// Copyright (C) 2019-2025, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.

package merkledb

import (
	"context"
	"math/rand"
	"testing"
	"time"

	"github.com/stretchr/testify/require"

	"github.com/ava-labs/avalanchego/database"
	"github.com/ava-labs/avalanchego/database/memdb"
	"github.com/ava-labs/avalanchego/ids"
	"github.com/ava-labs/avalanchego/utils/maybe"
	"github.com/ava-labs/avalanchego/x/sync"
)

func Test_History_Simple(t *testing.T) {
	require := require.New(t)

	db, err := newDB(
		context.Background(),
		memdb.New(),
		NewConfig(),
	)
	require.NoError(err)
	batch := db.NewBatch()
	require.NoError(batch.Put([]byte("key"), []byte("value")))
	require.NoError(batch.Write())

	val, err := db.Get([]byte("key"))
	require.NoError(err)
	require.Equal([]byte("value"), val)

	origProof, err := db.GetRangeProof(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.NoError(err)
	require.NotNil(origProof)
	origRootID := db.rootID
	require.NoError(origProof.Verify(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), origRootID, db.tokenSize, db.hasher, len(origProof.KeyChanges)))

	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("key"), []byte("value0")))
	require.NoError(batch.Write())
	newProof, err := db.GetRangeProofAtRoot(context.Background(), origRootID, maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.NoError(err)
	require.NotNil(newProof)
	require.NoError(newProof.Verify(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), origRootID, db.tokenSize, db.hasher, len(newProof.KeyChanges)))

	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("key1"), []byte("value1")))
	require.NoError(batch.Put([]byte("key8"), []byte("value8")))
	require.NoError(batch.Write())
	newProof, err = db.GetRangeProofAtRoot(context.Background(), origRootID, maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.NoError(err)
	require.NotNil(newProof)
	require.NoError(newProof.Verify(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), origRootID, db.tokenSize, db.hasher, len(newProof.KeyChanges)))

	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("k"), []byte("v")))
	require.NoError(batch.Write())
	newProof, err = db.GetRangeProofAtRoot(context.Background(), origRootID, maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.NoError(err)
	require.NotNil(newProof)
	require.NoError(newProof.Verify(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), origRootID, db.tokenSize, db.hasher, len(newProof.KeyChanges)))

	batch = db.NewBatch()
	require.NoError(batch.Delete([]byte("k")))
	require.NoError(batch.Delete([]byte("ke")))
	require.NoError(batch.Delete([]byte("key")))
	require.NoError(batch.Delete([]byte("key1")))
	require.NoError(batch.Put([]byte("key2"), []byte("value2")))
	require.NoError(batch.Delete([]byte("key3")))
	require.NoError(batch.Delete([]byte("key4")))
	require.NoError(batch.Delete([]byte("key5")))
	require.NoError(batch.Delete([]byte("key8")))
	require.NoError(batch.Write())
	newProof, err = db.GetRangeProofAtRoot(context.Background(), origRootID, maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.NoError(err)
	require.NotNil(newProof)
	require.NoError(newProof.Verify(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), origRootID, db.tokenSize, db.hasher, len(newProof.KeyChanges)))
}

func Test_History_Large(t *testing.T) {
	require := require.New(t)

	numIters := 250

	for i := 1; i < 5; i++ {
		config := NewConfig()
		// History must be large enough to get the change proof
		// after this loop.
		config.HistoryLength = uint(numIters)
		db, err := New(
			context.Background(),
			memdb.New(),
			config,
		)
		require.NoError(err)
		roots := []ids.ID{}

		now := time.Now().UnixNano()
		t.Logf("seed for iter %d: %d", i, now)
		r := rand.New(rand.NewSource(now)) // #nosec G404
		// make sure they stay in sync
		for x := 0; x < numIters; x++ {
			batch := db.NewBatch()
			addkey := make([]byte, r.Intn(50))
			_, err := r.Read(addkey)
			require.NoError(err)
			val := make([]byte, r.Intn(50))
			_, err = r.Read(val)
			require.NoError(err)

