#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/gpio.h"
#include "esp_rom_sys.h"

// 🔌 Pin Definitions
#define TRIG_PIN GPIO_NUM_4
#define ECHO_PIN GPIO_NUM_14
#define RELAY_PIN GPIO_NUM_26

// ⚡ Relay Logic (ACTIVE HIGH for your case)
#define RELAY_ON  1   // LED ON
#define RELAY_OFF 0   // LED OFF

// 🎯 Threshold
#define THRESHOLD 20  // cm

// 📏 Distance Measurement Function
float measure_distance() {

    // Trigger pulse
    gpio_set_level(TRIG_PIN, 0);
    esp_rom_delay_us(2);
    gpio_set_level(TRIG_PIN, 1);
    esp_rom_delay_us(10);
    gpio_set_level(TRIG_PIN, 0);

    // Wait for echo HIGH
    int timeout = 30000;
    while (gpio_get_level(ECHO_PIN) == 0 && timeout--) {
        esp_rom_delay_us(1);
    }
    if (timeout <= 0) return -1;

    // Measure HIGH duration
    int duration = 0;
    timeout = 30000;
    while (gpio_get_level(ECHO_PIN) == 1 && timeout--) {
        duration++;
        esp_rom_delay_us(1);
    }
    if (timeout <= 0) return -1;

    // Convert to distance
    float distance = duration * 0.034 / 2;
    return distance;
}

void app_main(void) {

    // ⚙️ GPIO Setup
    gpio_set_direction(TRIG_PIN, GPIO_MODE_OUTPUT);
    gpio_set_direction(ECHO_PIN, GPIO_MODE_INPUT);
    gpio_set_direction(RELAY_PIN, GPIO_MODE_OUTPUT);

    // Initial state → LED OFF
    gpio_set_level(RELAY_PIN, RELAY_OFF);

    while (1) {

        float distance = measure_distance();

        if (distance < 0) {
            printf("No Echo Signal\n");
            vTaskDelay(pdMS_TO_TICKS(1000));
            continue;
        }

        printf("Distance: %.2f cm\n", distance);

        // 🎯 CONTROL LOGIC
        if (distance < THRESHOLD) {
            gpio_set_level(RELAY_PIN, RELAY_OFF);  // LED OFF
            printf("Distance < 20 cm → LED OFF\n");
        }
        else {
            gpio_set_level(RELAY_PIN, RELAY_ON);   // LED ON
            printf("Distance >= 20 cm → LED ON\n");
        }

        vTaskDelay(pdMS_TO_TICKS(1000));
    }
}