// Copyright 2015-2020 Parity Technologies (UK) Ltd.
// This file is part of OpenEthereum.

// OpenEthereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// OpenEthereum is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with OpenEthereum.  If not, see <http://www.gnu.org/licenses/>.

//! A blockchain engine that supports a basic, non-BFT proof-of-authority.

use super::validator_set::{new_validator_set, SimpleList, ValidatorSet};
use block::*;
use client::EngineClient;
use crypto::publickey::{self, Signature};
use engines::{signer::EngineSigner, ConstructedVerifier, Engine, EngineError, Seal};
use error::{BlockError, Error};
use ethereum_types::{H256, H520};
use ethjson;
use machine::{AuxiliaryData, Call, EthereumMachine};
use parking_lot::RwLock;
use std::sync::Weak;
use types::header::{ExtendedHeader, Header};

/// `BasicAuthority` params.
#[derive(Debug, PartialEq)]
pub struct BasicAuthorityParams {
    /// Valid signatories.
    pub validators: ethjson::spec::ValidatorSet,
}

impl From<ethjson::spec::BasicAuthorityParams> for BasicAuthorityParams {
    fn from(p: ethjson::spec::BasicAuthorityParams) -> Self {
        BasicAuthorityParams {
            validators: p.validators,
        }
    }
}

struct EpochVerifier {
    list: SimpleList,
}

impl super::EpochVerifier<EthereumMachine> for EpochVerifier {
    fn verify_light(&self, header: &Header) -> Result<(), Error> {
        verify_external(header, &self.list)
    }
}

fn verify_external(header: &Header, validators: &dyn ValidatorSet) -> Result<(), Error> {
    use rlp::Rlp;

    // Check if the signature belongs to a validator, can depend on parent state.
    let sig = Rlp::new(&header.seal()[0]).as_val::<H520>()?;
    let signer =
        publickey::public_to_address(&publickey::recover(&sig.into(), &header.bare_hash())?);

    if *header.author() != signer {
        return Err(EngineError::NotAuthorized(*header.author()).into());
    }

    match validators.contains(header.parent_hash(), &signer) {
        false => Err(BlockError::InvalidSeal.into()),
        true => Ok(()),
    }
}

/// Engine using `BasicAuthority`, trivial proof-of-authority consensus.
pub struct BasicAuthority {
    machine: EthereumMachine,
    signer: RwLock<Option<Box<dyn EngineSigner>>>,
    validators: Box<dyn ValidatorSet>,
}

impl BasicAuthority {
    /// Create a new instance of BasicAuthority engine
    pub fn new(our_params: BasicAuthorityParams, machine: EthereumMachine) -> Self {
        BasicAuthority {
            machine: machine,
            signer: RwLock::new(None),
            validators: new_validator_set(our_params.validators),
        }
    }
}

impl Engine<EthereumMachine> for BasicAuthority {
    fn name(&self) -> &str {
        "BasicAuthority"
    }

    fn machine(&self) -> &EthereumMachine {
        &self.machine
    }

    // One field - the signature
    fn seal_fields(&self, _header: &Header) -> usize {
        1
    }

    fn seals_internally(&self) -> Option<bool> {
        Some(self.signer.read().is_some())
    }

    /// Attempt to seal the block internally.
    fn generate_seal(&self, block: &ExecutedBlock, _parent: &Header) -> Seal {
        let header = &block.header;
        let author = header.author();
        if self.validators.contains(header.parent_hash(), author) {
            // account should be pernamently unlocked, otherwise sealing will fail
            if let Ok(signature) = self.sign(header.bare_hash()) {
                return Seal::Regular(vec![::rlp::encode(&(H520::from(signature).as_bytes()))]);
            } else {
                trace!(target: "basicauthority", "generate_seal: FAIL: accounts secret key unavailable");
            }
        }
        Seal::None
    }

    fn verify_local_seal(&self, _header: &Header) -> Result<(), Error> {
        Ok(())
    }

    fn verify_block_external(&self, header: &Header) -> Result<(), Error> {
        verify_external(header, &*self.validators)
    }

    fn genesis_epoch_data(&self, header: &Header, call: &Call) -> Result<Vec<u8>, String> {
        self.validators.genesis_epoch_data(header, call)
    }

    #[cfg(not(test))]
    fn signals_epoch_end(
        &self,
        _header: &Header,
        _auxiliary: AuxiliaryData,
    ) -> super::EpochChange<EthereumMachine> {
        // don't bother signalling even though a contract might try.
        super::EpochChange::No
    }