			require.NoError(batch.Put(addkey, val))

			addNilkey := make([]byte, r.Intn(50))
			_, err = r.Read(addNilkey)
			require.NoError(err)
			require.NoError(batch.Put(addNilkey, nil))

			deleteKeyStart := make([]byte, r.Intn(50))
			_, err = r.Read(deleteKeyStart)
			require.NoError(err)

			it := db.NewIteratorWithStart(deleteKeyStart)
			if it.Next() {
				require.NoError(batch.Delete(it.Key()))
			}
			require.NoError(it.Error())
			it.Release()

			require.NoError(batch.Write())
			root, err := db.GetMerkleRoot(context.Background())
			require.NoError(err)
			roots = append(roots, root)
		}

		for i := 0; i < numIters; i += numIters / 10 {
			proof, err := db.GetRangeProofAtRoot(context.Background(), roots[i], maybe.Nothing[[]byte](), maybe.Nothing[[]byte](), 10)
			require.NoError(err)
			require.NotNil(proof)

			require.NoError(proof.Verify(context.Background(), maybe.Nothing[[]byte](), maybe.Nothing[[]byte](), roots[i], BranchFactorToTokenSize[config.BranchFactor], config.Hasher, len(proof.KeyChanges)))
		}
	}
}

func Test_History_Bad_GetValueChanges_Input(t *testing.T) {
	require := require.New(t)

	config := NewConfig()
	config.HistoryLength = 5

	db, err := newDB(
		context.Background(),
		memdb.New(),
		config,
	)
	require.NoError(err)

	// Do 5 puts (i.e. the history length)
	batch := db.NewBatch()
	require.NoError(batch.Put([]byte("key"), []byte("value")))
	require.NoError(batch.Write())

	root1 := db.getMerkleRoot()

	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("key"), []byte("value0")))
	require.NoError(batch.Write())

	root2 := db.getMerkleRoot()

	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("key1"), []byte("value0")))
	require.NoError(batch.Write())

	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("key1"), []byte("value1")))
	require.NoError(batch.Write())

	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("key2"), []byte("value3")))
	require.NoError(batch.Write())

	root3 := db.getMerkleRoot()

	// ensure these start as valid calls
	_, err = db.history.getValueChanges(root1, root3, maybe.Nothing[[]byte](), maybe.Nothing[[]byte](), 1)
	require.NoError(err)
	_, err = db.history.getValueChanges(root2, root3, maybe.Nothing[[]byte](), maybe.Nothing[[]byte](), 1)
	require.NoError(err)

	_, err = db.history.getValueChanges(root2, root3, maybe.Nothing[[]byte](), maybe.Nothing[[]byte](), -1)
	require.ErrorIs(err, ErrInvalidMaxLength)

	_, err = db.history.getValueChanges(root3, root2, maybe.Nothing[[]byte](), maybe.Nothing[[]byte](), 1)
	require.ErrorIs(err, sync.ErrInsufficientHistory)

	// Cause root1 to be removed from the history
	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("key2"), []byte("value4")))
	require.NoError(batch.Write())

	_, err = db.history.getValueChanges(root1, root3, maybe.Nothing[[]byte](), maybe.Nothing[[]byte](), 1)
	require.ErrorIs(err, sync.ErrInsufficientHistory)

	// same start/end roots should yield an empty changelist
	changes, err := db.history.getValueChanges(root3, root3, maybe.Nothing[[]byte](), maybe.Nothing[[]byte](), 10)
	require.NoError(err)
	require.Empty(changes)
}

func Test_History_Trigger_History_Queue_Looping(t *testing.T) {
	require := require.New(t)

	config := NewConfig()
	config.HistoryLength = 2

	db, err := newDB(
		context.Background(),
		memdb.New(),
		config,
	)
	require.NoError(err)

