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use hacl_sys::{Hacl_Curve25519_51_ecdh, Hacl_Curve25519_51_secret_to_public};

#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub enum Error {
    InvalidInput,
}

/// Compute the ECDH with the `private_key` and `public_key`.
///
/// Returns the 32 bytes shared key.
#[must_use]
pub fn ecdh(private_key: &[u8; 32], public_key: &[u8; 32]) -> Result<[u8; 32], Error> {
    let mut shared = [0u8; 32];
    let ok = unsafe {
        Hacl_Curve25519_51_ecdh(
            shared.as_mut_ptr(),
            private_key.as_ptr() as _,
            public_key.as_ptr() as _,
        )
    };
    if !ok {
        Err(Error::InvalidInput)
    } else {
        Ok(shared)
    }
}

/// Compute the public key for the provided `private_key` (scalar multiplication
/// with the base point).
///
/// Returns the 32 bytes shared key.
#[must_use]
pub fn secret_to_public(private_key: &[u8; 32]) -> [u8; 32] {
    let mut public = [0u8; 32];
    unsafe { Hacl_Curve25519_51_secret_to_public(public.as_mut_ptr(), private_key.as_ptr() as _) };
    public
}

#[cfg(all(bmi2, adx, target_arch = "x86_64"))]
pub mod vale {
    use super::Error;
    use hacl_sys::Hacl_Curve25519_64_ecdh;

    /// Compute the ECDH with the `private_key` and `public_key`.
    ///
    /// Returns the 32 bytes shared key.
    #[must_use]
    pub fn ecdh(private_key: &[u8; 32], public_key: &[u8; 32]) -> Result<[u8; 32], Error> {
        let mut shared = [0u8; 32];
        let ok = unsafe {
            Hacl_Curve25519_64_ecdh(
                shared.as_mut_ptr(),
                private_key.as_ptr() as _,
                public_key.as_ptr() as _,
            )
        };
        if !ok {
            Err(Error::InvalidInput)
        } else {
            Ok(shared)
        }
    }
}