// Copyright 2017 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 (
	"time"

	"github.com/ethereum/go-ethereum/common/bitutil"
	"github.com/ethereum/go-ethereum/core/rawdb"
)

const (
	// bloomServiceThreads is the number of goroutines used globally by an Ethereum
	// instance to service bloombits lookups for all running filters.
	bloomServiceThreads = 16

	// bloomFilterThreads is the number of goroutines used locally per filter to
	// multiplex requests onto the global servicing goroutines.
	bloomFilterThreads = 3

	// bloomRetrievalBatch is the maximum number of bloom bit retrievals to service
	// in a single batch.
	bloomRetrievalBatch = 16

	// bloomRetrievalWait is the maximum time to wait for enough bloom bit requests
	// to accumulate request an entire batch (avoiding hysteresis).
	bloomRetrievalWait = time.Duration(0)
)

// startBloomHandlers starts a batch of goroutines to accept bloom bit database
// retrievals from possibly a range of filters and serving the data to satisfy.
func (eth *Ethereum) startBloomHandlers(sectionSize uint64) {
	for i := 0; i < bloomServiceThreads; i++ {
		go func() {
			for {
				select {
				case <-eth.closeBloomHandler:
					return

				case request := <-eth.bloomRequests:
					task := <-request
					task.Bitsets = make([][]byte, len(task.Sections))
					for i, section := range task.Sections {
						head := rawdb.ReadCanonicalHash(eth.chainDb, (section+1)*sectionSize-1)
						if compVector, err := rawdb.ReadBloomBits(eth.chainDb, task.Bit, section, head); err == nil {
							if blob, err := bitutil.DecompressBytes(compVector, int(sectionSize/8)); err == nil {
								task.Bitsets[i] = blob
							} else {
								task.Error = err
							}
						} else {
							task.Error = err
						}
					}
					request <- task
				}
			}
		}()
	}
}