marbles_chaincode.go

/*
 SPDX-License-Identifier: Apache-2.0
*/

// ====CHAINCODE EXECUTION SAMPLES (CLI) ==================

// ==== Invoke marbles ====
// peer chaincode invoke -C myc1 -n marbles -c '{"Args":["initMarble","marble1","blue","35","tom"]}'
// peer chaincode invoke -C myc1 -n marbles -c '{"Args":["initMarble","marble2","red","50","tom"]}'
// peer chaincode invoke -C myc1 -n marbles -c '{"Args":["initMarble","marble3","blue","70","tom"]}'
// peer chaincode invoke -C myc1 -n marbles -c '{"Args":["transferMarble","marble2","jerry"]}'
// peer chaincode invoke -C myc1 -n marbles -c '{"Args":["transferMarblesBasedOnColor","blue","jerry"]}'
// peer chaincode invoke -C myc1 -n marbles -c '{"Args":["delete","marble1"]}'

// ==== Query marbles ====
// peer chaincode query -C myc1 -n marbles -c '{"Args":["readMarble","marble1"]}'
// peer chaincode query -C myc1 -n marbles -c '{"Args":["getMarblesByRange","marble1","marble3"]}'
// peer chaincode query -C myc1 -n marbles -c '{"Args":["getHistoryForMarble","marble1"]}'

// Rich Query (Only supported if CouchDB is used as state database):
//   peer chaincode query -C myc1 -n marbles -c '{"Args":["queryMarblesByOwner","tom"]}'
//   peer chaincode query -C myc1 -n marbles -c '{"Args":["queryMarbles","{\"selector\":{\"owner\":\"tom\"}}"]}'

// INDEXES TO SUPPORT COUCHDB RICH QUERIES
//
// Indexes in CouchDB are required in order to make JSON queries efficient and are required for
// any JSON query with a sort. As of Hyperledger Fabric 1.1, indexes may be packaged alongside
// chaincode in a META-INF/statedb/couchdb/indexes directory. Each index must be defined in its own
// text file with extension *.json with the index definition formatted in JSON following the
// CouchDB index JSON syntax as documented at:
// http://docs.couchdb.org/en/2.1.1/api/database/find.html#db-index
//
// This marbles02 example chaincode demonstrates a packaged
// index which you can find in META-INF/statedb/couchdb/indexes/indexOwner.json.
// For deployment of chaincode to production environments, it is recommended
// to define any indexes alongside chaincode so that the chaincode and supporting indexes
// are deployed automatically as a unit, once the chaincode has been installed on a peer and
// instantiated on a channel. See Hyperledger Fabric documentation for more details.
//
// If you have access to the your peer's CouchDB state database in a development environment,
// you may want to iteratively test various indexes in support of your chaincode queries.  You
// can use the CouchDB Fauxton interface or a command line curl utility to create and update
// indexes. Then once you finalize an index, include the index definition alongside your
// chaincode in the META-INF/statedb/couchdb/indexes directory, for packaging and deployment
// to managed environments.
//
// In the examples below you can find index definitions that support marbles02
// chaincode queries, along with the syntax that you can use in development environments
// to create the indexes in the CouchDB Fauxton interface or a curl command line utility.
//

//Example hostname:port configurations to access CouchDB.
//
//To access CouchDB docker container from within another docker container or from vagrant environments:
// http://couchdb:5984/
//
//Inside couchdb docker container
// http://127.0.0.1:5984/

// Index for docType, owner.
//
// Index definition for use with Fauxton interface
// {"index":{"fields":["docType","owner"]},"ddoc":"indexOwnerDoc", "name":"indexOwner","type":"json"}
//
// Example curl command line to define index in the CouchDB channel_chaincode database
// curl -i -X POST -H "Content-Type: application/json" -d "{\"index\":{\"fields\":[\"docType\",\"owner\"]},\"name\":\"indexOwner\",\"ddoc\":\"indexOwnerDoc\",\"type\":\"json\"}" http://hostname:port/myc1_marbles/_index
//

