// Copyright 2015-2017 Parity Technologies (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/>.

use std::collections::BTreeMap;
use util::Address;
use builtin::Builtin;
use block::*;
use util::*;
use engines::{Engine, CloseOutcome};
use spec::CommonParams;
use evm::Schedule;
use header::BlockNumber;
use error::Error;
use state::CleanupMode;
use trace::{Tracer, ExecutiveTracer};
use types::trace_types::trace::{RewardType};

/// An engine which does not provide any consensus mechanism and does not seal blocks.
pub struct NullEngine {
	params: CommonParams,
	builtins: BTreeMap<Address, Builtin>,
}

impl NullEngine {
	/// Returns new instance of NullEngine with default VM Factory
	pub fn new(params: CommonParams, builtins: BTreeMap<Address, Builtin>) -> Self {
		NullEngine{
			params: params,
			builtins: builtins,
		}
	}
}

impl Default for NullEngine {
	fn default() -> Self {
		Self::new(Default::default(), Default::default())
	}
}

impl Engine for NullEngine {
	fn name(&self) -> &str {
		"NullEngine"
	}

	fn params(&self) -> &CommonParams {
		&self.params
	}

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

	fn schedule(&self, _block_number: BlockNumber) -> Schedule {
		Schedule::new_homestead()
	}

	fn snapshot_components(&self) -> Option<Box<::snapshot::SnapshotComponents>> {
		Some(Box::new(::snapshot::PowSnapshot(10000)))
	}

	fn on_close_block(&self, block: &mut ExecutedBlock) -> Result<CloseOutcome, Error> {
		if !self.params.apply_reward {
			return Ok(CloseOutcome{trace: None});
		}

		let fields = block.fields_mut();		
		let mut tracer = ExecutiveTracer::default();

		let result_block_reward = U256::from(1000000000);
		fields.state.add_balance(
			fields.header.author(),
			&result_block_reward,
			CleanupMode::NoEmpty
		)?;

		let block_miner = fields.header.author().clone();
		tracer.trace_reward(block_miner, result_block_reward, RewardType::Block);

		fields.state.commit()?;
		match *fields.tracing_enabled {
			true => Ok(CloseOutcome{trace: Some(tracer.traces())}),
			false => Ok(CloseOutcome{trace: None})
		}
	}
}