// (c) 2022, Lux Partners Limited.
//
// 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 2022 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 snapshot

import (
	"bytes"
	"fmt"
	"time"

	"github.com/luxfi/coreth/core/rawdb"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/ethdb"
	"github.com/ethereum/go-ethereum/log"
)

// CheckDanglingStorage iterates the snap storage data, and verifies that all
// storage also has corresponding account data.
func CheckDanglingStorage(chaindb ethdb.KeyValueStore) error {
	if err := checkDanglingDiskStorage(chaindb); err != nil {
		log.Error("Database check error", "err", err)
		return err
	}
	return nil
}

// checkDanglingDiskStorage checks if there is any 'dangling' storage data in the
// disk-backed snapshot layer.
func checkDanglingDiskStorage(chaindb ethdb.KeyValueStore) error {
	var (
		lastReport = time.Now()
		start      = time.Now()
		lastKey    []byte
		it         = rawdb.NewKeyLengthIterator(chaindb.NewIterator(rawdb.SnapshotStoragePrefix, nil), 1+2*common.HashLength)
	)
	log.Info("Checking dangling snapshot disk storage")

	defer it.Release()
	for it.Next() {
		k := it.Key()
		accKey := k[1:33]
		if bytes.Equal(accKey, lastKey) {
			// No need to look up for every slot
			continue
		}
		lastKey = common.CopyBytes(accKey)
		if time.Since(lastReport) > time.Second*8 {
			log.Info("Iterating snap storage", "at", fmt.Sprintf("%#x", accKey), "elapsed", common.PrettyDuration(time.Since(start)))
			lastReport = time.Now()
		}
		if data := rawdb.ReadAccountSnapshot(chaindb, common.BytesToHash(accKey)); len(data) == 0 {
			log.Warn("Dangling storage - missing account", "account", fmt.Sprintf("%#x", accKey), "storagekey", fmt.Sprintf("%#x", k))
			return fmt.Errorf("dangling snapshot storage account %#x", accKey)
		}
	}
	log.Info("Verified the snapshot disk storage", "time", common.PrettyDuration(time.Since(start)), "err", it.Error())
	return nil
}
