// Copyright 2018 Parity Technologies (UK) Ltd.
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//! This module handles the key agreement process. Typically ECDH.

use futures::prelude::*;
use crate::SecioError;

#[path = "exchange/impl_ring.rs"]
#[cfg(not(any(target_os = "emscripten", target_os = "unknown")))]
mod platform;
#[path = "exchange/impl_webcrypto.rs"]
#[cfg(any(target_os = "emscripten", target_os = "unknown"))]
mod platform;

/// Possible key agreement algorithms.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum KeyAgreement {
    EcdhP256,
    EcdhP384
}

/// Opaque private key type.
pub struct AgreementPrivateKey(platform::AgreementPrivateKey);

/// Generates a new key pair as part of the exchange.
///
/// Returns the opaque private key and the corresponding public key.
#[inline]
pub fn generate_agreement(algorithm: KeyAgreement) -> impl Future<Output = Result<(AgreementPrivateKey, Vec<u8>), SecioError>> {
    platform::generate_agreement(algorithm).map_ok(|(pr, pu)| (AgreementPrivateKey(pr), pu))
}

/// Finish the agreement. On success, returns the shared key that both remote agreed upon.
#[inline]
pub fn agree(algorithm: KeyAgreement, my_private_key: AgreementPrivateKey, other_public_key: &[u8], out_size: usize)
    -> impl Future<Output = Result<Vec<u8>, SecioError>>
{
    platform::agree(algorithm, my_private_key.0, other_public_key, out_size)
}