[FAB-6019] Implement private data puller

This commit implements an object that pulls private data
on demand according to a given specification that includes
details like:
- Collection name
- TxID
- Channel

Change-Id: I15244736628a8cd91f77eb80a4e8083267d9dcbd
Signed-off-by: yacovm <yacovm@il.ibm.com>

Author: yacovm

gossip/filter/filter.go

@@ -75,3 +75,17 @@ func First(peerPool []discovery.NetworkMember, filter RoutingFilter) *comm.Remot
 	}
 	return nil
 }
+
+// AnyMatch filters out peers that don't match any of the given filters
+func AnyMatch(peerPool []discovery.NetworkMember, filters ...RoutingFilter) []discovery.NetworkMember {
+	var res []discovery.NetworkMember
+	for _, peer := range peerPool {
+		for _, matches := range filters {
+			if matches(peer) {
+				res = append(res, peer)
+				break
+			}
+		}
+	}
+	return res
+}

gossip/filter/filter_test.go

@@ -37,6 +37,27 @@ func TestCombineRoutingFilters(t *testing.T) {
 	assert.False(t, CombineRoutingFilters(a, b)(discovery.NetworkMember{InternalEndpoint: "b"}))
 }
 
+func TestAnyMatch(t *testing.T) {
+	peerA := discovery.NetworkMember{Endpoint: "a"}
+	peerB := discovery.NetworkMember{Endpoint: "b"}
+	peerC := discovery.NetworkMember{Endpoint: "c"}
+	peerD := discovery.NetworkMember{Endpoint: "d"}
+
+	peers := []discovery.NetworkMember{peerA, peerB, peerC, peerD}
+
+	matchB := func(nm discovery.NetworkMember) bool {
+		return nm.Endpoint == "b"
+	}
+	matchC := func(nm discovery.NetworkMember) bool {
+		return nm.Endpoint == "c"
+	}
+
+	matched := AnyMatch(peers, matchB, matchC)
+	assert.Len(t, matched, 2)
+	assert.Contains(t, matched, peerB)
+	assert.Contains(t, matched, peerC)
+}
+
 func TestFirst(t *testing.T) {
 	peerA := discovery.NetworkMember{Endpoint: "a"}
 	peerB := discovery.NetworkMember{Endpoint: "b"}