Maint: utils.FilterByProtocol function

internal/provider/utils/protocol.go

@@ -11,3 +11,15 @@ func GetProtocol(selection configuration.ServerSelection) (protocol string) {
 	}
 	return constants.UDP
 }
+
+func FilterByProtocol(selection configuration.ServerSelection,
+	serverTCP, serverUDP bool) (filtered bool) {
+	switch selection.VPN {
+	case constants.Wireguard:
+		return !serverUDP
+	default: // OpenVPN
+		wantTCP := selection.OpenVPN.TCP
+		wantUDP := !wantTCP
+		return (wantTCP && !serverTCP) || (wantUDP && !serverUDP)
+	}
+}

internal/provider/utils/protocol_test.go

@@ -52,3 +52,81 @@ func Test_GetProtocol(t *testing.T) {
 		})
 	}
 }
+
+func Test_FilterByProtocol(t *testing.T) {
+	t.Parallel()
+
+	testCases := map[string]struct {
+		selection configuration.ServerSelection
+		serverTCP bool
+		serverUDP bool
+		filtered  bool
+	}{
+		"Wireguard and server has UDP": {
+			selection: configuration.ServerSelection{
+				VPN: constants.Wireguard,
+			},
+			serverUDP: true,
+			filtered:  false,
+		},
+		"Wireguard and server has not UDP": {
+			selection: configuration.ServerSelection{
+				VPN: constants.Wireguard,
+			},
+			serverUDP: false,
+			filtered:  true,
+		},
+		"OpenVPN UDP and server has UDP": {
+			selection: configuration.ServerSelection{
+				VPN: constants.OpenVPN,
+				OpenVPN: configuration.OpenVPNSelection{
+					TCP: false,
+				},
+			},
+			serverUDP: true,
+			filtered:  false,
+		},
+		"OpenVPN UDP and server has not UDP": {
+			selection: configuration.ServerSelection{
+				VPN: constants.OpenVPN,
+				OpenVPN: configuration.OpenVPNSelection{
+					TCP: false,
+				},
+			},
+			serverUDP: false,
+			filtered:  true,
+		},
+		"OpenVPN TCP and server has TCP": {
+			selection: configuration.ServerSelection{
+				VPN: constants.OpenVPN,
+				OpenVPN: configuration.OpenVPNSelection{
+					TCP: true,
+				},
+			},
+			serverTCP: true,
+			filtered:  false,
+		},
+		"OpenVPN TCP and server has not TCP": {
+			selection: configuration.ServerSelection{
+				VPN: constants.OpenVPN,
+				OpenVPN: configuration.OpenVPNSelection{
+					TCP: true,
+				},
+			},
+			serverTCP: false,
+			filtered:  true,
+		},
+	}
+
+	for name, testCase := range testCases {
+		testCase := testCase
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			filtered := FilterByProtocol(testCase.selection,
+				testCase.serverTCP, testCase.serverUDP)
+
+			assert.Equal(t, testCase.filtered, filtered)
+		})
+	}
+}