#include <memory>
#include <string>
#include <iostream>
#include <thread>
#include <unordered_map>
#include <chrono>
#include <algorithm>

#include <opencv2/core/core.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <mosquitto.h>
#include <zbar.h>
#include <nlohmann/json.hpp>

#include "settings.hpp"
#include "mqtt_client.hpp"
#include "t3hs_proto.hpp"
#include "utils.hpp"
#include "static_settings.hpp"

// on SMP systems this should be under mutex locks
cv::Mat bgr, gray;
std::unique_ptr<Settings> params;
std::unique_ptr<MqttClient> mqtt;
int px_in_frame;

std::string usage(const std::string&);
std::string parse_cli(int, char**);
void mjpeg_stream(float, int, FrameMode);
void on_mqtt_message(mosquitto*, void*, const mosquitto_message*);

int main(int argc, char* argv[]) {
  // read config file path from cli args
  std::string cfg_path;
  try {
    cfg_path = parse_cli(argc, argv);
  } catch (const std::runtime_error& e) {
    std::cerr << "ERROR: Cannot parse CLI args: " << e.what() << std::endl;
    std::cerr << usage(argv[0]) << std::endl;
    return 1;
  }

  // get settings from config file
  try {
    params = std::make_unique<Settings>(cfg_path);
  } catch (const std::exception& e) {
    std::cerr << "ERROR: Cannot parse settings from file: " << e.what() << "\n";
    return 1;
  }
  std::cout << "CONFIG:" << std::endl << params->to_string() << std::endl;

  // initialize mqtt client
  try {
    mqtt = std::make_unique<MqttClient>(
      params->mqtt_client.host,
      params->mqtt_client.port,
      params->mqtt_client.user,
      params->mqtt_client.password,
      params->mqtt_client.sign_secret
    );
  } catch (const std::exception& e) {
    std::cerr << "ERROR: Cannot create mqtt client: " << e.what() << "\n";
    return 1;
  }
  mqtt->set_message_callback(on_mqtt_message);
  if (!mqtt->subscribe(params->mqtt_frame_exporter.listen_topic)) {
    std::cerr << "ERROR: Cannot subscribe on topic '" << params->mqtt_frame_exporter.listen_topic << "', exiting" << std::endl;
    return 1;
  }

  // Camera init
  cv::VideoCapture cap;
  cap.set(cv::CAP_PROP_FRAME_WIDTH, params->frame.width);
  cap.set(cv::CAP_PROP_FRAME_HEIGHT, params->frame.height);
  cap.open(V4L2_DEVICE_NUM);

  // "Warmup" camera
  while (bgr.total() * bgr.elemSize() == 0) {
    cap >> bgr;
    std::this_thread::sleep_for(std::chrono::milliseconds(100));
  }

  // QR scanner init
  zbar::ImageScanner scanner;
  std::unordered_map<std::string, long long> qr_appears;
  if (params->qr_scanner.enabled) {
    scanner.set_config(zbar::ZBAR_NONE, zbar::ZBAR_CFG_ENABLE, 1);
    scanner.set_config(zbar::ZBAR_QRCODE, zbar::ZBAR_CFG_ENABLE, 1);
  }

  // MJPEG stream init
  std::thread mjpeg_thread;
  if (params->mjpeg.mode != FrameMode::DISABLE) {
    mjpeg_thread = std::thread(mjpeg_stream, params->mjpeg.fps, params->mjpeg.port, params->mjpeg.mode);
  }

  long long last_frame = millis_timestamp();
  float frame_time = 1000.0 / params->frame.fps;
  px_in_frame = params->frame.width * params->frame.height;
  while (true) {
    // capture a frame
    cap >> bgr;
    if (bgr.empty()) {
      std::cerr << "ERROR: Captured frame is empty" << std::endl;
      break;
    }

