feat: add simulation for nft module (cosmos#10522)

<!--
The default pull request template is for types feat, fix, or refactor.
For other templates, add one of the following parameters to the url:
- template=docs.md
- template=other.md
-->

## Description

Add nft module simulation and unit test,refer cosmos#9826

<!-- Add a description of the changes that this PR introduces and the files that
are the most critical to review. -->

---

### Author Checklist

*All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.*

I have...

- [ ] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [ ] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#pr-targeting))
- [ ] provided a link to the relevant issue or specification
- [ ] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/master/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
- [ ] reviewed "Files changed" and left comments if necessary
- [ ] confirmed all CI checks have passed

### Reviewers Checklist

*All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.*

I have...

- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed 
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

simapp/app.go

@@ -391,6 +391,7 @@ func NewSimApp(
 		params.NewAppModule(app.ParamsKeeper),
 		evidence.NewAppModule(app.EvidenceKeeper),
 		authzmodule.NewAppModule(appCodec, app.AuthzKeeper, app.AccountKeeper, app.BankKeeper, app.interfaceRegistry),
+		nftmodule.NewAppModule(appCodec, app.NFTKeeper, app.AccountKeeper, app.BankKeeper, app.interfaceRegistry),
 	)
 
 	app.sm.RegisterStoreDecoders()

x/nft/module/module.go

@@ -3,6 +3,7 @@ package nft
 import (
 	"context"
 	"encoding/json"
+	"math/rand"
 
 	"github.com/gorilla/mux"
 	"github.com/grpc-ecosystem/grpc-gateway/runtime"
@@ -15,15 +16,18 @@ import (
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
 	"github.com/cosmos/cosmos-sdk/types/module"
+	simtypes "github.com/cosmos/cosmos-sdk/types/simulation"
 
 	"github.com/cosmos/cosmos-sdk/x/nft"
 	"github.com/cosmos/cosmos-sdk/x/nft/client/cli"
 	"github.com/cosmos/cosmos-sdk/x/nft/keeper"
+	"github.com/cosmos/cosmos-sdk/x/nft/simulation"
 )
 
 var (
-	_ module.AppModule      = AppModule{}
-	_ module.AppModuleBasic = AppModuleBasic{}
+	_ module.AppModule           = AppModule{}
+	_ module.AppModuleBasic      = AppModuleBasic{}
+	_ module.AppModuleSimulation = AppModule{}
 )
 
 // AppModuleBasic defines the basic application module used by the nft module.
@@ -159,3 +163,37 @@ func (am AppModule) BeginBlock(ctx sdk.Context, req abci.RequestBeginBlock) {}
 func (am AppModule) EndBlock(ctx sdk.Context, _ abci.RequestEndBlock) []abci.ValidatorUpdate {
 	return []abci.ValidatorUpdate{}
 }
+
+// ____________________________________________________________________________
+
+// AppModuleSimulation functions
+
+// GenerateGenesisState creates a randomized GenState of the nft module.
+func (AppModule) GenerateGenesisState(simState *module.SimulationState) {
+	simulation.RandomizedGenState(simState)
+}
+
+// ProposalContents returns all the nft content functions used to
+// simulate governance proposals.
+func (am AppModule) ProposalContents(simState module.SimulationState) []simtypes.WeightedProposalContent {
+	return nil
+}
+
+// RandomizedParams creates randomized nft param changes for the simulator.
+func (AppModule) RandomizedParams(r *rand.Rand) []simtypes.ParamChange {
+	return nil
+}
+
+// RegisterStoreDecoder registers a decoder for nft module's types
+func (am AppModule) RegisterStoreDecoder(sdr sdk.StoreDecoderRegistry) {
+	sdr[keeper.StoreKey] = simulation.NewDecodeStore(am.cdc)
+}
+
+// WeightedOperations returns the all the nft module operations with their respective weights.
+func (am AppModule) WeightedOperations(simState module.SimulationState) []simtypes.WeightedOperation {
+	return simulation.WeightedOperations(
+		am.registry,
+		simState.AppParams, simState.Cdc,
+		am.accountKeeper, am.bankKeeper, am.keeper,
+	)
+}

