/*

MQTT MODULE

Copyright (C) 2016-2017 by Xose Pérez <xose dot perez at gmail dot com>

*/

#include <ESP8266WiFi.h>
#include <vector>

#if MQTT_USE_ASYNC
#include <AsyncMqttClient.h>
AsyncMqttClient mqtt;
#else
#include <PubSubClient.h>
WiFiClient mqttWiFiClient;
PubSubClient mqtt(mqttWiFiClient);
bool _mqttConnected = false;
#endif

String mqttTopic;
std::vector<void (*)(unsigned int, const char *, const char *)> _mqtt_callbacks;
#if MQTT_SKIP_RETAINED
    unsigned long mqttConnectedAt = 0;
#endif

// -----------------------------------------------------------------------------
// Public API
// -----------------------------------------------------------------------------

bool mqttConnected() {
    return mqtt.connected();
}

void mqttDisconnect() {
    mqtt.disconnect();
}

void buildTopics() {
    // Replace identifier
    mqttTopic = getSetting("mqttTopic", MQTT_TOPIC);
    mqttTopic.replace("{identifier}", getSetting("hostname"));
}

char * mqttSubtopic(char * topic) {
    int pos = min(mqttTopic.length(), strlen(topic));
    return topic + pos;
}

void mqttSendRaw(const char * topic, const char * message) {
    if (mqtt.connected()) {
        DEBUG_MSG("[MQTT] Sending %s => %s\n", topic, message);
        #if MQTT_USE_ASYNC
            mqtt.publish(topic, MQTT_QOS, MQTT_RETAIN, message);
        #else
            mqtt.publish(topic, message, MQTT_RETAIN);
        #endif
    }
}

void mqttSend(const char * topic, const char * message) {
    String path = mqttTopic + String(topic);
    mqttSendRaw(path.c_str(), message);
}

void mqttSubscribeRaw(const char * topic) {
    if (mqtt.connected()) {
        DEBUG_MSG("[MQTT] Subscribing to %s\n", topic);
        mqtt.subscribe(topic, MQTT_QOS);
    }
}

void mqttSubscribe(const char * topic) {
    String path = mqttTopic + String(topic);
    mqttSubscribeRaw(path.c_str());
}

// -----------------------------------------------------------------------------
// Callbacks
// -----------------------------------------------------------------------------

void mqttRegister(void (*callback)(unsigned int, const char *, const char *)) {
    _mqtt_callbacks.push_back(callback);
}

void _mqttOnConnect() {

    DEBUG_MSG("[MQTT] Connected!\n");

    #if MQTT_SKIP_RETAINED
        mqttConnectedAt = millis();
    #endif

    // Build MQTT topics
    buildTopics();

    // Say hello and report our IP and VERSION
    mqttSend(MQTT_IP_TOPIC, getIP().c_str());
    mqttSend(MQTT_VERSION_TOPIC, APP_VERSION);

    // Subscribe to system topics
    mqttSubscribe(MQTT_ACTION_TOPIC);

    // Send connect event to subscribers
    for (unsigned char i = 0; i < _mqtt_callbacks.size(); i++) {
        (*_mqtt_callbacks[i])(MQTT_CONNECT_EVENT, NULL, NULL);
    }

}

void _mqttOnDisconnect() {

    DEBUG_MSG("[MQTT] Disconnected!\n");

    // Send disconnect event to subscribers
    for (unsigned char i = 0; i < _mqtt_callbacks.size(); i++) {
        (*_mqtt_callbacks[i])(MQTT_DISCONNECT_EVENT, NULL, NULL);
    }

}

void _mqttOnMessage(char* topic, char* payload, unsigned int len) {

    char message[len + 1];
    strlcpy(message, (char *) payload, len + 1);

    DEBUG_MSG("[MQTT] Received %s => %s", topic, message);
    #if MQTT_SKIP_RETAINED
        if (millis() - mqttConnectedAt < MQTT_SKIP_TIME) {
			DEBUG_MSG(" - SKIPPED\n");
			return;
		}
    #endif
	DEBUG_MSG("\n");

    // Check system topics
    char * p = mqttSubtopic(topic);
    if (strcmp(p, MQTT_ACTION_TOPIC) == 0) {
        if (strcmp(message, MQTT_ACTION_RESET) == 0) {
            ESP.restart();
        }
    }

