#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include <time.h>

// WiFi credentials
const char *ssid = "WIFI_SSID";             // Replace with your WiFi name
const char *password = "WIFI_PASSWORD";   // Replace with your WiFi password

// MQTT Broker settings
const int mqtt_port = 8883;  // MQTT port (TLS)
const char *mqtt_broker = "broker.emqx.io";  // EMQX broker endpoint
const char *mqtt_topic = "emqx/esp8266";     // MQTT topic
const char *mqtt_username = "emqx";  // MQTT username for authentication
const char *mqtt_password = "public";  // MQTT password for authentication

// NTP Server settings
const char *ntp_server = "pool.ntp.org";     // Default NTP server
// const char* ntp_server = "cn.pool.ntp.org"; // Recommended NTP server for users in China
const long gmt_offset_sec = 0;            // GMT offset in seconds (adjust for your time zone)
const int daylight_offset_sec = 0;        // Daylight saving time offset in seconds

// WiFi and MQTT client initialization
BearSSL::WiFiClientSecure espClient;
PubSubClient mqtt_client(espClient);

// SSL certificate for MQTT broker
// Load DigiCert Global Root G2, which is used by EMQX Public Broker: broker.emqx.io
static const char ca_cert[]
PROGMEM = R"EOF(
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
)EOF";

// Load DigiCert Global Root CA ca_cert, which is used by EMQX Cloud Serverless Deployment
/*
static const char ca_cert[] PROGMEM = R"EOF(
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
)EOF";
*/


// Function declarations
void connectToWiFi();

void connectToMQTT();

void syncTime();

void mqttCallback(char *topic, byte *payload, unsigned int length);


void setup() {
    Serial.begin(115200);
    connectToWiFi();
    syncTime();  // X.509 validation requires synchronization time
    mqtt_client.setServer(mqtt_broker, mqtt_port);
    mqtt_client.setCallback(mqttCallback);
    connectToMQTT();
}

void connectToWiFi() {
    WiFi.begin(ssid, password);
    while (WiFi.status() != WL_CONNECTED) {
        delay(1000);
        Serial.println("Connecting to WiFi...");
    }
    Serial.println("Connected to WiFi");
}

void syncTime() {
    configTime(gmt_offset_sec, daylight_offset_sec, ntp_server);
    Serial.print("Waiting for NTP time sync: ");
    while (time(nullptr) < 8 * 3600 * 2) {
        delay(1000);
        Serial.print(".");
    }
    Serial.println("Time synchronized");
    struct tm timeinfo;
    if (getLocalTime(&timeinfo)) {
        Serial.print("Current time: ");
        Serial.println(asctime(&timeinfo));
    } else {
        Serial.println("Failed to obtain local time");
    }
}

void connectToMQTT() {
    BearSSL::X509List serverTrustedCA(ca_cert);
    espClient.setTrustAnchors(&serverTrustedCA);
    while (!mqtt_client.connected()) {
        String client_id = "esp8266-client-" + String(WiFi.macAddress());
        Serial.printf("Connecting to MQTT Broker as %s.....\n", client_id.c_str());
        if (mqtt_client.connect(client_id.c_str(), mqtt_username, mqtt_password)) {
            Serial.println("Connected to MQTT broker");
            mqtt_client.subscribe(mqtt_topic);
            // Publish message upon successful connection
            mqtt_client.publish(mqtt_topic, "Hi EMQX I'm ESP8266 ^^");
        } else {
            char err_buf[128];
            espClient.getLastSSLError(err_buf, sizeof(err_buf));
            Serial.print("Failed to connect to MQTT broker, rc=");
            Serial.println(mqtt_client.state());
            Serial.print("SSL error: ");
            Serial.println(err_buf);
            delay(5000);
        }
    }
}

void mqttCallback(char *topic, byte *payload, unsigned int length) {
    Serial.print("Message received on topic: ");
    Serial.print(topic);
    Serial.print("]: ");
    for (int i = 0; i < length; i++) {
        Serial.print((char) payload[i]);
    }
    Serial.println();
}

void loop() {
    if (!mqtt_client.connected()) {
        connectToMQTT();
    }
    mqtt_client.loop();
}