    // convert to grayscale
    if (params->qr_scanner.enabled || params->mjpeg.mode == FrameMode::GRAYSCALE) {
      cv::cvtColor(bgr, gray, cv::COLOR_BGR2GRAY);
    }

    long long now = millis_timestamp();
    if (params->qr_scanner.enabled) {
      zbar::Image zbar_image(
        params->frame.width,
        params->frame.height,
        "Y800",
        gray.data,
        px_in_frame
      );
      int n = scanner.scan(zbar_image);
      if (n > 0) {
        std::cout << "INFO: Found " << n << " QRs:" << std::endl;
        std::vector<std::string> qrs_to_send;
        for (
          zbar::Image::SymbolIterator symbol = zbar_image.symbol_begin();
          symbol != zbar_image.symbol_end();
          ++symbol
        ) {
          std::string data = symbol->get_data();
          auto appear = qr_appears.find(data);
          if (appear == qr_appears.end()) {
            qr_appears.insert({data, now});
            std::cout << "    [x] " << data << std::endl;
            qrs_to_send.emplace_back(data);
          } else {
            std::cout << "    [ ] " << data << std::endl;
          }
        }
        if (!qrs_to_send.empty()) {
          t3hs::QrMessage msg = {
            .srcid = params->mqtt_client.id,
            .dstid = params->qr_scanner.dstid,
            .msgid = t3hs::gen_id(),
            .timestamp = micros_timestamp(),
            .qrs = std::move(qrs_to_send)
          };
          nlohmann::json qr_json = std::move(msg);
          if (!mqtt->send_message(params->qr_scanner.send_topic, qr_json)) {
            std::cerr << "ERROR: Cannot send MQTT message" << std::endl;
            exit(1);
          } else {
            std::cout << "INFO: Sent QR data" << std::endl;
          }
        }
      }

      auto it = qr_appears.begin();
      while (it != qr_appears.end()) {
        if (it->second + params->qr_scanner.rescan_timeout <= now) {
          it = qr_appears.erase(it);
        } else {
          ++it;
        }
      }
    }

    long long frame_duration = now - last_frame;
    long long remaining_frame_time = static_cast<long long>(std::min(frame_time - frame_duration, 0.0f));
    std::this_thread::sleep_for(std::chrono::milliseconds(remaining_frame_time));
    last_frame = now;
  }

  cap.release();
  return 0;
}

std::string usage(const std::string& basename) {
  std::ostringstream oss;
  oss << "Usage: " << basename << " [<config_file_path>]";
  return oss.str();
}

std::string parse_cli(int argc, char* argv[]) {
  std::string cfg_path;
  if (argc == 1) {
    std::cout << "INFO: Using default config file: " << DEFAULT_CONFIG_PATH << std::endl;
    cfg_path = DEFAULT_CONFIG_PATH;
  } else if (argc == 2) {
    cfg_path = argv[1];
    if (file_exists(cfg_path)) {
      std::cout << "INFO: Using config file '" << cfg_path << "'" << std::endl;
    } else {
      std::cerr << "ERROR: Config file '" << cfg_path << "' does not exist or is not accessible. Using default config in " << DEFAULT_CONFIG_PATH << std::endl;
      cfg_path = DEFAULT_CONFIG_PATH;
    }
  } else {
    throw std::runtime_error("Invalid CLI args");
  }
  return cfg_path;
}

void mjpeg_stream(float fps, int port, FrameMode mode) {
  cv::VideoWriter http;
  http.open("httpjpg", port);
  std::cout << "INFO: MJPEG thread started" << std::endl;

  long long last_frame = millis_timestamp();
  float frame_time = 1000.0f;
  while (true) {
    if (!http.isOpened()) {
      std::cerr << "ERROR: MJPEG writer failed" << std::endl;
      return;
    }

    if (mode == FrameMode::COLOR) {
      http << bgr;
    } else {
      http << gray;
    }

    long long now = millis_timestamp();
    long long frame_duration = now - last_frame;
    long long remaining_frame_time = static_cast<long long>(std::min(frame_time - frame_duration, 0.0f));
    std::this_thread::sleep_for(std::chrono::milliseconds(remaining_frame_time));
    last_frame = now;
  }
}

void on_mqtt_message(mosquitto *, void *, const mosquitto_message *msg) {
  // validating incomming message
  if (!msg->payload || msg->payloadlen == 0) {
    std::cerr << "WARNING: Received MQTT empty message" << std::endl;;
    return;
  }
  nlohmann::json msg_json;
  try {
    const char* char_data = static_cast<const char*>(msg->payload);
    std::string_view json_str(char_data, msg->payloadlen);
    msg_json = nlohmann::json::parse(json_str);
  } catch (const nlohmann::json::parse_error& e) {
    std::cerr << "WARNING: JSON parse error: " << e.what() << std::endl;
    return;
  } catch (const nlohmann::json::type_error& e) {
    std::cerr << "WARNING: JSON type error: " << e.what() << std::endl;
    return;
  } catch (const nlohmann::json::out_of_range& e) {
    std::cerr << "WARNING: JSON out of range: " << e.what() << std::endl;
    return;
  } catch (const std::exception& e) {
    std::cerr << "WARNING: JSON error: " << e.what() << std::endl;
    return;
  }

