// 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/>.

//! Replacing Transactions
//!
//! When queue limits are reached, a new transaction may replace one already
//! in the pool. The decision whether to reject, replace or retain both is
//! delegated to an implementation of `ShouldReplace`.
//!
//! Here we decide based on the sender, the nonce and gas price, and finally
//! on the `Readiness` of the transactions when comparing them

use std::cmp;

use super::{client, ScoredTransaction};
use ethereum_types::{H160 as Address, U256};
use txpool::{
    self,
    scoring::{Choice, Scoring},
    ReplaceTransaction, VerifiedTransaction,
};

/// Choose whether to replace based on the sender, the score and finally the
/// `Readiness` of the transactions being compared.
#[derive(Debug)]
pub struct ReplaceByScoreAndReadiness<S, C> {
    scoring: S,
    client: C,
}

impl<S, C> ReplaceByScoreAndReadiness<S, C> {
    /// Create a new `ReplaceByScoreAndReadiness`
    pub fn new(scoring: S, client: C) -> Self {
        ReplaceByScoreAndReadiness { scoring, client }
    }
}

impl<T, S, C> txpool::ShouldReplace<T> for ReplaceByScoreAndReadiness<S, C>
where
    T: VerifiedTransaction<Sender = Address> + ScoredTransaction + PartialEq,
    S: Scoring<T>,
    C: client::NonceClient,
{
    fn should_replace(&self, old: &ReplaceTransaction<T>, new: &ReplaceTransaction<T>) -> Choice {
        let both_local = old.priority().is_local() && new.priority().is_local();
        if old.sender() == new.sender() {
            // prefer earliest transaction
            match new.nonce().cmp(&old.nonce()) {
                cmp::Ordering::Equal => self.scoring.choose(&old, &new),
                _ if both_local => Choice::InsertNew,
                cmp::Ordering::Less => Choice::ReplaceOld,
                cmp::Ordering::Greater => Choice::RejectNew,
            }
        } else if both_local {
            Choice::InsertNew
        } else {
            let old_score = (old.priority(), old.gas_price());
            let new_score = (new.priority(), new.gas_price());
            if new_score > old_score {
                // Check if this is a replacement transaction.
                //
                // With replacement transactions we can safely return `InsertNew` here, because
                // we don't need to remove `old` (worst transaction in the pool) since `new` will replace
                // some other transaction in the pool so we will never go above limit anyway.
                if let Some(txs) = new.pooled_by_sender {
                    if let Ok(index) = txs.binary_search_by(|old| self.scoring.compare(old, new)) {
                        return match self.scoring.choose(&txs[index], new) {
                            Choice::ReplaceOld => Choice::InsertNew,
                            choice => choice,
                        };
                    }
                }

                let state = &self.client;
                // calculate readiness based on state nonce + pooled txs from same sender
                let is_ready = |replace: &ReplaceTransaction<T>| {
                    let mut nonce = state.account_nonce(replace.sender());
                    if let Some(txs) = replace.pooled_by_sender {
                        for tx in txs.iter() {
                            if nonce == tx.nonce() && *tx.transaction != ***replace.transaction {
                                nonce = nonce.saturating_add(U256::from(1))
                            } else {
                                break;
                            }
                        }
                    }
                    nonce == replace.nonce()
                };

                if !is_ready(new) && is_ready(old) {
                    // prevent a ready transaction being replace by a non-ready transaction
                    Choice::RejectNew
                } else {
                    Choice::ReplaceOld
                }
            } else {
                Choice::RejectNew
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    use crypto::publickey::{Generator, KeyPair, Random};
    use pool::{
        scoring::*,
        tests::{
            client::TestClient,
            tx::{Tx, TxExt},
        },
        PrioritizationStrategy, VerifiedTransaction,
    };
    use std::sync::Arc;
    use txpool::{scoring::Choice::*, ShouldReplace};

    fn local_tx_verified(tx: Tx, keypair: &KeyPair) -> VerifiedTransaction {
        let mut verified_tx = tx.unsigned().sign(keypair.secret(), None).verified();
        verified_tx.priority = ::pool::Priority::Local;
        verified_tx
    }

    fn should_replace(
        replace: &dyn ShouldReplace<VerifiedTransaction>,
        old: VerifiedTransaction,
        new: VerifiedTransaction,
    ) -> Choice {
        let old_tx = txpool::Transaction {
            insertion_id: 0,
            transaction: Arc::new(old),
        };
        let new_tx = txpool::Transaction {
            insertion_id: 0,
            transaction: Arc::new(new),
        };
        let old = ReplaceTransaction::new(&old_tx, Default::default());
        let new = ReplaceTransaction::new(&new_tx, Default::default());
        replace.should_replace(&old, &new)
    }

