// Copyright 2015-2019 Parity Technologies (UK) Ltd.
// This file is part of Parity Ethereum.

// Parity Ethereum 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 Ethereum 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 Ethereum.  If not, see <http://www.gnu.org/licenses/>.

//! Blockchain access for transaction pool.

use std::{collections::HashMap, fmt, sync::Arc};

use ethcore_miner::{
    local_accounts::LocalAccounts, pool, pool::client::NonceClient,
    service_transaction_checker::ServiceTransactionChecker,
};
use ethereum_types::{Address, H256, U256};
use parking_lot::RwLock;
use types::{
    header::Header,
    transaction::{self, SignedTransaction, UnverifiedTransaction},
};

use call_contract::CallContract;
use client::{BlockInfo, Nonce, TransactionId};
use engines::EthEngine;
use miner;
use transaction_ext::Transaction;

/// Cache for state nonces.
#[derive(Debug, Clone)]
pub struct NonceCache {
    nonces: Arc<RwLock<HashMap<Address, U256>>>,
    limit: usize,
}

impl NonceCache {
    /// Create new cache with a limit of `limit` entries.
    pub fn new(limit: usize) -> Self {
        NonceCache {
            nonces: Arc::new(RwLock::new(HashMap::with_capacity(limit / 2))),
            limit,
        }
    }

    /// Retrieve a cached nonce for given sender.
    pub fn get(&self, sender: &Address) -> Option<U256> {
        self.nonces.read().get(sender).cloned()
    }

    /// Clear all entries from the cache.
    pub fn clear(&self) {
        self.nonces.write().clear();
    }
}

/// Blockchain accesss for transaction pool.
pub struct PoolClient<'a, C: 'a> {
    chain: &'a C,
    cached_nonces: CachedNonceClient<'a, C>,
    engine: &'a EthEngine,
    accounts: &'a LocalAccounts,
    best_block_header: Header,
    service_transaction_checker: Option<&'a ServiceTransactionChecker>,
}

impl<'a, C: 'a> Clone for PoolClient<'a, C> {
    fn clone(&self) -> Self {
        PoolClient {
            chain: self.chain,
            cached_nonces: self.cached_nonces.clone(),
            engine: self.engine,
            accounts: self.accounts.clone(),
            best_block_header: self.best_block_header.clone(),
            service_transaction_checker: self.service_transaction_checker.clone(),
        }
    }
}

impl<'a, C: 'a> PoolClient<'a, C>
where
    C: BlockInfo + CallContract,
{
    /// Creates new client given chain, nonce cache, accounts and service transaction verifier.
    pub fn new(
        chain: &'a C,
        cache: &'a NonceCache,
        engine: &'a EthEngine,
        accounts: &'a LocalAccounts,
        service_transaction_checker: Option<&'a ServiceTransactionChecker>,
    ) -> Self {
        let best_block_header = chain.best_block_header();
        PoolClient {
            chain,
            cached_nonces: CachedNonceClient::new(chain, cache),
            engine,
            accounts,
            best_block_header,
            service_transaction_checker,
        }
    }

    /// Verifies transaction against its block (before its import into this block)
    /// Also Verifies if signed transaction is executable.
    ///
    /// This should perform any verifications that rely on chain status.
    pub fn verify_for_pending_block(
        &self,
        tx: &SignedTransaction,
        header: &Header,
    ) -> Result<(), transaction::Error> {
        self.engine.machine().verify_transaction_basic(tx, header)?;
        self.engine
            .machine()
            .verify_transaction(tx, &self.best_block_header, self.chain)
    }
}

impl<'a, C: 'a> fmt::Debug for PoolClient<'a, C> {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        write!(fmt, "PoolClient")
    }
}

impl<'a, C: 'a> pool::client::Client for PoolClient<'a, C>
where
    C: miner::TransactionVerifierClient + Sync,
{
    fn transaction_already_included(&self, hash: &H256) -> bool {
        self.chain
            .transaction_block(TransactionId::Hash(*hash))
            .is_some()
    }

