// 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 api::WARP_SYNC_PROTOCOL_ID;
use block_sync::{BlockDownloaderImportError as DownloaderImportError, DownloadAction};
use bytes::Bytes;
use enum_primitive::FromPrimitive;
use ethcore::{
    error::{BlockError, Error as EthcoreError, ErrorKind as EthcoreErrorKind, ImportErrorKind},
    snapshot::{ManifestData, RestorationStatus},
    verification::queue::kind::blocks::Unverified,
};
use ethereum_types::{H256, U256};
use hash::keccak;
use network::{client_version::ClientVersion, PeerId};
use rlp::Rlp;
use snapshot::ChunkType;
use std::{cmp, mem, time::Instant};
use sync_io::SyncIo;
use types::{block_status::BlockStatus, ids::BlockId, BlockNumber};

use super::sync_packet::{
    PacketInfo, SyncPacket,
    SyncPacket::{
        BlockBodiesPacket, BlockHeadersPacket, NewBlockHashesPacket, NewBlockPacket,
        PrivateTransactionPacket, ReceiptsPacket, SignedPrivateTransactionPacket,
        SnapshotDataPacket, SnapshotManifestPacket, StatusPacket,
    },
};

use super::{
    BlockSet, ChainSync, ForkConfirmation, PacketDecodeError, PeerAsking, PeerInfo, SyncRequester,
    SyncState, ETH_PROTOCOL_VERSION_62, ETH_PROTOCOL_VERSION_63, MAX_NEW_BLOCK_AGE, MAX_NEW_HASHES,
    PAR_PROTOCOL_VERSION_1, PAR_PROTOCOL_VERSION_3,
};

/// The Chain Sync Handler: handles responses from peers
pub struct SyncHandler;

impl SyncHandler {
    /// Handle incoming packet from peer
    pub fn on_packet(
        sync: &mut ChainSync,
        io: &mut dyn SyncIo,
        peer: PeerId,
        packet_id: u8,
        data: &[u8],
    ) {
        let rlp = Rlp::new(data);
        if let Some(packet_id) = SyncPacket::from_u8(packet_id) {
            let result = match packet_id {
                StatusPacket => SyncHandler::on_peer_status(sync, io, peer, &rlp),
                BlockHeadersPacket => SyncHandler::on_peer_block_headers(sync, io, peer, &rlp),
                BlockBodiesPacket => SyncHandler::on_peer_block_bodies(sync, io, peer, &rlp),
                ReceiptsPacket => SyncHandler::on_peer_block_receipts(sync, io, peer, &rlp),
                NewBlockPacket => SyncHandler::on_peer_new_block(sync, io, peer, &rlp),
                NewBlockHashesPacket => SyncHandler::on_peer_new_hashes(sync, io, peer, &rlp),
                SnapshotManifestPacket => SyncHandler::on_snapshot_manifest(sync, io, peer, &rlp),
                SnapshotDataPacket => SyncHandler::on_snapshot_data(sync, io, peer, &rlp),
                PrivateTransactionPacket => {
                    SyncHandler::on_private_transaction(sync, io, peer, &rlp)
                }
                SignedPrivateTransactionPacket => {
                    SyncHandler::on_signed_private_transaction(sync, io, peer, &rlp)
                }
                _ => {
                    debug!(target: "sync", "{}: Unknown packet {}", peer, packet_id.id());
                    Ok(())
                }
            };

            match result {
                Err(DownloaderImportError::Invalid) => {
                    debug!(target:"sync", "{} -> Invalid packet {}", peer, packet_id.id());
                    io.disable_peer(peer);
                    sync.deactivate_peer(io, peer);
                }
                Err(DownloaderImportError::Useless) => {
                    sync.deactivate_peer(io, peer);
                }
                Ok(()) => {
                    // give a task to the same peer first
                    sync.sync_peer(io, peer, false);
                }
            }
        } else {
            debug!(target: "sync", "{}: Unknown packet {}", peer, packet_id);
        }
    }

    /// Called when peer sends us new consensus packet
    pub fn on_consensus_packet(io: &mut dyn SyncIo, peer_id: PeerId, r: &Rlp) {
        trace!(target: "sync", "Received consensus packet from {:?}", peer_id);
        io.chain().queue_consensus_message(r.as_raw().to_vec());
    }

