/*******************************************************************************
 The MIT License (MIT)

 Copyright (c) 2015 Alexander Zolotarev <me@alex.bio> from Minsk, Belarus

 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in all
 copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
 *******************************************************************************/

#ifndef LOCATION_H
#define LOCATION_H

#if defined(__BYTE_ORDER__) && (__BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__)
#error "This code does not support serialization on Big Endian archs (see TODOs below)."
#endif

#include <cstdint>
#include <exception>
#include <iomanip>
#include <sstream>  // For ToDebugString()
#include <string>
#include <type_traits>

namespace alohalytics {

class Location {
  enum Mask : uint8_t {
    NOT_INITIALIZED = 0,
    HAS_LATLON = 1 << 0,
    HAS_ALTITUDE = 1 << 1,
    HAS_BEARING = 1 << 2,
    HAS_SPEED = 1 << 3,
    HAS_SOURCE = 1 << 4
  } valid_values_mask_ = NOT_INITIALIZED;

 public:
  class LocationDecodeException : public std::exception {};

  // Milliseconds from January 1, 1970.
  uint64_t timestamp_ms_;
  double latitude_deg_;
  double longitude_deg_;
  double horizontal_accuracy_m_;
  double altitude_m_;
  double vertical_accuracy_m_;
  // Positive degrees from the true North.
  double bearing_deg_;
  // Meters per second.
  double speed_mps_;

  // We use degrees with precision of 7 decimal places - it's approx 2cm precision on the Earth.
  static constexpr double TEN_MILLION = 10000000.;
  // Some params below can be stored with 2 decimal places precision.
  static constexpr double ONE_HUNDRED = 100.;

  // Compacts location into the byte representation.
  // TODO(AlexZ): We don't care about endiannes for now.
  std::string Encode() const {
    std::string s;
    s.push_back(valid_values_mask_);
    if (valid_values_mask_ & HAS_LATLON) {
      static_assert(sizeof(timestamp_ms_) == 8, "We cut off timestamp from 8 bytes to 6 to save space.");
      AppendToStringAsBinary(s, timestamp_ms_, sizeof(timestamp_ms_) - 2);
      const int32_t lat10mil = latitude_deg_ * TEN_MILLION;
      AppendToStringAsBinary(s, lat10mil);
      const int32_t lon10mil = longitude_deg_ * TEN_MILLION;
      AppendToStringAsBinary(s, lon10mil);
      const uint32_t horizontal_accuracy_cm = horizontal_accuracy_m_ * ONE_HUNDRED;
      AppendToStringAsBinary(s, horizontal_accuracy_cm);
      if (valid_values_mask_ & HAS_SOURCE) {
        s.push_back(source_);
      }
    }
    if (valid_values_mask_ & HAS_ALTITUDE) {
      const int32_t altitude_cm = altitude_m_ * ONE_HUNDRED;
      AppendToStringAsBinary(s, altitude_cm);
      const uint16_t vertical_accuracy_cm = vertical_accuracy_m_ * ONE_HUNDRED;
      AppendToStringAsBinary(s, vertical_accuracy_cm);
    }
    if (valid_values_mask_ & HAS_BEARING) {
      const uint32_t bearing10mil = bearing_deg_ * TEN_MILLION;
      AppendToStringAsBinary(s, bearing10mil);
    }
    if (valid_values_mask_ & HAS_SPEED) {
      const uint16_t speedx100mps = speed_mps_ * ONE_HUNDRED;
      AppendToStringAsBinary(s, speedx100mps);
    }
    return s;
  }

  // Initializes location from serialized byte array created by ToString() method.
  // TODO(AlexZ): we don't care about endianness right now.
  explicit Location(const std::string & encoded) { Decode(encoded); }

  void Decode(const std::string & encoded) {
    if (encoded.empty()) {
      throw LocationDecodeException();
    }
    std::string::size_type i = 0;
    const std::string::size_type size = encoded.size();
    valid_values_mask_ = static_cast<Mask>(encoded[i++]);
    if (valid_values_mask_ & HAS_LATLON) {
      if ((size - i) < 18) {
        throw LocationDecodeException();
      }
      timestamp_ms_ = *reinterpret_cast<const uint32_t *>(&encoded[i]) |
                      (static_cast<uint64_t>(*reinterpret_cast<const uint16_t *>(&encoded[i + 4])) << 32);
      i += sizeof(uint64_t) - 2;  // We use 6 bytes to store timestamps.
      latitude_deg_ = *reinterpret_cast<const int32_t *>(&encoded[i]) / TEN_MILLION;
      i += sizeof(int32_t);
      longitude_deg_ = *reinterpret_cast<const int32_t *>(&encoded[i]) / TEN_MILLION;
      i += sizeof(int32_t);
      horizontal_accuracy_m_ = *reinterpret_cast<const uint32_t *>(&encoded[i]) / ONE_HUNDRED;
      i += sizeof(uint32_t);
      if (valid_values_mask_ & HAS_SOURCE) {
        if ((size - i) < 1) {
          throw LocationDecodeException();
        }
        source_ = static_cast<Source>(encoded[i++]);
      }
    }
    if (valid_values_mask_ & HAS_ALTITUDE) {
      if ((size - i) < 6) {
        throw LocationDecodeException();
      }
      altitude_m_ = *reinterpret_cast<const int32_t *>(&encoded[i]) / ONE_HUNDRED;
      i += sizeof(int32_t);
      vertical_accuracy_m_ = *reinterpret_cast<const uint16_t *>(&encoded[i]) / ONE_HUNDRED;
      i += sizeof(uint16_t);
    }
    if (valid_values_mask_ & HAS_BEARING) {
      if ((size - i) < 4) {
        throw LocationDecodeException();
      }
      bearing_deg_ = *reinterpret_cast<const uint32_t *>(&encoded[i]) / TEN_MILLION;
      i += sizeof(uint32_t);
    }
    if (valid_values_mask_ & HAS_SPEED) {
      if ((size - i) < 2) {
        throw LocationDecodeException();
      }
      speed_mps_ = *reinterpret_cast<const uint16_t *>(&encoded[i]) / ONE_HUNDRED;
      i += sizeof(uint16_t);
    }
  }