// Index for docType, owner, size (descending order).
//
// Index definition for use with Fauxton interface
// {"index":{"fields":[{"size":"desc"},{"docType":"desc"},{"owner":"desc"}]},"ddoc":"indexSizeSortDoc", "name":"indexSizeSortDesc","type":"json"}
//
// Example curl command line to define index in the CouchDB channel_chaincode database
// curl -i -X POST -H "Content-Type: application/json" -d "{\"index\":{\"fields\":[{\"size\":\"desc\"},{\"docType\":\"desc\"},{\"owner\":\"desc\"}]},\"ddoc\":\"indexSizeSortDoc\", \"name\":\"indexSizeSortDesc\",\"type\":\"json\"}" http://hostname:port/myc1_marbles/_index

// Rich Query with index design doc and index name specified (Only supported if CouchDB is used as state database):
//   peer chaincode query -C myc1 -n marbles -c '{"Args":["queryMarbles","{\"selector\":{\"docType\":\"marble\",\"owner\":\"tom\"}, \"use_index\":[\"_design/indexOwnerDoc\", \"indexOwner\"]}"]}'

// Rich Query with index design doc specified only (Only supported if CouchDB is used as state database):
//   peer chaincode query -C myc1 -n marbles -c '{"Args":["queryMarbles","{\"selector\":{\"docType\":{\"$eq\":\"marble\"},\"owner\":{\"$eq\":\"tom\"},\"size\":{\"$gt\":0}},\"fields\":[\"docType\",\"owner\",\"size\"],\"sort\":[{\"size\":\"desc\"}],\"use_index\":\"_design/indexSizeSortDoc\"}"]}'

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"strconv"
	"strings"
	"time"

	"github.com/hyperledger/fabric/core/chaincode/shim"
	pb "github.com/hyperledger/fabric/protos/peer"
)

// SimpleChaincode example simple Chaincode implementation
type SimpleChaincode struct {
}

type marble struct {
	ObjectType string `json:"docType"` //docType is used to distinguish the various types of objects in state database
	Name       string `json:"name"`    //the fieldtags are needed to keep case from bouncing around
	Color      string `json:"color"`
	Size       int    `json:"size"`
	Owner      string `json:"owner"`
}

// ===================================================================================
// Main
// ===================================================================================
func main() {
	err := shim.Start(new(SimpleChaincode))
	if err != nil {
		fmt.Printf("Error starting Simple chaincode: %s", err)
	}
}

// Init initializes chaincode
// ===========================
func (t *SimpleChaincode) Init(stub shim.ChaincodeStubInterface) pb.Response {
	return shim.Success(nil)
}

// Invoke - Our entry point for Invocations
// ========================================
func (t *SimpleChaincode) Invoke(stub shim.ChaincodeStubInterface) pb.Response {
	function, args := stub.GetFunctionAndParameters()
	fmt.Println("invoke is running " + function)

	// Handle different functions
	if function == "initMarble" { //create a new marble
		return t.initMarble(stub, args)
	} else if function == "transferMarble" { //change owner of a specific marble
		return t.transferMarble(stub, args)
	} else if function == "transferMarblesBasedOnColor" { //transfer all marbles of a certain color
		return t.transferMarblesBasedOnColor(stub, args)
	} else if function == "delete" { //delete a marble
		return t.delete(stub, args)
	} else if function == "readMarble" { //read a marble
		return t.readMarble(stub, args)
	} else if function == "queryMarblesByOwner" { //find marbles for owner X using rich query
		return t.queryMarblesByOwner(stub, args)
	} else if function == "queryMarbles" { //find marbles based on an ad hoc rich query
		return t.queryMarbles(stub, args)
	} else if function == "getHistoryForMarble" { //get history of values for a marble
		return t.getHistoryForMarble(stub, args)
	} else if function == "getMarblesByRange" { //get marbles based on range query
		return t.getMarblesByRange(stub, args)
	}

	fmt.Println("invoke did not find func: " + function) //error
	return shim.Error("Received unknown function invocation")
}

// ============================================================
// initMarble - create a new marble, store into chaincode state
// ============================================================
func (t *SimpleChaincode) initMarble(stub shim.ChaincodeStubInterface, args []string) pb.Response {
	var err error

	//   0       1       2     3
	// "asdf", "blue", "35", "bob"
	if len(args) != 4 {
		return shim.Error("Incorrect number of arguments. Expecting 4")
	}