    /// Called by peer when it is disconnecting
    pub fn on_peer_aborting(sync: &mut ChainSync, io: &mut dyn SyncIo, peer_id: PeerId) {
        trace!(target: "sync", "== Disconnecting {}: {}", peer_id, io.peer_version(peer_id));
        sync.handshaking_peers.remove(&peer_id);
        if sync.peers.contains_key(&peer_id) {
            debug!(target: "sync", "Disconnected {}", peer_id);
            sync.clear_peer_download(peer_id);
            sync.peers.remove(&peer_id);
            sync.active_peers.remove(&peer_id);

            if sync.state == SyncState::SnapshotManifest {
                // Check if we are asking other peers for
                // the snapshot manifest as well.
                // If not, return to initial state
                let still_asking_manifest = sync
                    .peers
                    .iter()
                    .filter(|&(id, p)| {
                        sync.active_peers.contains(id) && p.asking == PeerAsking::SnapshotManifest
                    })
                    .next()
                    .is_none();

                if still_asking_manifest {
                    sync.state = ChainSync::get_init_state(sync.warp_sync, io.chain());
                }
            }
            sync.continue_sync(io);
        }
    }

    /// Called when a new peer is connected
    pub fn on_peer_connected(sync: &mut ChainSync, io: &mut dyn SyncIo, peer: PeerId) {
        trace!(target: "sync", "== Connected {}: {}", peer, io.peer_version(peer));
        if let Err(e) = sync.send_status(io, peer) {
            debug!(target:"sync", "Error sending status request: {:?}", e);
            io.disconnect_peer(peer);
        } else {
            sync.handshaking_peers.insert(peer, Instant::now());
        }
    }

    /// Called by peer once it has new block bodies
    pub fn on_peer_new_block(
        sync: &mut ChainSync,
        io: &mut dyn SyncIo,
        peer_id: PeerId,
        r: &Rlp,
    ) -> Result<(), DownloaderImportError> {
        if !sync.peers.get(&peer_id).map_or(false, |p| p.can_sync()) {
            trace!(target: "sync", "Ignoring new block from unconfirmed peer {}", peer_id);
            return Ok(());
        }
        let difficulty: U256 = r.val_at(1)?;
        if let Some(ref mut peer) = sync.peers.get_mut(&peer_id) {
            if peer.difficulty.map_or(true, |pd| difficulty > pd) {
                peer.difficulty = Some(difficulty);
            }
        }
        let block = Unverified::from_rlp(r.at(0)?.as_raw().to_vec())?;
        let hash = block.header.hash();
        let number = block.header.number();
        trace!(target: "sync", "{} -> NewBlock ({})", peer_id, hash);
        if number > sync.highest_block.unwrap_or(0) {
            sync.highest_block = Some(number);
        }
        let mut unknown = false;

        if let Some(ref mut peer) = sync.peers.get_mut(&peer_id) {
            peer.latest_hash = hash;
        }

        let last_imported_number = sync.new_blocks.last_imported_block_number();
        if last_imported_number > number && last_imported_number - number > MAX_NEW_BLOCK_AGE {
            trace!(target: "sync", "Ignored ancient new block {:?}", hash);
            return Err(DownloaderImportError::Invalid);
        }
        match io.chain().import_block(block) {
            Err(EthcoreError(EthcoreErrorKind::Import(ImportErrorKind::AlreadyInChain), _)) => {
                trace!(target: "sync", "New block already in chain {:?}", hash);
            }
            Err(EthcoreError(EthcoreErrorKind::Import(ImportErrorKind::AlreadyQueued), _)) => {
                trace!(target: "sync", "New block already queued {:?}", hash);
            }
            Ok(_) => {
                // abort current download of the same block
                sync.complete_sync(io);
                sync.new_blocks.mark_as_known(&hash, number);
                trace!(target: "sync", "New block queued {:?} ({})", hash, number);
            }
            Err(EthcoreError(EthcoreErrorKind::Block(BlockError::UnknownParent(p)), _)) => {
                unknown = true;
                trace!(target: "sync", "New block with unknown parent ({:?}) {:?}", p, hash);
            }
            Err(e) => {
                debug!(target: "sync", "Bad new block {:?} : {:?}", hash, e);
                return Err(DownloaderImportError::Invalid);
            }
        };
        if unknown {
            if sync.state != SyncState::Idle {
                trace!(target: "sync", "NewBlock ignored while seeking");
            } else {
                trace!(target: "sync", "New unknown block {:?}", hash);
                //TODO: handle too many unknown blocks
                sync.sync_peer(io, peer_id, true);
            }
        }
        Ok(())
    }