    fn verify_transaction_basic(
        &self,
        tx: &UnverifiedTransaction,
    ) -> Result<(), transaction::Error> {
        self.engine
            .verify_transaction_basic(tx, &self.best_block_header)?;
        Ok(())
    }

    fn verify_transaction(
        &self,
        tx: UnverifiedTransaction,
    ) -> Result<SignedTransaction, transaction::Error> {
        self.engine
            .verify_transaction_basic(&tx, &self.best_block_header)?;
        let tx = self
            .engine
            .verify_transaction_unordered(tx, &self.best_block_header)?;

        self.engine
            .machine()
            .verify_transaction(&tx, &self.best_block_header, self.chain)?;
        Ok(tx)
    }

    fn account_details(&self, address: &Address) -> pool::client::AccountDetails {
        pool::client::AccountDetails {
            nonce: self.cached_nonces.account_nonce(address),
            balance: self.chain.latest_balance(address),
            is_local: self.accounts.is_local(address),
        }
    }

    fn required_gas(&self, tx: &transaction::Transaction) -> U256 {
        tx.gas_required(&self.chain.latest_schedule()).into()
    }

    fn transaction_type(&self, tx: &SignedTransaction) -> pool::client::TransactionType {
        match self.service_transaction_checker {
            None => pool::client::TransactionType::Regular,
            Some(ref checker) => match checker.check(self.chain, &tx) {
                Ok(true) => pool::client::TransactionType::Service,
                Ok(false) => pool::client::TransactionType::Regular,
                Err(e) => {
                    debug!(target: "txqueue", "Unable to verify service transaction: {:?}", e);
                    pool::client::TransactionType::Regular
                }
            },
        }
    }

    fn decode_transaction(
        &self,
        transaction: &[u8],
    ) -> Result<UnverifiedTransaction, transaction::Error> {
        self.engine.decode_transaction(transaction)
    }
}

impl<'a, C: 'a> NonceClient for PoolClient<'a, C>
where
    C: Nonce + Sync,
{
    fn account_nonce(&self, address: &Address) -> U256 {
        self.cached_nonces.account_nonce(address)
    }
}

pub(crate) struct CachedNonceClient<'a, C: 'a> {
    client: &'a C,
    cache: &'a NonceCache,
}

impl<'a, C: 'a> Clone for CachedNonceClient<'a, C> {
    fn clone(&self) -> Self {
        CachedNonceClient {
            client: self.client,
            cache: self.cache,
        }
    }
}

impl<'a, C: 'a> fmt::Debug for CachedNonceClient<'a, C> {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        fmt.debug_struct("CachedNonceClient")
            .field("cache", &self.cache.nonces.read().len())
            .field("limit", &self.cache.limit)
            .finish()
    }
}

impl<'a, C: 'a> CachedNonceClient<'a, C> {
    pub fn new(client: &'a C, cache: &'a NonceCache) -> Self {
        CachedNonceClient { client, cache }
    }
}

impl<'a, C: 'a> NonceClient for CachedNonceClient<'a, C>
where
    C: Nonce + Sync,
{
    fn account_nonce(&self, address: &Address) -> U256 {
        if let Some(nonce) = self.cache.nonces.read().get(address) {
            return *nonce;
        }

        // We don't check again if cache has been populated.
        // It's not THAT expensive to fetch the nonce from state.
        let mut cache = self.cache.nonces.write();
        let nonce = self.client.latest_nonce(address);
        cache.insert(*address, nonce);

        if cache.len() < self.cache.limit {
            return nonce;
        }

        debug!(target: "txpool", "NonceCache: reached limit.");
        trace_time!("nonce_cache:clear");

        // Remove excessive amount of entries from the cache
        let to_remove: Vec<_> = cache.keys().take(self.cache.limit / 2).cloned().collect();
        for x in to_remove {
            cache.remove(&x);
        }

        nonce
    }
}