Add select entities and implement template select (#2067)

Co-authored-by: Otto Winter <otto@otto-winter.com>

esphome/components/mqtt/mqtt_select.cpp

@@ -0,0 +1,58 @@
+#include "mqtt_select.h"
+#include "esphome/core/log.h"
+
+#ifdef USE_SELECT
+
+namespace esphome {
+namespace mqtt {
+
+static const char *const TAG = "mqtt.select";
+
+using namespace esphome::select;
+
+MQTTSelectComponent::MQTTSelectComponent(Select *select) : MQTTComponent(), select_(select) {}
+
+void MQTTSelectComponent::setup() {
+  this->subscribe(this->get_command_topic_(), [this](const std::string &topic, const std::string &state) {
+    auto call = this->select_->make_call();
+    call.set_option(state);
+    call.perform();
+  });
+  this->select_->add_on_state_callback([this](const std::string &state) { this->publish_state(state); });
+}
+
+void MQTTSelectComponent::dump_config() {
+  ESP_LOGCONFIG(TAG, "MQTT Select '%s':", this->select_->get_name().c_str());
+  LOG_MQTT_COMPONENT(true, false)
+}
+
+std::string MQTTSelectComponent::component_type() const { return "select"; }
+
+std::string MQTTSelectComponent::friendly_name() const { return this->select_->get_name(); }
+void MQTTSelectComponent::send_discovery(JsonObject &root, mqtt::SendDiscoveryConfig &config) {
+  const auto &traits = select_->traits;
+  // https://www.home-assistant.io/integrations/select.mqtt/
+  if (!traits.get_icon().empty())
+    root["icon"] = traits.get_icon();
+  JsonArray &options = root.createNestedArray("options");
+  for (const auto &option : traits.get_options())
+    options.add(option);
+
+  config.command_topic = true;
+}
+bool MQTTSelectComponent::send_initial_state() {
+  if (this->select_->has_state()) {
+    return this->publish_state(this->select_->state);
+  } else {
+    return true;
+  }
+}
+bool MQTTSelectComponent::is_internal() { return this->select_->is_internal(); }
+bool MQTTSelectComponent::publish_state(const std::string &value) {
+  return this->publish(this->get_state_topic_(), value);
+}
+
+}  // namespace mqtt
+}  // namespace esphome
+
+#endif