    /// Handles `NewHashes` packet. Initiates headers download for any unknown hashes.
    pub fn on_peer_new_hashes(
        sync: &mut ChainSync,
        io: &mut dyn SyncIo,
        peer_id: PeerId,
        r: &Rlp,
    ) -> Result<(), DownloaderImportError> {
        if !sync.peers.get(&peer_id).map_or(false, |p| p.can_sync()) {
            trace!(target: "sync", "Ignoring new hashes from unconfirmed peer {}", peer_id);
            return Ok(());
        }
        let hashes: Vec<_> = r
            .iter()
            .take(MAX_NEW_HASHES)
            .map(|item| (item.val_at::<H256>(0), item.val_at::<BlockNumber>(1)))
            .collect();
        if let Some(ref mut peer) = sync.peers.get_mut(&peer_id) {
            // Peer has new blocks with unknown difficulty
            peer.difficulty = None;
            if let Some(&(Ok(ref h), _)) = hashes.last() {
                peer.latest_hash = h.clone();
            }
        }
        if sync.state != SyncState::Idle {
            trace!(target: "sync", "Ignoring new hashes since we're already downloading.");
            let max = r
                .iter()
                .take(MAX_NEW_HASHES)
                .map(|item| item.val_at::<BlockNumber>(1).unwrap_or(0))
                .fold(0u64, cmp::max);
            if max > sync.highest_block.unwrap_or(0) {
                sync.highest_block = Some(max);
            }
            return Ok(());
        }
        trace!(target: "sync", "{} -> NewHashes ({} entries)", peer_id, r.item_count()?);
        let mut max_height: BlockNumber = 0;
        let mut new_hashes = Vec::new();
        let last_imported_number = sync.new_blocks.last_imported_block_number();
        for (rh, rn) in hashes {
            let hash = rh?;
            let number = rn?;
            if number > sync.highest_block.unwrap_or(0) {
                sync.highest_block = Some(number);
            }
            if sync.new_blocks.is_downloading(&hash) {
                continue;
            }
            if last_imported_number > number && last_imported_number - number > MAX_NEW_BLOCK_AGE {
                trace!(target: "sync", "Ignored ancient new block hash {:?}", hash);
                return Err(DownloaderImportError::Invalid);
            }
            match io.chain().block_status(BlockId::Hash(hash.clone())) {
                BlockStatus::InChain => {
                    trace!(target: "sync", "New block hash already in chain {:?}", hash);
                }
                BlockStatus::Queued => {
                    trace!(target: "sync", "New hash block already queued {:?}", hash);
                }
                BlockStatus::Unknown => {
                    new_hashes.push(hash.clone());
                    if number > max_height {
                        trace!(target: "sync", "New unknown block hash {:?}", hash);
                        if let Some(ref mut peer) = sync.peers.get_mut(&peer_id) {
                            peer.latest_hash = hash.clone();
                        }
                        max_height = number;
                    }
                }
                BlockStatus::Bad => {
                    debug!(target: "sync", "Bad new block hash {:?}", hash);
                    return Err(DownloaderImportError::Invalid);
                }
            }
        }
        if max_height != 0 {
            trace!(target: "sync", "Downloading blocks for new hashes");
            sync.new_blocks.reset_to(new_hashes);
            sync.state = SyncState::NewBlocks;
            sync.sync_peer(io, peer_id, true);
        }
        Ok(())
    }

    /// Called by peer once it has new block bodies
    fn on_peer_block_bodies(
        sync: &mut ChainSync,
        io: &mut dyn SyncIo,
        peer_id: PeerId,
        r: &Rlp,
    ) -> Result<(), DownloaderImportError> {
        sync.clear_peer_download(peer_id);
        let block_set = sync
            .peers
            .get(&peer_id)
            .and_then(|p| p.block_set)
            .unwrap_or(BlockSet::NewBlocks);
        let allowed = sync
            .peers
            .get(&peer_id)
            .map(|p| p.is_allowed())
            .unwrap_or(false);

