test: add json stability and discovery payload coverage

lib/dd3_legacy_core/src/data_model.cpp

@@ -0,0 +1,29 @@
+#include "data_model.h"
+#include <esp_mac.h>
+
+void init_device_ids(uint16_t &short_id, char *device_id, size_t device_id_len) {
+  uint8_t mac[6] = {0};
+  // Read base MAC without needing WiFi to be started.
+  esp_read_mac(mac, ESP_MAC_WIFI_STA);
+  short_id = (static_cast<uint16_t>(mac[4]) << 8) | mac[5];
+  snprintf(device_id, device_id_len, "dd3-%04X", short_id);
+}
+
+const char *rx_reject_reason_text(RxRejectReason reason) {
+  switch (reason) {
+    case RxRejectReason::CrcFail:
+      return "crc_fail";
+    case RxRejectReason::InvalidMsgKind:
+      return "invalid_msg_kind";
+    case RxRejectReason::LengthMismatch:
+      return "length_mismatch";
+    case RxRejectReason::DeviceIdMismatch:
+      return "device_id_mismatch";
+    case RxRejectReason::BatchIdMismatch:
+      return "batch_id_mismatch";
+    case RxRejectReason::UnknownSender:
+      return "unknown_sender";
+    default:
+      return "none";
+  }
+}

lib/dd3_legacy_core/src/json_codec.cpp

@@ -0,0 +1,96 @@
+#include "json_codec.h"
+#include <ArduinoJson.h>
+#include <limits.h>
+#include <math.h>
+
+static constexpr size_t STATE_JSON_DOC_CAPACITY = 512;
+
+static float round2(float value) {
+  if (isnan(value)) {
+    return value;
+  }
+  return roundf(value * 100.0f) / 100.0f;
+}
+
+static int32_t round_to_i32(float value) {
+  if (isnan(value)) {
+    return 0;
+  }
+  long rounded = lroundf(value);
+  if (rounded > INT32_MAX) {
+    return INT32_MAX;
+  }
+  if (rounded < INT32_MIN) {
+    return INT32_MIN;
+  }
+  return static_cast<int32_t>(rounded);
+}
+
+static const char *short_id_from_device_id(const char *device_id) {
+  if (!device_id) {
+    return "";
+  }
+  size_t len = strlen(device_id);
+  if (len >= 4) {
+    return device_id + (len - 4);
+  }
+  return device_id;
+}
+
+static void format_float_2(char *buf, size_t buf_len, float value) {
+  if (!buf || buf_len == 0) {
+    return;
+  }
+  if (isnan(value)) {
+    snprintf(buf, buf_len, "null");
+    return;
+  }
+  snprintf(buf, buf_len, "%.2f", round2(value));
+}
+
+static void set_int_or_null(JsonDocument &doc, const char *key, float value) {
+  if (!key || key[0] == '\0') {
+    return;
+  }
+  if (isnan(value)) {
+    doc[key] = nullptr;
+    return;
+  }
+  doc[key] = round_to_i32(value);
+}
+
+bool meterDataToJson(const MeterData &data, String &out_json) {
+  StaticJsonDocument<STATE_JSON_DOC_CAPACITY> doc;
+  doc["id"] = short_id_from_device_id(data.device_id);
+  doc["ts"] = data.ts_utc;
+  char buf[16];
+  format_float_2(buf, sizeof(buf), data.energy_total_kwh);
+  doc["e_kwh"] = serialized(buf);
+  set_int_or_null(doc, "p_w", data.total_power_w);
+  set_int_or_null(doc, "p1_w", data.phase_power_w[0]);
+  set_int_or_null(doc, "p2_w", data.phase_power_w[1]);
+  set_int_or_null(doc, "p3_w", data.phase_power_w[2]);
+  format_float_2(buf, sizeof(buf), data.battery_voltage_v);
+  doc["bat_v"] = serialized(buf);
+  doc["bat_pct"] = data.battery_percent;
+  if (data.link_valid) {
+    doc["rssi"] = data.link_rssi_dbm;
+    doc["snr"] = data.link_snr_db;
+  }
+  if (data.err_meter_read > 0) {
+    doc["err_m"] = data.err_meter_read;
+  }
+  if (data.err_decode > 0) {
+    doc["err_d"] = data.err_decode;
+  }
+  if (data.err_lora_tx > 0) {
+    doc["err_tx"] = data.err_lora_tx;
+  }
+  doc["err_last"] = static_cast<uint8_t>(data.last_error);
+  doc["rx_reject"] = data.rx_reject_reason;
+  doc["rx_reject_text"] = rx_reject_reason_text(static_cast<RxRejectReason>(data.rx_reject_reason));
+
+  out_json = "";
+  size_t len = serializeJson(doc, out_json);
+  return len > 0;
+}