x/nft/simulation/decoder.go

@@ -0,0 +1,45 @@
+package simulation
+
+import (
+	"bytes"
+	"fmt"
+
+	"github.com/cosmos/cosmos-sdk/codec"
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/cosmos/cosmos-sdk/types/kv"
+	"github.com/cosmos/cosmos-sdk/x/nft"
+	"github.com/cosmos/cosmos-sdk/x/nft/keeper"
+)
+
+// NewDecodeStore returns a decoder function closure that umarshals the KVPair's
+// Value to the corresponding nft type.
+func NewDecodeStore(cdc codec.Codec) func(kvA, kvB kv.Pair) string {
+	return func(kvA, kvB kv.Pair) string {
+		switch {
+		case bytes.Equal(kvA.Key[:1], keeper.ClassKey):
+			var classA, classB nft.Class
+			cdc.MustUnmarshal(kvA.Value, &classA)
+			cdc.MustUnmarshal(kvB.Value, &classB)
+			return fmt.Sprintf("%v\n%v", classA, classB)
+		case bytes.Equal(kvA.Key[:1], keeper.NFTKey):
+			var nftA, nftB nft.NFT
+			cdc.MustUnmarshal(kvA.Value, &nftA)
+			cdc.MustUnmarshal(kvB.Value, &nftB)
+			return fmt.Sprintf("%v\n%v", nftA, nftB)
+		case bytes.Equal(kvA.Key[:1], keeper.NFTOfClassByOwnerKey):
+			return fmt.Sprintf("%v\n%v", kvA.Value, kvB.Value)
+		case bytes.Equal(kvA.Key[:1], keeper.OwnerKey):
+			var ownerA, ownerB sdk.AccAddress
+			ownerA = sdk.AccAddress(kvA.Value)
+			ownerB = sdk.AccAddress(kvB.Value)
+			return fmt.Sprintf("%v\n%v", ownerA, ownerB)
+		case bytes.Equal(kvA.Key[:1], keeper.ClassTotalSupply):
+			var supplyA, supplyB uint64
+			supplyA = sdk.BigEndianToUint64(kvA.Value)
+			supplyB = sdk.BigEndianToUint64(kvB.Value)
+			return fmt.Sprintf("%v\n%v", supplyA, supplyB)
+		default:
+			panic(fmt.Sprintf("invalid nft key %X", kvA.Key))
+		}
+	}
+}

x/nft/simulation/decoder_test.go

@@ -0,0 +1,84 @@
+package simulation_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/cosmos/cosmos-sdk/crypto/keys/ed25519"
+	"github.com/cosmos/cosmos-sdk/simapp"
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/cosmos/cosmos-sdk/types/kv"
+	"github.com/cosmos/cosmos-sdk/x/nft"
+	"github.com/cosmos/cosmos-sdk/x/nft/keeper"
+	"github.com/cosmos/cosmos-sdk/x/nft/simulation"
+)
+
+var (
+	ownerPk1   = ed25519.GenPrivKey().PubKey()
+	ownerAddr1 = sdk.AccAddress(ownerPk1.Address())
+)
+
+func TestDecodeStore(t *testing.T) {
+	cdc := simapp.MakeTestEncodingConfig().Codec
+	dec := simulation.NewDecodeStore(cdc)
+
+	class := nft.Class{
+		Id:          "ClassID",
+		Name:        "ClassName",
+		Symbol:      "ClassSymbol",
+		Description: "ClassDescription",
+		Uri:         "ClassURI",
+	}
+	classBz, err := cdc.Marshal(&class)
+	require.NoError(t, err)
+
+	nft := nft.NFT{
+		ClassId: "ClassID",
+		Id:      "NFTID",
+		Uri:     "NFTURI",
+	}
+	nftBz, err := cdc.Marshal(&nft)
+	require.NoError(t, err)
+
+	nftOfClassByOwnerValue := []byte{0x01}
+
+	totalSupply := 1
+	totalSupplyBz := sdk.Uint64ToBigEndian(1)
+
+	kvPairs := kv.Pairs{
+		Pairs: []kv.Pair{
+			{Key: []byte(keeper.ClassKey), Value: classBz},
+			{Key: []byte(keeper.NFTKey), Value: nftBz},
+			{Key: []byte(keeper.NFTOfClassByOwnerKey), Value: nftOfClassByOwnerValue},
+			{Key: []byte(keeper.OwnerKey), Value: ownerAddr1},
+			{Key: []byte(keeper.ClassTotalSupply), Value: totalSupplyBz},
+			{Key: []byte{0x99}, Value: []byte{0x99}},
+		},
+	}
+
+	tests := []struct {
+		name        string
+		expectErr   bool
+		expectedLog string
+	}{
+		{"Class", false, fmt.Sprintf("%v\n%v", class, class)},
+		{"NFT", false, fmt.Sprintf("%v\n%v", nft, nft)},
+		{"NFTOfClassByOwnerKey", false, fmt.Sprintf("%v\n%v", nftOfClassByOwnerValue, nftOfClassByOwnerValue)},
+		{"OwnerKey", false, fmt.Sprintf("%v\n%v", ownerAddr1, ownerAddr1)},
+		{"ClassTotalSupply", false, fmt.Sprintf("%v\n%v", totalSupply, totalSupply)},
+		{"other", true, ""},
+	}
+
+	for i, tt := range tests {
+		i, tt := i, tt
+		t.Run(tt.name, func(t *testing.T) {
+			if tt.expectErr {
+				require.Panics(t, func() { dec(kvPairs.Pairs[i], kvPairs.Pairs[i]) }, tt.name)
+			} else {
+				require.Equal(t, tt.expectedLog, dec(kvPairs.Pairs[i], kvPairs.Pairs[i]), tt.name)
+			}
+		})
+	}
+}

