/*
 * EMS-ESP - https://github.com/proddy/EMS-ESP
 * Copyright 2019  Paul Derbyshire
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "mqtt.h"
#include "emsesp.h"
#include "version.h"

MAKE_PSTR_WORD(connected)
MAKE_PSTR_WORD(disconnected)

MAKE_PSTR(logger_name, "mqtt")

namespace emsesp {

#ifndef EMSESP_STANDALONE
AsyncMqttClient * Mqtt::mqttClient_;
#endif

// static parameters we make global
std::string Mqtt::hostname_;
uint8_t     Mqtt::mqtt_qos_;
uint16_t    Mqtt::publish_time_;

std::vector<Mqtt::MQTTFunction>     Mqtt::mqtt_functions_;
uint16_t                            Mqtt::mqtt_publish_fails_    = 0;
size_t                              Mqtt::maximum_mqtt_messages_ = Mqtt::MAX_MQTT_MESSAGES;
uint16_t                            Mqtt::mqtt_message_id_       = 0;
std::deque<Mqtt::QueuedMqttMessage> Mqtt::mqtt_messages_;
char                                will_topic_[Mqtt::MQTT_TOPIC_MAX_SIZE]; // because MQTT library keeps only char pointer

uuid::log::Logger Mqtt::logger_{F_(logger_name), uuid::log::Facility::DAEMON};

Mqtt::QueuedMqttMessage::QueuedMqttMessage(uint16_t id, std::shared_ptr<MqttMessage> && content)
    : id_(id)
    , content_(std::move(content)) {
    retry_count_ = 0;
    packet_id_   = 0;
}

MqttMessage::MqttMessage(uint8_t operation, const std::string & topic, const std::string & payload, bool retain)
    : operation(operation)
    , topic(topic)
    , payload(payload)
    , retain(retain) {
}

Mqtt::MQTTFunction::MQTTFunction(uint8_t device_id, const std::string && topic, mqtt_function_p mqtt_function)
    : device_id_(device_id)
    , topic_(topic)
    , mqtt_function_(mqtt_function) {
}

// subscribe to an MQTT topic, and store the associated callback function
void Mqtt::subscribe(const uint8_t device_id, const std::string & topic, mqtt_function_p cb) {
    // We don't want to store the whole topic string in our lookup, just the last cmd, as this is wasteful.
    // strip out everything until the last /
    size_t found = topic.find_last_of("/");                                          // returns npos which is -1
    mqtt_functions_.emplace_back(device_id, std::move(topic.substr(found + 1)), cb); // register a call back function for a specific telegram type

    queue_subscribe_message(topic); // add subscription to queue
}

// subscribe to an MQTT topic, and store the associated callback function. For generic functions not tied to a device
void Mqtt::subscribe(const std::string & topic, mqtt_function_p cb) {
    subscribe(0, topic, cb); // no device_id needed, if generic to EMS-ESP
}

// Main MQTT loop
// Checks for connection, establishes a connection if not
// sends out top item on publish queue
void Mqtt::loop() {
    // exit if MQTT is not enabled or ig there is no WIFI
#ifndef EMSESP_STANDALONE
    if (!connected()) {
#else
    if (false) {
#endif
        return;
    }

    uint32_t currentMillis = uuid::get_uptime();
    // create publish messages for each of the EMS device values, adding to queue
    if (publish_time_ && (currentMillis - last_publish_ > publish_time_)) {
        last_publish_ = currentMillis;
        EMSESP::publish_all_values();
    }

    // publish top item from MQTT queue to stop flooding
    if ((uint32_t)(currentMillis - last_mqtt_poll_) > MQTT_PUBLISH_WAIT) {
        last_mqtt_poll_ = currentMillis;
        process_queue();
    }
}

// print MQTT log and other stuff to console
void Mqtt::show_mqtt(uuid::console::Shell & shell) {
    shell.printfln(F("MQTT is %s"), connected() ? uuid::read_flash_string(F_(connected)).c_str() : uuid::read_flash_string(F_(disconnected)).c_str());
    shell.printfln(F("MQTT publish fails: %lu"), mqtt_publish_fails_);
    shell.println();

