error

/// // Here &[u8] implements BufRead

///

/// fn decode_bufreader(bytes: Vec<u8>) -> io::Result<String> {

///     let mut z = ZlibDecoder::new(&bytes[..]);

///     let mut s = String::new();

///     z.read_to_string(&mut s)?;

///     Ok(s)

/// }

/// ```

#[derive(Debug)]

pub struct ZlibDecoder<R> {

    obj: R,

    data: Decompress,

}

impl<R: BufRead> ZlibDecoder<R> {

    /// Creates a new decoder which will decompress data read from the given

    /// stream.

    pub fn new(r: R) -> ZlibDecoder<R> {

        ZlibDecoder {

            obj: r,

            data: Decompress::new(true),

        }

    }

    /// Creates a new decoder which will decompress data read from the given

    /// stream, using the given `decompression` settings.

    pub fn new_with_decompress(r: R, decompression: Decompress) -> ZlibDecoder<R> {

        ZlibDecoder {

            obj: r,

            data: decompression,

        }

    }

}

pub fn reset_decoder_data<R>(zlib: &mut ZlibDecoder<R>) {

    zlib.data = Decompress::new(true);

}

impl<R> ZlibDecoder<R> {

    /// Resets the state of this decoder entirely, swapping out the input

    /// stream for another.

    ///

    /// This will reset the internal state of this decoder and replace the

    /// input stream with the one provided, returning the previous input

    /// stream. Future data read from this decoder will be the decompressed

    /// version of `r`'s data.

    pub fn reset(&mut self, r: R) -> R {

        reset_decoder_data(self);

        mem::replace(&mut self.obj, r)

    }

    /// Acquires a reference to the underlying stream

    pub fn get_ref(&self) -> &R {

        &self.obj

    }

    /// Acquires a mutable reference to the underlying stream

    ///

    /// Note that mutation of the stream may result in surprising results if

    /// this decoder is continued to be used.

    pub fn get_mut(&mut self) -> &mut R {

        &mut self.obj

    }

    /// Consumes this decoder, returning the underlying reader.

    pub fn into_inner(self) -> R {

        self.obj

    }

    /// Returns the number of bytes that the decompressor has consumed.

    ///

    /// Note that this will likely be smaller than what the decompressor

    /// actually read from the underlying stream due to buffering.

    pub fn total_in(&self) -> u64 {

        self.data.total_in()

    }

    /// Returns the number of bytes that the decompressor has produced.

    pub fn total_out(&self) -> u64 {

        self.data.total_out()

    }

}

impl<R: BufRead> Read for ZlibDecoder<R> {

    fn read(&mut self, into: &mut [u8]) -> io::Result<usize> {

        zio::read(&mut self.obj, &mut self.data, into)

    }

}

impl<R: BufRead + Write> Write for ZlibDecoder<R> {

    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {

        self.get_mut().write(buf)

    }

    fn flush(&mut self) -> io::Result<()> {

        self.get_mut().flush()

    }

}

#[cfg(test)]

mod test {

    use crate::bufread::ZlibDecoder;

    use crate::zlib::write;

    use crate::Compression;

    use std::io::{Read, Write};

    // ZlibDecoder consumes one zlib archive and then returns 0 for subsequent reads, allowing any

    // additional data to be consumed by the caller.

    #[test]

    fn decode_extra_data() {

        let expected = "Hello World";

        let compressed = {

            let mut e = write::ZlibEncoder::new(Vec::new(), Compression::default());

            e.write(expected.as_ref()).unwrap();

            let mut b = e.finish().unwrap();

            b.push(b'x');

            b

        };

        let mut output = Vec::new();

        let mut decoder = ZlibDecoder::new(compressed.as_slice());

        let decoded_bytes = decoder.read_to_end(&mut output).unwrap();

        assert_eq!(decoded_bytes, output.len());

        let actual = std::str::from_utf8(&output).expect("String parsing error");

        assert_eq!(

            actual, expected,

            "after decompression we obtain the original input"

        );

        output.clear();

        assert_eq!(

            decoder.read(&mut output).unwrap(),

            0,

            "subsequent read of decoder returns 0, but inner reader can return additional data"

        );

        let mut reader = decoder.into_inner();

        assert_eq!(

            reader.read_to_end(&mut output).unwrap(),

            1,

            "extra data is accessible in underlying buf-read"

        );

        assert_eq!(output, b"x");

    }

}