    // Send message event to subscribers
    // Topic is set to the specific part each one might be checking
    for (unsigned char i = 0; i < _mqtt_callbacks.size(); i++) {
        (*_mqtt_callbacks[i])(MQTT_MESSAGE_EVENT, topic, message);
    }

}

void mqttConnect() {

    if (!mqtt.connected()) {

        if (getSetting("mqttServer", MQTT_SERVER).length() == 0) return;

        // Last option: reconnect to wifi after MQTT_MAX_TRIES attemps in a row
        #if MQTT_MAX_TRIES > 0
            static unsigned int tries = 0;
            static unsigned long last_try = millis();
            if (millis() - last_try < MQTT_TRY_INTERVAL) {
                if (++tries > MQTT_MAX_TRIES) {
                    DEBUG_MSG("[MQTT] MQTT_MAX_TRIES met, disconnecting from WiFi\n");
                    wifiDisconnect();
                    tries = 0;
                    return;
                }
            } else {
                tries = 0;
            }
            last_try = millis();
        #endif

        mqtt.disconnect();

        char * host = strdup(getSetting("mqttServer", MQTT_SERVER).c_str());
        unsigned int port = getSetting("mqttPort", MQTT_PORT).toInt();
        char * user = strdup(getSetting("mqttUser").c_str());
        char * pass = strdup(getSetting("mqttPassword").c_str());

        DEBUG_MSG("[MQTT] Connecting to broker at %s", host);
        mqtt.setServer(host, port);

        #if MQTT_USE_ASYNC

            mqtt.setKeepAlive(MQTT_KEEPALIVE).setCleanSession(false);
    	    mqtt.setWill((mqttTopic + MQTT_HEARTBEAT_TOPIC).c_str(), MQTT_QOS, MQTT_RETAIN, "0");
            if ((strlen(user) > 0) && (strlen(pass) > 0)) {
                DEBUG_MSG(" as user '%s'.", user);
                mqtt.setCredentials(user, pass);
            }
            DEBUG_MSG("\n");
            mqtt.connect();

        #else

            bool response;

            if ((strlen(user) > 0) && (strlen(pass) > 0)) {
                DEBUG_MSG(" as user '%s'\n", user);
                response = mqtt.connect(getIdentifier().c_str(), user, pass, (mqttTopic + MQTT_HEARTBEAT_TOPIC).c_str(), MQTT_QOS, MQTT_RETAIN, "0");
            } else {
                DEBUG_MSG("\n");
                response = mqtt.connect(getIdentifier().c_str(), (mqttTopic + MQTT_HEARTBEAT_TOPIC).c_str(), MQTT_QOS, MQTT_RETAIN, "0");
            }

            if (response) {
                _mqttOnConnect();
                _mqttConnected = true;
            } else {
                DEBUG_MSG("[MQTT] Connection failed\n");
            }

        #endif

        free(host);
        free(user);
        free(pass);

    }

}

void mqttSetup() {
    #if MQTT_USE_ASYNC
        mqtt.onConnect([](bool sessionPresent) {
            _mqttOnConnect();
        });
        mqtt.onDisconnect([](AsyncMqttClientDisconnectReason reason) {
            _mqttOnDisconnect();
        });
        mqtt.onMessage([](char* topic, char* payload, AsyncMqttClientMessageProperties properties, size_t len, size_t index, size_t total) {
            _mqttOnMessage(topic, payload, len);
        });
    #else
        mqtt.setCallback([](char* topic, byte* payload, unsigned int length) {
            _mqttOnMessage(topic, (char *) payload, length);
        });
    #endif
    buildTopics();
}

void mqttLoop() {

    static unsigned long lastPeriod = 0;

    if (WiFi.status() == WL_CONNECTED) {

        if (!mqtt.connected()) {

            #if not MQTT_USE_ASYNC
                if (_mqttConnected) {
                    _mqttOnDisconnect();
                    _mqttConnected = false;
                }
            #endif

        	unsigned long currPeriod = millis() / MQTT_RECONNECT_DELAY;
        	if (currPeriod != lastPeriod) {
        	    lastPeriod = currPeriod;
                mqttConnect();
            }

        #if not MQTT_USE_ASYNC
        } else {
            mqtt.loop();
        #endif

        }

    }

}