    // show queues
    if (mqtt_messages_.empty()) {
        shell.printfln(F("MQTT queue is empty"));
        shell.println();
        return;
    }

    shell.printfln(F("MQTT queue (%d messages):"), mqtt_messages_.size());

    for (const auto & message : mqtt_messages_) {
        auto content = message.content_;
        if (content->operation == Operation::PUBLISH) {
            // Publish messages
            if (message.retry_count_ == 0) {
                if (message.packet_id_ == 0) {
                    shell.printfln(F(" [%02d] (Pub) topic=%s payload=%s"), message.id_, content->topic.c_str(), content->payload.c_str());
                } else {
                    shell.printfln(F(" [%02d] (Pub) topic=%s payload=%s (pid %d)"),
                                   message.id_,
                                   content->topic.c_str(),
                                   content->payload.c_str(),
                                   message.packet_id_);
                }
            } else {
                shell.printfln(F(" [%02d] (Pub) topic=%s payload=%s (pid %d, retry #%d)"),
                               message.id_,
                               content->topic.c_str(),
                               content->payload.c_str(),
                               message.packet_id_,
                               message.retry_count_);
            }
        } else {
            // Subscribe messages
            shell.printfln(F(" [%02d] (Sub) topic=%s"), message.id_, content->topic.c_str());
        }
    }
    shell.println();
}

// simulate receiving a MQTT message, only for testing
void Mqtt::incoming(char * topic, char * payload) {
    on_message(topic, payload, strlen(payload));
}

// received MQTT message
void Mqtt::on_message(char * topic, char * payload, size_t len) {
    if (len == 0) {
        return;
    }

    // convert payload to a null-terminated char string
    char message[len + 2];
    strlcpy(message, payload, len + 1);

#ifdef EMSESP_DEBUG
    LOG_DEBUG(F("[DEBUG] Received %s => %s (length %d)"), topic, message, len);
#endif

    // strip out everything until the last /
    char * topic_magnitude = strrchr(topic, '/');
    if (topic_magnitude != nullptr) {
        topic = topic_magnitude + 1;
    }

    // Send message event to custom service
    // this will pick the first topic that matches, so for multiple devices of the same type it's gonna fail
    for (const auto & mf : mqtt_functions_) {
        if (strcmp(topic, mf.topic_.c_str()) == 0) {
            (mf.mqtt_function_)(message);
            return;
        }
    }

    // if we got here we didn't find a topic match
    LOG_DEBUG(F("No responding handler found for topic %s"), topic);
}

// print all the topics related to a specific device_id
void Mqtt::show_topic_handlers(uuid::console::Shell & shell, const uint8_t device_id) {
    if (std::count_if(mqtt_functions_.cbegin(), mqtt_functions_.cend(), [=](MQTTFunction const & mqtt_function) { return device_id == mqtt_function.device_id_; })
        == 0) {
        return;
    }

    shell.print(F(" Subscribed MQTT topics: "));
    for (const auto & mqtt_function : mqtt_functions_) {
        if (mqtt_function.device_id_ == device_id) {
            shell.printf(F("%s "), mqtt_function.topic_.c_str());
        }
    }
    shell.println();
}

// called when an MQTT Publish ACK is received
// its a poor man's QOS we assume the ACK represents the last Publish sent
// check if ACK matches the last Publish we sent, if not report an error. Only if qos is 1 or 2
// and always remove from queue
void Mqtt::on_publish(uint16_t packetId) {
    // find the MQTT message in the queue and remove it
    if (mqtt_messages_.empty()) {
        return;
    }

    auto mqtt_message = mqtt_messages_.front();