    #[test]
    fn should_always_accept_local_transactions_unless_same_sender_and_nonce() {
        let scoring = NonceAndGasPrice(PrioritizationStrategy::GasPriceOnly);
        let client = TestClient::new().with_nonce(1);
        let replace = ReplaceByScoreAndReadiness::new(scoring, client);

        // same sender txs
        let keypair = Random.generate();

        let same_sender_tx1 = local_tx_verified(
            Tx {
                nonce: 1,
                gas_price: 1,
                ..Default::default()
            },
            &keypair,
        );

        let same_sender_tx2 = local_tx_verified(
            Tx {
                nonce: 2,
                gas_price: 100,
                ..Default::default()
            },
            &keypair,
        );

        let same_sender_tx3 = local_tx_verified(
            Tx {
                nonce: 2,
                gas_price: 200,
                ..Default::default()
            },
            &keypair,
        );

        // different sender txs
        let sender1 = Random.generate();
        let different_sender_tx1 = local_tx_verified(
            Tx {
                nonce: 2,
                gas_price: 1,
                ..Default::default()
            },
            &sender1,
        );

        let sender2 = Random.generate();
        let different_sender_tx2 = local_tx_verified(
            Tx {
                nonce: 1,
                gas_price: 10,
                ..Default::default()
            },
            &sender2,
        );

        assert_eq!(
            should_replace(&replace, same_sender_tx1.clone(), same_sender_tx2.clone()),
            InsertNew
        );
        assert_eq!(
            should_replace(&replace, same_sender_tx2.clone(), same_sender_tx1.clone()),
            InsertNew
        );

        assert_eq!(
            should_replace(
                &replace,
                different_sender_tx1.clone(),
                different_sender_tx2.clone()
            ),
            InsertNew
        );
        assert_eq!(
            should_replace(
                &replace,
                different_sender_tx2.clone(),
                different_sender_tx1.clone()
            ),
            InsertNew
        );

        // txs with same sender and nonce
        assert_eq!(
            should_replace(&replace, same_sender_tx2.clone(), same_sender_tx3.clone()),
            ReplaceOld
        );
        assert_eq!(
            should_replace(&replace, same_sender_tx3.clone(), same_sender_tx2.clone()),
            RejectNew
        );
    }

    #[test]
    fn should_replace_same_sender_by_nonce() {
        let scoring = NonceAndGasPrice(PrioritizationStrategy::GasPriceOnly);
        let client = TestClient::new().with_nonce(1);
        let replace = ReplaceByScoreAndReadiness::new(scoring, client);

        let tx1 = Tx {
            nonce: 1,
            gas_price: 1,
            ..Default::default()
        };
        let tx2 = Tx {
            nonce: 2,
            gas_price: 100,
            ..Default::default()
        };
        let tx3 = Tx {
            nonce: 2,
            gas_price: 110,
            ..Default::default()
        };
        let tx4 = Tx {
            nonce: 2,
            gas_price: 130,
            ..Default::default()
        };

        let keypair = Random.generate();
        let txs = vec![tx1, tx2, tx3, tx4]
            .into_iter()
            .map(|tx| tx.unsigned().sign(keypair.secret(), None).verified())
            .collect::<Vec<_>>();

        assert_eq!(
            should_replace(&replace, txs[0].clone(), txs[1].clone()),
            RejectNew
        );
        assert_eq!(
            should_replace(&replace, txs[1].clone(), txs[0].clone()),
            ReplaceOld
        );

        assert_eq!(
            should_replace(&replace, txs[1].clone(), txs[2].clone()),
            RejectNew
        );
        assert_eq!(
            should_replace(&replace, txs[2].clone(), txs[1].clone()),
            RejectNew
        );

        assert_eq!(
            should_replace(&replace, txs[1].clone(), txs[3].clone()),
            ReplaceOld
        );
        assert_eq!(
            should_replace(&replace, txs[3].clone(), txs[1].clone()),
            RejectNew
        );
    }

    #[test]
    fn should_replace_different_sender_by_priority_and_gas_price() {
        // given
        let scoring = NonceAndGasPrice(PrioritizationStrategy::GasPriceOnly);
        let client = TestClient::new().with_nonce(0);
        let replace = ReplaceByScoreAndReadiness::new(scoring, client);

