//! Types and Traits for creating and verifying Digest headers
//!
//! Digest headers are commonly used in conjunction with HTTP Signatures to verify the whole
//! request when request bodies are present

use actix_web::{client::ClientRequest, error::BlockingError, http::header::InvalidHeaderValue};
use awc::SendClientRequest;
use std::{fmt::Display, future::Future, pin::Pin};

use crate::{Config, PrepareSignError, Sign};

pub mod middleware;
#[cfg(feature = "sha-2")]
mod sha2;
#[cfg(feature = "sha-3")]
mod sha3;

mod sign;

/// A trait for creating digests of an array of bytes
pub trait DigestCreate {
    /// The name of the digest algorithm
    const NAME: &'static str;

    /// Compute the digest of the input bytes
    fn compute(&mut self, input: &[u8]) -> String;
}

/// A trait for verifying digests
pub trait DigestVerify {
    /// Update the verifier with bytes from the request body
    fn update(&mut self, part: &[u8]);

    /// Verify the request body against the digests from the request headers
    fn verify(&mut self, digests: &[DigestPart]) -> bool;
}

/// Extend the Sign trait with support for adding Digest Headers to the request
///
/// It generates HTTP Signatures after the Digest header has been added, in order to have
/// verification that the body has not been tampered with, or that the request can't be replayed by
/// a malicious entity
pub trait SignExt: Sign {
    /// Set the Digest and Authorization headers on the request
    fn authorization_signature_with_digest<F, E, K, D, V>(
        self,
        config: Config,
        key_id: K,
        digest: D,
        v: V,
        f: F,
    ) -> Pin<Box<dyn Future<Output = Result<DigestClient<V>, E>>>>
    where
        F: FnOnce(&str) -> Result<String, E> + Send + 'static,
        E: From<BlockingError>
            + From<PrepareSignError>
            + From<InvalidHeaderValue>
            + std::fmt::Debug
            + Send
            + 'static,
        K: Display + 'static,
        D: DigestCreate + Send + 'static,
        V: AsRef<[u8]> + Send + 'static,
        Self: Sized;

    /// Set the Digest and Signature headers on the request
    fn signature_with_digest<F, E, K, D, V>(
        self,
        config: Config,
        key_id: K,
        digest: D,
        v: V,
        f: F,
    ) -> Pin<Box<dyn Future<Output = Result<DigestClient<V>, E>>>>
    where
        F: FnOnce(&str) -> Result<String, E> + Send + 'static,
        E: From<BlockingError>
            + From<PrepareSignError>
            + From<InvalidHeaderValue>
            + std::fmt::Debug
            + Send
            + 'static,
        K: Display + 'static,
        D: DigestCreate + Send + 'static,
        V: AsRef<[u8]> + Send + 'static,
        Self: Sized;
}

/// A parsed digest from the request
pub struct DigestPart {
    /// The alrogithm used to produce the digest
    pub algorithm: String,

    /// The digest itself
    pub digest: String,
}

/// An intermediate type between setting the Digest and Signature or Authorization headers, and
/// actually sending the request
///
/// This exists so that the return type for the [`SignExt`] trait can be named
pub struct DigestClient<V> {
    req: ClientRequest,
    body: V,
}

impl<V> DigestClient<V>
where
    V: AsRef<[u8]>,
{
    fn new(req: ClientRequest, body: V) -> Self {
        DigestClient { req, body }
    }

    /// Send the request
    ///
    /// This is analogous to `ClientRequest::send_body` and uses the body provided when producing
    /// the digest
    pub fn send(self) -> SendClientRequest {
        self.req.send_body(self.body.as_ref().to_vec())
    }
}