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// 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"
	"math/big"

	"github.com/ava-labs/coreth/core"
	"github.com/ava-labs/coreth/core/bloombits"
	"github.com/ava-labs/coreth/core/types"
	"github.com/ava-labs/coreth/rpc"
	"github.com/ava-labs/go-ethereum/common"
	"github.com/ava-labs/go-ethereum/ethdb"
	"github.com/ava-labs/go-ethereum/event"
)

type Backend interface {
	ChainDb() ethdb.Database
	EventMux() *event.TypeMux
	HeaderByNumber(ctx context.Context, blockNr rpc.BlockNumber) (*types.Header, error)
	HeaderByHash(ctx context.Context, blockHash common.Hash) (*types.Header, error)
	GetReceipts(ctx context.Context, blockHash common.Hash) (types.Receipts, error)
	GetLogs(ctx context.Context, blockHash common.Hash) ([][]*types.Log, error)

	SubscribeNewTxsEvent(chan<- core.NewTxsEvent) event.Subscription
	SubscribeChainEvent(ch chan<- core.ChainEvent) event.Subscription
	SubscribeRemovedLogsEvent(ch chan<- core.RemovedLogsEvent) event.Subscription
	SubscribeLogsEvent(ch chan<- []*types.Log) event.Subscription

	BloomStatus() (uint64, uint64)
	ServiceFilter(ctx context.Context, session *bloombits.MatcherSession)
}

// Filter can be used to retrieve and filter logs.
type Filter struct {
	backend Backend

	db        ethdb.Database
	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 NewRangeFilter(backend Backend, begin, end int64, addresses []common.Address, topics [][]common.Hash) *Filter {
	// 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, _ := backend.BloomStatus()

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

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

	return filter
}

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

// 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 != (common.Hash{}) {
		header, err := f.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)
	}
	// Figure out the limits of the filter range
	header, _ := f.backend.HeaderByNumber(ctx, rpc.LatestBlockNumber)
	if header == nil {
		return nil, nil
	}
	head := header.Number.Uint64()

	if f.begin == -1 {
		f.begin = int64(head)
	}
	end := uint64(f.end)
	if f.end == -1 {
		end = head
	}
	// Gather all indexed logs, and finish with non indexed ones
	var (
		logs []*types.Log
		err  error
	)
	size, sections := f.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.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.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()
		}
	}
}

// indexedLogs 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++ {
		header, err := f.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) (logs []*types.Log, err error) {
	if bloomFilter(header.Bloom, f.addresses, f.topics) {
		found, err := f.checkMatches(ctx, header)
		if err != nil {
			retur