// 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::U256;
use jsonrpc_core::{
    futures::{Async, Future, IntoFuture, Poll},
    Error, Result,
};
use types::transaction::SignedTransaction;

use super::{Accounts, PostSign, SignWith, WithToken};
use v1::helpers::{errors, nonce, FilledTransactionRequest};

#[derive(Debug, Clone, Copy)]
enum ProspectiveSignerState {
    TryProspectiveSign,
    WaitForPostSign,
    WaitForNonce,
}

pub struct ProspectiveSigner<P: PostSign> {
    signer: Arc<Accounts>,
    filled: FilledTransactionRequest,
    chain_id: Option<u64>,
    reserved: nonce::Reserved,
    password: SignWith,
    state: ProspectiveSignerState,
    prospective: Option<WithToken<SignedTransaction>>,
    ready: Option<nonce::Ready>,
    post_sign: Option<P>,
    post_sign_future: Option<<P::Out as IntoFuture>::Future>,
}

impl<P: PostSign> ProspectiveSigner<P> {
    pub fn new(
        signer: Arc<Accounts>,
        filled: FilledTransactionRequest,
        chain_id: Option<u64>,
        reserved: nonce::Reserved,
        password: SignWith,
        post_sign: P,
    ) -> Self {
        let supports_prospective = signer.supports_prospective_signing(&filled.from, &password);

        ProspectiveSigner {
            signer,
            filled,
            chain_id,
            reserved,
            password,
            state: if supports_prospective {
                ProspectiveSignerState::TryProspectiveSign
            } else {
                ProspectiveSignerState::WaitForNonce
            },
            prospective: None,
            ready: None,
            post_sign: Some(post_sign),
            post_sign_future: None,
        }
    }

    fn sign(&self, nonce: &U256) -> Result<WithToken<SignedTransaction>> {
        self.signer.sign_transaction(
            self.filled.clone(),
            self.chain_id,
            *nonce,
            self.password.clone(),
        )
    }

    fn poll_reserved(&mut self) -> Poll<nonce::Ready, Error> {
        self.reserved
            .poll()
            .map_err(|_| errors::internal("Nonce reservation failure", ""))
    }
}

impl<P: PostSign> Future for ProspectiveSigner<P> {
    type Item = P::Item;
    type Error = Error;

    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
        use self::ProspectiveSignerState::*;

        loop {
            match self.state {
                TryProspectiveSign => {
                    // Try to poll reserved, it might be ready.
                    match self.poll_reserved()? {
                        Async::NotReady => {
                            self.state = WaitForNonce;
                            self.prospective = Some(self.sign(self.reserved.prospective_value())?);
                        }
                        Async::Ready(nonce) => {
                            self.state = WaitForPostSign;
                            self.post_sign_future = Some(
                                self.post_sign
                                    .take()
                                    .expect("post_sign is set on creation; qed")
                                    .execute(self.sign(nonce.value())?)
                                    .into_future(),
                            );
                            self.ready = Some(nonce);
                        }
                    }
                }
                WaitForNonce => {
                    let nonce = try_ready!(self.poll_reserved());
                    let prospective = match (self.prospective.take(), nonce.matches_prospective()) {
                        (Some(prospective), true) => prospective,
                        _ => self.sign(nonce.value())?,
                    };
                    self.ready = Some(nonce);
                    self.state = WaitForPostSign;
                    self.post_sign_future = Some(
                        self.post_sign
                            .take()
                            .expect("post_sign is set on creation; qed")
                            .execute(prospective)
                            .into_future(),
                    );
                }
                WaitForPostSign => {
                    if let Some(mut fut) = self.post_sign_future.as_mut() {
                        match fut.poll()? {
                            Async::Ready(item) => {
                                let nonce = self.ready.take().expect(
                                    "nonce is set before state transitions to WaitForPostSign; qed",
                                );
                                nonce.mark_used();
                                return Ok(Async::Ready(item));
                            }
                            Async::NotReady => return Ok(Async::NotReady),
                        }
                    } else {
                        panic!("Poll after ready.");
                    }
                }
            }
        }
    }
}