From 63e5b31fe53287908906b1b05affd236a0c047d4 Mon Sep 17 00:00:00 2001
From: Rapsssito <contact@rodrigomartin.dev>
Date: Sat, 13 Jul 2024 12:56:43 +0200
Subject: [PATCH] Set characteristic value previous to a notify action

---
 .../ble_server_automations.cpp                | 26 ++++++++++++++++---
 .../esp32_ble_server/ble_server_automations.h | 26 ++++++++++++++-----
 2 files changed, 42 insertions(+), 10 deletions(-)

diff --git a/esphome/components/esp32_ble_server/ble_server_automations.cpp b/esphome/components/esp32_ble_server/ble_server_automations.cpp
index e5009ce5f8..66a27660cb 100644
--- a/esphome/components/esp32_ble_server/ble_server_automations.cpp
+++ b/esphome/components/esp32_ble_server/ble_server_automations.cpp
@@ -19,14 +19,32 @@ Trigger<std::vector<uint8_t>> *BLETriggers::create_on_write_trigger(BLECharacter
 }
 
 void BLECharacteristicSetValueActionManager::set_listener(BLECharacteristic *characteristic,
-                                                          EventEmitterListenerID listener_id) {
+                                                          EventEmitterListenerID listener_id,
+                                                          std::function<void()> pre_notify_listener) {
   // Check if there is already a listener for this characteristic
-  if (this->listeners_.find(characteristic) != this->listeners_.end()) {
+  if (this->listeners_.count(characteristic) > 0) {
+    // Unpack the pair listener_id, pre_notify_listener_id
+    auto listener_pairs = this->listeners_[characteristic];
+    EventEmitterListenerID old_listener_id = listener_pairs.first;
+    EventEmitterListenerID old_pre_notify_listener_id = listener_pairs.second;
     // Remove the previous listener
     characteristic->EventEmitter<BLECharacteristicEvt::EmptyEvt>::off(BLECharacteristicEvt::EmptyEvt::ON_READ,
-                                                                      this->listeners_[characteristic]);
+                                                                      old_listener_id);
+    // Remove the pre-notify listener
+    this->off(BLECharacteristicSetValueActionEvt::PRE_NOTIFY, old_pre_notify_listener_id);
   }
-  this->listeners_[characteristic] = listener_id;
+  // Create a new listener for the pre-notify event
+  EventEmitterListenerID pre_notify_listener_id = this->on(
+      BLECharacteristicSetValueActionEvt::PRE_NOTIFY,
+      [pre_notify_listener, characteristic](const BLECharacteristic *evt_characteristic) {
+        // Only call the pre-notify listener if the characteristic is the one we are interested in
+        if (characteristic == evt_characteristic) {
+          pre_notify_listener();
+        }
+      }
+  );
+  // Save the pair listener_id, pre_notify_listener_id to the map
+  this->listeners_[characteristic] = std::make_pair(listener_id, pre_notify_listener_id);
 }
 
 }  // namespace esp32_ble_server_automations
diff --git a/esphome/components/esp32_ble_server/ble_server_automations.h b/esphome/components/esp32_ble_server/ble_server_automations.h
index d37959537e..7d4ccaf2b8 100644
--- a/esphome/components/esp32_ble_server/ble_server_automations.h
+++ b/esphome/components/esp32_ble_server/ble_server_automations.h
@@ -7,6 +7,7 @@
 
 #include <vector>
 #include <unordered_map>
+#include <functional>
 
 #ifdef USE_ESP32
 
@@ -22,19 +23,24 @@ class BLETriggers {
   static Trigger<std::vector<uint8_t>> *create_on_write_trigger(BLECharacteristic *characteristic);
 };
 
+enum BLECharacteristicSetValueActionEvt {
+  PRE_NOTIFY,
+};
+
 // Class to make sure only one BLECharacteristicSetValueAction is active at a time
-class BLECharacteristicSetValueActionManager {
+class BLECharacteristicSetValueActionManager : public EventEmitter<BLECharacteristicSetValueActionEvt, BLECharacteristic *> {
  public:
   // Singleton pattern
   static BLECharacteristicSetValueActionManager *get_instance() {
     static BLECharacteristicSetValueActionManager instance;
     return &instance;
   }
-  void set_listener(BLECharacteristic *characteristic, EventEmitterListenerID listener_id);
-  EventEmitterListenerID get_listener(BLECharacteristic *characteristic) { return this->listeners_[characteristic]; }
+  void set_listener(BLECharacteristic *characteristic, EventEmitterListenerID listener_id, std::function<void()> pre_notify_listener);
+  EventEmitterListenerID get_listener(BLECharacteristic *characteristic) { return this->listeners_[characteristic].first; }
+  void emit_pre_notify(BLECharacteristic *characteristic) { this->emit_(BLECharacteristicSetValueActionEvt::PRE_NOTIFY, characteristic); }
 
  private:
-  std::unordered_map<BLECharacteristic *, EventEmitterListenerID> listeners_;
+  std::unordered_map<BLECharacteristic *, std::pair<EventEmitterListenerID, EventEmitterListenerID>> listeners_;
 };
 
 template<typename... Ts> class BLECharacteristicSetValueAction : public Action<Ts...> {
@@ -54,7 +60,10 @@ template<typename... Ts> class BLECharacteristicSetValueAction : public Action<T
           this->parent_->set_value(this->value_.value(x...));
         });
     // Set the listener in the global manager so only one BLECharacteristicSetValueAction is set for each characteristic
-    BLECharacteristicSetValueActionManager::get_instance()->set_listener(this->parent_, this->listener_id_);
+    BLECharacteristicSetValueActionManager::get_instance()->set_listener(
+        this->parent_, this->listener_id_, [this, x...]() {
+          this->parent_->set_value(this->value_.value(x...));
+        });
   }
 
  protected:
@@ -65,7 +74,12 @@ template<typename... Ts> class BLECharacteristicSetValueAction : public Action<T
 template<typename... Ts> class BLECharacteristicNotifyAction : public Action<Ts...> {
  public:
   BLECharacteristicNotifyAction(BLECharacteristic *characteristic) : parent_(characteristic) {}
-  void play(Ts... x) override { this->parent_->notify(); }
+  void play(Ts... x) override {
+    // Call the pre-notify event
+    BLECharacteristicSetValueActionManager::get_instance()->emit_pre_notify(this->parent_);
+    // Notify the characteristic
+    this->parent_->notify();
+  }
 
  protected:
   BLECharacteristic *parent_;