// Copyright 2015, 2016 Ethcore (UK) Ltd.
// This file is part of Parity.

// Parity 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.

// Parity 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 Parity.  If not, see <http://www.gnu.org/licenses/>.

//! Tendermint BFT consensus engine with round robin proof-of-authority.

use common::*;
use account_provider::AccountProvider;
use block::*;
use spec::CommonParams;
use engines::{Engine, ProposeCollect};
use evm::Schedule;
use ethjson;

/// `Tendermint` params.
#[derive(Debug)]
pub struct TendermintParams {
	/// Gas limit divisor.
	pub gas_limit_bound_divisor: U256,
	/// Block duration.
	pub duration_limit: u64,
	/// List of validators.
	pub validators: Vec<Address>,
	/// Number of validators.
	pub validator_n: usize,
	/// Consensus round.
	r: u64,
	/// Consensus step.
	s: Step,
	/// Used to swith proposer.
	proposer_nonce: usize
}

#[derive(Debug)]
enum Step {
	Propose,
	Prevote(ProposeCollect),
	Precommit(ProposeCollect),
	Commit
}

impl From<ethjson::spec::TendermintParams> for TendermintParams {
	fn from(p: ethjson::spec::TendermintParams) -> Self {
		let val: Vec<_> = p.validators.into_iter().map(Into::into).collect();
		let val_n = val.len();
		TendermintParams {
			gas_limit_bound_divisor: p.gas_limit_bound_divisor.into(),
			duration_limit: p.duration_limit.into(),
			validators: val,
			validator_n: val_n,
			r: 0,
			s: Step::Propose,
			proposer_nonce: 0
		}
	}
}

/// Engine using `Tendermint` consensus algorithm, suitable for EVM chain.
pub struct Tendermint {
	params: CommonParams,
	our_params: TendermintParams,
	builtins: BTreeMap<Address, Builtin>,
}

impl Tendermint {
	/// Create a new instance of Tendermint engine
	pub fn new(params: CommonParams, our_params: TendermintParams, builtins: BTreeMap<Address, Builtin>) -> Self {
		Tendermint {
			params: params,
			our_params: our_params,
			builtins: builtins,
		}
	}

	fn proposer(&self) -> Address {
		let ref p = self.our_params;
		p.validators.get(p.proposer_nonce%p.validator_n).unwrap().clone()
	}

	fn propose_message(&self, message: UntrustedRlp) -> Option<UntrustedRlp> {
		None
	}
}

impl Engine for Tendermint {
	fn name(&self) -> &str { "Tendermint" }
	fn version(&self) -> SemanticVersion { SemanticVersion::new(1, 0, 0) }
	/// Possibly signatures of all validators.
	fn seal_fields(&self) -> usize { self.our_params.validator_n }

	fn params(&self) -> &CommonParams { &self.params }
	fn builtins(&self) -> &BTreeMap<Address, Builtin> { &self.builtins }

	/// Additional engine-specific information for the user/developer concerning `header`.
	fn extra_info(&self, _header: &Header) -> HashMap<String, String> { hash_map!["signature".to_owned() => "TODO".to_owned()] }

	fn schedule(&self, _env_info: &EnvInfo) -> Schedule {
		Schedule::new_homestead()
	}

	fn populate_from_parent(&self, header: &mut Header, parent: &Header, gas_floor_target: U256, _gas_ceil_target: U256) {
		header.difficulty = parent.difficulty;
		header.gas_limit = {
			let gas_limit = parent.gas_limit;
			let bound_divisor = self.our_params.gas_limit_bound_divisor;
			if gas_limit < gas_floor_target {
				min(gas_floor_target, gas_limit + gas_limit / bound_divisor - 1.into())
			} else {
				max(gas_floor_target, gas_limit - gas_limit / bound_divisor + 1.into())
			}
		};
		header.note_dirty();
	}

	/// Apply the block reward on finalisation of the block.
	/// This assumes that all uncles are valid uncles (i.e. of at least one generation before the current).
	fn on_close_block(&self, _block: &mut ExecutedBlock) {}

	/// Attempt to seal the block internally using all available signatures.
	///
	/// None is returned if not enough signatures can be collected.
	fn generate_seal(&self, block: &ExecutedBlock, accounts: Option<&AccountProvider>) -> Option<Vec<Bytes>> {
		accounts.and_then(|ap| {
			let header = block.header();
			if header.author() == &self.proposer() {
				ap.sign(*header.author(), header.bare_hash())
					.ok()
					.and_then(|signature| Some(vec![encode(&(&*signature as &[u8])).to_vec()]))
			} else {
				None
			}
		})
	}

	fn handle_message(&self, sender: Address, message: UntrustedRlp) -> Option<UntrustedRlp> {
		match message.val_at(0).unwrap_or(return None) {
			0u8 if sender == self.proposer() => self.propose_message(message),
			_ => None,
		}
	}

