fix(readers): enumerate libnfc ACR122 devices

pkg/readers/libnfc/libnfc.go

@@ -375,10 +375,7 @@ func (r *Reader) Detect(connected []string) string {
 
 	switch r.mode {
 	case modeACR122Only:
-		// Auto-detect for ACR122 and other USB/PCSC devices
-		if !helpers.Contains(connected, autoConnStr) {
-			return autoConnStr
-		}
+		return detectACR122Readers(connected)
 	case modeLegacyUART:
 		// Only detect UART devices, return with legacy prefix
 		device := detectSerialReaders(connected)
@@ -398,10 +395,7 @@ func (r *Reader) Detect(connected []string) string {
 			return device
 		}
 
-		// Auto-detect for ACR122 and other USB/PCSC devices
-		if !helpers.Contains(connected, autoConnStr) {
-			return autoConnStr
-		}
+		return detectACR122Readers(connected)
 	}
 
 	return ""
@@ -652,6 +646,69 @@ func detectI2CReaders(connected []string) string {
 	return ""
 }
 
+func detectACR122Readers(connected []string) string {
+	devices, err := nfc.ListDevices()
+	if err != nil {
+		log.Trace().Err(err).Msg("error listing libnfc devices")
+		return fallbackAutoACR122(connected)
+	}
+
+	return detectACR122Device(connected, devices)
+}
+
+func detectACR122Device(connected, devices []string) string {
+	foundACR122 := false
+	for _, device := range devices {
+		connStr := strings.TrimRight(device, "\x00")
+		if !isACR122ConnStr(connStr) {
+			continue
+		}
+		foundACR122 = true
+
+		path := connectionPath(connStr)
+		if path == "" || isConnectedPath(connected, path) {
+			continue
+		}
+
+		log.Trace().Msgf("acr122 libnfc reader found: %s", connStr)
+		return connStr
+	}
+
+	if foundACR122 {
+		return ""
+	}
+
+	return fallbackAutoACR122(connected)
+}
+
+func fallbackAutoACR122(connected []string) string {
+	if helpers.Contains(connected, autoConnStr) || isConnectedPath(connected, "") {
+		return ""
+	}
+	return autoConnStr
+}
+
+func isACR122ConnStr(connStr string) bool {
+	return strings.HasPrefix(connStr, "acr122_usb:") || strings.HasPrefix(connStr, "acr122_pcsc:")
+}
+
+func connectionPath(connStr string) string {
+	parts := strings.SplitN(connStr, ":", 2)
+	if len(parts) != 2 {
+		return ""
+	}
+	return parts[1]
+}
+
+func isConnectedPath(connected []string, path string) bool {
+	for _, connStr := range connected {
+		if connectionPath(connStr) == path {
+			return true
+		}
+	}
+	return false
+}
+
 // toLibnfcConnStr translates internal normalized connection strings to the
 // format expected by libnfc. libnfc driver names use underscores
 // (e.g. "pn532_i2c", "pn532_uart") but ConnectionString() strips them for
@@ -665,6 +722,8 @@ func toLibnfcConnStr(mode readerMode, connStr string) string {
 	default:
 		connStr = strings.Replace(connStr, "pn532uart:", "pn532_uart:", 1)
 		connStr = strings.Replace(connStr, "pn532i2c:", "pn532_i2c:", 1)
+		connStr = strings.Replace(connStr, "acr122usb:", "acr122_usb:", 1)
+		connStr = strings.Replace(connStr, "acr122pcsc:", "acr122_pcsc:", 1)
 		return connStr
 	}
 }

pkg/readers/libnfc/libnfc_test.go

@@ -479,6 +479,67 @@ func TestOpenConnectionStringTranslation(t *testing.T) {
 	}
 }
 
+func TestDetectACR122Device(t *testing.T) {
+	tests := []struct {
+		name      string
+		expected  string
+		devices   []string
+		connected []string
+	}{
+		{
+			name:     "returns first concrete acr122 usb device",
+			devices:  []string{"acr122_usb:003:004", "acr122_usb:003:005"},
+			expected: "acr122_usb:003:004",
+		},
+		{
+			name:      "skips connected path from libnfcacr122 driver",
+			devices:   []string{"acr122_usb:003:004", "acr122_usb:003:005"},
+			connected: []string{"libnfcacr122:003:004"},
+			expected:  "acr122_usb:003:005",
+		},
+		{
+			name:      "skips connected path from concrete driver",
+			devices:   []string{"acr122_usb:003:004", "acr122_usb:003:005"},
+			connected: []string{"acr122_usb:003:004"},
+			expected:  "acr122_usb:003:005",
+		},
+		{
+			name:      "does not fall back when all concrete acr122 paths are connected",
+			devices:   []string{"acr122_usb:003:004", "acr122_usb:003:005"},
+			connected: []string{"acr122_usb:003:004", "acr122_usb:003:005"},
+			expected:  "",
+		},
+		{
+			name:     "ignores non acr122 devices",
+			devices:  []string{"pn532_uart:/dev/ttyUSB0", "acr122_pcsc:ACS ACR122U PICC Interface"},
+			expected: "acr122_pcsc:ACS ACR122U PICC Interface",
+		},
+		{
+			name:     "trims nul from libnfc connection strings",
+			devices:  []string{"acr122_usb:003:004\x00"},
+			expected: "acr122_usb:003:004",
+		},
+		{
+			name:     "falls back to libnfc auto when no acr122 devices found",
+			devices:  []string{"pn532_uart:/dev/ttyUSB0"},
+			expected: autoConnStr,
+		},
+		{
+			name:      "does not return auto fallback when auto reader path is connected",
+			devices:   []string{"pn532_uart:/dev/ttyUSB0"},
+			connected: []string{"libnfcacr122:"},
+			expected:  "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := detectACR122Device(tt.connected, tt.devices)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}
+
 // TestToLibnfcConnStr verifies that internal connection strings are translated
 // to the libnfc format with underscored driver names (e.g. "pn532_i2c").
 // Regression test: libnfc requires underscores in driver names but the internal
@@ -535,6 +596,20 @@ func TestToLibnfcConnStr(t *testing.T) {
 			expected: "pn532_uart:/dev/ttyUSB0",
 		},
 
+		// ACR122 device names
+		{
+			name:     "acr122 usb normalized driver",
+			mode:     modeACR122Only,
+			input:    "acr122usb:003:004",
+			expected: "acr122_usb:003:004",
+		},
+		{
+			name:     "acr122 pcsc normalized driver",
+			mode:     modeACR122Only,
+			input:    "acr122pcsc:ACS ACR122U PICC Interface",
+			expected: "acr122_pcsc:ACS ACR122U PICC Interface",
+		},
+
 		// Passthrough cases — strings that shouldn't be changed
 		{
 			name:     "acr122 mode passthrough",
@@ -625,6 +700,24 @@ func TestToLibnfcConnStrEndToEnd(t *testing.T) {
 			},
 			expected: "pn532_uart:/dev/ttyUSB0",
 		},
+		{
+			name: "acr122_usb config to libnfc",
+			mode: modeACR122Only,
+			device: config.ReadersConnect{
+				Driver: "acr122_usb",
+				Path:   "003:004",
+			},
+			expected: "acr122_usb:003:004",
+		},
+		{
+			name: "acr122_pcsc config to libnfc",
+			mode: modeACR122Only,
+			device: config.ReadersConnect{
+				Driver: "acr122_pcsc",
+				Path:   "ACS ACR122U PICC Interface",
+			},
+			expected: "acr122_pcsc:ACS ACR122U PICC Interface",
+		},
 	}
 
 	for _, tt := range tests {