x/nft/simulation/genesis.go

@@ -0,0 +1,67 @@
+package simulation
+
+import (
+	"math/rand"
+
+	"github.com/cosmos/cosmos-sdk/types/module"
+	simtypes "github.com/cosmos/cosmos-sdk/types/simulation"
+	"github.com/cosmos/cosmos-sdk/x/nft"
+)
+
+// genClasses returns a slice of nft class.
+func genClasses(r *rand.Rand, accounts []simtypes.Account) []*nft.Class {
+	classes := make([]*nft.Class, len(accounts)-1)
+	for i := 0; i < len(accounts)-1; i++ {
+		classes[i] = &nft.Class{
+			Id:          simtypes.RandStringOfLength(r, 10),
+			Name:        simtypes.RandStringOfLength(r, 10),
+			Symbol:      simtypes.RandStringOfLength(r, 10),
+			Description: simtypes.RandStringOfLength(r, 10),
+			Uri:         simtypes.RandStringOfLength(r, 10),
+		}
+	}
+	return classes
+}
+
+// genNFT returns a slice of nft.
+func genNFT(r *rand.Rand, classID string, accounts []simtypes.Account) []*nft.Entry {
+	entries := make([]*nft.Entry, len(accounts)-1)
+	for i := 0; i < len(accounts)-1; i++ {
+		owner := accounts[i]
+		entries[i] = &nft.Entry{
+			Owner: owner.Address.String(),
+			Nfts: []*nft.NFT{
+				{
+					ClassId: classID,
+					Id:      simtypes.RandStringOfLength(r, 10),
+					Uri:     simtypes.RandStringOfLength(r, 10),
+				},
+			},
+		}
+	}
+	return entries
+}
+
+// RandomizedGenState generates a random GenesisState for nft.
+func RandomizedGenState(simState *module.SimulationState) {
+	var classes []*nft.Class
+	simState.AppParams.GetOrGenerate(
+		simState.Cdc, "nft", &classes, simState.Rand,
+		func(r *rand.Rand) { classes = genClasses(r, simState.Accounts) },
+	)
+
+	var entries []*nft.Entry
+	simState.AppParams.GetOrGenerate(
+		simState.Cdc, "nft", &entries, simState.Rand,
+		func(r *rand.Rand) {
+			class := classes[r.Int63n(int64(len(classes)))]
+			entries = genNFT(r, class.Id, simState.Accounts)
+		},
+	)
+
+	nftGenesis := &nft.GenesisState{
+		Classes: classes,
+		Entries: entries,
+	}
+	simState.GenState[nft.ModuleName] = simState.Cdc.MustMarshalJSON(nftGenesis)
+}

x/nft/simulation/genesis_test.go

@@ -0,0 +1,39 @@
+package simulation_test
+
+import (
+	"encoding/json"
+	"math/rand"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/cosmos/cosmos-sdk/simapp"
+	"github.com/cosmos/cosmos-sdk/types/module"
+	simtypes "github.com/cosmos/cosmos-sdk/types/simulation"
+	"github.com/cosmos/cosmos-sdk/x/nft"
+	"github.com/cosmos/cosmos-sdk/x/nft/simulation"
+)
+
+func TestRandomizedGenState(t *testing.T) {
+	app := simapp.Setup(t, false)
+
+	s := rand.NewSource(1)
+	r := rand.New(s)
+
+	simState := module.SimulationState{
+		AppParams:    make(simtypes.AppParams),
+		Cdc:          app.AppCodec(),
+		Rand:         r,
+		NumBonded:    3,
+		Accounts:     simtypes.RandomAccounts(r, 3),
+		InitialStake: 1000,
+		GenState:     make(map[string]json.RawMessage),
+	}
+
+	simulation.RandomizedGenState(&simState)
+	var nftGenesis nft.GenesisState
+	simState.Cdc.MustUnmarshalJSON(simState.GenState[nft.ModuleName], &nftGenesis)
+
+	require.Len(t, nftGenesis.Classes, len(simState.Accounts)-1)
+	require.Len(t, nftGenesis.Entries, len(simState.Accounts)-1)
+}