// 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/>.

//! External Miner hashrate tracker.

use ethereum_types::{H256, U256};
use parking_lot::Mutex;
use std::{
    collections::HashMap,
    sync::Arc,
    time::{Duration, Instant},
};

/// External miner interface.
pub trait ExternalMinerService: Send + Sync {
    /// Submit hashrate for given miner.
    fn submit_hashrate(&self, hashrate: U256, id: H256);

    /// Total hashrate.
    fn hashrate(&self) -> U256;
}

/// External Miner.
pub struct ExternalMiner {
    hashrates: Arc<Mutex<HashMap<H256, (Instant, U256)>>>,
}

impl Default for ExternalMiner {
    fn default() -> Self {
        ExternalMiner {
            hashrates: Arc::new(Mutex::new(HashMap::new())),
        }
    }
}

impl ExternalMiner {
    /// Creates new external miner with prefilled hashrates.
    pub fn new(hashrates: Arc<Mutex<HashMap<H256, (Instant, U256)>>>) -> Self {
        ExternalMiner {
            hashrates: hashrates,
        }
    }
}

const ENTRY_TIMEOUT: Duration = Duration::from_secs(2);

impl ExternalMinerService for ExternalMiner {
    fn submit_hashrate(&self, hashrate: U256, id: H256) {
        self.hashrates
            .lock()
            .insert(id, (Instant::now() + ENTRY_TIMEOUT, hashrate));
    }

    fn hashrate(&self) -> U256 {
        let mut hashrates = self.hashrates.lock();
        let h = hashrates
            .drain()
            .filter(|&(_, (t, _))| t > Instant::now())
            .collect();
        *hashrates = h;
        hashrates
            .iter()
            .fold(U256::from(0), |sum, (_, &(_, v))| sum + v)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use ethereum_types::{H256, U256};
    use std::{thread::sleep, time::Duration};

    fn miner() -> ExternalMiner {
        ExternalMiner::default()
    }

    #[test]
    fn it_should_forget_old_hashrates() {
        // given
        let m = miner();
        assert_eq!(m.hashrate(), U256::from(0));
        m.submit_hashrate(U256::from(10), H256::from_low_u64_be(1));
        assert_eq!(m.hashrate(), U256::from(10));

        // when
        sleep(Duration::from_secs(3));

        // then
        assert_eq!(m.hashrate(), U256::from(0));
    }

    #[test]
    fn should_sum_up_hashrate() {
        // given
        let m = miner();
        assert_eq!(m.hashrate(), U256::from(0));
        m.submit_hashrate(U256::from(10), H256::from_low_u64_be(1));
        assert_eq!(m.hashrate(), U256::from(10));

        // when
        m.submit_hashrate(U256::from(15), H256::from_low_u64_be(1));
        m.submit_hashrate(U256::from(20), H256::from_low_u64_be(2));

        // then
        assert_eq!(m.hashrate(), U256::from(35));
    }
}
