//! Misc utilities used by library

use std::fmt;
use std::io::{self, Write};

///Wrapper over `bytes::BytesMut` with convenient `io::Write` interface
///
///Automatically allocates instead of returning error.
pub struct BytesWriter {
    buf: bytes::BytesMut,
}

impl BytesWriter {
    #[inline]
    ///Creates new instance with provided capacity
    pub fn with_capacity(capacity: usize) -> Self {
        Self {
            buf: bytes::BytesMut::with_capacity(capacity)
        }
    }

    #[inline]
    ///Converts to `bytes::Bytes`
    pub fn freeze(self) -> bytes::Bytes {
        self.buf.freeze()
    }
}

impl Default for BytesWriter {
    fn default() -> Self {
        Self::with_capacity(0)
    }
}

impl Into<bytes::Bytes> for BytesWriter {
    #[inline]
    fn into(self) -> bytes::Bytes {
        self.freeze()
    }
}

impl io::Write for BytesWriter {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.buf.extend_from_slice(buf);
        Ok(buf.len())
    }

    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
        self.buf.extend_from_slice(buf);
        Ok(())
    }

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

impl fmt::Write for BytesWriter {
    fn write_str(&mut self, text: &str) -> fmt::Result {
        self.buf.extend_from_slice(text.as_bytes());
        Ok(())
    }
}

///Transforms `Display` into `HeaderValue`
pub fn display_to_header<T: fmt::Display>(data: &T) -> http::header::HeaderValue {
    let mut res = BytesWriter::default();
    let _ = write!(&mut res, "{}", data);
    unsafe { http::header::HeaderValue::from_shared_unchecked(res.freeze()) }
}