  Location() = default;

  enum Source : std::uint8_t { UNKNOWN = 0, GPS = 1, NETWORK = 2, PASSIVE = 3 } source_;

  bool HasLatLon() const { return valid_values_mask_ & HAS_LATLON; }
  Location & SetLatLon(uint64_t timestamp_ms, double latitude_deg, double longitude_deg, double horizontal_accuracy_m) {
    // We do not support values without known horizontal accuracy.
    if (horizontal_accuracy_m > 0.0) {
      timestamp_ms_ = timestamp_ms;
      latitude_deg_ = latitude_deg;
      longitude_deg_ = longitude_deg;
      horizontal_accuracy_m_ = horizontal_accuracy_m;
      valid_values_mask_ = static_cast<Mask>(valid_values_mask_ | HAS_LATLON);
    }
    return *this;
  }

  bool HasSource() const { return valid_values_mask_ & HAS_SOURCE; }
  Location & SetSource(Source source) {
    source_ = source;
    valid_values_mask_ = static_cast<Mask>(valid_values_mask_ | HAS_SOURCE);
    return *this;
  }

  bool HasAltitude() const { return valid_values_mask_ & HAS_ALTITUDE; }
  Location & SetAltitude(double altitude_m, double vertical_accuracy_m) {
    if (vertical_accuracy_m > 0.0) {
      altitude_m_ = altitude_m;
      vertical_accuracy_m_ = vertical_accuracy_m;
      valid_values_mask_ = static_cast<Mask>(valid_values_mask_ | HAS_ALTITUDE);
    }
    return *this;
  }

  bool HasBearing() const { return valid_values_mask_ & HAS_BEARING; }
  Location & SetBearing(double bearing_deg) {
    if (bearing_deg >= 0.0) {
      bearing_deg_ = bearing_deg;
      valid_values_mask_ = static_cast<Mask>(valid_values_mask_ | HAS_BEARING);
    }
    return *this;
  }

  bool HasSpeed() const { return valid_values_mask_ & HAS_SPEED; }
  Location & SetSpeed(double speed_mps) {
    if (speed_mps >= 0.0) {
      speed_mps_ = speed_mps;
      valid_values_mask_ = static_cast<Mask>(valid_values_mask_ | HAS_SPEED);
    }
    return *this;
  }

  template <class Archive>
  void save(Archive & ar) const {
    ar(Encode());
  }

  template <class Archive>
  void load(Archive & ar) {
    std::string encoded_location;
    ar(encoded_location);
    Decode(encoded_location);
  }

  std::string ToDebugString() const {
    std::ostringstream stream;
    stream << '<' << std::fixed;
    if (valid_values_mask_ & HAS_LATLON) {
      stream << "utc=" << timestamp_ms_ << ",lat=" << std::setprecision(7) << latitude_deg_
             << ",lon=" << std::setprecision(7) << longitude_deg_ << ",acc=" << std::setprecision(2)
             << horizontal_accuracy_m_;
    }
    if (valid_values_mask_ & HAS_ALTITUDE) {
      stream << ",alt=" << std::setprecision(2) << altitude_m_ << ",vac=" << std::setprecision(2)
             << vertical_accuracy_m_;
    }
    if (valid_values_mask_ & HAS_BEARING) {
      stream << ",bea=" << std::setprecision(7) << bearing_deg_;
    }
    if (valid_values_mask_ & HAS_SPEED) {
      stream << ",spd=" << std::setprecision(2) << speed_mps_;
    }
    if (valid_values_mask_ & HAS_SOURCE) {
      stream << ",src=";
      switch (source_) {
        case Source::GPS:
          stream << "GPS";
          break;
        case Source::NETWORK:
          stream << "Net";
          break;
        case Source::PASSIVE:
          stream << "Psv";
          break;
        default:
          stream << "Unk";
          break;
      }
    }
    stream << '>';
    return stream.str();
  }

 private:
  template <typename T>
  static inline void AppendToStringAsBinary(std::string & str, const T & value, size_t bytes = sizeof(T)) {
    // TODO(AlexZ): Uncomment when gcc and clang will correctly support is_trivially_copyable.
    // static_assert(std::is_trivially_copyable<T>::value, "This type is not supported.");
    str.append(reinterpret_cast<const char *>(&value), bytes);
  }
};
}  // namespace alohalytics

#endif  // LOCATION_H