// 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 module with types for declaring block rewards and a client interface for interacting with a
//! block reward contract.

use ethabi::{self, ParamType};
use ethereum_types::{Address, H160, U256};

use super::{SystemOrCodeCall, SystemOrCodeCallKind};
use block::ExecutedBlock;
use error::Error;
use hash::keccak;
use machine::Machine;
use std::sync::Arc;
use trace::{self, ExecutiveTracer, Tracer, Tracing};
use types::BlockNumber;

use_contract!(block_reward_contract, "res/contracts/block_reward.json");

/// The kind of block reward.
/// Depending on the consensus engine the allocated block reward might have
/// different semantics which could lead e.g. to different reward values.
#[derive(PartialEq, Eq, Clone, Copy, Debug)]
pub enum RewardKind {
    /// Reward attributed to the block author.
    Author,
    /// Reward attributed to the author(s) of empty step(s) included in the block (AuthorityRound engine).
    EmptyStep,
    /// Reward attributed by an external protocol (e.g. block reward contract).
    External,
    /// Reward attributed to the block uncle(s) with given difference.
    Uncle(u8),
}

impl RewardKind {
    /// Create `RewardKind::Uncle` from given current block number and uncle block number.
    pub fn uncle(number: BlockNumber, uncle: BlockNumber) -> Self {
        RewardKind::Uncle(
            if number > uncle && number - uncle <= u8::max_value().into() {
                (number - uncle) as u8
            } else {
                0
            },
        )
    }
}

impl From<RewardKind> for u16 {
    fn from(reward_kind: RewardKind) -> Self {
        match reward_kind {
            RewardKind::Author => 0,
            RewardKind::EmptyStep => 2,
            RewardKind::External => 3,

            RewardKind::Uncle(depth) => 100 + depth as u16,
        }
    }
}

impl Into<trace::RewardType> for RewardKind {
    fn into(self) -> trace::RewardType {
        match self {
            RewardKind::Author => trace::RewardType::Block,
            RewardKind::Uncle(_) => trace::RewardType::Uncle,
            RewardKind::EmptyStep => trace::RewardType::EmptyStep,
            RewardKind::External => trace::RewardType::External,
        }
    }
}

/// A client for the block reward contract.
#[derive(PartialEq, Debug)]
pub struct BlockRewardContract {
    kind: SystemOrCodeCallKind,
}

impl BlockRewardContract {
    /// Create a new block reward contract client targeting the system call kind.
    pub fn new(kind: SystemOrCodeCallKind) -> BlockRewardContract {
        BlockRewardContract { kind }
    }

    /// Create a new block reward contract client targeting the contract address.
    pub fn new_from_address(address: Address) -> BlockRewardContract {
        Self::new(SystemOrCodeCallKind::Address(address))
    }

    /// Create a new block reward contract client targeting the given code.
    pub fn new_from_code(code: Arc<Vec<u8>>) -> BlockRewardContract {
        let code_hash = keccak(&code[..]);

        Self::new(SystemOrCodeCallKind::Code(code, code_hash))
    }

    /// Calls the block reward contract with the given beneficiaries list (and associated reward kind)
    /// and returns the reward allocation (address - value). The block reward contract *must* be
    /// called by the system address so the `caller` must ensure that (e.g. using
    /// `machine.execute_as_system`).
    pub fn reward(
        &self,
        beneficiaries: &[(Address, RewardKind)],
        caller: &mut SystemOrCodeCall,
    ) -> Result<Vec<(Address, U256)>, Error> {
        let input = block_reward_contract::functions::reward::encode_input(
            beneficiaries
                .iter()
                .map(|&(address, _)| H160::from(address)),
            beneficiaries
                .iter()
                .map(|&(_, ref reward_kind)| u16::from(*reward_kind)),
        );

        let output = caller(self.kind.clone(), input)
            .map_err(Into::into)
            .map_err(::engines::EngineError::FailedSystemCall)?;