    #[cfg(test)]
    fn signals_epoch_end(
        &self,
        header: &Header,
        auxiliary: AuxiliaryData,
    ) -> super::EpochChange<EthereumMachine> {
        // in test mode, always signal even though they don't be finalized.
        let first = header.number() == 0;
        self.validators.signals_epoch_end(first, header, auxiliary)
    }

    fn is_epoch_end(
        &self,
        chain_head: &Header,
        _finalized: &[H256],
        _chain: &super::Headers<Header>,
        _transition_store: &super::PendingTransitionStore,
    ) -> Option<Vec<u8>> {
        let first = chain_head.number() == 0;

        // finality never occurs so only apply immediate transitions.
        self.validators.is_epoch_end(first, chain_head)
    }

    fn epoch_verifier<'a>(
        &self,
        header: &Header,
        proof: &'a [u8],
    ) -> ConstructedVerifier<'a, EthereumMachine> {
        let first = header.number() == 0;

        match self
            .validators
            .epoch_set(first, &self.machine, header.number(), proof)
        {
            Ok((list, finalize)) => {
                let verifier = Box::new(EpochVerifier { list: list });

                // our epoch verifier will ensure no unverified verifier is ever verified.
                match finalize {
                    Some(finalize) => ConstructedVerifier::Unconfirmed(verifier, proof, finalize),
                    None => ConstructedVerifier::Trusted(verifier),
                }
            }
            Err(e) => ConstructedVerifier::Err(e),
        }
    }

    fn register_client(&self, client: Weak<dyn EngineClient>) {
        self.validators.register_client(client);
    }

    fn set_signer(&self, signer: Box<dyn EngineSigner>) {
        *self.signer.write() = Some(signer);
    }

    fn sign(&self, hash: H256) -> Result<Signature, Error> {
        Ok(self
            .signer
            .read()
            .as_ref()
            .ok_or_else(|| publickey::Error::InvalidAddress)?
            .sign(hash)?)
    }

    fn snapshot_components(&self) -> Option<Box<dyn crate::snapshot::SnapshotComponents>> {
        None
    }

    fn fork_choice(&self, new: &ExtendedHeader, current: &ExtendedHeader) -> super::ForkChoice {
        super::total_difficulty_fork_choice(new, current)
    }
}

#[cfg(test)]
mod tests {
    use accounts::AccountProvider;
    use block::*;
    use engines::Seal;
    use ethereum_types::H520;
    use hash::keccak;
    use spec::Spec;
    use std::sync::Arc;
    use tempdir::TempDir;
    use test_helpers::get_temp_state_db;
    use types::header::Header;

    /// Create a new test chain spec with `BasicAuthority` consensus engine.
    fn new_test_authority() -> Spec {
        let bytes: &[u8] = include_bytes!("../../res/chainspec/test/basic_authority.json");
        let tempdir = TempDir::new("").unwrap();
        Spec::load(&tempdir.path(), bytes).expect("invalid chain spec")
    }

    #[test]
    fn has_valid_metadata() {
        let engine = new_test_authority().engine;
        assert!(!engine.name().is_empty());
    }

    #[test]
    fn can_return_schedule() {
        let engine = new_test_authority().engine;
        let schedule = engine.schedule(10000000);
        assert!(schedule.stack_limit > 0);
    }

    #[test]
    fn can_do_signature_verification_fail() {
        let engine = new_test_authority().engine;
        let mut header: Header = Header::default();
        header.set_seal(vec![::rlp::encode(&H520::default())]);

        let verify_result = engine.verify_block_external(&header);
        assert!(verify_result.is_err());
    }

    #[test]
    fn can_generate_seal() {
        let tap = AccountProvider::transient_provider();
        let addr = tap.insert_account(keccak("").into(), &"".into()).unwrap();

        let spec = new_test_authority();
        let engine = &*spec.engine;
        engine.set_signer(Box::new((Arc::new(tap), addr, "".into())));
        let genesis_header = spec.genesis_header();
        let db = spec
            .ensure_db_good(get_temp_state_db(), &Default::default())
            .unwrap();
        let last_hashes = Arc::new(vec![genesis_header.hash()]);
        let b = OpenBlock::new(
            engine,
            Default::default(),
            false,
            db,
            &genesis_header,
            last_hashes,
            addr,
            (3141562.into(), 31415620.into()),
            vec![],
            false,
            None,
        )
        .unwrap();
        let b = b.close_and_lock().unwrap();
        if let Seal::Regular(seal) = engine.generate_seal(&b, &genesis_header) {
            assert!(b.try_seal(engine, seal).is_ok());
        }
    }

    #[test]
    fn seals_internally() {
        let tap = AccountProvider::transient_provider();
        let authority = tap.insert_account(keccak("").into(), &"".into()).unwrap();

        let engine = new_test_authority().engine;
        assert!(!engine.seals_internally().unwrap());
        engine.set_signer(Box::new((Arc::new(tap), authority, "".into())));
        assert!(engine.seals_internally().unwrap());
    }
}