	// Do 2 puts (i.e. the history length)
	batch := db.NewBatch()
	require.NoError(batch.Put([]byte("key"), []byte("value")))
	require.NoError(batch.Write())
	origRootID := db.getMerkleRoot()

	origProof, err := db.GetRangeProof(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.NoError(err)
	require.NotNil(origProof)
	require.NoError(origProof.Verify(
		context.Background(),
		maybe.Some([]byte("k")),
		maybe.Some([]byte("key3")),
		origRootID,
		db.tokenSize,
		db.hasher,
		len(origProof.KeyChanges),
	))

	// write a new value into the db, now there should be 2 roots in the history
	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("key"), []byte("value0")))
	require.NoError(batch.Write())

	// ensure that previous root is still present and generates a valid proof
	newProof, err := db.GetRangeProofAtRoot(context.Background(), origRootID, maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.NoError(err)
	require.NotNil(newProof)
	require.NoError(newProof.Verify(
		context.Background(),
		maybe.Some([]byte("k")),
		maybe.Some([]byte("key3")),
		origRootID,
		db.tokenSize,
		db.hasher,
		len(newProof.KeyChanges),
	))

	// trigger a new root to be added to the history, which should cause rollover since there can only be 2
	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("key1"), []byte("value1")))
	require.NoError(batch.Write())

	// proof from first root shouldn't be generatable since it should have been removed from the history
	_, err = db.GetRangeProofAtRoot(context.Background(), origRootID, maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.ErrorIs(err, sync.ErrInsufficientHistory)
}

func Test_History_Values_Lookup_Over_Queue_Break(t *testing.T) {
	require := require.New(t)

	config := NewConfig()
	config.HistoryLength = 4
	db, err := newDB(
		context.Background(),
		memdb.New(),
		config,
	)
	require.NoError(err)

	// Do 4 puts (i.e. the history length)
	batch := db.NewBatch()
	require.NoError(batch.Put([]byte("key"), []byte("value")))
	require.NoError(batch.Write())

	// write a new value into the db
	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("key"), []byte("value0")))
	require.NoError(batch.Write())

	startRoot := db.getMerkleRoot()

	// write a new value into the db
	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("key1"), []byte("value0")))
	require.NoError(batch.Write())

	// write a new value into the db that overwrites key1
	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("key1"), []byte("value1")))
	require.NoError(batch.Write())

	// trigger a new root to be added to the history, which should cause rollover since there can only be 3
	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("key2"), []byte("value3")))
	require.NoError(batch.Write())

	endRoot := db.getMerkleRoot()

	// changes should still be collectable even though the history has had to loop due to hitting max size
	changes, err := db.history.getValueChanges(startRoot, endRoot, maybe.Nothing[[]byte](), maybe.Nothing[[]byte](), 10)
	require.NoError(err)

	require.Equal([]valueChange{
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Nothing[[]byte](),
				after:  maybe.Some([]byte("value1")),
			},
			key: ToKey([]byte("key1")),
		},
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Nothing[[]byte](),
				after:  maybe.Some([]byte("value3")),
			},
			key: ToKey([]byte("key2")),
		},
	}, changes)
}

func Test_History_RepeatedRoot(t *testing.T) {
	require := require.New(t)

	db, err := newDB(
		context.Background(),
		memdb.New(),
		NewConfig(),
	)
	require.NoError(err)
	batch := db.NewBatch()
	require.NoError(batch.Put([]byte("key1"), []byte("value1")))
	require.NoError(batch.Put([]byte("key2"), []byte("value2")))
	require.NoError(batch.Put([]byte("key3"), []byte("value3")))
	require.NoError(batch.Write())

	origProof, err := db.GetRangeProof(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.NoError(err)
	require.NotNil(origProof)
	origRootID := db.rootID
	require.NoError(origProof.Verify(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), origRootID, db.tokenSize, db.hasher, len(origProof.KeyChanges)))

	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("key1"), []byte("other")))
	require.NoError(batch.Put([]byte("key2"), []byte("other")))
	require.NoError(batch.Put([]byte("key3"), []byte("other")))
	require.NoError(batch.Write())
	newProof, err := db.GetRangeProofAtRoot(context.Background(), origRootID, maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.NoError(err)
	require.NotNil(newProof)
	require.NoError(newProof.Verify(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), origRootID, db.tokenSize, db.hasher, len(newProof.KeyChanges)))

