refactor filter operands

pkg/types/readsb/filter.go

@@ -174,13 +174,22 @@ func MinRSSI(dbfs float64) AircraftFilter {
 	return func(a *Aircraft) bool { return a.RSSI >= dbfs }
 }
 
+// And, Or, and Not compose filters as boolean operators. Filter/All already AND
+// their arguments; And is the value form, letting you nest, e.g.
+// Or(And(a, b), And(c, d)).
+
 // Not inverts a filter.
 func Not(f AircraftFilter) AircraftFilter {
 	return func(a *Aircraft) bool { return !f(a) }
 }
 
-// Any keeps aircraft matching at least one of the supplied filters (logical OR).
-func Any(filters ...AircraftFilter) AircraftFilter {
+// And keeps aircraft matching every supplied filter (logical AND).
+func And(filters ...AircraftFilter) AircraftFilter {
+	return func(a *Aircraft) bool { return keep(a, filters) }
+}
+
+// Or keeps aircraft matching at least one of the supplied filters (logical OR).
+func Or(filters ...AircraftFilter) AircraftFilter {
 	return func(a *Aircraft) bool {
 		for _, f := range filters {
 			if f(a) {

pkg/types/readsb/readsb_test.go

@@ -113,21 +113,34 @@ func TestWithinNMOf(t *testing.T) {
 	}
 }
 
-func TestAnyOR(t *testing.T) {
-	// Two non-overlapping 5 nm circles; Any should keep aircraft in either.
+func TestOr(t *testing.T) {
+	// Two non-overlapping 5 nm circles; Or should keep aircraft in either.
 	r := &AircraftReport{Aircraft: []Aircraft{
 		{Hex: "nearA", Lat: 40.01, Lon: -75.0},
 		{Hex: "nearB", Lat: 41.0, Lon: -76.01},
 		{Hex: "between", Lat: 40.5, Lon: -75.5},
 		{Hex: "nopos"},
 	}}
-	near := r.Filter(Any(WithinNMOf(40, -75, 5), WithinNMOf(41, -76, 5)))
+	near := r.Filter(Or(WithinNMOf(40, -75, 5), WithinNMOf(41, -76, 5)))
 	got := map[string]bool{}
 	for _, a := range near {
 		got[a.Hex] = true
 	}
 	if !got["nearA"] || !got["nearB"] || got["between"] || got["nopos"] || len(got) != 2 {
-		t.Errorf("Any(WithinNMOf...) OR mismatch, matched: %v", got)
+		t.Errorf("Or(WithinNMOf...) mismatch, matched: %v", got)
+	}
+}
+
+func TestAnd(t *testing.T) {
+	// And matches only aircraft passing every filter; here position AND in-circle.
+	r := &AircraftReport{Aircraft: []Aircraft{
+		{Hex: "in", Lat: 40.01, Lon: -75.0},
+		{Hex: "out", Lat: 50.0, Lon: -75.0},
+		{Hex: "nopos"},
+	}}
+	near := r.Filter(And(WithPosition(), WithinNMOf(40, -75, 5)))
+	if len(near) != 1 || near[0].Hex != "in" {
+		t.Errorf("And mismatch, matched: %+v", near)
 	}
 }