	// ==== Input sanitation ====
	fmt.Println("- start init marble")
	if len(args[0]) <= 0 {
		return shim.Error("1st argument must be a non-empty string")
	}
	if len(args[1]) <= 0 {
		return shim.Error("2nd argument must be a non-empty string")
	}
	if len(args[2]) <= 0 {
		return shim.Error("3rd argument must be a non-empty string")
	}
	if len(args[3]) <= 0 {
		return shim.Error("4th argument must be a non-empty string")
	}
	marbleName := args[0]
	color := strings.ToLower(args[1])
	owner := strings.ToLower(args[3])
	size, err := strconv.Atoi(args[2])
	if err != nil {
		return shim.Error("3rd argument must be a numeric string")
	}

	// ==== Check if marble already exists ====
	marbleAsBytes, err := stub.GetState(marbleName)
	if err != nil {
		return shim.Error("Failed to get marble: " + err.Error())
	} else if marbleAsBytes != nil {
		fmt.Println("This marble already exists: " + marbleName)
		return shim.Error("This marble already exists: " + marbleName)
	}

	// ==== Create marble object and marshal to JSON ====
	objectType := "marble"
	marble := &marble{objectType, marbleName, color, size, owner}
	marbleJSONasBytes, err := json.Marshal(marble)
	if err != nil {
		return shim.Error(err.Error())
	}
	//Alternatively, build the marble json string manually if you don't want to use struct marshalling
	//marbleJSONasString := `{"docType":"Marble",  "name": "` + marbleName + `", "color": "` + color + `", "size": ` + strconv.Itoa(size) + `, "owner": "` + owner + `"}`
	//marbleJSONasBytes := []byte(str)

	// === Save marble to state ===
	err = stub.PutState(marbleName, marbleJSONasBytes)
	if err != nil {
		return shim.Error(err.Error())
	}

	//  ==== Index the marble to enable color-based range queries, e.g. return all blue marbles ====
	//  An 'index' is a normal key/value entry in state.
	//  The key is a composite key, with the elements that you want to range query on listed first.
	//  In our case, the composite key is based on indexName~color~name.
	//  This will enable very efficient state range queries based on composite keys matching indexName~color~*
	indexName := "color~name"
	colorNameIndexKey, err := stub.CreateCompositeKey(indexName, []string{marble.Color, marble.Name})
	if err != nil {
		return shim.Error(err.Error())
	}
	//  Save index entry to state. Only the key name is needed, no need to store a duplicate copy of the marble.
	//  Note - passing a 'nil' value will effectively delete the key from state, therefore we pass null character as value
	value := []byte{0x00}
	stub.PutState(colorNameIndexKey, value)

	// ==== Marble saved and indexed. Return success ====
	fmt.Println("- end init marble")
	return shim.Success(nil)
}

// ===============================================
// readMarble - read a marble from chaincode state
// ===============================================
func (t *SimpleChaincode) readMarble(stub shim.ChaincodeStubInterface, args []string) pb.Response {
	var name, jsonResp string
	var err error

	if len(args) != 1 {
		return shim.Error("Incorrect number of arguments. Expecting name of the marble to query")
	}

	name = args[0]
	valAsbytes, err := stub.GetState(name) //get the marble from chaincode state
	if err != nil {
		jsonResp = "{\"Error\":\"Failed to get state for " + name + "\"}"
		return shim.Error(jsonResp)
	} else if valAsbytes == nil {
		jsonResp = "{\"Error\":\"Marble does not exist: " + name + "\"}"
		return shim.Error(jsonResp)
	}

	return shim.Success(valAsbytes)
}

// ==================================================
// delete - remove a marble key/value pair from state
// ==================================================
func (t *SimpleChaincode) delete(stub shim.ChaincodeStubInterface, args []string) pb.Response {
	var jsonResp string
	var marbleJSON marble
	if len(args) != 1 {
		return shim.Error("Incorrect number of arguments. Expecting 1")
	}
	marbleName := args[0]

	// to maintain the color~name index, we need to read the marble first and get its color
	valAsbytes, err := stub.GetState(marbleName) //get the marble from chaincode state
	if err != nil {
		jsonResp = "{\"Error\":\"Failed to get state for " + marbleName + "\"}"
		return shim.Error(jsonResp)
	} else if valAsbytes == nil {
		jsonResp = "{\"Error\":\"Marble does not exist: " + marbleName + "\"}"
		return shim.Error(jsonResp)
	}

	err = json.Unmarshal([]byte(valAsbytes), &marbleJSON)
	if err != nil {
		jsonResp = "{\"Error\":\"Failed to decode JSON of: " + marbleName + "\"}"
		return shim.Error(jsonResp)
	}

	err = stub.DelState(marbleName) //remove the marble from chaincode state
	if err != nil {
		return shim.Error("Failed to delete state:" + err.Error())
	}

