// Copyright 2020 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library 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 Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package eth

import (
	"errors"
	"fmt"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/core"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/eth/protocols/eth"
	"github.com/ethereum/go-ethereum/p2p/enode"
)

// ethHandler implements the eth.Backend interface to handle the various network
// packets that are sent as replies or broadcasts.
type ethHandler handler

func (h *ethHandler) Chain() *core.BlockChain { return h.chain }
func (h *ethHandler) TxPool() eth.TxPool      { return h.txpool }

// RunPeer is invoked when a peer joins on the `eth` protocol.
func (h *ethHandler) RunPeer(peer *eth.Peer, hand eth.Handler) error {
	return (*handler)(h).runEthPeer(peer, hand)
}

// PeerInfo retrieves all known `eth` information about a peer.
func (h *ethHandler) PeerInfo(id enode.ID) interface{} {
	if p := h.peers.peer(id.String()); p != nil {
		return p.info()
	}
	return nil
}

// AcceptTxs retrieves whether transaction processing is enabled on the node
// or if inbound transactions should simply be dropped.
func (h *ethHandler) AcceptTxs() bool {
	return h.synced.Load()
}

// Handle is invoked from a peer's message handler when it receives a new remote
// message that the handler couldn't consume and serve itself.
func (h *ethHandler) Handle(peer *eth.Peer, packet eth.Packet) error {
	// Consume any broadcasts and announces, forwarding the rest to the downloader
	switch packet := packet.(type) {
	case *eth.NewPooledTransactionHashesPacket:
		return h.txFetcher.Notify(peer.ID(), packet.Types, packet.Sizes, packet.Hashes)

	case *eth.TransactionsPacket:
		txs, err := packet.Items()
		if err != nil {
			return fmt.Errorf("Transactions: %v", err)
		}
		if err := handleTransactions(peer, txs, true); err != nil {
			return fmt.Errorf("Transactions: %v", err)
		}
		h.enqueueAndTrack(peer.ID(), txs, false)
		return nil

	case *eth.PooledTransactionsPacket:
		txs, err := packet.List.Items()
		if err != nil {
			return fmt.Errorf("PooledTransactions: %v", err)
		}
		if err := handleTransactions(peer, txs, false); err != nil {
			return fmt.Errorf("PooledTransactions: %v", err)
		}
		h.enqueueAndTrack(peer.ID(), txs, true)
		return nil

	default:
		return fmt.Errorf("unexpected eth packet type: %T", packet)
	}
}

// enqueueAndTrack sends transactions to the fetcher for pool submission and
// notifies the tracker for any that were accepted by the pool.
func (h *ethHandler) enqueueAndTrack(peer string, txs []*types.Transaction, direct bool) {
	// Collect hashes before enqueue (Enqueue may reorder/filter the slice).
	hashes := make([]common.Hash, len(txs))
	for i, tx := range txs {
		hashes[i] = tx.Hash()
	}
	// Enqueue submits to pool via addTxs callback. After return, check
	// which txs the pool now knows about (accepted, not rejected).
	h.txFetcher.Enqueue(peer, txs, direct)

	// Credit the peer for txs the pool accepted. We check pool.Has
	// because Enqueue doesn't return per-tx acceptance status.
	var accepted []common.Hash
	for _, hash := range hashes {
		if h.txpool.Has(hash) {
			accepted = append(accepted, hash)
		}
	}
	if len(accepted) > 0 {
		h.txTracker.NotifyAccepted(peer, accepted)
	}
}

// handleTransactions marks all given transactions as known to the peer
// and performs basic validations.
func handleTransactions(peer *eth.Peer, list []*types.Transaction, directBroadcast bool) error {
	seen := make(map[common.Hash]struct{})
	for _, tx := range list {
		if tx.Type() == types.BlobTxType {
			if directBroadcast {
				return errors.New("disallowed broadcast blob transaction")
			} else {
				// If we receive any blob transactions missing sidecars, or with
				// sidecars that don't correspond to the versioned hashes reported
				// in the header, disconnect from the sending peer.
				if tx.BlobTxSidecar() == nil {
					return errors.New("received sidecar-less blob transaction")
				}
				if err := tx.BlobTxSidecar().ValidateBlobCommitmentHashes(tx.BlobHashes()); err != nil {
					return err
				}
			}
		}

		// Check for duplicates.
		hash := tx.Hash()
		if _, exists := seen[hash]; exists {
			return fmt.Errorf("multiple copies of the same hash %v", hash)
		}
		seen[hash] = struct{}{}

		// Mark as known.
		peer.MarkTransaction(hash)
	}
	return nil
}