/*
Copyright IBM Corp. All Rights Reserved.
SPDX-License-Identifier: Apache-2.0
*/

package lockbasedtxmgr

import (
	"sync"

	"github.com/hyperledger/fabric/common/flogging"
	"github.com/hyperledger/fabric/core/ledger"
	"github.com/hyperledger/fabric/core/ledger/kvledger/txmgmt/privacyenabledstate"
	"github.com/hyperledger/fabric/core/ledger/kvledger/txmgmt/validator"
	"github.com/hyperledger/fabric/core/ledger/kvledger/txmgmt/validator/valimpl"
	"github.com/hyperledger/fabric/core/ledger/kvledger/txmgmt/version"
	"github.com/hyperledger/fabric/protos/common"
)

var logger = flogging.MustGetLogger("lockbasedtxmgr")

// LockBasedTxMgr a simple implementation of interface `txmgmt.TxMgr`.
// This implementation uses a read-write lock to prevent conflicts between transaction simulation and committing
type LockBasedTxMgr struct {
	db           privacyenabledstate.DB
	validator    validator.Validator
	batch        *privacyenabledstate.UpdateBatch
	currentBlock *common.Block
	commitRWLock sync.RWMutex
}

// NewLockBasedTxMgr constructs a new instance of NewLockBasedTxMgr
func NewLockBasedTxMgr(db privacyenabledstate.DB) *LockBasedTxMgr {
	db.Open()
	txmgr := &LockBasedTxMgr{db: db}
	txmgr.validator = valimpl.NewStatebasedValidator(txmgr, db)
	return txmgr
}

// GetLastSavepoint returns the block num recorded in savepoint,
// returns 0 if NO savepoint is found
func (txmgr *LockBasedTxMgr) GetLastSavepoint() (*version.Height, error) {
	return txmgr.db.GetLatestSavePoint()
}

// NewQueryExecutor implements method in interface `txmgmt.TxMgr`
func (txmgr *LockBasedTxMgr) NewQueryExecutor(txid string) (ledger.QueryExecutor, error) {
	qe := newQueryExecutor(txmgr, txid)
	txmgr.commitRWLock.RLock()
	return qe, nil
}

// NewTxSimulator implements method in interface `txmgmt.TxMgr`
func (txmgr *LockBasedTxMgr) NewTxSimulator(txid string) (ledger.TxSimulator, error) {
	logger.Debugf("constructing new tx simulator")
	s, err := newLockBasedTxSimulator(txmgr, txid)
	if err != nil {
		return nil, err
	}
	txmgr.commitRWLock.RLock()
	return s, nil
}

// ValidateAndPrepare implements method in interface `txmgmt.TxMgr`
func (txmgr *LockBasedTxMgr) ValidateAndPrepare(blockAndPvtdata *ledger.BlockAndPvtData, doMVCCValidation bool) error {
	block := blockAndPvtdata.Block
	logger.Debugf("Validating new block with num trans = [%d]", len(block.Data.Data))
	batch, err := txmgr.validator.ValidateAndPrepareBatch(blockAndPvtdata, doMVCCValidation)
	if err != nil {
		txmgr.clearCache()
		return err
	}
	txmgr.currentBlock = block
	txmgr.batch = batch
	return err
}

// Shutdown implements method in interface `txmgmt.TxMgr`
func (txmgr *LockBasedTxMgr) Shutdown() {
	txmgr.db.Close()
}

// Commit implements method in interface `txmgmt.TxMgr`
func (txmgr *LockBasedTxMgr) Commit() error {
	// If statedb implementation needed bulk read optimization, cache might have been populated by
	// ValidateAndPrepare(). Once the block is validated and committed, populated cache needs to
	// be cleared.
	defer txmgr.clearCache()

	logger.Debugf("Committing updates to state database")
	txmgr.commitRWLock.Lock()
	defer txmgr.commitRWLock.Unlock()
	logger.Debugf("Write lock acquired for committing updates to state database")
	if txmgr.batch == nil {
		panic("validateAndPrepare() method should have been called before calling commit()")
	}
	defer func() { txmgr.batch = nil }()
	if err := txmgr.db.ApplyPrivacyAwareUpdates(txmgr.batch,
		version.NewHeight(txmgr.currentBlock.Header.Number, uint64(len(txmgr.currentBlock.Data.Data)-1))); err != nil {
		return err
	}
	logger.Debugf("Updates committed to state database")

	return nil
}

// Rollback implements method in interface `txmgmt.TxMgr`
func (txmgr *LockBasedTxMgr) Rollback() {
	txmgr.batch = nil
	// If statedb implementation needed bulk read optimization, cache might have been populated by
	// ValidateAndPrepareBatch(). As the block commit is rollbacked, populated cache needs to
	// be cleared now.
	txmgr.clearCache()
}

// clearCache empty the cache maintained by the statedb implementation
func (txmgr *LockBasedTxMgr) clearCache() {
	if txmgr.db.IsBulkOptimizable() {
		txmgr.db.ClearCachedVersions()
	}
}

// ShouldRecover implements method in interface kvledger.Recoverer
func (txmgr *LockBasedTxMgr) ShouldRecover(lastAvailableBlock uint64) (bool, uint64, error) {
	savepoint, err := txmgr.GetLastSavepoint()
	if err != nil {
		return false, 0, err
	}
	if savepoint == nil {
		return true, 0, nil
	}
	return savepoint.BlockNum != lastAvailableBlock, savepoint.BlockNum + 1, nil
}

// CommitLostBlock implements method in interface kvledger.Recoverer
func (txmgr *LockBasedTxMgr) CommitLostBlock(blockAndPvtdata *ledger.BlockAndPvtData) error {
	block := blockAndPvtdata.Block
	logger.Debugf("Constructing updateSet for the block %d", block.Header.Number)
	if err := txmgr.ValidateAndPrepare(blockAndPvtdata, false); err != nil {
		return err
	}
	logger.Debugf("Committing block %d to state database", block.Header.Number)
	if err := txmgr.Commit(); err != nil {
		return err
	}
	return nil
}