filter.go

// (c) 2019-2020, Ava Labs, Inc.
//
// This file is a derived work, based on the go-ethereum library whose original
// notices appear below.
//
// It is distributed under a license compatible with the licensing terms of the
// original code from which it is derived.
//
// Much love to the original authors for their work.
// **********
// Copyright 2014 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 filters

import (
	"context"
	"errors"
	"fmt"
	"math/big"

	"github.com/ava-labs/subnet-evm/core/bloombits"
	"github.com/ava-labs/subnet-evm/core/types"
	"github.com/ava-labs/subnet-evm/rpc"
	"github.com/ethereum/go-ethereum/common"
)

// Filter can be used to retrieve and filter logs.
type Filter struct {
	sys *FilterSystem

	addresses []common.Address
	topics    [][]common.Hash

	block      *common.Hash // Block hash if filtering a single block
	begin, end int64        // Range interval if filtering multiple blocks

	matcher *bloombits.Matcher
}

// NewRangeFilter creates a new filter which uses a bloom filter on blocks to
// figure out whether a particular block is interesting or not.
func (sys *FilterSystem) NewRangeFilter(begin, end int64, addresses []common.Address, topics [][]common.Hash) (*Filter, error) {
	allowUnfinalizedQueries := sys.backend.GetVMConfig().AllowUnfinalizedQueries
	acceptedBlock := sys.backend.LastAcceptedBlock()

	// Flatten the address and topic filter clauses into a single bloombits filter
	// system. Since the bloombits are not positional, nil topics are permitted,
	// which get flattened into a nil byte slice.
	var filters [][][]byte
	if len(addresses) > 0 {
		filter := make([][]byte, len(addresses))
		for i, address := range addresses {
			filter[i] = address.Bytes()
		}
		filters = append(filters, filter)
	}
	for _, topicList := range topics {
		filter := make([][]byte, len(topicList))
		for i, topic := range topicList {
			filter[i] = topic.Bytes()
		}
		filters = append(filters, filter)
	}
	size, _ := sys.backend.BloomStatus()

	if !allowUnfinalizedQueries && acceptedBlock != nil {
		lastAccepted := acceptedBlock.Number().Int64()
		if begin >= 0 && begin > lastAccepted {
			return nil, fmt.Errorf("requested from block %d after last accepted block %d", begin, lastAccepted)
		}
		if end >= 0 && end > lastAccepted {
			return nil, fmt.Errorf("requested to block %d after last accepted block %d", end, lastAccepted)
		}
	}

	// Create a generic filter and convert it into a range filter
	filter := newFilter(sys, addresses, topics)

	filter.matcher = bloombits.NewMatcher(size, filters)
	filter.begin = begin
	filter.end = end

	return filter, nil
}

// NewBlockFilter creates a new filter which directly inspects the contents of
// a block to figure out whether it is interesting or not.
func (sys *FilterSystem) NewBlockFilter(block common.Hash, addresses []common.Address, topics [][]common.Hash) *Filter {
	// Create a generic filter and convert it into a block filter
	filter := newFilter(sys, addresses, topics)
	filter.block = &block
	return filter
}

// newFilter creates a generic filter that can either filter based on a block hash,
// or based on range queries. The search criteria needs to be explicitly set.
func newFilter(sys *FilterSystem, addresses []common.Address, topics [][]common.Hash) *Filter {
	return &Filter{
		sys:       sys,
		addresses: addresses,
		topics:    topics,
	}
}

// Logs searches the blockchain for matching log entries, returning all from the
// first block that contains matches, updating the start of the filter accordingly.
func (f *Filter) Logs(ctx context.Context) ([]*types.Log, error) {
	// If we're doing singleton block filtering, execute and return
	if f.block != nil {
		header, err := f.sys.backend.HeaderByHash(ctx, *f.block)
		if err != nil {
			return nil, err
		}
		if header == nil {
			return nil, errors.New("unknown block")
		}
		return f.blockLogs(ctx, header)
	}
	// Short-cut if all we care about is pending logs
	if f.begin == rpc.PendingBlockNumber.Int64() {
		if f.end != rpc.PendingBlockNumber.Int64() {
			return nil, errors.New("invalid block range")
		}
		// There is no pending block, if the request specifies only the pending block, then return nil.
		return nil, nil
	}
	// Figure out the limits of the filter range
	// LatestBlockNumber is transformed into the last accepted block in HeaderByNumber
	// so it is left in place here.
	header, err := f.sys.backend.HeaderByNumber(ctx, rpc.LatestBlockNumber)
	if err != nil {
		return nil, err
	}
	if header == nil {
		return nil, nil
	}
	var (
		head = header.Number.Uint64()
		end  = uint64(f.end)
	)
	if f.begin < 0 {
		f.begin = int64(head)
	}
	if f.end < 0 {
		end = head
	}

	// When querying unfinalized data without a populated end block, it is
	// possible that the begin will be greater than the end.
	//
	// We error in this case to prevent a bad UX where the caller thinks there
	// are no logs from the specified beginning to end (when in reality there may
	// be some).
	if end < uint64(f.begin) {
		return nil, fmt.Errorf("begin block %d is greater than end block %d", f.begin, end)
	}

	// If the requested range of blocks exceeds the maximum number of blocks allowed by the backend
	// return an error instead of searching for the logs.
	if maxBlocks := f.sys.backend.GetMaxBlocksPerRequest(); int64(end)-f.begin >= maxBlocks && maxBlocks > 0 {
		return nil, fmt.Errorf("requested too many blocks from %d to %d, maximum is set to %d", f.begin, int64(end), maxBlocks)
	}
	// Gather all indexed logs, and finish with non indexed ones
	var (
		logs           []*types.Log
		size, sections = f.sys.backend.BloomStatus()
	)
	if indexed := sections * size; indexed > uint64(f.begin) {
		if indexed > end {
			logs, err = f.indexedLogs(ctx, end)
		} else {
			logs, err = f.indexedLogs(ctx, indexed-1)
		}
		if err != nil {
			return logs, err
		}
	}
	rest, err := f.unindexedLogs(ctx, end)
	logs = append(logs, rest...)
	return logs, err
}