    // if the last published failed, don't bother checking it. wait for the next retry
    if (mqtt_message.packet_id_ == 0) {
        return;
    }

    if (mqtt_message.packet_id_ != packetId) {
        LOG_DEBUG(F("Mismatch, expecting PID %d, got %d"), mqtt_message.packet_id_, packetId);
        mqtt_publish_fails_++; // increment error count
    }

    mqtt_messages_.pop_front(); // always remove from queue, regardless if there was a successful ACK
}

// builds up a topic by prefixing the hostname
char * Mqtt::make_topic(char * result, const std::string & topic) {
    strlcpy(result, hostname_.c_str(), MQTT_TOPIC_MAX_SIZE);
    strlcat(result, "/", MQTT_TOPIC_MAX_SIZE);
    strlcat(result, topic.c_str(), MQTT_TOPIC_MAX_SIZE);

    return result;
}

void Mqtt::start(AsyncMqttClient * mqttClient) {
    mqttClient_ = mqttClient; // copy over from esp8266-react's MQTT service

    // get the hostname, which we'll use to prefix to all topics
    EMSESP::esp8266React.getWiFiSettingsService()->read([&](WiFiSettings & wifiSettings) { hostname_ = wifiSettings.hostname.c_str(); });

    // fetch MQTT settings
    // EMSESP::esp8266React.getMqttSettingsService()->read([&](MqttSettings & mqttSettings) { mqtt_enabled_ = mqttSettings.enabled; });

    EMSESP::emsespSettingsService.read([&](EMSESPSettings & settings) {
        publish_time_ = settings.publish_time * 1000; // convert to milliseconds
        mqtt_qos_     = settings.mqtt_qos;
    });

#ifndef EMSESP_STANDALONE
    mqttClient_->onConnect([this](bool sessionPresent) { on_connect(); });
    mqttClient_->setWill(make_topic(will_topic_, "status"), 1, true, "offline"); // with qos 1, retain true
    mqttClient_->onMessage([this](char * topic, char * payload, AsyncMqttClientMessageProperties properties, size_t len, size_t index, size_t total) {
        on_message(topic, payload, len);
        mqttClient_->onPublish([this](uint16_t packetId) { on_publish(packetId); });
    });
#endif
}

void Mqtt::set_publish_time(uint16_t publish_time) {
    publish_time_ = publish_time * 1000; // convert to milliseconds
}

void Mqtt::set_qos(uint8_t mqtt_qos) {
    mqtt_qos_ = mqtt_qos;
}

// MQTT onConnect - when a connect is established
void Mqtt::on_connect() {
    // send info topic appended with the version information as JSON
    StaticJsonDocument<90> doc;
    doc["event"]   = "start";
    doc["version"] = EMSESP_APP_VERSION;
    doc["ip"]      = WiFi.localIP().toString();
    publish("info", doc, false); // send with retain off

    publish("status", "online", true); // say we're alive to the Last Will topic, with retain on
    LOG_INFO(F("MQTT connected"));
}

// add MQTT message to queue, payload is a string
void Mqtt::queue_publish_message(const std::string & topic, const std::string & payload, const bool retain) {
    // can't have bogus topics, but empty payloads are ok
    if (topic.empty()) {
        return;
    }

    auto message = std::make_shared<MqttMessage>(Operation::PUBLISH, topic, payload, retain);

    // if the queue is full, make room but removing the last one
    if (mqtt_messages_.size() >= maximum_mqtt_messages_) {
        mqtt_messages_.pop_front();
    }

    mqtt_messages_.emplace_back(mqtt_message_id_++, std::move(message));
}

// add MQTT subscribe message to queue
void Mqtt::queue_subscribe_message(const std::string & topic) {
    if (topic.empty()) {
        return;
    }

    auto message = std::make_shared<MqttMessage>(Operation::SUBSCRIBE, topic, "", false);
    LOG_DEBUG(F("Adding a subscription for %s"), topic.c_str());