	// revert state to be the same as in orig proof
	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("key1"), []byte("value1")))
	require.NoError(batch.Put([]byte("key2"), []byte("value2")))
	require.NoError(batch.Put([]byte("key3"), []byte("value3")))
	require.NoError(batch.Write())

	newProof, err = db.GetRangeProofAtRoot(context.Background(), origRootID, maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.NoError(err)
	require.NotNil(newProof)
	require.NoError(newProof.Verify(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), origRootID, db.tokenSize, db.hasher, len(newProof.KeyChanges)))
}

func Test_History_ExcessDeletes(t *testing.T) {
	require := require.New(t)

	db, err := newDB(
		context.Background(),
		memdb.New(),
		NewConfig(),
	)
	require.NoError(err)
	batch := db.NewBatch()
	require.NoError(batch.Put([]byte("key"), []byte("value")))
	require.NoError(batch.Write())

	origProof, err := db.GetRangeProof(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.NoError(err)
	require.NotNil(origProof)
	origRootID := db.rootID
	require.NoError(origProof.Verify(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), origRootID, db.tokenSize, db.hasher, len(origProof.KeyChanges)))

	batch = db.NewBatch()
	require.NoError(batch.Delete([]byte("key1")))
	require.NoError(batch.Delete([]byte("key2")))
	require.NoError(batch.Delete([]byte("key3")))
	require.NoError(batch.Delete([]byte("key4")))
	require.NoError(batch.Delete([]byte("key5")))
	require.NoError(batch.Write())
	newProof, err := db.GetRangeProofAtRoot(context.Background(), origRootID, maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.NoError(err)
	require.NotNil(newProof)
	require.NoError(newProof.Verify(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), origRootID, db.tokenSize, db.hasher, len(newProof.KeyChanges)))
}

func Test_History_DontIncludeAllNodes(t *testing.T) {
	require := require.New(t)

	db, err := newDB(
		context.Background(),
		memdb.New(),
		NewConfig(),
	)
	require.NoError(err)
	batch := db.NewBatch()
	require.NoError(batch.Put([]byte("key"), []byte("value")))
	require.NoError(batch.Write())

	origProof, err := db.GetRangeProof(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.NoError(err)
	require.NotNil(origProof)
	origRootID := db.rootID
	require.NoError(origProof.Verify(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), origRootID, db.tokenSize, db.hasher, len(origProof.KeyChanges)))

	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("z"), []byte("z")))
	require.NoError(batch.Write())
	newProof, err := db.GetRangeProofAtRoot(context.Background(), origRootID, maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.NoError(err)
	require.NotNil(newProof)
	require.NoError(newProof.Verify(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), origRootID, db.tokenSize, db.hasher, len(newProof.KeyChanges)))
}

func Test_History_Branching2Nodes(t *testing.T) {
	require := require.New(t)

	db, err := newDB(
		context.Background(),
		memdb.New(),
		NewConfig(),
	)
	require.NoError(err)
	batch := db.NewBatch()
	require.NoError(batch.Put([]byte("key"), []byte("value")))
	require.NoError(batch.Write())

	origProof, err := db.GetRangeProof(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.NoError(err)
	require.NotNil(origProof)
	origRootID := db.rootID
	require.NoError(origProof.Verify(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), origRootID, db.tokenSize, db.hasher, len(origProof.KeyChanges)))

	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("k"), []byte("v")))
	require.NoError(batch.Write())
	newProof, err := db.GetRangeProofAtRoot(context.Background(), origRootID, maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.NoError(err)
	require.NotNil(newProof)
	require.NoError(newProof.Verify(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), origRootID, db.tokenSize, db.hasher, len(newProof.KeyChanges)))
}

func Test_History_Branching3Nodes(t *testing.T) {
	require := require.New(t)

	db, err := newDB(
		context.Background(),
		memdb.New(),
		NewConfig(),
	)
	require.NoError(err)
	batch := db.NewBatch()
	require.NoError(batch.Put([]byte("key123"), []byte("value123")))
	require.NoError(batch.Write())

	origProof, err := db.GetRangeProof(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.NoError(err)
	require.NotNil(origProof)
	origRootID := db.rootID
	require.NoError(origProof.Verify(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), origRootID, db.tokenSize, db.hasher, len(origProof.KeyChanges)))

