Add uart_cmd helpers to deduplicate UART command handlers.

Centralize protobuf decode, response init/send, registration, and common
nanopb encode callbacks; refactor existing cmd_* modules to use them.

Co-authored-by: Cursor <cursoragent@cursor.com>

main/uart_cmd.c

@@ -0,0 +1,82 @@
+#include "uart_cmd.h"
+#include "esp_log.h"
+#include "pb_decode.h"
+#include "pb_encode.h"
+#include "uart_proto.h"
+#include <string.h>
+
+static const char *TAG = "[UART_CMD]";
+
+esp_err_t uart_cmd_decode(const uint8_t *data, size_t len, alox_UartMessage *out) {
+  if (out == NULL) {
+    return ESP_ERR_INVALID_ARG;
+  }
+
+  alox_UartMessage zero = alox_UartMessage_init_zero;
+  *out = zero;
+  if (len == 0) {
+    return ESP_OK;
+  }
+  if (data == NULL) {
+    return ESP_ERR_INVALID_ARG;
+  }
+
+  pb_istream_t stream = pb_istream_from_buffer(data, len);
+  if (!pb_decode(&stream, alox_UartMessage_fields, out)) {
+    return ESP_FAIL;
+  }
+  return ESP_OK;
+}
+
+void uart_cmd_init_response(alox_UartMessage *msg, alox_MessageType type,
+                            pb_size_t which_payload) {
+  if (msg == NULL) {
+    return;
+  }
+  alox_UartMessage zero = alox_UartMessage_init_zero;
+  *msg = zero;
+  msg->type = type;
+  msg->which_payload = which_payload;
+}
+
+esp_err_t uart_cmd_send(const alox_UartMessage *msg, const char *log_tag) {
+  esp_err_t err = uart_send_uart_message(msg);
+  if (err != ESP_OK && log_tag != NULL) {
+    ESP_LOGE(log_tag, "failed to send UART response");
+  }
+  return err;
+}
+
+esp_err_t uart_cmd_register(alox_MessageType type, msg_callback_t cb) {
+  esp_err_t err = msg_register_handler((uint16_t)type, cb);
+  if (err != ESP_OK) {
+    ESP_LOGE(TAG, "register handler for type %u failed", (unsigned)type);
+  }
+  return err;
+}
+
+bool uart_cmd_encode_string(pb_ostream_t *stream, const pb_field_t *field,
+                            void *const *arg) {
+  const char *str = (const char *)*arg;
+  if (str == NULL) {
+    str = "";
+  }
+  if (!pb_encode_tag_for_field(stream, field)) {
+    return false;
+  }
+  return pb_encode_string(stream, (const pb_byte_t *)str, strlen(str));
+}
+
+bool uart_cmd_encode_bytes(pb_ostream_t *stream, const pb_field_t *field,
+                           void *const *arg) {
+  const uart_cmd_bytes_t *blob = (const uart_cmd_bytes_t *)*arg;
+
+  (void)field;
+  if (blob == NULL || blob->data == NULL) {
+    return true;
+  }
+  if (!pb_encode_tag_for_field(stream, field)) {
+    return false;
+  }
+  return pb_encode_string(stream, blob->data, blob->len);
+}