        if !sync.reset_peer_asking(peer_id, PeerAsking::BlockBodies) || !allowed {
            trace!(target: "sync", "{}: Ignored unexpected bodies", peer_id);
            return Ok(());
        }
        let expected_blocks = match sync.peers.get_mut(&peer_id) {
            Some(peer) => mem::replace(&mut peer.asking_blocks, Vec::new()),
            None => {
                trace!(target: "sync", "{}: Ignored unexpected bodies (peer not found)", peer_id);
                return Ok(());
            }
        };
        let item_count = r.item_count()?;
        trace!(target: "sync", "{} -> BlockBodies ({} entries), set = {:?}", peer_id, item_count, block_set);
        if item_count == 0 {
            Err(DownloaderImportError::Useless)
        } else if sync.state == SyncState::Waiting {
            trace!(target: "sync", "Ignored block bodies while waiting");
            Ok(())
        } else {
            {
                let downloader = match block_set {
                    BlockSet::NewBlocks => &mut sync.new_blocks,
                    BlockSet::OldBlocks => match sync.old_blocks {
                        None => {
                            trace!(target: "sync", "Ignored block headers while block download is inactive");
                            return Ok(());
                        }
                        Some(ref mut blocks) => blocks,
                    },
                };
                downloader.import_bodies(r, expected_blocks.as_slice())?;
            }
            sync.collect_blocks(io, block_set);
            Ok(())
        }
    }

    fn on_peer_fork_header(
        sync: &mut ChainSync,
        io: &mut dyn SyncIo,
        peer_id: PeerId,
        r: &Rlp,
    ) -> Result<(), DownloaderImportError> {
        {
            let peer = sync
                .peers
                .get_mut(&peer_id)
                .expect("Is only called when peer is present in peers");
            peer.asking = PeerAsking::Nothing;
            let item_count = r.item_count()?;
            let (fork_number, fork_hash) = sync
                .fork_block
                .expect("ForkHeader request is sent only fork block is Some; qed")
                .clone();

            if item_count == 0 || item_count != 1 {
                trace!(target: "sync", "{}: Chain is too short to confirm the block", peer_id);
                peer.confirmation = ForkConfirmation::TooShort;
            } else {
                let header = r.at(0)?.as_raw();
                if keccak(&header) != fork_hash {
                    trace!(target: "sync", "{}: Fork mismatch", peer_id);
                    return Err(DownloaderImportError::Invalid);
                }

                trace!(target: "sync", "{}: Confirmed peer", peer_id);
                peer.confirmation = ForkConfirmation::Confirmed;

                if !io.chain_overlay().read().contains_key(&fork_number) {
                    trace!(target: "sync", "Inserting (fork) block {} header", fork_number);
                    io.chain_overlay()
                        .write()
                        .insert(fork_number, header.to_vec());
                }
            }
        }

        return Ok(());
    }

    /// Called by peer once it has new block headers during sync
    fn on_peer_block_headers(
        sync: &mut ChainSync,
        io: &mut dyn SyncIo,
        peer_id: PeerId,
        r: &Rlp,
    ) -> Result<(), DownloaderImportError> {
        let is_fork_header_request = match sync.peers.get(&peer_id) {
            Some(peer) if peer.asking == PeerAsking::ForkHeader => true,
            _ => false,
        };

        if is_fork_header_request {
            return SyncHandler::on_peer_fork_header(sync, io, peer_id, r);
        }

        sync.clear_peer_download(peer_id);
        let expected_hash = sync.peers.get(&peer_id).and_then(|p| p.asking_hash);
        let allowed = sync
            .peers
            .get(&peer_id)
            .map(|p| p.is_allowed())
            .unwrap_or(false);
        let block_set = sync
            .peers
            .get(&peer_id)
            .and_then(|p| p.block_set)
            .unwrap_or(BlockSet::NewBlocks);

        if !sync.reset_peer_asking(peer_id, PeerAsking::BlockHeaders) {
            debug!(target: "sync", "{}: Ignored unexpected headers", peer_id);
            return Ok(());
        }
        let expected_hash = match expected_hash {
            Some(hash) => hash,
            None => {
                debug!(target: "sync", "{}: Ignored unexpected headers (expected_hash is None)", peer_id);
                return Ok(());
            }
        };
        if !allowed {
            debug!(target: "sync", "{}: Ignored unexpected headers (peer not allowed)", peer_id);
            return Ok(());
        }

        let item_count = r.item_count()?;
        trace!(target: "sync", "{} -> BlockHeaders ({} entries), state = {:?}, set = {:?}", peer_id, item_count, sync.state, block_set);
        if (sync.state == SyncState::Idle || sync.state == SyncState::WaitingPeers)
            && sync.old_blocks.is_none()
        {
            trace!(target: "sync", "Ignored unexpected block headers");
            return Ok(());
        }
        if sync.state == SyncState::Waiting {
            trace!(target: "sync", "Ignored block headers while waiting");
            return Ok(());
        }

        let result = {
            let downloader = match block_set {
                BlockSet::NewBlocks => &mut sync.new_blocks,
                BlockSet::OldBlocks => match sync.old_blocks {
                    None => {
                        trace!(target: "sync", "Ignored block headers while block download is inactive");
                        return Ok(());
                    }
                    Some(ref mut blocks) => blocks,
                },
            };
            downloader.import_headers(io, r, expected_hash)?
        };