	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("key321"), []byte("value321")))
	require.NoError(batch.Write())
	newProof, err := db.GetRangeProofAtRoot(context.Background(), origRootID, maybe.Some([]byte("k")), maybe.Some([]byte("key3")), 10)
	require.NoError(err)
	require.NotNil(newProof)
	require.NoError(newProof.Verify(context.Background(), maybe.Some([]byte("k")), maybe.Some([]byte("key3")), origRootID, db.tokenSize, db.hasher, len(newProof.KeyChanges)))
}

func Test_History_MaxLength(t *testing.T) {
	require := require.New(t)

	config := NewConfig()
	config.HistoryLength = 2
	db, err := newDB(
		context.Background(),
		memdb.New(),
		config,
	)
	require.NoError(err)

	batch := db.NewBatch()
	require.NoError(batch.Put([]byte("key"), []byte("value")))
	require.NoError(batch.Write())

	oldRoot, err := db.GetMerkleRoot(context.Background())
	require.NoError(err)

	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("k"), []byte("v")))
	require.NoError(batch.Write())

	require.Contains(db.history.lastChangesInsertNumber, oldRoot)

	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("k1"), []byte("v2"))) // Overwrites oldest element in history
	require.NoError(batch.Write())

	require.NotContains(db.history.lastChangesInsertNumber, oldRoot)
}

func Test_Change_List(t *testing.T) {
	require := require.New(t)

	db, err := newDB(
		context.Background(),
		memdb.New(),
		NewConfig(),
	)
	require.NoError(err)

	emptyRoot, err := db.GetMerkleRoot(context.Background())
	require.NoError(err)

	batch := db.NewBatch()
	require.NoError(batch.Put([]byte("key20"), []byte("value20")))
	require.NoError(batch.Put([]byte("key21"), []byte("value21")))
	require.NoError(batch.Put([]byte("key22"), []byte("value22")))
	require.NoError(batch.Put([]byte("key23"), []byte("value23")))
	require.NoError(batch.Put([]byte("key24"), []byte("value24")))
	require.NoError(batch.Write())
	startRoot, err := db.GetMerkleRoot(context.Background())
	require.NoError(err)

	changes, err := db.history.getValueChanges(emptyRoot, startRoot, maybe.Nothing[[]byte](), maybe.Nothing[[]byte](), 100)
	require.NoError(err)
	require.Equal([]valueChange{
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Nothing[[]byte](),
				after:  maybe.Some([]byte("value20")),
			},
			key: ToKey([]byte("key20")),
		},
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Nothing[[]byte](),
				after:  maybe.Some([]byte("value21")),
			},
			key: ToKey([]byte("key21")),
		},
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Nothing[[]byte](),
				after:  maybe.Some([]byte("value22")),
			},
			key: ToKey([]byte("key22")),
		},
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Nothing[[]byte](),
				after:  maybe.Some([]byte("value23")),
			},
			key: ToKey([]byte("key23")),
		},
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Nothing[[]byte](),
				after:  maybe.Some([]byte("value24")),
			},
			key: ToKey([]byte("key24")),
		},
	}, changes)

