// 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/>.

use std::sync::Arc;

use ethereum_types::{Address, H256, U256};
use light::{
    cache::Cache as LightDataCache,
    client::LightChainClient,
    on_demand::{request, OnDemandRequester},
    TransactionQueue as LightTransactionQueue,
};
use parking_lot::{Mutex, RwLock};
use stats::Corpus;
use sync::{LightNetworkDispatcher, LightSyncProvider, ManageNetwork};
use types::{
    basic_account::BasicAccount,
    ids::BlockId,
    transaction::{Error as TransactionError, PendingTransaction, SignedTransaction},
};

use jsonrpc_core::{
    futures::{future, future::Either, Future, IntoFuture},
    BoxFuture, Result,
};
use v1::{
    helpers::{errors, nonce, FilledTransactionRequest, TransactionRequest},
    types::RichRawTransaction as RpcRichRawTransaction,
};

use super::{Accounts, Dispatcher, PostSign, SignWith};

/// Dispatcher for light clients -- fetches default gas price, next nonce, etc. from network.
pub struct LightDispatcher<S, OD>
where
    S: LightSyncProvider + LightNetworkDispatcher + ManageNetwork + 'static,
    OD: OnDemandRequester + 'static,
{
    /// Sync service.
    pub sync: Arc<S>,
    /// Header chain client.
    pub client: Arc<LightChainClient>,
    /// On-demand request service.
    pub on_demand: Arc<OD>,
    /// Data cache.
    pub cache: Arc<Mutex<LightDataCache>>,
    /// Transaction queue.
    pub transaction_queue: Arc<RwLock<LightTransactionQueue>>,
    /// Nonce reservations
    pub nonces: Arc<Mutex<nonce::Reservations>>,
    /// Gas Price percentile value used as default gas price.
    pub gas_price_percentile: usize,
}

impl<S, OD> LightDispatcher<S, OD>
where
    S: LightSyncProvider + LightNetworkDispatcher + ManageNetwork + 'static,
    OD: OnDemandRequester + 'static,
{
    /// Create a new `LightDispatcher` from its requisite parts.
    ///
    /// For correct operation, the OnDemand service is assumed to be registered as a network handler,
    pub fn new(
        sync: Arc<S>,
        client: Arc<LightChainClient>,
        on_demand: Arc<OD>,
        cache: Arc<Mutex<LightDataCache>>,
        transaction_queue: Arc<RwLock<LightTransactionQueue>>,
        nonces: Arc<Mutex<nonce::Reservations>>,
        gas_price_percentile: usize,
    ) -> Self {
        LightDispatcher {
            sync,
            client,
            on_demand,
            cache,
            transaction_queue,
            nonces,
            gas_price_percentile,
        }
    }

    /// Get a recent gas price corpus.
    // TODO: this could be `impl Trait`.
    pub fn gas_price_corpus(&self) -> BoxFuture<Corpus<U256>> {
        fetch_gas_price_corpus(
            self.sync.clone(),
            self.client.clone(),
            self.on_demand.clone(),
            self.cache.clone(),
        )
    }

    /// Get an account's state
    fn account(&self, addr: Address) -> BoxFuture<Option<BasicAccount>> {
        let best_header = self.client.best_block_header();
        let account_future = self.sync.with_context(|ctx| {
            self.on_demand
                .request(
                    ctx,
                    request::Account {
                        header: best_header.into(),
                        address: addr,
                    },
                )
                .expect("no back-references; therefore all back-references valid; qed")
        });

        match account_future {
            Some(response) => Box::new(response.map_err(|_| errors::no_light_peers())),
            None => Box::new(future::err(errors::network_disabled())),
        }
    }

    /// Get an account's next nonce.
    pub fn next_nonce(&self, addr: Address) -> BoxFuture<U256> {
        let account_start_nonce = self
            .client
            .engine()
            .account_start_nonce(self.client.best_block_header().number());
        Box::new(self.account(addr).and_then(move |maybe_account| {
            future::ok(maybe_account.map_or(account_start_nonce, |account| account.nonce))
        }))
    }
}

impl<S, OD> Clone for LightDispatcher<S, OD>
where
    S: LightSyncProvider + LightNetworkDispatcher + ManageNetwork + 'static,
    OD: OnDemandRequester + 'static,
{
    fn clone(&self) -> Self {
        Self {
            sync: self.sync.clone(),
            client: self.client.clone(),
            on_demand: self.on_demand.clone(),
            cache: self.cache.clone(),
            transaction_queue: self.transaction_queue.clone(),
            nonces: self.nonces.clone(),
            gas_price_percentile: self.gas_price_percentile,
        }
    }
}

impl<S, OD> Dispatcher for LightDispatcher<S, OD>
where
    S: LightSyncProvider + LightNetworkDispatcher + ManageNetwork + 'static,
    OD: OnDemandRequester + 'static,
{
    // Ignore the `force_nonce` flag in order to always query the network when fetching the nonce and
    // the account state. If the nonce is specified in the transaction use that nonce instead but do the
    // network request anyway to the account state (balance)
    fn fill_optional_fields(
        &self,
        request: TransactionRequest,
        default_sender: Address,
        _force_nonce: bool,
    ) -> BoxFuture<FilledTransactionRequest> {
        const DEFAULT_GAS_PRICE: U256 = U256([0, 0, 0, 21_000_000]);

        let gas_limit = self.client.best_block_header().gas_limit();
        let request_gas_price = request.gas_price;
        let from = request.from.unwrap_or(default_sender);

        let with_gas_price = move |gas_price| {
            let request = request;
            FilledTransactionRequest {
                from,
                used_default_from: request.from.is_none(),
                to: request.to,
                nonce: request.nonce,
                gas_price,
                gas: request.gas.unwrap_or_else(|| gas_limit / 3),
                value: request.value.unwrap_or_default(),
                data: request.data.unwrap_or_else(Vec::new),
                condition: request.condition,
            }
        };

