Add MQTT command for reading settings

firmware/main/commands.cc

@@ -19,10 +19,16 @@ static bool handlePing(mqtt::Client &client, const mqtt::Message &msg) {
   esp_restart();
 }
 
+static bool handleReadSettings(mqtt::Client &client, const mqtt::Message &msg) {
+  const std::string json = appSettings.format();
+  client.send(msg.respTopic, json.c_str());
+  return true;
+}
+
 static bool handleWriteSetting(mqtt::Client &client, const mqtt::Message &msg,
                                const std::vector<std::string> &args) {
   if (args.size() != 3) {
-    client.send(msg.respTopic, "usage: setting/set name_spaces value_also");
+    client.send(msg.respTopic, "usage: setting/set name_no_spaces value_also");
     return false;
   }
   const esp_err_t err = appSettings.write(args[1].c_str(), args[2].c_str());
@@ -99,6 +105,9 @@ static bool handleMessage(mqtt::Client &client, const mqtt::Message &msg) {
   if (command == "setting/set") {
     return handleWriteSetting(client, msg, tokens);
   }
+  if (command == "setting/get") {
+    return handleReadSettings(client, msg);
+  }
   return handleUnknown(client, msg);
 }
 
@@ -114,6 +123,5 @@ static bool handleMessage(mqtt::Client &client, const mqtt::Message &msg) {
 }
 
 void initCommandHandler(mqtt::Client &client) {
-  xTaskCreate(taskCommandHandler, "mqtt_cmd_handler", KiB(2), &client, 4,
-              nullptr);
+  xTaskCreate(taskCommandHandler, "mqtt_cmd", KiB(4), &client, 4, nullptr);
 }

firmware/main/settings.cc

@@ -1,5 +1,6 @@
 #include "settings.hh"
 #include "common.hh"
+#include <cstring>
 
 AppSettings appSettings;
 
@@ -67,3 +68,18 @@ esp_err_t AppSettings::write(const char *const name, const char *const value) {
   }
   return err;
 }
+
+std::string AppSettings::format() const {
+  constexpr auto tpl =
+      R"({"dev":"%s","wifi":{"ssid":"%s","pass":"%s"},"mqtt":{"broker":"%s","user":"%s","pass":"%s"}})";
+  // this is pretty slow, but we rarely call this command, and it will prevent
+  // using more heap than necessary
+  const size_t size = strlen(tpl) + strlen(devName) + strlen(wifi.ssid) +
+                      strlen(wifi.pass) + strlen(mqtt.broker) +
+                      strlen(mqtt.username) + strlen(mqtt.password);
+  std::string json;
+  json.reserve(size);
+  snprintf(&json[0], json.capacity(), tpl, devName, wifi.ssid, wifi.pass,
+           mqtt.broker, mqtt.username, mqtt.password);
+  return json;
+}

firmware/main/settings.hh

@@ -19,6 +19,7 @@ struct AppSettings {
 
   esp_err_t write(const char *name, const char *value);
 
+  std::string format() const;
 private:
   static esp_err_t readString(nvs::NVSHandle &nvs, const char *name,
                               const char *&dst);