	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("key25"), []byte("value25")))
	require.NoError(batch.Put([]byte("key26"), []byte("value26")))
	require.NoError(batch.Put([]byte("key27"), []byte("value27")))
	require.NoError(batch.Put([]byte("key28"), []byte("value28")))
	require.NoError(batch.Put([]byte("key29"), []byte("value29")))
	require.NoError(batch.Write())

	endRoot, err := db.GetMerkleRoot(context.Background())
	require.NoError(err)

	changes, err = db.history.getValueChanges(startRoot, endRoot, maybe.Nothing[[]byte](), maybe.Nothing[[]byte](), 100)
	require.NoError(err)
	require.Equal([]valueChange{
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Nothing[[]byte](),
				after:  maybe.Some([]byte("value25")),
			},
			key: ToKey([]byte("key25")),
		},
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Nothing[[]byte](),
				after:  maybe.Some([]byte("value26")),
			},
			key: ToKey([]byte("key26")),
		},
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Nothing[[]byte](),
				after:  maybe.Some([]byte("value27")),
			},
			key: ToKey([]byte("key27")),
		},
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Nothing[[]byte](),
				after:  maybe.Some([]byte("value28")),
			},
			key: ToKey([]byte("key28")),
		},
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Nothing[[]byte](),
				after:  maybe.Some([]byte("value29")),
			},
			key: ToKey([]byte("key29")),
		},
	}, changes)

	batch = db.NewBatch()
	require.NoError(batch.Put([]byte("key30"), []byte{}))
	require.NoError(batch.Put([]byte("key31"), []byte("value31")))
	require.NoError(batch.Put([]byte("key32"), []byte("value32")))
	require.NoError(batch.Delete([]byte("key21")))
	require.NoError(batch.Delete([]byte("key22")))
	require.NoError(batch.Put([]byte("key24"), []byte("value24new")))
	require.NoError(batch.Write())

	endRoot, err = db.GetMerkleRoot(context.Background())
	require.NoError(err)

	changes, err = db.history.getValueChanges(startRoot, endRoot, maybe.Some[[]byte]([]byte("key22")), maybe.Some[[]byte]([]byte("key31")), 8)
	require.NoError(err)

	require.Equal([]valueChange{
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Some([]byte("value22")),
				after:  maybe.Nothing[[]byte](),
			},
			key: ToKey([]byte("key22")),
		},
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Some([]byte("value24")),
				after:  maybe.Some([]byte("value24new")),
			},
			key: ToKey([]byte("key24")),
		},
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Nothing[[]byte](),
				after:  maybe.Some([]byte("value25")),
			},
			key: ToKey([]byte("key25")),
		},
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Nothing[[]byte](),
				after:  maybe.Some([]byte("value26")),
			},
			key: ToKey([]byte("key26")),
		},
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Nothing[[]byte](),
				after:  maybe.Some([]byte("value27")),
			},
			key: ToKey([]byte("key27")),
		},
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Nothing[[]byte](),
				after:  maybe.Some([]byte("value28")),
			},
			key: ToKey([]byte("key28")),
		},
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Nothing[[]byte](),
				after:  maybe.Some([]byte("value29")),
			},
			key: ToKey([]byte("key29")),
		},
		{
			change: &change[maybe.Maybe[[]byte]]{
				before: maybe.Nothing[[]byte](),
				after:  maybe.Some([]byte{}),
			},
			key: ToKey([]byte("key30")),
		},
	}, changes)
}

func TestHistoryRecord(t *testing.T) {
	require := require.New(t)

	maxHistoryLen := 3
	th := newTrieHistory(maxHistoryLen)

	changes := []*changeSummary{}
	for i := 0; i < maxHistoryLen; i++ { // Fill the history
		changes = append(changes, &changeSummary{rootID: ids.GenerateTestID()})

		th.record(changes[i])
		require.Equal(uint64(i+1), th.getNextInsertNumber())
		require.Equal(i+1, th.history.Len())
		require.Len(th.lastChangesInsertNumber, i+1)
		require.Contains(th.lastChangesInsertNumber, changes[i].rootID)
		changeAndIndex, ok := th.getRootChanges(changes[i].rootID)
		require.True(ok)
		require.Equal(uint64(i), changeAndIndex.insertNumber)
		got, ok := th.history.Index(int(changeAndIndex.insertNumber))
		require.True(ok)
		require.Equal(changes[i], got.changeSummary)
	}
	// history is [changes[0], changes[1], changes[2]]