        if result == DownloadAction::Reset {
            sync.reset_downloads(block_set);
        }

        sync.collect_blocks(io, block_set);
        Ok(())
    }

    /// Called by peer once it has new block receipts
    fn on_peer_block_receipts(
        sync: &mut ChainSync,
        io: &mut dyn SyncIo,
        peer_id: PeerId,
        r: &Rlp,
    ) -> Result<(), DownloaderImportError> {
        sync.clear_peer_download(peer_id);
        let block_set = sync
            .peers
            .get(&peer_id)
            .and_then(|p| p.block_set)
            .unwrap_or(BlockSet::NewBlocks);
        let allowed = sync
            .peers
            .get(&peer_id)
            .map(|p| p.is_allowed())
            .unwrap_or(false);
        if !sync.reset_peer_asking(peer_id, PeerAsking::BlockReceipts) || !allowed {
            trace!(target: "sync", "{}: Ignored unexpected receipts", peer_id);
            return Ok(());
        }
        let expected_blocks = match sync.peers.get_mut(&peer_id) {
            Some(peer) => mem::replace(&mut peer.asking_blocks, Vec::new()),
            None => {
                trace!(target: "sync", "{}: Ignored unexpected bodies (peer not found)", peer_id);
                return Ok(());
            }
        };
        let item_count = r.item_count()?;
        trace!(target: "sync", "{} -> BlockReceipts ({} entries)", peer_id, item_count);
        if item_count == 0 {
            Err(DownloaderImportError::Useless)
        } else if sync.state == SyncState::Waiting {
            trace!(target: "sync", "Ignored block receipts while waiting");
            Ok(())
        } else {
            {
                let downloader = match block_set {
                    BlockSet::NewBlocks => &mut sync.new_blocks,
                    BlockSet::OldBlocks => match sync.old_blocks {
                        None => {
                            trace!(target: "sync", "Ignored block headers while block download is inactive");
                            return Ok(());
                        }
                        Some(ref mut blocks) => blocks,
                    },
                };
                downloader.import_receipts(r, expected_blocks.as_slice())?;
            }
            sync.collect_blocks(io, block_set);
            Ok(())
        }
    }

    /// Called when snapshot manifest is downloaded from a peer.
    fn on_snapshot_manifest(
        sync: &mut ChainSync,
        io: &mut dyn SyncIo,
        peer_id: PeerId,
        r: &Rlp,
    ) -> Result<(), DownloaderImportError> {
        if !sync.peers.get(&peer_id).map_or(false, |p| p.can_sync()) {
            trace!(target: "sync", "Ignoring snapshot manifest from unconfirmed peer {}", peer_id);
            return Ok(());
        }
        sync.clear_peer_download(peer_id);
        if !sync.reset_peer_asking(peer_id, PeerAsking::SnapshotManifest)
            || sync.state != SyncState::SnapshotManifest
        {
            trace!(target: "sync", "{}: Ignored unexpected/expired manifest", peer_id);
            return Ok(());
        }

        let manifest_rlp = r.at(0)?;
        let manifest = ManifestData::from_rlp(manifest_rlp.as_raw())?;

        let is_supported_version = io
            .snapshot_service()
            .supported_versions()
            .map_or(false, |(l, h)| {
                manifest.version >= l && manifest.version <= h
            });

        if !is_supported_version {
            trace!(target: "sync", "{}: Snapshot manifest version not supported: {}", peer_id, manifest.version);
            return Err(DownloaderImportError::Invalid);
        }
        sync.snapshot
            .reset_to(&manifest, &keccak(manifest_rlp.as_raw()));
        io.snapshot_service().begin_restore(manifest);
        sync.state = SyncState::SnapshotData;

        Ok(())
    }

    /// Called when snapshot data is downloaded from a peer.
    fn on_snapshot_data(
        sync: &mut ChainSync,
        io: &mut dyn SyncIo,
        peer_id: PeerId,
        r: &Rlp,
    ) -> Result<(), DownloaderImportError> {
        if !sync.peers.get(&peer_id).map_or(false, |p| p.can_sync()) {
            trace!(target: "sync", "Ignoring snapshot data from unconfirmed peer {}", peer_id);
            return Ok(());
        }
        sync.clear_peer_download(peer_id);
        if !sync.reset_peer_asking(peer_id, PeerAsking::SnapshotData)
            || (sync.state != SyncState::SnapshotData && sync.state != SyncState::SnapshotWaiting)
        {
            trace!(target: "sync", "{}: Ignored unexpected snapshot data", peer_id);
            return Ok(());
        }

