/*
Copyright IBM Corp. 2016 All Rights Reserved.

SPDX-License-Identifier: Apache-2.0
*/

package statebasedval

import (
	"bytes"

	"github.com/hyperledger/fabric-protos-go/ledger/rwset/kvrwset"
	"github.com/hyperledger/fabric/core/ledger"
	"github.com/hyperledger/fabric/core/ledger/kvledger/txmgmt/rwsetutil"
	"github.com/hyperledger/fabric/core/ledger/kvledger/txmgmt/statedb"
	"github.com/hyperledger/fabric/core/ledger/kvledger/txmgmt/version"
)

type rangeQueryValidator interface {
	init(rqInfo *kvrwset.RangeQueryInfo, itr statedb.ResultsIterator) error
	validate() (bool, error)
}

type rangeQueryResultsValidator struct {
	rqInfo *kvrwset.RangeQueryInfo
	itr    statedb.ResultsIterator
}

func (v *rangeQueryResultsValidator) init(rqInfo *kvrwset.RangeQueryInfo, itr statedb.ResultsIterator) error {
	v.rqInfo = rqInfo
	v.itr = itr
	return nil
}

// validate iterates through the results that are present in the range-query-info (captured during simulation)
// and the iterator (latest view of the `committed state` i.e., db + updates). At first mismatch between the results
// from the two sources (the range-query-info and the iterator), the validate returns false.
func (v *rangeQueryResultsValidator) validate() (bool, error) {
	rqResults := v.rqInfo.GetRawReads().GetKvReads()
	itr := v.itr
	var result statedb.QueryResult
	var err error
	if result, err = itr.Next(); err != nil {
		return false, err
	}
	if len(rqResults) == 0 {
		return result == nil, nil
	}
	for i := 0; i < len(rqResults); i++ {
		kvRead := rqResults[i]
		logger.Debugf("comparing kvRead=[%#v] to queryResponse=[%#v]", kvRead, result)
		if result == nil {
			logger.Debugf("Query response nil. Key [%s] got deleted", kvRead.Key)
			return false, nil
		}
		versionedKV := result.(*statedb.VersionedKV)
		if versionedKV.Key != kvRead.Key {
			logger.Debugf("key name mismatch: Key in rwset = [%s], key in query results = [%s]", kvRead.Key, versionedKV.Key)
			return false, nil
		}
		if !version.AreSame(versionedKV.Version, convertToVersionHeight(kvRead.Version)) {
			logger.Debugf(`Version mismatch for key [%s]: Version in rwset = [%#v], latest version = [%#v]`,
				versionedKV.Key, versionedKV.Version, kvRead.Version)
			return false, nil
		}
		if result, err = itr.Next(); err != nil {
			return false, err
		}
	}
	if result != nil {
		// iterator is not exhausted - which means that there are extra results in the given range
		logger.Debugf("Extra result = [%#v]", result)
		return false, nil
	}
	return true, nil
}

type rangeQueryHashValidator struct {
	rqInfo        *kvrwset.RangeQueryInfo
	itr           statedb.ResultsIterator
	resultsHelper *rwsetutil.RangeQueryResultsHelper
	hasher        ledger.Hasher
}

func (v *rangeQueryHashValidator) init(rqInfo *kvrwset.RangeQueryInfo, itr statedb.ResultsIterator) error {
	v.rqInfo = rqInfo
	v.itr = itr
	var err error
	v.resultsHelper, err = rwsetutil.NewRangeQueryResultsHelper(true, rqInfo.GetReadsMerkleHashes().MaxDegree, v.hasher)
	return err
}

// validate iterates through the iterator (latest view of the `committed state` i.e., db + updates)
// and starts building the merkle tree incrementally (Both, during simulation and during validation,
// rwset.RangeQueryResultsHelper is used for building the merkle tree incrementally ).
//
// This function also keeps comparing the under-construction merkle tree with the merkle tree
// summary present in the range-query-info (built during simulation).
// This function returns false on first mismatch between the nodes of the two merkle trees
// at the desired level (the maxLevel of the merkle tree in range-query-info).
func (v *rangeQueryHashValidator) validate() (bool, error) {
	itr := v.itr
	lastMatchedIndex := -1
	inMerkle := v.rqInfo.GetReadsMerkleHashes()
	var merkle *kvrwset.QueryReadsMerkleSummary
	logger.Debugf("inMerkle: %#v", inMerkle)
	for {
		var result statedb.QueryResult
		var err error
		if result, err = itr.Next(); err != nil {
			return false, err
		}
		logger.Debugf("Processing result = %#v", result)
		if result == nil {
			if _, merkle, err = v.resultsHelper.Done(); err != nil {
				return false, err
			}
			equals := merkleSummariesEqual(inMerkle, merkle)
			logger.Debugf("Combined iterator exhausted. merkle=%#v, equals=%t", merkle, equals)
			return equals, nil
		}
		versionedKV := result.(*statedb.VersionedKV)
		v.resultsHelper.AddResult(rwsetutil.NewKVRead(versionedKV.Key, versionedKV.Version))
		merkle := v.resultsHelper.GetMerkleSummary()

		if merkle.MaxLevel < inMerkle.MaxLevel {
			logger.Debugf("Hashes still under construction. Noting to compare yet. Need more results. Continuing...")
			continue
		}
		if lastMatchedIndex == len(merkle.MaxLevelHashes)-1 {
			logger.Debugf("Need more results to build next entry [index=%d] at level [%d]. Continuing...",
				lastMatchedIndex+1, merkle.MaxLevel)
			continue
		}
		if len(merkle.MaxLevelHashes) > len(inMerkle.MaxLevelHashes) {
			logger.Debugf("Entries exceeded from what are present in the incoming merkleSummary. Validation failed")
			return false, nil
		}
		lastMatchedIndex++
		if !bytes.Equal(merkle.MaxLevelHashes[lastMatchedIndex], inMerkle.MaxLevelHashes[lastMatchedIndex]) {
			logger.Debugf("Hashes does not match at index [%d]. Validation failed", lastMatchedIndex)
			return false, nil
		}
	}
}

func merkleSummariesEqual(ms, anotherMS *kvrwset.QueryReadsMerkleSummary) bool {
	if anotherMS == nil {
		return false
	}
	if ms.MaxDegree != anotherMS.MaxDegree ||
		ms.MaxLevel != anotherMS.MaxLevel ||
		len(ms.MaxLevelHashes) != len(anotherMS.MaxLevelHashes) {
		return false
	}
	for i := 0; i < len(ms.MaxLevelHashes); i++ {
		if !bytes.Equal(ms.MaxLevelHashes[i], anotherMS.MaxLevelHashes[i]) {
			return false
		}
	}
	return true
}

func convertToVersionHeight(v *kvrwset.Version) *version.Height {
	return version.NewHeight(v.BlockNum, v.TxNum)
}