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// Copyright 2021 MaidSafe.net limited.
//
// This SAFE Network Software is licensed to you under the MIT license <LICENSE-MIT
// https://opensource.org/licenses/MIT> or the Modified BSD license <LICENSE-BSD
// https://opensource.org/licenses/BSD-3-Clause>, at your option. This file may not be copied,
// modified, or distributed except according to those terms. Please review the Licences for the
// specific language governing permissions and limitations relating to use of the SAFE Network
// Software.

//! Module providing keys, keypairs, and signatures.
//!
//! The easiest way to get a `PublicKey` is to create a random `Keypair` first through one of the
//! `new` functions. A `PublicKey` can't be generated by itself; it must always be derived from a
//! secret key.

use hex_fmt::HexFmt;
use serde::{Deserialize, Serialize};
use std::{fmt, hash::Hash};

/// A signature share, with its index in the combined collection.
#[derive(Clone, Hash, Eq, PartialEq, PartialOrd, Serialize, Deserialize, Debug)]
pub struct SignatureShare {
    /// Index in the combined collection.
    pub index: usize,
    /// Signature over some data.
    pub share: bls::SignatureShare,
}

/// Wrapper for different signature types.
#[derive(Clone, Eq, PartialEq, Serialize, Deserialize, custom_debug::Debug)]
#[allow(clippy::large_enum_variant)]
pub enum Signature {
    /// Ed25519 signature.
    Ed25519(
        #[debug(with = "Self::fmt_ed25519")]
        #[serde(with = "serde_bytes")]
        ed25519_dalek::Signature,
    ),
    /// BLS signature.
    Bls(bls::Signature),
    /// BLS signature share.
    BlsShare(SignatureShare),
}

impl Signature {
    /// Returns bls::Signature if Self is a BLS variant.
    pub fn into_bls(self) -> Option<bls::Signature> {
        match self {
            Self::Bls(sig) => Some(sig),
            _ => None,
        }
    }

    /// Returns ed25519_dalek::Signature if Self is a Ed25519 variant.
    pub fn into_ed(self) -> Option<ed25519_dalek::Signature> {
        match self {
            Self::Ed25519(sig) => Some(sig),
            _ => None,
        }
    }

    // ed25519_dalek::Signature has overly verbose debug output, so we provide our own
    pub(crate) fn fmt_ed25519(
        sig: &ed25519_dalek::Signature,
        f: &mut fmt::Formatter<'_>,
    ) -> fmt::Result {
        write!(f, "Signature({:0.10})", HexFmt(sig))
    }
}

impl From<bls::Signature> for Signature {
    fn from(sig: bls::Signature) -> Self {
        Self::Bls(sig)
    }
}

impl From<ed25519_dalek::Signature> for Signature {
    fn from(sig: ed25519_dalek::Signature) -> Self {
        Self::Ed25519(sig)
    }
}

impl From<SignatureShare> for Signature {
    fn from(sig: SignatureShare) -> Self {
        Self::BlsShare(sig)
    }
}

impl From<(usize, bls::SignatureShare)> for Signature {
    fn from(sig: (usize, bls::SignatureShare)) -> Self {
        let (index, share) = sig;
        Self::BlsShare(SignatureShare { index, share })
    }
}

#[cfg(test)]
mod tests {
    use super::Signature;

    #[test]
    fn ed25519_rmp_roundtrip() -> Result<(), Box<dyn std::error::Error>> {
        let signature = gen_ed25519_sig();
        let serialized = rmp_serde::to_vec(&signature)?;

        assert_eq!(
            rmp_serde::from_read::<_, Signature>(&serialized[..])?,
            signature
        );

        Ok(())
    }

    #[test]
    fn ed25519_rmp_fmt() -> Result<(), Box<dyn std::error::Error>> {
        let signature = gen_ed25519_sig();
        let serialized = rmp_serde::to_vec(&signature)?;

        assert_eq!(serialized.len(), 68);
        assert_eq!(serialized[0], 0x81); // fixmap of length 1
        assert_eq!(serialized[1], 0x00); // variant index
        assert_eq!(serialized[2], 0xc4); // bin 8 bytearray
        assert_eq!(serialized[3], 64); // bytearray length
        assert_eq!(&serialized[4..], signature.into_ed().unwrap().as_ref());

        Ok(())
    }

    fn gen_ed25519_sig() -> Signature {
        use rand::Rng;

        let mut bytes = [0u8; ed25519_dalek::SIGNATURE_LENGTH];
        rand::thread_rng().fill(&mut bytes);
        Signature::Ed25519(ed25519_dalek::Signature::new(bytes))
    }
}