        let tx_regular_low_gas = {
            let tx = Tx {
                nonce: 1,
                gas_price: 1,
                ..Default::default()
            };
            tx.signed().verified()
        };
        let tx_regular_high_gas = {
            let tx = Tx {
                nonce: 2,
                gas_price: 10,
                ..Default::default()
            };
            tx.signed().verified()
        };
        let tx_local_low_gas = {
            let tx = Tx {
                nonce: 2,
                gas_price: 1,
                ..Default::default()
            };
            let mut verified_tx = tx.signed().verified();
            verified_tx.priority = ::pool::Priority::Local;
            verified_tx
        };
        let tx_local_high_gas = {
            let tx = Tx {
                nonce: 1,
                gas_price: 10,
                ..Default::default()
            };
            let mut verified_tx = tx.signed().verified();
            verified_tx.priority = ::pool::Priority::Local;
            verified_tx
        };

        assert_eq!(
            should_replace(
                &replace,
                tx_regular_low_gas.clone(),
                tx_regular_high_gas.clone()
            ),
            ReplaceOld
        );
        assert_eq!(
            should_replace(
                &replace,
                tx_regular_high_gas.clone(),
                tx_regular_low_gas.clone()
            ),
            RejectNew
        );

        assert_eq!(
            should_replace(
                &replace,
                tx_regular_high_gas.clone(),
                tx_local_low_gas.clone()
            ),
            ReplaceOld
        );
        assert_eq!(
            should_replace(
                &replace,
                tx_local_low_gas.clone(),
                tx_regular_high_gas.clone()
            ),
            RejectNew
        );

        assert_eq!(
            should_replace(
                &replace,
                tx_local_low_gas.clone(),
                tx_local_high_gas.clone()
            ),
            InsertNew
        );
        assert_eq!(
            should_replace(
                &replace,
                tx_local_high_gas.clone(),
                tx_regular_low_gas.clone()
            ),
            RejectNew
        );
    }

    #[test]
    fn should_not_replace_ready_transaction_with_future_transaction() {
        let scoring = NonceAndGasPrice(PrioritizationStrategy::GasPriceOnly);
        let client = TestClient::new().with_nonce(1);
        let replace = ReplaceByScoreAndReadiness::new(scoring, client);

        let tx_ready_low_score = {
            let tx = Tx {
                nonce: 1,
                gas_price: 1,
                ..Default::default()
            };
            tx.signed().verified()
        };
        let tx_future_high_score = {
            let tx = Tx {
                nonce: 3, // future nonce
                gas_price: 10,
                ..Default::default()
            };
            tx.signed().verified()
        };

        assert_eq!(
            should_replace(&replace, tx_ready_low_score, tx_future_high_score),
            RejectNew
        );
    }

    #[test]
    fn should_compute_readiness_with_pooled_transactions_from_the_same_sender_as_the_existing_transaction(
    ) {
        let scoring = NonceAndGasPrice(PrioritizationStrategy::GasPriceOnly);
        let client = TestClient::new().with_nonce(1);
        let replace = ReplaceByScoreAndReadiness::new(scoring, client);

        let old_sender = Random.generate();
        let tx_old_ready_1 = {
            let tx = Tx {
                nonce: 1,
                gas_price: 1,
                ..Default::default()
            };
            tx.unsigned().sign(&old_sender.secret(), None).verified()
        };
        let tx_old_ready_2 = {
            let tx = Tx {
                nonce: 2,
                gas_price: 1,
                ..Default::default()
            };
            tx.unsigned().sign(&old_sender.secret(), None).verified()
        };
        let tx_old_ready_3 = {
            let tx = Tx {
                nonce: 3,
                gas_price: 1,
                ..Default::default()
            };
            tx.unsigned().sign(&old_sender.secret(), None).verified()
        };

        let new_tx = {
            let tx = Tx {
                nonce: 3, // future nonce
                gas_price: 10,
                ..Default::default()
            };
            tx.signed().verified()
        };

        let old_tx = txpool::Transaction {
            insertion_id: 0,
            transaction: Arc::new(tx_old_ready_3),
        };
        let pooled_txs = [
            txpool::Transaction {
                insertion_id: 0,
                transaction: Arc::new(tx_old_ready_1),
            },
            txpool::Transaction {
                insertion_id: 0,
                transaction: Arc::new(tx_old_ready_2),
            },
        ];

        let new_tx = txpool::Transaction {
            insertion_id: 0,
            transaction: Arc::new(new_tx),
        };

        let old = ReplaceTransaction::new(&old_tx, Some(&pooled_txs));
        let new = ReplaceTransaction::new(&new_tx, Default::default());

        assert_eq!(replace.should_replace(&old, &new), RejectNew);
    }

    #[test]
    fn should_compute_readiness_with_pooled_transactions_from_the_same_sender_as_the_new_transaction(
    ) {
        let scoring = NonceAndGasPrice(PrioritizationStrategy::GasPriceOnly);
        let client = TestClient::new().with_nonce(1);
        let replace = ReplaceByScoreAndReadiness::new(scoring, client);

