// Copyright 2018 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 ethdb

// IdealBatchSize defines the size of the data batches should ideally add in one
// write.
const IdealBatchSize = 100 * 1024

// Batch is a write-only database that commits changes to its host database
// when Write is called. A batch cannot be used concurrently.
type Batch interface {
	KeyValueWriter

	// ValueSize retrieves the amount of data queued up for writing.
	ValueSize() int

	// Write flushes any accumulated data to disk.
	Write() error

	// Reset resets the batch for reuse.
	Reset()

	// Replay replays the batch contents.
	Replay(w KeyValueWriter) error
}

// Works like a normal batch, but allows for interspersing read while writing
// to the batch. Note that the modifications done in the batch itself will not be
// available to be read
type BatchWithReader interface {
	Batch
	KeyValueReader
}

// Batcher wraps the NewBatch method of a backing data store.
type Batcher interface {
	// NewBatch creates a write-only database that buffers changes to its host db
	// until a final write is called.
	NewBatch() Batch

	// NewBatchWithReader creates a standard batch, but allows for reading
	// "pre-batch" state.
	NewBatchWithReader() BatchWithReader
}

// HookedBatch wraps an arbitrary batch where each operation may be hooked into
// to monitor from black box code.
type HookedBatch struct {
	Batch

	OnPut    func(key []byte, value []byte) // Callback if a key is inserted
	OnDelete func(key []byte)               // Callback if a key is deleted
}

// Put inserts the given value into the key-value data store.
func (b HookedBatch) Put(key []byte, value []byte) error {
	if b.OnPut != nil {
		b.OnPut(key, value)
	}
	return b.Batch.Put(key, value)
}

// Delete removes the key from the key-value data store.
func (b HookedBatch) Delete(key []byte) error {
	if b.OnDelete != nil {
		b.OnDelete(key)
	}
	return b.Batch.Delete(key)
}