        // check service status
        let status = io.snapshot_service().status();
        match status {
            RestorationStatus::Inactive | RestorationStatus::Failed => {
                trace!(target: "sync", "{}: Snapshot restoration aborted", peer_id);
                sync.state = SyncState::WaitingPeers;

                // only note bad if restoration failed.
                if let (Some(hash), RestorationStatus::Failed) =
                    (sync.snapshot.snapshot_hash(), status)
                {
                    trace!(target: "sync", "Noting snapshot hash {} as bad", hash);
                    sync.snapshot.note_bad(hash);
                }

                sync.snapshot.clear();
                return Ok(());
            }
            RestorationStatus::Initializing { .. } => {
                trace!(target: "warp", "{}: Snapshot restoration is initializing", peer_id);
                return Ok(());
            }
            RestorationStatus::Ongoing { .. } => {
                trace!(target: "sync", "{}: Snapshot restoration is ongoing", peer_id);
            }
        }

        let snapshot_data: Bytes = r.val_at(0)?;
        match sync.snapshot.validate_chunk(&snapshot_data) {
            Ok(ChunkType::Block(hash)) => {
                trace!(target: "sync", "{}: Processing block chunk", peer_id);
                io.snapshot_service()
                    .restore_block_chunk(hash, snapshot_data);
            }
            Ok(ChunkType::State(hash)) => {
                trace!(target: "sync", "{}: Processing state chunk", peer_id);
                io.snapshot_service()
                    .restore_state_chunk(hash, snapshot_data);
            }
            Err(()) => {
                trace!(target: "sync", "{}: Got bad snapshot chunk", peer_id);
                io.disconnect_peer(peer_id);
                return Ok(());
            }
        }

        if sync.snapshot.is_complete() {
            // wait for snapshot restoration process to complete
            sync.state = SyncState::SnapshotWaiting;
        }

        Ok(())
    }

    /// Called by peer to report status
    fn on_peer_status(
        sync: &mut ChainSync,
        io: &mut dyn SyncIo,
        peer_id: PeerId,
        r: &Rlp,
    ) -> Result<(), DownloaderImportError> {
        sync.handshaking_peers.remove(&peer_id);
        let protocol_version: u8 = r.val_at(0)?;
        let warp_protocol_version = io.protocol_version(&WARP_SYNC_PROTOCOL_ID, peer_id);
        let warp_protocol = warp_protocol_version != 0;
        let private_tx_protocol = warp_protocol_version >= PAR_PROTOCOL_VERSION_3.0;
        let peer = PeerInfo {
            protocol_version: protocol_version,
            network_id: r.val_at(1)?,
            difficulty: Some(r.val_at(2)?),
            latest_hash: r.val_at(3)?,
            genesis: r.val_at(4)?,
            asking: PeerAsking::Nothing,
            asking_blocks: Vec::new(),
            asking_hash: None,
            ask_time: Instant::now(),
            last_sent_transactions: Default::default(),
            last_sent_private_transactions: Default::default(),
            expired: false,
            confirmation: if sync.fork_block.is_none() {
                ForkConfirmation::Confirmed
            } else {
                ForkConfirmation::Unconfirmed
            },
            asking_snapshot_data: None,
            snapshot_hash: if warp_protocol {
                Some(r.val_at(5)?)
            } else {
                None
            },
            snapshot_number: if warp_protocol {
                Some(r.val_at(6)?)
            } else {
                None
            },
            block_set: None,
            private_tx_enabled: if private_tx_protocol {
                r.val_at(7).unwrap_or(false)
            } else {
                false
            },
            client_version: ClientVersion::from(io.peer_version(peer_id)),
        };

        trace!(target: "sync", "New peer {} (\
            protocol: {}, \
            network: {:?}, \
            difficulty: {:?}, \
            latest:{}, \
            genesis:{}, \
            snapshot:{:?}, \
            private_tx_enabled:{})",
            peer_id,
            peer.protocol_version,
            peer.network_id,
            peer.difficulty,
            peer.latest_hash,
            peer.genesis,
            peer.snapshot_number,
            peer.private_tx_enabled
        );
        if io.is_expired() {
            trace!(target: "sync", "Status packet from expired session {}:{}", peer_id, io.peer_version(peer_id));
            return Ok(());
        }

