use std::io;

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

use crate::zio;

use crate::{Compress, Decompress};

/// A DEFLATE encoder, or compressor.

///

/// This structure implements a [`Write`] interface and takes a stream of

/// uncompressed data, writing the compressed data to the wrapped writer.

///

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

///

/// # Examples

///

/// ```

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

/// use flate2::Compression;

/// use flate2::write::DeflateEncoder;

///

/// // Vec<u8> implements Write to print the compressed bytes of sample string

/// # fn main() {

///

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

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

/// println!("{:?}", e.finish().unwrap());

/// # }

/// ```

#[derive(Debug)]

pub struct DeflateEncoder<W: Write> {

    inner: zio::Writer<W, Compress>,

}

impl<W: Write> DeflateEncoder<W> {

    /// Creates a new encoder which will write compressed data to the stream

    /// given at the given compression level.

    ///

    /// When this encoder is dropped or unwrapped the final pieces of data will

    /// be flushed.

    pub fn new(w: W, level: crate::Compression) -> DeflateEncoder<W> {

        DeflateEncoder {

            inner: zio::Writer::new(w, Compress::new(level, false)),

        }

    }

    /// Acquires a reference to the underlying writer.

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

        self.inner.get_ref()

    }

    /// Acquires a mutable reference to the underlying writer.

    ///

    /// Note that mutating the output/input state of the stream may corrupt this

    /// object, so care must be taken when using this method.

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

        self.inner.get_mut()

    }

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

    /// stream for another.

    ///

    /// This function will finish encoding the current stream into the current

    /// output stream before swapping out the two output streams. If the stream

    /// cannot be finished an error is returned.

    ///

    /// After the current stream has been finished, this will reset the internal

    /// state of this encoder and replace the output stream with the one

    /// provided, returning the previous output stream. Future data written to

    /// this encoder will be the compressed into the stream `w` provided.

    ///

    /// # Errors

    ///

    /// This function will perform I/O to complete this stream, and any I/O

    /// errors which occur will be returned from this function.

    pub fn reset(&mut self, w: W) -> io::Result<W> {

        self.inner.finish()?;

        self.inner.data.reset();

        Ok(self.inner.replace(w))

    }

    /// Attempt to finish this output stream, writing out final chunks of data.

    ///

    /// Note that this function can only be used once data has finished being

    /// written to the output stream. After this function is called then further

    /// calls to `write` may result in a panic.

    ///

    /// # Panics

    ///

    /// Attempts to write data to this stream may result in a panic after this

    /// function is called.

    ///

    /// # Errors

    ///

    /// This function will perform I/O to complete this stream, and any I/O

    /// errors which occur will be returned from this function.

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

        self.inner.finish()

    }

    /// Consumes this encoder, flushing the output stream.

    ///

    /// This will flush the underlying data stream, close off the compressed

    /// stream and, if successful, return the contained writer.

    ///

    /// Note that this function may not be suitable to call in a situation where

    /// the underlying stream is an asynchronous I/O stream. To finish a stream

    /// the `try_finish` (or `shutdown`) method should be used instead. To

    /// re-acquire ownership of a stream it is safe to call this method after

    /// `try_finish` or `shutdown` has returned `Ok`.

    ///

    /// # Errors

    ///

    /// This function will perform I/O to complete this stream, and any I/O

    /// errors which occur will be returned from this function.

    pub fn finish(mut self) -> io::Result<W> {

        self.inner.finish()?;

        Ok(self.inner.take_inner())

    }

    /// Consumes this encoder, flushing the output stream.

    ///

    /// This will flush the underlying data stream and then return the contained

    /// writer if the flush succeeded.

    /// The compressed stream will not closed but only flushed. This

    /// means that obtained byte array can by extended by another deflated

    /// stream. To close the stream add the two bytes 0x3 and 0x0.

    ///

    /// # Errors

    ///

    /// This function will perform I/O to complete this stream, and any I/O

    /// errors which occur will be returned from this function.

    pub fn flush_finish(mut self) -> io::Result<W> {

        self.inner.flush()?;

        Ok(self.inner.take_inner())

    }

    /// Returns the number of bytes that have been written to this compressor.

    ///

    /// Note that not all bytes written to this object may be accounted for,

    /// there may still be some active buffering.

    pub fn total_in(&self) -> u64 {

        self.inner.data.total_in()

    }

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

    ///

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

    /// buffered.

    pub fn total_out(&self) -> u64 {

        self.inner.data.total_out()

    }

}

impl<W: Write> Write for DeflateEncoder<W> {

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

        self.inner.write(buf)

    }

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

        self.inner.flush()

    }

}

impl<W: Read + Write> Read for DeflateEncoder<W> {

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

        self.inner.get_mut().read(buf)

    }

}

/// A DEFLATE decoder, or decompressor.

///

/// This structure implements a [`Write`] and will emit a stream of decompressed

/// data when fed a stream of compressed data.

///

/// After decoding a single member of the DEFLATE data this writer will return the number of bytes up to

/// to the end of the DEFLATE member and subsequent writes will return Ok(0) allowing the caller to

/// handle any data following the DEFLATE member.