	// maintain the index
	indexName := "color~name"
	colorNameIndexKey, err := stub.CreateCompositeKey(indexName, []string{marbleJSON.Color, marbleJSON.Name})
	if err != nil {
		return shim.Error(err.Error())
	}

	//  Delete index entry to state.
	err = stub.DelState(colorNameIndexKey)
	if err != nil {
		return shim.Error("Failed to delete state:" + err.Error())
	}
	return shim.Success(nil)
}

// ===========================================================
// transfer a marble by setting a new owner name on the marble
// ===========================================================
func (t *SimpleChaincode) transferMarble(stub shim.ChaincodeStubInterface, args []string) pb.Response {

	//   0       1
	// "name", "bob"
	if len(args) < 2 {
		return shim.Error("Incorrect number of arguments. Expecting 2")
	}

	marbleName := args[0]
	newOwner := strings.ToLower(args[1])
	fmt.Println("- start transferMarble ", marbleName, newOwner)

	marbleAsBytes, err := stub.GetState(marbleName)
	if err != nil {
		return shim.Error("Failed to get marble:" + err.Error())
	} else if marbleAsBytes == nil {
		return shim.Error("Marble does not exist")
	}

	marbleToTransfer := marble{}
	err = json.Unmarshal(marbleAsBytes, &marbleToTransfer) //unmarshal it aka JSON.parse()
	if err != nil {
		return shim.Error(err.Error())
	}
	marbleToTransfer.Owner = newOwner //change the owner

	marbleJSONasBytes, _ := json.Marshal(marbleToTransfer)
	err = stub.PutState(marbleName, marbleJSONasBytes) //rewrite the marble
	if err != nil {
		return shim.Error(err.Error())
	}

	fmt.Println("- end transferMarble (success)")
	return shim.Success(nil)
}

// ===========================================================================================
// getMarblesByRange performs a range query based on the start and end keys provided.

// Read-only function results are not typically submitted to ordering. If the read-only
// results are submitted to ordering, or if the query is used in an update transaction
// and submitted to ordering, then the committing peers will re-execute to guarantee that
// result sets are stable between endorsement time and commit time. The transaction is
// invalidated by the committing peers if the result set has changed between endorsement
// time and commit time.
// Therefore, range queries are a safe option for performing update transactions based on query results.
// ===========================================================================================
func (t *SimpleChaincode) getMarblesByRange(stub shim.ChaincodeStubInterface, args []string) pb.Response {

	if len(args) < 2 {
		return shim.Error("Incorrect number of arguments. Expecting 2")
	}

	startKey := args[0]
	endKey := args[1]

	resultsIterator, err := stub.GetStateByRange(startKey, endKey)
	if err != nil {
		return shim.Error(err.Error())
	}
	defer resultsIterator.Close()

	// buffer is a JSON array containing QueryResults
	var buffer bytes.Buffer
	buffer.WriteString("[")

	bArrayMemberAlreadyWritten := false
	for resultsIterator.HasNext() {
		queryResponse, err := resultsIterator.Next()
		if err != nil {
			return shim.Error(err.Error())
		}
		// Add a comma before array members, suppress it for the first array member
		if bArrayMemberAlreadyWritten == true {
			buffer.WriteString(",")
		}
		buffer.WriteString("{\"Key\":")
		buffer.WriteString("\"")
		buffer.WriteString(queryResponse.Key)
		buffer.WriteString("\"")

		buffer.WriteString(", \"Record\":")
		// Record is a JSON object, so we write as-is
		buffer.WriteString(string(queryResponse.Value))
		buffer.WriteString("}")
		bArrayMemberAlreadyWritten = true
	}
	buffer.WriteString("]")

	fmt.Printf("- getMarblesByRange queryResult:\n%s\n", buffer.String())

	return shim.Success(buffer.Bytes())
}

// ==== Example: GetStateByPartialCompositeKey/RangeQuery =========================================
// transferMarblesBasedOnColor will transfer marbles of a given color to a certain new owner.
// Uses a GetStateByPartialCompositeKey (range query) against color~name 'index'.
// Committing peers will re-execute range queries to guarantee that result sets are stable
// between endorsement time and commit time. The transaction is invalidated by the
// committing peers if the result set has changed between endorsement time and commit time.
// Therefore, range queries are a safe option for performing update transactions based on query results.
// ===========================================================================================
func (t *SimpleChaincode) transferMarblesBasedOnColor(stub shim.ChaincodeStubInterface, args []string) pb.Response {