  t3hs::Request req;
  try {
    req = std::move(msg_json);
  } catch (const std::invalid_argument& e) {
    std::cerr << "WARNING: JSON format is incorrect: " << e.what() << std::endl;
    return;
  }

  // skip message if not for this device
  if (req.dstid != params->mqtt_client.id) {
    return;
  }

  const nlohmann::json& req_vars = req.variables;
  if (req_vars.find("quality") == req_vars.end() || !req_vars["quality"].is_number_integer()) {
    std::cerr << "WARNING: JSON format is incorrect: Field 'quality' in 'variables' is missing or not an integer" << std::endl;
    return;
  } else if (req_vars["quality"] < 1 || req_vars["quality"] > 100) {
    std::cerr << "WARNING: Field 'quality' in 'variables' is expected to be between 1 and 100%" << std::endl;
    return;
  }
  if (req_vars.find("mode") == req_vars.end() || !req_vars["mode"].is_string()) {
    std::cerr << "WARNING: JSON format is incorrect: Field 'mode' in 'variables' is missing or not a string" << std::endl;
    return;
  } else if (req_vars["mode"] != "color" && req_vars["mode"] != "grayscale") {
    std::cerr << "WARNING: Field 'mode' in 'variables' is expected to be equal 'color' or 'grayscale'" << std::endl;
    return;
  }

  unsigned int quality = req_vars["quality"].get<unsigned int>();
  FrameMode mode = FrameModeUtils::from_string(req_vars["mode"].get<std::string>());

  // obtain fresh grayscale frame if needed
  if (mode == FrameMode::GRAYSCALE && !(params->qr_scanner.enabled || params->mjpeg.mode == FrameMode::GRAYSCALE)) {
    cv::cvtColor(bgr, gray, cv::COLOR_BGR2GRAY);
  }

  // preapre jpeg data
  std::vector<unsigned char> jpeg;
  if (mode == FrameMode::COLOR) {
    jpeg = frame_to_jpeg(bgr, quality);
  } else {
    jpeg = frame_to_jpeg(gray, quality);
  }

  // split frame into chunks and send answers
  std::vector<t3hs::FileBlock> blocks = t3hs::FileBlock::from_raw(jpeg, t3hs::FileBlockOpertype::WRITE, DEFAULT_MQTT_FRAME_EXPORTER_MAX_BLOCK_SIZE, "frame");
  long long now = micros_timestamp();
  for (const auto& block : blocks) {
    nlohmann::json block_json = std::move(block);
    nlohmann::json resp_vars = {
      {"quality", quality},
      {"mode", FrameModeUtils::to_string(mode)},
      {"file_block", std::move(block_json)}
    };
    if (req_vars.find("exposure") != req_vars.end()) {
      std::string pname = "exposure";
      auto [min, max, value] = get_camera_param(pname);
      resp_vars["exposure"] = {
        {"min", min},
        {"max", max},
        {"value", value},
      };
    }
    if (req_vars.find("analogue_gain") != req_vars.end()) {
      std::string pname = "analogue_gain";
      auto [min, max, value] = get_camera_param(pname);
      resp_vars["analogue_gain"] = {
        {"min", min},
        {"max", max},
        {"value", value},
      };
    }

    t3hs::Response resp = {
      .srcid = params->mqtt_client.id,
      .dstid = params->mqtt_frame_exporter.dstid,
      .msgid = t3hs::gen_id(),
      .timestamp = now,
      .variables = std::move(resp_vars)
    };
    nlohmann::json resp_json = std::move(resp);
    if (!mqtt->send_message(params->mqtt_frame_exporter.send_topic, resp_json)) {
      std::cerr << "ERROR: Cannot send MQTT message" << std::endl;
      exit(1);
    } else {
      std::cout << "INFO: Sent frame part" << std::endl;
    }
  }
}