use near_sdk::{CryptoHash, env};

use super::{Curve, CurveType, TypedCurve};

pub struct Secp256k1;

impl Curve for Secp256k1 {
    type PublicKey = [u8; 64];

    /// Concatenated `r`, `s` and `v` (recovery byte).
    ///
    /// Note: Ethereum clients shift the recovery byte and this
    /// logic might depend on chain id, so clients must rollback
    /// these changes to v ∈ {0, 1}.
    /// References:
    /// * <https://github.com/ethereumjs/ethereumjs-monorepo/blob/dc7169c16df6d36adeb6e234fcc66eb6cfc5ea3f/packages/util/src/signature.ts#L31-L62>
    /// * <https://github.com/ethereum/go-ethereum/issues/19751#issuecomment-504900739>
    type Signature = [u8; 65];

    // Output of cryptographic hash function
    type Message = CryptoHash;

    /// ECDSA signatures are recoverable, so you don't need a verifying key
    type VerifyingKey = ();

    #[inline]
    fn verify(
        [signature @ .., v]: &Self::Signature,
        hash: &Self::Message,
        _verifying_key: &(),
    ) -> Option<Self::PublicKey> {
        env::ecrecover(
            hash, signature, *v,
            // Do not accept malleable signatures:
            // https://github.com/near/nearcore/blob/d73041cc1d1a70af4456fceefaceb1bf7f684fde/core/crypto/src/signature.rs#L448-L455
            true,
        )
    }
}

impl TypedCurve for Secp256k1 {
    const CURVE_TYPE: CurveType = CurveType::Secp256k1;
}