/*
 * BoardA_Sender.ino — XIAO ESP32-C3 + HC-SR04
 * ESP32 Arduino Core v3.x
 *
 * Wiring:
 *   TRIG → D1
 *   ECHO → D2
 *   VCC  → 5V
 *   GND  → GND
 */

#include <esp_now.h>
#include <WiFi.h>

// Board B (XIAO ESP32-S3) MAC address
uint8_t receiverMac[] = {0x80, 0xB5, 0x4E, 0xF1, 0xBA, 0x58};

const int TRIG_PIN = D1;
const int ECHO_PIN = D2;

const unsigned long PULSE_TIMEOUT_US = 30000;
const int SAMPLES = 5;
const float SEND_THRESHOLD_CM = 1.0;

typedef struct Message {
  float distanceCm;
} Message;

Message outgoing;
float lastSent = -1.0;

float readDistanceCm() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  unsigned long duration = pulseIn(ECHO_PIN, HIGH, PULSE_TIMEOUT_US);
  if (duration == 0) return -1.0;
  return duration * 0.0343 / 2.0;
}

float averageDistance() {
  float sum = 0;
  int valid = 0;
  for (int i = 0; i < SAMPLES; i++) {
    float d = readDistanceCm();
    if (d > 0) { sum += d; valid++; }
    delay(10);
  }
  return (valid == 0) ? -1.0 : sum / valid;
}

// v3.x send callback — first argument is wifi_tx_info_t*
void onSent(const wifi_tx_info_t *info, esp_now_send_status_t status) {
  Serial.print("Send status: ");
  Serial.println(status == ESP_NOW_SEND_SUCCESS ? "OK" : "FAIL");
}

void setup() {
  Serial.begin(115200);
  delay(1000);

  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);

  WiFi.mode(WIFI_STA);
  WiFi.STA.begin();

  Serial.print("Board A MAC: ");
  Serial.println(WiFi.macAddress());

  if (esp_now_init() != ESP_OK) {
    Serial.println("ESP-NOW init failed!");
    return;
  }

  esp_now_register_send_cb(onSent);

  esp_now_peer_info_t peer = {};
  memcpy(peer.peer_addr, receiverMac, 6);
  peer.channel = 0;
  peer.encrypt = false;
  esp_now_add_peer(&peer);

  Serial.println("Board A (Sender) ready");
  Serial.println("Target MAC: 80:B5:4E:F1:BA:58");
}

void loop() {
  float distance = averageDistance();

  if (distance > 0) {
    float delta = distance - lastSent;
    if (delta < 0) delta = -delta;

    if (lastSent < 0 || delta >= SEND_THRESHOLD_CM) {
      outgoing.distanceCm = distance;
      esp_now_send(receiverMac, (uint8_t *)&outgoing, sizeof(outgoing));
      lastSent = distance;

      Serial.print("Distance: ");
      Serial.print(distance, 1);
      Serial.println(" cm → sent");
    }
  }

  delay(200);
}