///

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

///

/// # Examples

///

/// ```

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

/// use std::io;

/// # use flate2::Compression;

/// # use flate2::write::DeflateEncoder;

/// use flate2::write::DeflateDecoder;

///

/// # fn main() {

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

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

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

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

/// # }

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

/// // Here Vec<u8> implements Write

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

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

///    let mut deflater = DeflateDecoder::new(writer);

///    deflater.write_all(&bytes[..])?;

///    writer = deflater.finish()?;

///    let return_string = String::from_utf8(writer).expect("String parsing error");

///    Ok(return_string)

/// }

/// ```

#[derive(Debug)]

pub struct DeflateDecoder<W: Write> {

    inner: zio::Writer<W, Decompress>,

}

impl<W: Write> DeflateDecoder<W> {

    /// Creates a new decoder which will write uncompressed data to the stream.

    ///

    /// When this encoder is dropped or unwrapped the final pieces of data will

    /// be flushed.

    pub fn new(w: W) -> DeflateDecoder<W> {

        DeflateDecoder {

            inner: zio::Writer::new(w, Decompress::new(false)),

        }

    }

    /// Acquires a reference to the underlying writer.

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

        self.inner.get_ref()

    }

    /// Acquires a mutable reference to the underlying writer.

    ///

    /// Note that mutating the output/input state of the stream may corrupt this

    /// object, so care must be taken when using this method.

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

        self.inner.get_mut()

    }

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

    /// stream for another.

    ///

    /// This function will finish encoding the current stream into the current

    /// output stream before swapping out the two output streams.

    ///

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

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

    /// stream. Future data written to this decoder will be decompressed into

    /// the output stream `w`.

    ///

    /// # Errors

    ///

    /// This function will perform I/O to finish the stream, and if that I/O

    /// returns an error then that will be returned from this function.

    pub fn reset(&mut self, w: W) -> io::Result<W> {

        self.inner.finish()?;

        self.inner.data = Decompress::new(false);

        Ok(self.inner.replace(w))

    }

    /// Attempt to finish this output stream, writing out final chunks of data.

    ///

    /// Note that this function can only be used once data has finished being

    /// written to the output stream. After this function is called then further

    /// calls to `write` may result in a panic.

    ///

    /// # Panics

    ///

    /// Attempts to write data to this stream may result in a panic after this

    /// function is called.

    ///

    /// # Errors

    ///

    /// This function will perform I/O to finish the stream, returning any

    /// errors which happen.

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

        self.inner.finish()

    }

    /// Consumes this encoder, flushing the output stream.

    ///

    /// This will flush the underlying data stream and then return the contained

    /// writer if the flush succeeded.

    ///

    /// Note that this function may not be suitable to call in a situation where

    /// the underlying stream is an asynchronous I/O stream. To finish a stream

    /// the `try_finish` (or `shutdown`) method should be used instead. To

    /// re-acquire ownership of a stream it is safe to call this method after

    /// `try_finish` or `shutdown` has returned `Ok`.

    ///

    /// # Errors

    ///

    /// This function will perform I/O to complete this stream, and any I/O

    /// errors which occur will be returned from this function.

    pub fn finish(mut self) -> io::Result<W> {

        self.inner.finish()?;

        Ok(self.inner.take_inner())

    }

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

    /// decompression.

    ///

    /// Note that this will likely be smaller than the number of bytes

    /// successfully written to this stream due to internal buffering.

    pub fn total_in(&self) -> u64 {

        self.inner.data.total_in()

    }

    /// Returns the number of bytes that the decompressor has written to its

    /// output stream.

    pub fn total_out(&self) -> u64 {

        self.inner.data.total_out()

    }

}

impl<W: Write> Write for DeflateDecoder<W> {

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

        self.inner.write(buf)

    }

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

        self.inner.flush()

    }

}

impl<W: Read + Write> Read for DeflateDecoder<W> {

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

        self.inner.get_mut().read(buf)

    }

}

#[cfg(test)]

mod tests {

    use super::*;

    use crate::Compression;

    const STR: &str = "Hello World Hello World Hello World Hello World Hello World \

        Hello World Hello World Hello World Hello World Hello World \

        Hello World Hello World Hello World Hello World Hello World \

        Hello World Hello World Hello World Hello World Hello World \

        Hello World Hello World Hello World Hello World Hello World";

    // DeflateDecoder consumes one zlib archive and then returns 0 for subsequent writes, allowing any

    // additional data to be consumed by the caller.

    #[test]

    fn decode_extra_data() {

        let compressed = {

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

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

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

            b.push(b'x');

            b

        };

        let mut writer = Vec::new();

        let mut decoder = DeflateDecoder::new(writer);

        let mut consumed_bytes = 0;

        loop {

            let n = decoder.write(&compressed[consumed_bytes..]).unwrap();

            if n == 0 {

                break;

            }

            consumed_bytes += n;

        }

        writer = decoder.finish().unwrap();

        let actual = String::from_utf8(writer).expect("String parsing error");

        assert_eq!(actual, STR);

        assert_eq!(&compressed[consumed_bytes..], b"x");

    }

}