// 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 service transactions contract checker.

use call_contract::{CallContract, RegistryInfo};
use ethabi::FunctionOutputDecoder;
use ethereum_types::Address;
use parking_lot::RwLock;
use std::{collections::HashMap, mem, sync::Arc};
use types::{ids::BlockId, transaction::SignedTransaction};

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

const SERVICE_TRANSACTION_CONTRACT_REGISTRY_NAME: &'static str = "service_transaction_checker";

/// Service transactions checker.
#[derive(Default, Clone)]
pub struct ServiceTransactionChecker {
    certified_addresses_cache: Arc<RwLock<HashMap<Address, bool>>>,
}

impl ServiceTransactionChecker {
    /// Checks if given address in tx is whitelisted to send service transactions.
    pub fn check<C: CallContract + RegistryInfo>(
        &self,
        client: &C,
        tx: &SignedTransaction,
    ) -> Result<bool, String> {
        let sender = tx.sender();
        // Skip checking the contract if the transaction does not have zero gas price
        if !tx.tx().gas_price.is_zero() {
            return Ok(false);
        }

        self.check_address(client, sender)
    }

    /// Checks if given address is whitelisted to send service transactions.
    pub fn check_address<C: CallContract + RegistryInfo>(
        &self,
        client: &C,
        sender: Address,
    ) -> Result<bool, String> {
        trace!(target: "txqueue", "Checking service transaction checker contract from {}", sender);
        if let Some(allowed) = self
            .certified_addresses_cache
            .try_read()
            .as_ref()
            .and_then(|c| c.get(&sender))
        {
            return Ok(*allowed);
        }
        let contract_address = client
            .registry_address(
                SERVICE_TRANSACTION_CONTRACT_REGISTRY_NAME.to_owned(),
                BlockId::Latest,
            )
            .ok_or_else(|| "contract is not configured")?;
        self.call_contract(client, contract_address, sender)
            .and_then(|allowed| {
                if let Some(mut cache) = self.certified_addresses_cache.try_write() {
                    cache.insert(sender, allowed);
                };
                Ok(allowed)
            })
    }

    /// Refresh certified addresses cache
    pub fn refresh_cache<C: CallContract + RegistryInfo>(
        &self,
        client: &C,
    ) -> Result<bool, String> {
        trace!(target: "txqueue", "Refreshing certified addresses cache");
        // replace the cache with an empty list,
        // since it's not recent it won't be used anyway.
        let cache = mem::replace(
            &mut *self.certified_addresses_cache.write(),
            HashMap::default(),
        );

        if let Some(contract_address) = client.registry_address(
            SERVICE_TRANSACTION_CONTRACT_REGISTRY_NAME.to_owned(),
            BlockId::Latest,
        ) {
            let addresses: Vec<_> = cache.keys().collect();
            let mut cache: HashMap<Address, bool> = HashMap::default();
            for address in addresses {
                let allowed = self.call_contract(client, contract_address, *address)?;
                cache.insert(*address, allowed);
            }
            *self.certified_addresses_cache.write() = cache;
            Ok(true)
        } else {
            Ok(false)
        }
    }

    fn call_contract<C: CallContract + RegistryInfo>(
        &self,
        client: &C,
        contract_address: Address,
        sender: Address,
    ) -> Result<bool, String> {
        let (data, decoder) = service_transaction::functions::certified::call(sender);
        let value = client.call_contract(BlockId::Latest, contract_address, data)?;
        decoder.decode(&value).map_err(|e| e.to_string())
    }
}