	//   0       1
	// "color", "bob"
	if len(args) < 2 {
		return shim.Error("Incorrect number of arguments. Expecting 2")
	}

	color := args[0]
	newOwner := strings.ToLower(args[1])
	fmt.Println("- start transferMarblesBasedOnColor ", color, newOwner)

	// Query the color~name index by color
	// This will execute a key range query on all keys starting with 'color'
	coloredMarbleResultsIterator, err := stub.GetStateByPartialCompositeKey("color~name", []string{color})
	if err != nil {
		return shim.Error(err.Error())
	}
	defer coloredMarbleResultsIterator.Close()

	// Iterate through result set and for each marble found, transfer to newOwner
	var i int
	for i = 0; coloredMarbleResultsIterator.HasNext(); i++ {
		// Note that we don't get the value (2nd return variable), we'll just get the marble name from the composite key
		responseRange, err := coloredMarbleResultsIterator.Next()
		if err != nil {
			return shim.Error(err.Error())
		}

		// get the color and name from color~name composite key
		objectType, compositeKeyParts, err := stub.SplitCompositeKey(responseRange.Key)
		if err != nil {
			return shim.Error(err.Error())
		}
		returnedColor := compositeKeyParts[0]
		returnedMarbleName := compositeKeyParts[1]
		fmt.Printf("- found a marble from index:%s color:%s name:%s\n", objectType, returnedColor, returnedMarbleName)

		// Now call the transfer function for the found marble.
		// Re-use the same function that is used to transfer individual marbles
		response := t.transferMarble(stub, []string{returnedMarbleName, newOwner})
		// if the transfer failed break out of loop and return error
		if response.Status != shim.OK {
			return shim.Error("Transfer failed: " + response.Message)
		}
	}

	responsePayload := fmt.Sprintf("Transferred %d %s marbles to %s", i, color, newOwner)
	fmt.Println("- end transferMarblesBasedOnColor: " + responsePayload)
	return shim.Success([]byte(responsePayload))
}

// =======Rich queries =========================================================================
// Two examples of rich queries are provided below (parameterized query and ad hoc query).
// Rich queries pass a query string to the state database.
// Rich queries are only supported by state database implementations
//  that support rich query (e.g. CouchDB).
// The query string is in the syntax of the underlying state database.
// With rich queries there is no guarantee that the result set hasn't changed between
//  endorsement time and commit time, aka 'phantom reads'.
// Therefore, rich queries should not be used in update transactions, unless the
// application handles the possibility of result set changes between endorsement and commit time.
// Rich queries can be used for point-in-time queries against a peer.
// ============================================================================================

// ===== Example: Parameterized rich query =================================================
// queryMarblesByOwner queries for marbles based on a passed in owner.
// This is an example of a parameterized query where the query logic is baked into the chaincode,
// and accepting a single query parameter (owner).
// Only available on state databases that support rich query (e.g. CouchDB)
// =========================================================================================
func (t *SimpleChaincode) queryMarblesByOwner(stub shim.ChaincodeStubInterface, args []string) pb.Response {

	//   0
	// "bob"
	if len(args) < 1 {
		return shim.Error("Incorrect number of arguments. Expecting 1")
	}

	owner := strings.ToLower(args[0])

	queryString := fmt.Sprintf("{\"selector\":{\"docType\":\"marble\",\"owner\":\"%s\"}}", owner)

	queryResults, err := getQueryResultForQueryString(stub, queryString)
	if err != nil {
		return shim.Error(err.Error())
	}
	return shim.Success(queryResults)
}

