use super::*;
use sha2::{
    Sha256,
    Digest,
};
use std::{
    fmt,
    io::{
	self, Read,
    },
};

pub const SHA256_SIZE: usize = 32;
#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
pub struct Sha256Hash([u8; SHA256_SIZE]);

impl Sha256Hash
{
    pub fn new(from: [u8; SHA256_SIZE]) -> Self
    {
	Self(from)
    }
    pub fn from_slice<T>(from: T) -> Self
    where T: AsRef<[u8]>
    {
	let mut out = [0u8; SHA256_SIZE];
	bytes::copy_slice(&mut out, from.as_ref());
	Self(out)
    }
    
}

impl fmt::Display for Sha256Hash
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
    {
	write!(f, "Sha256hash (")?;
	for b in self.0.iter()
	{
	    write!(f,"{:02x}", *b)?;
	}
	write!(f, ")")
    }
}

impl Default for Sha256Hash
{
    fn default() -> Self
    {
	Self([0u8; SHA256_SIZE])
    }
}

impl From<Sha256> for Sha256Hash
{
    fn from(hash: Sha256) -> Sha256Hash
    {
	let mut out = [0u8; SHA256_SIZE];
	assert_eq!(bytes::copy_slice(&mut out, hash.finalize()), SHA256_SIZE);
	Self(out)
    }
}
impl AsRef<[u8]> for Sha256Hash
{
    fn as_ref(&self) -> &[u8]
    {
	&self.0[..]
    }
}



/// Compute SHA256 hash from a stream.
pub fn compute<R: Read>(stream: &mut R, result: &mut Sha256Hash) -> io::Result<usize>
{
    let mut buffer = [0u8; BUFFER_SIZE];
    let mut read;
    let mut done=0;
    let mut digest = Sha256::new();

    while {read = stream.read(&mut buffer[..])?; read!=0} {
	digest.update(&buffer[..read]);
	done+=read;
    }
    *result = digest.into();
    Ok(done)
}

/// Compute SHA256 hash from a stream.
#[cfg(feature="threads")]
pub async fn compute_async<R>(stream: &mut R, result: &mut Sha256Hash) -> io::Result<usize>
where R: tokio::io::AsyncRead + std::marker::Send + std::marker::Sync + std::marker::Unpin
{
    use tokio::prelude::*;

    let mut buffer = [0u8; BUFFER_SIZE];
    let mut read;
    let mut done=0;
    let mut digest = Sha256::new();

    while {read = stream.read(&mut buffer[..]).await?; read!=0} {
	digest.update(&buffer[..read]);
	done+=read;
    }
    *result = digest.into();
    Ok(done)
}