        // current transaction is ready but has a lower gas price than the new one
        let old_tx = {
            let tx = Tx {
                nonce: 1,
                gas_price: 1,
                ..Default::default()
            };
            tx.signed().verified()
        };

        let new_sender = Random.generate();
        let tx_new_ready_1 = {
            let tx = Tx {
                nonce: 1,
                gas_price: 1,
                ..Default::default()
            };
            tx.unsigned().sign(&new_sender.secret(), None).verified()
        };
        let tx_new_ready_2 = {
            let tx = Tx {
                nonce: 2,
                gas_price: 1,
                ..Default::default()
            };
            tx.unsigned().sign(&new_sender.secret(), None).verified()
        };
        let tx_new_ready_3 = {
            let tx = Tx {
                nonce: 3,
                gas_price: 10, // hi
                ..Default::default()
            };
            tx.unsigned().sign(&new_sender.secret(), None).verified()
        };

        let old_tx = txpool::Transaction {
            insertion_id: 0,
            transaction: Arc::new(old_tx),
        };

        let new_tx = txpool::Transaction {
            insertion_id: 0,
            transaction: Arc::new(tx_new_ready_3),
        };
        let pooled_txs = [
            txpool::Transaction {
                insertion_id: 0,
                transaction: Arc::new(tx_new_ready_1),
            },
            txpool::Transaction {
                insertion_id: 0,
                transaction: Arc::new(tx_new_ready_2),
            },
        ];

        let old = ReplaceTransaction::new(&old_tx, None);
        let new = ReplaceTransaction::new(&new_tx, Some(&pooled_txs));

        assert_eq!(replace.should_replace(&old, &new), ReplaceOld);
    }

    #[test]
    fn should_accept_local_tx_with_same_sender_and_nonce_with_better_gas_price() {
        let scoring = NonceAndGasPrice(PrioritizationStrategy::GasPriceOnly);
        let client = TestClient::new().with_nonce(1);
        let replace = ReplaceByScoreAndReadiness::new(scoring, client);

        // current transaction is ready
        let old_tx = {
            let tx = Tx {
                nonce: 1,
                gas_price: 1,
                ..Default::default()
            };
            tx.signed().verified()
        };

        let new_sender = Random.generate();
        let tx_new_ready_1 = local_tx_verified(
            Tx {
                nonce: 1,
                gas_price: 1,
                ..Default::default()
            },
            &new_sender,
        );

        let tx_new_ready_2 = local_tx_verified(
            Tx {
                nonce: 1,
                gas_price: 2, // same nonce, higher gas price
                ..Default::default()
            },
            &new_sender,
        );

        let old_tx = txpool::Transaction {
            insertion_id: 0,
            transaction: Arc::new(old_tx),
        };

        let new_tx = txpool::Transaction {
            insertion_id: 0,
            transaction: Arc::new(tx_new_ready_2),
        };
        let pooled_txs = [txpool::Transaction {
            insertion_id: 0,
            transaction: Arc::new(tx_new_ready_1),
        }];

        let old = ReplaceTransaction::new(&old_tx, None);
        let new = ReplaceTransaction::new(&new_tx, Some(&pooled_txs));

        assert_eq!(replace.should_replace(&old, &new), InsertNew);
    }

    #[test]
    fn should_reject_local_tx_with_same_sender_and_nonce_with_worse_gas_price() {
        let scoring = NonceAndGasPrice(PrioritizationStrategy::GasPriceOnly);
        let client = TestClient::new().with_nonce(1);
        let replace = ReplaceByScoreAndReadiness::new(scoring, client);

        // current transaction is ready
        let old_tx = {
            let tx = Tx {
                nonce: 1,
                gas_price: 1,
                ..Default::default()
            };
            tx.signed().verified()
        };

        let new_sender = Random.generate();
        let tx_new_ready_1 = local_tx_verified(
            Tx {
                nonce: 1,
                gas_price: 2,
                ..Default::default()
            },
            &new_sender,
        );

        let tx_new_ready_2 = local_tx_verified(
            Tx {
                nonce: 1,
                gas_price: 1, // same nonce, lower gas price
                ..Default::default()
            },
            &new_sender,
        );

        let old_tx = txpool::Transaction {
            insertion_id: 0,
            transaction: Arc::new(old_tx),
        };

        let new_tx = txpool::Transaction {
            insertion_id: 0,
            transaction: Arc::new(tx_new_ready_2),
        };
        let pooled_txs = [txpool::Transaction {
            insertion_id: 0,
            transaction: Arc::new(tx_new_ready_1),
        }];

        let old = ReplaceTransaction::new(&old_tx, None);
        let new = ReplaceTransaction::new(&new_tx, Some(&pooled_txs));

        assert_eq!(replace.should_replace(&old, &new), RejectNew);
    }
}