	// Add a new change
	change3 := &changeSummary{rootID: ids.GenerateTestID()}
	th.record(change3)
	// history is [changes[1], changes[2], change3]
	require.Equal(uint64(maxHistoryLen+1), th.getNextInsertNumber())
	require.Equal(maxHistoryLen, th.history.Len())
	require.Len(th.lastChangesInsertNumber, maxHistoryLen)
	require.Contains(th.lastChangesInsertNumber, change3.rootID)
	changeAndIndex, ok := th.getRootChanges(change3.rootID)
	require.True(ok)
	require.Equal(uint64(maxHistoryLen), changeAndIndex.insertNumber)
	got, ok := th.history.PeekRight()
	require.True(ok)
	require.Equal(change3, got.changeSummary)

	// // Make sure the oldest change was evicted
	require.NotContains(th.lastChangesInsertNumber, changes[0].rootID)
	oldestChange, ok := th.history.PeekLeft()
	require.True(ok)
	require.Equal(uint64(1), oldestChange.insertNumber)

	// Add another change which was the same root ID as changes[2]
	change4 := &changeSummary{rootID: changes[2].rootID}
	th.record(change4)
	// history is [changes[2], change3, change4]

	change5 := &changeSummary{rootID: ids.GenerateTestID()}
	th.record(change5)
	// history is [change3, change4, change5]

	// Make sure that even though changes[2] was evicted, we still remember
	// that the most recent change resulting in that change's root ID.
	require.Len(th.lastChangesInsertNumber, maxHistoryLen)
	require.Contains(th.lastChangesInsertNumber, changes[2].rootID)
	changeAndIndex, ok = th.getRootChanges(changes[2].rootID)
	require.True(ok)
	require.Equal(uint64(maxHistoryLen+1), changeAndIndex.insertNumber)

	// Make sure [t.history] is right.
	require.Equal(maxHistoryLen, th.history.Len())
	got, ok = th.history.PopLeft()
	require.True(ok)
	require.Equal(uint64(maxHistoryLen), got.insertNumber)
	require.Equal(change3.rootID, got.rootID)
	got, ok = th.history.PopLeft()
	require.True(ok)
	require.Equal(uint64(maxHistoryLen+1), got.insertNumber)
	require.Equal(change4.rootID, got.rootID)
	got, ok = th.history.PopLeft()
	require.True(ok)
	require.Equal(uint64(maxHistoryLen+2), got.insertNumber)
	require.Equal(change5.rootID, got.rootID)
}

func TestHistoryKeyChangeRollback(t *testing.T) {
	require := require.New(t)

	db, err := getBasicDB()
	require.NoError(err)

	keyChangesBatches := [][]database.BatchOp{
		{
			// First changes
			{
				Key:   []byte("key1"),
				Value: []byte("value1a"),
			},
			{
				Key:   []byte("key2"),
				Value: []byte("value2a"),
			},
		},
		{
			// Second changes
			{
				Key:   []byte("key1"),
				Value: []byte("value1b"),
			},
			{
				Key:   []byte("key2"),
				Value: []byte("value2b"),
			},
		},
		{
			// Third changes
			{
				Key:   []byte("key1"),
				Value: []byte("value1a"),
			},
		},
	}

	rootIDs := []ids.ID{}
	for _, batchOps := range keyChangesBatches {
		view, err := db.NewView(context.Background(), ViewChanges{
			BatchOps: batchOps,
		})
		require.NoError(err)

		require.NoError(view.CommitToDB(context.Background()))

		rootID, err := db.GetMerkleRoot(context.Background())
		require.NoError(err)

		rootIDs = append(rootIDs, rootID)
	}

	changeProof, err := db.GetChangeProof(context.Background(), rootIDs[0], rootIDs[len(rootIDs)-1], maybe.Nothing[[]byte](), maybe.Nothing[[]byte](), 100)
	require.NoError(err)

	require.Equal([]KeyChange{
		{
			Key:   []byte("key2"),
			Value: maybe.Some([]byte("value2b")),
		},
	}, changeProof.KeyChanges)
}