        if sync.peers.contains_key(&peer_id) {
            debug!(target: "sync", "Unexpected status packet from {}:{}", peer_id, io.peer_version(peer_id));
            return Ok(());
        }
        let chain_info = io.chain().chain_info();
        if peer.genesis != chain_info.genesis_hash {
            trace!(target: "sync", "Peer {} genesis hash mismatch (ours: {}, theirs: {})", peer_id, chain_info.genesis_hash, peer.genesis);
            return Err(DownloaderImportError::Invalid);
        }
        if peer.network_id != sync.network_id {
            trace!(target: "sync", "Peer {} network id mismatch (ours: {}, theirs: {})", peer_id, sync.network_id, peer.network_id);
            return Err(DownloaderImportError::Invalid);
        }

        if false
            || (warp_protocol
                && (peer.protocol_version < PAR_PROTOCOL_VERSION_1.0
                    || peer.protocol_version > PAR_PROTOCOL_VERSION_3.0))
            || (!warp_protocol
                && (peer.protocol_version < ETH_PROTOCOL_VERSION_62.0
                    || peer.protocol_version > ETH_PROTOCOL_VERSION_63.0))
        {
            trace!(target: "sync", "Peer {} unsupported eth protocol ({})", peer_id, peer.protocol_version);
            return Err(DownloaderImportError::Invalid);
        }

        if sync.sync_start_time.is_none() {
            sync.sync_start_time = Some(Instant::now());
        }

        sync.peers.insert(peer_id.clone(), peer);
        // Don't activate peer immediatelly when searching for common block.
        // Let the current sync round complete first.
        sync.active_peers.insert(peer_id.clone());
        debug!(target: "sync", "Connected {}:{}", peer_id, io.peer_version(peer_id));

        if let Some((fork_block, _)) = sync.fork_block {
            SyncRequester::request_fork_header(sync, io, peer_id, fork_block);
        }

        Ok(())
    }

    /// Called when peer sends us new transactions
    pub fn on_peer_transactions(
        sync: &ChainSync,
        io: &mut dyn SyncIo,
        peer_id: PeerId,
        r: &Rlp,
    ) -> Result<(), PacketDecodeError> {
        // Accept transactions only when fully synced
        if !io.is_chain_queue_empty()
            || (sync.state != SyncState::Idle && sync.state != SyncState::NewBlocks)
        {
            trace!(target: "sync", "{} Ignoring transactions while syncing", peer_id);
            return Ok(());
        }
        if !sync.peers.get(&peer_id).map_or(false, |p| p.can_sync()) {
            trace!(target: "sync", "{} Ignoring transactions from unconfirmed/unknown peer", peer_id);
            return Ok(());
        }

        let item_count = r.item_count()?;
        trace!(target: "sync", "{:02} -> Transactions ({} entries)", peer_id, item_count);
        let mut transactions = Vec::with_capacity(item_count);
        for i in 0..item_count {
            let rlp = r.at(i)?;
            let tx = rlp.as_raw().to_vec();
            transactions.push(tx);
        }
        io.chain().queue_transactions(transactions, peer_id);
        Ok(())
    }

    /// Called when peer sends us signed private transaction packet
    fn on_signed_private_transaction(
        sync: &mut ChainSync,
        _io: &mut dyn SyncIo,
        peer_id: PeerId,
        r: &Rlp,
    ) -> Result<(), DownloaderImportError> {
        if !sync.peers.get(&peer_id).map_or(false, |p| p.can_sync()) {
            trace!(target: "sync", "{} Ignoring packet from unconfirmed/unknown peer", peer_id);
            return Ok(());
        }
        let private_handler = match sync.private_tx_handler {
            Some(ref handler) => handler,
            None => {
                trace!(target: "sync", "{} Ignoring private tx packet from peer", peer_id);
                return Ok(());
            }
        };
        trace!(target: "sync", "Received signed private transaction packet from {:?}", peer_id);
        match private_handler.import_signed_private_transaction(r.as_raw()) {
            Ok(transaction_hash) => {
                //don't send the packet back
                if let Some(ref mut peer) = sync.peers.get_mut(&peer_id) {
                    peer.last_sent_private_transactions.insert(transaction_hash);
                }
            }
            Err(e) => {
                trace!(target: "sync", "Ignoring the message, error queueing: {}", e);
            }
        }
        Ok(())
    }