// ===== Example: Ad hoc rich query ========================================================
// queryMarbles uses a query string to perform a query for marbles.
// Query string matching state database syntax is passed in and executed as is.
// Supports ad hoc queries that can be defined at runtime by the client.
// If this is not desired, follow the queryMarblesForOwner example for parameterized queries.
// Only available on state databases that support rich query (e.g. CouchDB)
// =========================================================================================
func (t *SimpleChaincode) queryMarbles(stub shim.ChaincodeStubInterface, args []string) pb.Response {

	//   0
	// "queryString"
	if len(args) < 1 {
		return shim.Error("Incorrect number of arguments. Expecting 1")
	}

	queryString := args[0]

	queryResults, err := getQueryResultForQueryString(stub, queryString)
	if err != nil {
		return shim.Error(err.Error())
	}
	return shim.Success(queryResults)
}

// =========================================================================================
// getQueryResultForQueryString executes the passed in query string.
// Result set is built and returned as a byte array containing the JSON results.
// =========================================================================================
func getQueryResultForQueryString(stub shim.ChaincodeStubInterface, queryString string) ([]byte, error) {

	fmt.Printf("- getQueryResultForQueryString queryString:\n%s\n", queryString)

	resultsIterator, err := stub.GetQueryResult(queryString)
	if err != nil {
		return nil, err
	}
	defer resultsIterator.Close()

	// buffer is a JSON array containing QueryRecords
	var buffer bytes.Buffer
	buffer.WriteString("[")

	bArrayMemberAlreadyWritten := false
	for resultsIterator.HasNext() {
		queryResponse, err := resultsIterator.Next()
		if err != nil {
			return nil, err
		}
		// Add a comma before array members, suppress it for the first array member
		if bArrayMemberAlreadyWritten == true {
			buffer.WriteString(",")
		}
		buffer.WriteString("{\"Key\":")
		buffer.WriteString("\"")
		buffer.WriteString(queryResponse.Key)
		buffer.WriteString("\"")

		buffer.WriteString(", \"Record\":")
		// Record is a JSON object, so we write as-is
		buffer.WriteString(string(queryResponse.Value))
		buffer.WriteString("}")
		bArrayMemberAlreadyWritten = true
	}
	buffer.WriteString("]")

	fmt.Printf("- getQueryResultForQueryString queryResult:\n%s\n", buffer.String())

	return buffer.Bytes(), nil
}

func (t *SimpleChaincode) getHistoryForMarble(stub shim.ChaincodeStubInterface, args []string) pb.Response {

	if len(args) < 1 {
		return shim.Error("Incorrect number of arguments. Expecting 1")
	}

	marbleName := args[0]

	fmt.Printf("- start getHistoryForMarble: %s\n", marbleName)

	resultsIterator, err := stub.GetHistoryForKey(marbleName)
	if err != nil {
		return shim.Error(err.Error())
	}
	defer resultsIterator.Close()

	// buffer is a JSON array containing historic values for the marble
	var buffer bytes.Buffer
	buffer.WriteString("[")

	bArrayMemberAlreadyWritten := false
	for resultsIterator.HasNext() {
		response, err := resultsIterator.Next()
		if err != nil {
			return shim.Error(err.Error())
		}
		// Add a comma before array members, suppress it for the first array member
		if bArrayMemberAlreadyWritten == true {
			buffer.WriteString(",")
		}
		buffer.WriteString("{\"TxId\":")
		buffer.WriteString("\"")
		buffer.WriteString(response.TxId)
		buffer.WriteString("\"")

		buffer.WriteString(", \"Value\":")
		// if it was a delete operation on given key, then we need to set the
		//corresponding value null. Else, we will write the response.Value
		//as-is (as the Value itself a JSON marble)
		if response.IsDelete {
			buffer.WriteString("null")
		} else {
			buffer.WriteString(string(response.Value))
		}

		buffer.WriteString(", \"Timestamp\":")
		buffer.WriteString("\"")
		buffer.WriteString(time.Unix(response.Timestamp.Seconds, int64(response.Timestamp.Nanos)).String())
		buffer.WriteString("\"")

		buffer.WriteString(", \"IsDelete\":")
		buffer.WriteString("\"")
		buffer.WriteString(strconv.FormatBool(response.IsDelete))
		buffer.WriteString("\"")

		buffer.WriteString("}")
		bArrayMemberAlreadyWritten = true
	}
	buffer.WriteString("]")

	fmt.Printf("- getHistoryForMarble returning:\n%s\n", buffer.String())

	return shim.Success(buffer.Bytes())
}