        // fast path for known gas price.
        let gas_price_percentile = self.gas_price_percentile;
        let gas_price = match request_gas_price {
            Some(gas_price) => Either::A(future::ok(with_gas_price(gas_price))),
            None => Either::B(
                fetch_gas_price_corpus(
                    self.sync.clone(),
                    self.client.clone(),
                    self.on_demand.clone(),
                    self.cache.clone(),
                )
                .and_then(move |corp| match corp.percentile(gas_price_percentile) {
                    Some(percentile) => Ok(*percentile),
                    None => Ok(DEFAULT_GAS_PRICE), // fall back to default on error.
                })
                .map(with_gas_price),
            ),
        };

        let future_account = self.account(from);

        Box::new(gas_price.and_then(move |mut filled| {
            future_account.and_then(move |maybe_account| {
                let cost = filled
                    .value
                    .saturating_add(filled.gas.saturating_mul(filled.gas_price));
                match maybe_account {
                    Some(ref account) if cost > account.balance => {
                        Err(errors::transaction(TransactionError::InsufficientBalance {
                            balance: account.balance,
                            cost,
                        }))
                    }
                    Some(account) => {
                        if filled.nonce.is_none() {
                            filled.nonce = Some(account.nonce);
                        }
                        Ok(filled)
                    }
                    None => Err(errors::account("Account not found", "")),
                }
            })
        }))
    }

    fn sign<P>(
        &self,
        filled: FilledTransactionRequest,
        signer: &Arc<Accounts>,
        password: SignWith,
        post_sign: P,
    ) -> BoxFuture<P::Item>
    where
        P: PostSign + 'static,
        <P::Out as futures::future::IntoFuture>::Future: Send,
    {
        let chain_id = self.client.signing_chain_id();
        let nonce = filled.nonce.expect("nonce is always provided; qed");
        let future = signer
            .sign_transaction(filled, chain_id, nonce, password)
            .into_future()
            .and_then(move |signed| post_sign.execute(signed));
        Box::new(future)
    }

    fn enrich(&self, signed_transaction: SignedTransaction) -> RpcRichRawTransaction {
        RpcRichRawTransaction::from_signed(signed_transaction)
    }

    fn dispatch_transaction(&self, signed_transaction: PendingTransaction) -> Result<H256> {
        let hash = signed_transaction.transaction.hash();

        self.transaction_queue
            .write()
            .import(signed_transaction)
            .map_err(errors::transaction)
            .map(|_| hash)
    }
}

/// Get a recent gas price corpus.
// TODO: this could be `impl Trait`.
pub fn fetch_gas_price_corpus<S, OD>(
    sync: Arc<S>,
    client: Arc<LightChainClient>,
    on_demand: Arc<OD>,
    cache: Arc<Mutex<LightDataCache>>,
) -> BoxFuture<Corpus<U256>>
where
    S: LightSyncProvider + LightNetworkDispatcher + ManageNetwork + 'static,
    OD: OnDemandRequester + 'static,
{
    const GAS_PRICE_SAMPLE_SIZE: usize = 100;

    if let Some(cached) = { cache.lock().gas_price_corpus() } {
        return Box::new(future::ok(cached));
    }

    let cache = cache.clone();
    let eventual_corpus = sync.with_context(|ctx| {
        // get some recent headers with gas used,
        // and request each of the blocks from the network.
        let block_requests = client
            .ancestry_iter(BlockId::Latest)
            .filter(|hdr| hdr.gas_used() != U256::default())
            .take(GAS_PRICE_SAMPLE_SIZE)
            .map(|hdr| request::Body(hdr.into()))
            .collect::<Vec<_>>();

        // when the blocks come in, collect gas prices into a vector
        on_demand
            .request(ctx, block_requests)
            .expect("no back-references; therefore all back-references are valid; qed")
            .map(|bodies| {
                bodies.into_iter().fold(Vec::new(), |mut v, block| {
                    for t in block.transaction_views().iter() {
                        v.push(t.gas_price())
                    }
                    v
                })
            })
            .map(move |prices| {
                // produce a corpus from the vector and cache it.
                // It's later used to get a percentile for default gas price.
                let corpus: ::stats::Corpus<_> = prices.into();
                cache.lock().set_gas_price_corpus(corpus.clone());
                corpus
            })
    });

    match eventual_corpus {
        Some(corp) => Box::new(corp.map_err(|_| errors::no_light_peers())),
        None => Box::new(future::err(errors::network_disabled())),
    }
}