    /// Called when peer sends us new private transaction packet
    fn on_private_transaction(
        sync: &mut ChainSync,
        _io: &mut dyn SyncIo,
        peer_id: PeerId,
        r: &Rlp,
    ) -> Result<(), DownloaderImportError> {
        if !sync.peers.get(&peer_id).map_or(false, |p| p.can_sync()) {
            trace!(target: "sync", "{} Ignoring packet from unconfirmed/unknown peer", peer_id);
            return Ok(());
        }
        let private_handler = match sync.private_tx_handler {
            Some(ref handler) => handler,
            None => {
                trace!(target: "sync", "{} Ignoring private tx packet from peer", peer_id);
                return Ok(());
            }
        };
        trace!(target: "sync", "Received private transaction packet from {:?}", peer_id);
        match private_handler.import_private_transaction(r.as_raw()) {
            Ok(transaction_hash) => {
                //don't send the packet back
                if let Some(ref mut peer) = sync.peers.get_mut(&peer_id) {
                    peer.last_sent_private_transactions.insert(transaction_hash);
                }
            }
            Err(e) => {
                trace!(target: "sync", "Ignoring the message, error queueing: {}", e);
            }
        }
        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use ethcore::client::{ChainInfo, EachBlockWith, TestBlockChainClient};
    use parking_lot::RwLock;
    use rlp::Rlp;
    use std::collections::VecDeque;
    use tests::{helpers::TestIo, snapshot::TestSnapshotService};

    use super::{
        super::tests::{dummy_sync_with_peer, get_dummy_block, get_dummy_blocks, get_dummy_hashes},
        *,
    };

    #[test]
    fn handles_peer_new_hashes() {
        let mut client = TestBlockChainClient::new();
        client.add_blocks(10, EachBlockWith::Uncle);
        let queue = RwLock::new(VecDeque::new());
        let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(5), &client);
        let ss = TestSnapshotService::new();
        let mut io = TestIo::new(&mut client, &ss, &queue, None);

        let hashes_data = get_dummy_hashes();
        let hashes_rlp = Rlp::new(&hashes_data);

        let result = SyncHandler::on_peer_new_hashes(&mut sync, &mut io, 0, &hashes_rlp);

        assert!(result.is_ok());
    }

    #[test]
    fn handles_peer_new_block_malformed() {
        let mut client = TestBlockChainClient::new();
        client.add_blocks(10, EachBlockWith::Uncle);

        let block_data = get_dummy_block(11, client.chain_info().best_block_hash);

        let queue = RwLock::new(VecDeque::new());
        let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(5), &client);
        //sync.have_common_block = true;
        let ss = TestSnapshotService::new();
        let mut io = TestIo::new(&mut client, &ss, &queue, None);

        let block = Rlp::new(&block_data);

        let result = SyncHandler::on_peer_new_block(&mut sync, &mut io, 0, &block);

        assert!(result.is_err());
    }

    #[test]
    fn handles_peer_new_block() {
        let mut client = TestBlockChainClient::new();
        client.add_blocks(10, EachBlockWith::Uncle);

        let block_data = get_dummy_blocks(11, client.chain_info().best_block_hash);

        let queue = RwLock::new(VecDeque::new());
        let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(5), &client);
        let ss = TestSnapshotService::new();
        let mut io = TestIo::new(&mut client, &ss, &queue, None);

        let block = Rlp::new(&block_data);

        SyncHandler::on_peer_new_block(&mut sync, &mut io, 0, &block).expect("result to be ok");
    }

    #[test]
    fn handles_peer_new_block_empty() {
        let mut client = TestBlockChainClient::new();
        client.add_blocks(10, EachBlockWith::Uncle);
        let queue = RwLock::new(VecDeque::new());
        let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(5), &client);
        let ss = TestSnapshotService::new();
        let mut io = TestIo::new(&mut client, &ss, &queue, None);

        let empty_data = vec![];
        let block = Rlp::new(&empty_data);

        let result = SyncHandler::on_peer_new_block(&mut sync, &mut io, 0, &block);

        assert!(result.is_err());
    }

    #[test]
    fn handles_peer_new_hashes_empty() {
        let mut client = TestBlockChainClient::new();
        client.add_blocks(10, EachBlockWith::Uncle);
        let queue = RwLock::new(VecDeque::new());
        let mut sync = dummy_sync_with_peer(client.block_hash_delta_minus(5), &client);
        let ss = TestSnapshotService::new();
        let mut io = TestIo::new(&mut client, &ss, &queue, None);

        let empty_hashes_data = vec![];
        let hashes_rlp = Rlp::new(&empty_hashes_data);

        let result = SyncHandler::on_peer_new_hashes(&mut sync, &mut io, 0, &hashes_rlp);

        assert!(result.is_ok());
    }
}