use bytes::Bytes;
use std::str::FromStr;
use warp::{body, header, Filter, Rejection};

#[cfg(feature = "sha-2")]
mod sha_2;

pub trait DigestVerify {
    fn verify(&mut self, digests: &[DigestPart], payload: &[u8]) -> bool;
}

pub struct DigestPart {
    pub algorithm: String,
    pub digest: String,
}

struct Digest {
    parts: Vec<DigestPart>,
}

#[derive(Clone, Debug, thiserror::Error)]
#[error("Could not verify digest")]
pub struct VerifyError;

#[derive(Clone, Debug, thiserror::Error)]
pub enum ParseDigestError {
    #[error("Missing algorithm")]
    Algorithm,

    #[error("Missing digest")]
    Digest,
}

#[derive(Clone, Debug, thiserror::Error)]
#[error("Could not parse request body")]
pub struct ParseBodyError;

pub fn verify_bytes(
    verifier: impl DigestVerify + Clone + Send,
) -> impl Filter<Extract = (Bytes,), Error = Rejection> + Clone {
    parse_digest_header().and(body::bytes()).and_then(
        move |parts: Vec<DigestPart>, bytes: Bytes| {
            let mut verifier = verifier.clone();
            async move {
                if verifier.verify(&parts, &bytes) {
                    Ok(bytes)
                } else {
                    Err(warp::reject::custom(VerifyError))
                }
            }
        },
    )
}

pub fn verify_json<T>(
    verifier: impl DigestVerify + Clone + Send,
) -> impl Filter<Extract = (T,), Error = Rejection> + Clone
where
    T: serde::de::DeserializeOwned,
{
    verify_bytes(verifier).and_then(|bytes: Bytes| {
        async move {
            serde_json::from_slice(&bytes).map_err(|_| warp::reject::custom(ParseBodyError))
        }
    })
}

pub fn verify_form<T>(
    verifier: impl DigestVerify + Clone + Send,
) -> impl Filter<Extract = (T,), Error = Rejection> + Clone
where
    T: serde::de::DeserializeOwned,
{
    verify_bytes(verifier).and_then(|bytes: Bytes| {
        async move {
            serde_urlencoded::from_bytes(&bytes).map_err(|_| warp::reject::custom(ParseBodyError))
        }
    })
}

fn parse_digest_header() -> impl Filter<Extract = (Vec<DigestPart>,), Error = Rejection> + Clone {
    header::header::<Digest>("Digest").map(|d: Digest| d.parts)
}

impl<T> DigestVerify for Vec<T>
where
    T: DigestVerify,
{
    fn verify(&mut self, parts: &[DigestPart], payload: &[u8]) -> bool {
        self.iter_mut().any(|d| d.verify(parts, payload))
    }
}

impl<T> DigestVerify for &mut [T]
where
    T: DigestVerify,
{
    fn verify(&mut self, parts: &[DigestPart], payload: &[u8]) -> bool {
        self.iter_mut().any(|d| d.verify(parts, payload))
    }
}

impl<T, U> DigestVerify for (T, U)
where
    T: DigestVerify,
    U: DigestVerify,
{
    fn verify(&mut self, parts: &[DigestPart], payload: &[u8]) -> bool {
        self.0.verify(parts, payload) || self.1.verify(parts, payload)
    }
}

impl<T, U, V> DigestVerify for (T, U, V)
where
    T: DigestVerify,
    U: DigestVerify,
    V: DigestVerify,
{
    fn verify(&mut self, parts: &[DigestPart], payload: &[u8]) -> bool {
        self.0.verify(parts, payload)
            || self.1.verify(parts, payload)
            || self.2.verify(parts, payload)
    }
}

impl<T, U, V, W> DigestVerify for (T, U, V, W)
where
    T: DigestVerify,
    U: DigestVerify,
    V: DigestVerify,
    W: DigestVerify,
{
    fn verify(&mut self, parts: &[DigestPart], payload: &[u8]) -> bool {
        self.0.verify(parts, payload)
            || self.1.verify(parts, payload)
            || self.2.verify(parts, payload)
            || self.3.verify(parts, payload)
    }
}

impl FromStr for DigestPart {
    type Err = ParseDigestError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let mut iter = s.splitn(2, "=");
        let algorithm = iter.next().ok_or(ParseDigestError::Algorithm)?;
        let digest = iter.next().ok_or(ParseDigestError::Digest)?;

        Ok(DigestPart {
            algorithm: algorithm.to_owned(),
            digest: digest.to_owned(),
        })
    }
}

impl FromStr for Digest {
    type Err = ParseDigestError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let parts: Result<Vec<DigestPart>, Self::Err> = s
            .split(",")
            .map(|s: &str| DigestPart::from_str(s))
            .collect();

        Ok(Digest { parts: parts? })
    }
}

impl warp::reject::Reject for VerifyError {}
impl warp::reject::Reject for ParseBodyError {}