        // since this is a non-constant call we can't use ethabi's function output
        // deserialization, sadness ensues.
        let types = &[
            ParamType::Array(Box::new(ParamType::Address)),
            ParamType::Array(Box::new(ParamType::Uint(256))),
        ];

        let tokens = ethabi::decode(types, &output)
            .map_err(|err| err.to_string())
            .map_err(::engines::EngineError::FailedSystemCall)?;

        assert!(tokens.len() == 2);

        let addresses = tokens[0]
            .clone()
            .to_array()
            .expect("type checked by ethabi::decode; qed");
        let rewards = tokens[1]
            .clone()
            .to_array()
            .expect("type checked by ethabi::decode; qed");

        if addresses.len() != rewards.len() {
            return Err(::engines::EngineError::FailedSystemCall(
                "invalid data returned by reward contract: both arrays must have the same size"
                    .into(),
            )
            .into());
        }

        let addresses = addresses
            .into_iter()
            .map(|t| t.to_address().expect("type checked by ethabi::decode; qed"));
        let rewards = rewards
            .into_iter()
            .map(|t| t.to_uint().expect("type checked by ethabi::decode; qed"));

        Ok(addresses.zip(rewards).collect())
    }
}

/// Applies the given block rewards, i.e. adds the given balance to each beneficiary' address.
/// If tracing is enabled the operations are recorded.
pub fn apply_block_rewards<M: Machine>(
    rewards: &[(Address, RewardKind, U256)],
    block: &mut ExecutedBlock,
    machine: &M,
) -> Result<(), M::Error> {
    for &(ref author, _, ref block_reward) in rewards {
        machine.add_balance(block, author, block_reward)?;
    }

    if let Tracing::Enabled(ref mut traces) = *block.traces_mut() {
        let mut tracer = ExecutiveTracer::default();

        for &(address, reward_kind, amount) in rewards {
            tracer.trace_reward(address, amount, reward_kind.into());
        }

        traces.push(tracer.drain().into());
    }

    Ok(())
}

#[cfg(test)]
mod test {
    use client::PrepareOpenBlock;
    use ethereum_types::{H160, U256};
    use spec::Spec;
    use test_helpers::generate_dummy_client_with_spec;

    use super::{BlockRewardContract, RewardKind};
    use engines::SystemOrCodeCallKind;
    use std::str::FromStr;

    #[test]
    fn block_reward_contract() {
        let client = generate_dummy_client_with_spec(Spec::new_test_round_block_reward_contract);

        let machine = Spec::new_test_machine();

        // the spec has a block reward contract defined at the given address
        let block_reward_contract = BlockRewardContract::new_from_address(
            H160::from_str("0000000000000000000000000000000000000042").unwrap(),
        );

        let mut call = |to, data| {
            let mut block = client
                .prepare_open_block(
                    H160::from_str("0000000000000000000000000000000000000001").unwrap(),
                    (3141562.into(), 31415620.into()),
                    vec![],
                )
                .unwrap();

            let result = match to {
                SystemOrCodeCallKind::Address(to) => {
                    machine.execute_as_system(block.block_mut(), to, U256::max_value(), Some(data))
                }
                _ => panic!(
                    "Test reward contract is created by an address, we never reach this branch."
                ),
            };

            result.map_err(|e| format!("{}", e))
        };

        // if no beneficiaries are given no rewards are attributed
        assert!(block_reward_contract
            .reward(&vec![], &mut call)
            .unwrap()
            .is_empty());

        // the contract rewards (1000 + kind) for each benefactor
        let beneficiaries = vec![
            (
                H160::from_str("0000000000000000000000000000000000000033").unwrap(),
                RewardKind::Author,
            ),
            (
                H160::from_str("0000000000000000000000000000000000000034").unwrap(),
                RewardKind::Uncle(1),
            ),
            (
                H160::from_str("0000000000000000000000000000000000000035").unwrap(),
                RewardKind::EmptyStep,
            ),
        ];

        let rewards = block_reward_contract
            .reward(&beneficiaries, &mut call)
            .unwrap();
        let expected = vec![
            (
                H160::from_str("0000000000000000000000000000000000000033").unwrap(),
                U256::from(1000),
            ),
            (
                H160::from_str("0000000000000000000000000000000000000034").unwrap(),
                U256::from(1000 + 101),
            ),
            (
                H160::from_str("0000000000000000000000000000000000000035").unwrap(),
                U256::from(1000 + 2),
            ),
        ];

        assert_eq!(expected, rewards);
    }
}