// 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/>.

/// Preconfigured validator list.

use heapsize::HeapSizeOf;
use ethereum_types::{H256, Address};

use machine::{AuxiliaryData, Call, EthereumMachine};
use header::{BlockNumber, Header};
use super::ValidatorSet;

/// Validator set containing a known set of addresses.
#[derive(Clone, Debug, PartialEq, Eq, Default)]
pub struct SimpleList {
	validators: Vec<Address>,
}

impl SimpleList {
	/// Create a new `SimpleList`.
	pub fn new(validators: Vec<Address>) -> Self {
		SimpleList {
			validators: validators,
		}
	}

	/// Convert into inner representation.
	pub fn into_inner(self) -> Vec<Address> {
		self.validators
	}
}

impl ::std::ops::Deref for SimpleList {
	type Target = [Address];

	fn deref(&self) -> &[Address] { &self.validators }
}

impl From<Vec<Address>> for SimpleList {
	fn from(validators: Vec<Address>) -> Self {
		SimpleList {
			validators: validators,
		}
	}
}

impl HeapSizeOf for SimpleList {
	fn heap_size_of_children(&self) -> usize {
		self.validators.heap_size_of_children()
	}
}

impl ValidatorSet for SimpleList {
	fn default_caller(&self, _block_id: ::ids::BlockId) -> Box<Call> {
		Box::new(|_, _| Err("Simple list doesn't require calls.".into()))
	}

	fn is_epoch_end(&self, first: bool, _chain_head: &Header) -> Option<Vec<u8>> {
		match first {
			true => Some(Vec::new()), // allow transition to fixed list, and instantly
			false => None,
		}
	}

	fn signals_epoch_end(&self, _: bool, _: &Header, _: AuxiliaryData)
		-> ::engines::EpochChange<EthereumMachine>
	{
		::engines::EpochChange::No
	}

	fn epoch_set(&self, _first: bool, _: &EthereumMachine, _: BlockNumber, _: &[u8]) -> Result<(SimpleList, Option<H256>), ::error::Error> {
		Ok((self.clone(), None))
	}

	fn contains_with_caller(&self, _bh: &H256, address: &Address, _: &Call) -> bool {
		self.validators.contains(address)
	}

	fn get_with_caller(&self, _bh: &H256, nonce: usize, _: &Call) -> Address {
		let validator_n = self.validators.len();

		if validator_n == 0 {
			panic!("Cannot operate with an empty validator set.");
		}

		self.validators.get(nonce % validator_n).expect("There are validator_n authorities; taking number modulo validator_n gives number in validator_n range; qed").clone()
	}

	fn count_with_caller(&self, _bh: &H256, _: &Call) -> usize {
		self.validators.len()
	}
}

#[cfg(test)]
mod tests {
	use std::str::FromStr;
	use ethereum_types::Address;
	use super::super::ValidatorSet;
	use super::SimpleList;

	#[test]
	fn simple_list() {
		let a1 = Address::from_str("cd1722f3947def4cf144679da39c4c32bdc35681").unwrap();
		let a2 = Address::from_str("0f572e5295c57f15886f9b263e2f6d2d6c7b5ec6").unwrap();
		let list = SimpleList::new(vec![a1.clone(), a2.clone()]);
		assert!(list.contains(&Default::default(), &a1));
		assert_eq!(list.get(&Default::default(), 0), a1);
		assert_eq!(list.get(&Default::default(), 1), a2);
		assert_eq!(list.get(&Default::default(), 2), a1);
	}
}