[FAB-11359] tms transactor: list tokens

- add GetStateRangeScanIterator() to the LedgerReader interface
- implement tms ListTokens
- add proto messages for unspent tokens
- test

Change-Id: I2b597974a17d47a73da3347480af1fdbc9dfe219
Signed-off-by: Kaoutar Elkhiyaoui <kao@zurich.ibm.com>

Author: KElkhiyaoui

token/ledger/ledger.go

@@ -6,10 +6,21 @@ SPDX-License-Identifier: Apache-2.0
 
 package ledger
 
+import "github.com/hyperledger/fabric/common/ledger"
+
+//go:generate counterfeiter -o mock/ledger_reader.go -fake-name LedgerReader . LedgerReader
+
 // LedgerReader interface, used to read from a ledger.
 type LedgerReader interface {
 	// GetState gets the value for given namespace and key. For a chaincode, the namespace corresponds to the chaincodeId
 	GetState(namespace string, key string) ([]byte, error)
+
+	// GetStateRangeScanIterator returns an iterator that contains all the Key-values between given Key ranges.
+	// startKey is included in the results and endKey is excluded. An empty startKey refers to the first available Key
+	// and an empty endKey refers to the last available Key. For scanning all the keys, both the startKey and the endKey
+	// can be supplied as empty strings. However, a full scan should be used judiciously for performance reasons.
+	// The returned ResultsIterator contains results of type *KV which is defined in protos/ledger/queryresult.
+	GetStateRangeScanIterator(namespace string, startKey string, endKey string) (ledger.ResultsIterator, error)
 }
 
 //go:generate counterfeiter -o mock/ledger_writer.go -fake-name LedgerWriter . LedgerWriter
@@ -20,3 +31,14 @@ type LedgerWriter interface {
 	// SetState sets the given value for the given namespace and key. For a chaincode, the namespace corresponds to the chaincodeId
 	SetState(namespace string, key string, value []byte) error
 }
+
+//go:generate counterfeiter -o mock/results_iterator.go -fake-name ResultsIterator . ResultsIterator
+
+// ResultsIterator - an iterator for query result set
+type ResultsIterator interface {
+	// Next returns the next item in the result set. The `QueryResult` is expected to be nil when
+	// the iterator gets exhausted
+	Next() (ledger.QueryResult, error)
+	// Close releases resources occupied by the iterator
+	Close()
+}