// indexedLogs returns the logs matching the filter criteria based on the bloom
// bits indexed available locally or via the network.
func (f *Filter) indexedLogs(ctx context.Context, end uint64) ([]*types.Log, error) {
	// Create a matcher session and request servicing from the backend
	matches := make(chan uint64, 64)

	session, err := f.matcher.Start(ctx, uint64(f.begin), end, matches)
	if err != nil {
		return nil, err
	}
	defer session.Close()

	f.sys.backend.ServiceFilter(ctx, session)

	// Iterate over the matches until exhausted or context closed
	var logs []*types.Log

	for {
		select {
		case number, ok := <-matches:
			// Abort if all matches have been fulfilled
			if !ok {
				err := session.Error()
				if err == nil {
					f.begin = int64(end) + 1
				}
				return logs, err
			}
			f.begin = int64(number) + 1

			// Retrieve the suggested block and pull any truly matching logs
			header, err := f.sys.backend.HeaderByNumber(ctx, rpc.BlockNumber(number))
			if header == nil || err != nil {
				return logs, err
			}
			found, err := f.checkMatches(ctx, header)
			if err != nil {
				return logs, err
			}
			logs = append(logs, found...)

		case <-ctx.Done():
			return logs, ctx.Err()
		}
	}
}

// unindexedLogs returns the logs matching the filter criteria based on raw block
// iteration and bloom matching.
func (f *Filter) unindexedLogs(ctx context.Context, end uint64) ([]*types.Log, error) {
	var logs []*types.Log

	for ; f.begin <= int64(end); f.begin++ {
		if f.begin%10 == 0 && ctx.Err() != nil {
			return logs, ctx.Err()
		}
		header, err := f.sys.backend.HeaderByNumber(ctx, rpc.BlockNumber(f.begin))
		if header == nil || err != nil {
			return logs, err
		}
		found, err := f.blockLogs(ctx, header)
		if err != nil {
			return logs, err
		}
		logs = append(logs, found...)
	}
	return logs, nil
}

// blockLogs returns the logs matching the filter criteria within a single block.
func (f *Filter) blockLogs(ctx context.Context, header *types.Header) ([]*types.Log, error) {
	if bloomFilter(header.Bloom, f.addresses, f.topics) {
		return f.checkMatches(ctx, header)
	}
	return nil, nil
}

// checkMatches checks if the receipts belonging to the given header contain any log events that
// match the filter criteria. This function is called when the bloom filter signals a potential match.
func (f *Filter) checkMatches(ctx context.Context, header *types.Header) ([]*types.Log, error) {
	logsList, err := f.sys.getLogs(ctx, header.Hash(), header.Number.Uint64())
	if err != nil {
		return nil, err
	}

	unfiltered := types.FlattenLogs(logsList)
	logs := filterLogs(unfiltered, nil, nil, f.addresses, f.topics)
	if len(logs) > 0 {
		// We have matching logs, check if we need to resolve full logs via the light client
		if logs[0].TxHash == (common.Hash{}) {
			receipts, err := f.sys.backend.GetReceipts(ctx, header.Hash())
			if err != nil {
				return nil, err
			}
			unfiltered = unfiltered[:0]
			for _, receipt := range receipts {
				unfiltered = append(unfiltered, receipt.Logs...)
			}
			logs = filterLogs(unfiltered, nil, nil, f.addresses, f.topics)
		}
		return logs, nil
	}
	return nil, nil
}

func includes(addresses []common.Address, a common.Address) bool {
	for _, addr := range addresses {
		if addr == a {
			return true
		}
	}

	return false
}

// filterLogs creates a slice of logs matching the given criteria.
func filterLogs(logs []*types.Log, fromBlock, toBlock *big.Int, addresses []common.Address, topics [][]common.Hash) []*types.Log {
	var ret []*types.Log
Logs:
	for _, log := range logs {
		if fromBlock != nil && fromBlock.Int64() >= 0 && fromBlock.Uint64() > log.BlockNumber {
			continue
		}
		if toBlock != nil && toBlock.Int64() >= 0 && toBlock.Uint64() < log.BlockNumber {
			continue
		}

		if len(addresses) > 0 && !includes(addresses, log.Address) {
			continue
		}
		// If the to filtered topics is greater than the amount of topics in logs, skip.
		if len(topics) > len(log.Topics) {
			continue
		}
		for i, sub := range topics {
			match := len(sub) == 0 // empty rule set == wildcard
			for _, topic := range sub {
				if log.Topics[i] == topic {
					match = true
					break
				}
			}
			if !match {
				continue Logs
			}
		}
		ret = append(ret, log)
	}
	return ret
}

func bloomFilter(bloom types.Bloom, addresses []common.Address, topics [][]common.Hash) bool {
	if len(addresses) > 0 {
		var included bool
		for _, addr := range addresses {
			if types.BloomLookup(bloom, addr) {
				included = true
				break
			}
		}
		if !included {
			return false
		}
	}

	for _, sub := range topics {
		included := len(sub) == 0 // empty rule set == wildcard
		for _, topic := range sub {
			if types.BloomLookup(bloom, topic) {
				included = true
				break
			}
		}
		if !included {
			return false
		}
	}
	return true
}