	fn verify_block_basic(&self, header: &Header, _block: Option<&[u8]>) -> result::Result<(), Error> {
		// check the seal fields.
		// TODO: pull this out into common code.
		if header.seal.len() != self.seal_fields() {
			return Err(From::from(BlockError::InvalidSealArity(
				Mismatch { expected: self.seal_fields(), found: header.seal.len() }
			)));
		}
		Ok(())
	}

	fn verify_block_unordered(&self, header: &Header, _block: Option<&[u8]>) -> result::Result<(), Error> {
		Ok(())
	}

	fn verify_block_family(&self, header: &Header, parent: &Header, _block: Option<&[u8]>) -> result::Result<(), Error> {
		// we should not calculate difficulty for genesis blocks
		if header.number() == 0 {
			return Err(From::from(BlockError::RidiculousNumber(OutOfBounds { min: Some(1), max: None, found: header.number() })));
		}

		// Check difficulty is correct given the two timestamps.
		if header.difficulty() != parent.difficulty() {
			return Err(From::from(BlockError::InvalidDifficulty(Mismatch { expected: *parent.difficulty(), found: *header.difficulty() })))
		}
		let gas_limit_divisor = self.our_params.gas_limit_bound_divisor;
		let min_gas = parent.gas_limit - parent.gas_limit / gas_limit_divisor;
		let max_gas = parent.gas_limit + parent.gas_limit / gas_limit_divisor;
		if header.gas_limit <= min_gas || header.gas_limit >= max_gas {
			return Err(From::from(BlockError::InvalidGasLimit(OutOfBounds { min: Some(min_gas), max: Some(max_gas), found: header.gas_limit })));
		}
		Ok(())
	}

	fn verify_transaction_basic(&self, t: &SignedTransaction, _header: &Header) -> result::Result<(), Error> {
		try!(t.check_low_s());
		Ok(())
	}

	fn verify_transaction(&self, t: &SignedTransaction, _header: &Header) -> Result<(), Error> {
		t.sender().map(|_|()) // Perform EC recovery and cache sender
	}
}


#[cfg(test)]
mod tests {
	use common::*;
	use block::*;
	use tests::helpers::*;
	use account_provider::AccountProvider;
	use spec::Spec;

	/// Create a new test chain spec with `Tendermint` consensus engine.
	fn new_test_authority() -> Spec { Spec::load(include_bytes!("../../res/bft.json")) }

	#[test]
	fn has_valid_metadata() {
		let engine = new_test_authority().engine;
		assert!(!engine.name().is_empty());
		assert!(engine.version().major >= 1);
	}

	#[test]
	fn can_return_schedule() {
		let engine = new_test_authority().engine;
		let schedule = engine.schedule(&EnvInfo {
			number: 10000000,
			author: 0.into(),
			timestamp: 0,
			difficulty: 0.into(),
			last_hashes: Arc::new(vec![]),
			gas_used: 0.into(),
			gas_limit: 0.into(),
		});

		assert!(schedule.stack_limit > 0);
	}

	#[test]
	fn can_do_seal_verification_fail() {
		let engine = new_test_authority().engine;
		let header: Header = Header::default();

		let verify_result = engine.verify_block_basic(&header, None);

		match verify_result {
			Err(Error::Block(BlockError::InvalidSealArity(_))) => {},
			Err(_) => { panic!("should be block seal-arity mismatch error (got {:?})", verify_result); },
			_ => { panic!("Should be error, got Ok"); },
		}
	}

	#[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(&Signature::zero()).to_vec()]);

		let verify_result = engine.verify_block_unordered(&header, None);

		match verify_result {
			Err(Error::Util(UtilError::Crypto(CryptoError::InvalidSignature))) => {},
			Err(_) => { panic!("should be block difficulty error (got {:?})", verify_result); },
			_ => { panic!("Should be error, got Ok"); },
		}
	}

	#[test]
	fn can_generate_seal() {
		let tap = AccountProvider::transient_provider();
		let addr = tap.insert_account("".sha3(), "").unwrap();
		tap.unlock_account_permanently(addr, "".into()).unwrap();

		let spec = new_test_authority();
		let engine = &*spec.engine;
		let genesis_header = spec.genesis_header();
		let mut db_result = get_temp_journal_db();
		let mut db = db_result.take();
		spec.ensure_db_good(db.as_hashdb_mut()).unwrap();
		let last_hashes = Arc::new(vec![genesis_header.hash()]);
		let vm_factory = Default::default();
		let b = OpenBlock::new(engine, &vm_factory, Default::default(), false, db, &genesis_header, last_hashes, addr, (3141562.into(), 31415620.into()), vec![]).unwrap();
		let b = b.close_and_lock();
		let seal = engine.generate_seal(b.block(), Some(&tap)).unwrap();
		assert!(b.try_seal(engine, seal).is_ok());
	}

	#[test]
	fn handle_message() {
		false;
	}
}