    // if the queue is full, make room but removing the last one
    if (mqtt_messages_.size() >= maximum_mqtt_messages_) {
        mqtt_messages_.pop_front();
    }

    mqtt_messages_.emplace_back(mqtt_message_id_++, std::move(message));
}

// MQTT Publish, using a specific retain flag
void Mqtt::publish(const std::string & topic, const std::string & payload, bool retain) {
    queue_publish_message(topic, payload, retain);
}

void Mqtt::publish(const std::string & topic, const JsonDocument & payload, bool retain) {
    // convert json to string
    std::string payload_text;
    serializeJson(payload, payload_text);
    queue_publish_message(topic, payload_text, retain);
}

// for booleans, which get converted to string values 1 and 0
void Mqtt::publish(const std::string & topic, const bool value) {
    queue_publish_message(topic, value ? "1" : "0", false);
}

// no payload
void Mqtt::publish(const std::string & topic) {
    queue_publish_message(topic, "", false);
}

// publish all queued messages to MQTT
void Mqtt::process_all_queue() {
    while (!mqtt_messages_.empty()) {
        process_queue();
    }
}

// take top from queue and try and publish it
// assumes there is an MQTT connection
void Mqtt::process_queue() {
    if (mqtt_messages_.empty()) {
        return;
    }

    // fetch first from queue and create the full topic name
    auto mqtt_message = mqtt_messages_.front();
    auto message      = mqtt_message.content_;

    // append the hostname to the topic, unless we're doing native HA which has a different format
    // if the topic starts with "homeassistant" we leave it untouched, otherwise append host
    char full_topic[MQTT_TOPIC_MAX_SIZE];
    if (strncmp(message->topic.c_str(), "homeassistant/", 13) == 0) {
        strcpy(full_topic, message->topic.c_str());
    } else {
        make_topic(full_topic, message->topic);
    }

    // if we're subscribing...
    if (message->operation == Operation::SUBSCRIBE) {
        LOG_DEBUG(F("Subscribing to topic: %s"), full_topic);
#ifndef EMSESP_STANDALONE
        uint16_t packet_id = mqttClient_->subscribe(full_topic, mqtt_qos_);
#else
        uint16_t packet_id = 1;
#endif
        if (!packet_id) {
            LOG_DEBUG(F("Error subscribing to %s, error %d"), full_topic, packet_id);
        }

        mqtt_messages_.pop_front(); // remove the message from the queue

        return;
    }

    // if this has already been published and we're waiting for an ACK, don't publish again
    // it will have a real packet ID
    if (mqtt_message.packet_id_ > 0) {
        return;
    }

    // else try and publish it

#ifndef EMSESP_STANDALONE
    uint16_t packet_id = mqttClient_->publish(full_topic, mqtt_qos_, message->retain, message->payload.c_str(), message->payload.size(), false, mqtt_message.id_);
#else
    uint16_t packet_id = 1;
#endif
    LOG_DEBUG(F("Publishing topic %s (#%02d, attempt #%d, pid %d)"), full_topic, mqtt_message.id_, mqtt_message.retry_count_ + 1, packet_id);

    if (packet_id == 0) {
        // it failed. if we retried n times, give up. remove from queue
        if (mqtt_message.retry_count_ == (MQTT_PUBLISH_MAX_RETRY - 1)) {
            LOG_ERROR(F("Failed to publish to %s after %d attempts"), full_topic, mqtt_message.retry_count_ + 1);
            mqtt_publish_fails_++;      // increment failure counter
            mqtt_messages_.pop_front(); // delete
            return;
        } else {
            mqtt_messages_.front().retry_count_++;
            LOG_DEBUG(F("Failed to publish to %s. Trying again, #%d"), full_topic, mqtt_message.retry_count_ + 1);
            return; // leave on queue for next time so it gets republished
        }
    }

    // if we have ACK set with QOS 1 or 2, leave on queue and let the ACK process remove it
    // but add the packet_id so we can check it later
    if (mqtt_qos_ != 0) {
        mqtt_messages_.front().packet_id_ = packet_id;
        // LOG_DEBUG(F("Setting packetID for ACK to %d"), packet_id);
        return;
    }

    mqtt_messages_.pop_front(); // remove the message from the queue
}

} // namespace emsesp