#pragma once

#include <cstddef>
#include <cstdint>
#include <map>
#include <set>
#include <string>
#include <utility>
#include <vector>

namespace roro::gnss {

enum class Constellation : uint8_t { Unknown, Gps, Glonass, Galileo, BeiDou, Qzss, Navic };
const char* constellationName(Constellation c);

enum class FixType : uint8_t { None, TwoD, ThreeD };

struct Satellite {
    Constellation system = Constellation::Unknown;
    int prn = 0;
    int elevation = 0;  // degrees above the horizon
    int azimuth = 0;    // degrees from north, clockwise
    int snr = -1;       // dB-Hz; -1 when not tracked
    bool used = false;  // part of the current Fix
};

// Everything the receiver has said, as of the last sentence (see CONTEXT.md: Fix).
struct GnssState {
    FixType fix = FixType::None;
    bool positionValid = false;
    double latitude = 0, longitude = 0;  // degrees, south and west negative
    bool altitudeValid = false;
    float altitudeM = 0;  // above mean sea level
    float speedKmh = 0;
    bool courseValid = false;
    float courseDeg = 0;
    int satellitesUsed = 0;
    float hdop = 99.9f;
    // UTC, trusted only with a Fix: the receiver reports a time without one, from its own clock.
    bool timeValid = false;
    int year = 0, month = 0, day = 0, hour = 0, minute = 0, second = 0;
    std::vector<Satellite> satellites;  // in view, all constellations, one entry per satellite

    int64_t utcSeconds() const;  // seconds since 1970-01-01 UTC; meaningful when timeValid
};

// NMEA 0183 (4.10 style, as the Cap's AT6668 sends it): RMC, GGA, GSA and GSV, with the
// constellation taken from the talker ID or GSA's system ID field. Host-tested; no hardware here.
class NmeaParser {
   public:
    // Raw bytes from the UART, in any chunks.
    void feed(const char* data, size_t len);
    // One sentence without its line end. False if malformed or its checksum is wrong.
    bool sentence(const std::string& line);

    const GnssState& state() const { return state_; }
    uint32_t goodSentences() const { return good_; }
    uint32_t badSentences() const { return bad_; }

   private:
    using Fields = std::vector<std::string>;
    void rmc(const Fields& f);
    void gga(const Fields& f);
    void gsa(const Fields& f, Constellation talker);
    void gsv(const Fields& f, Constellation talker);
    void rebuildSatellites();

    static constexpr size_t kMaxLine = 120;
    std::string line_;
    bool overflow_ = false;
    uint32_t good_ = 0, bad_ = 0;
    GnssState state_;
    // GSV sequences per (constellation, signal): pending until their last message.
    std::map<std::pair<int, int>, std::vector<Satellite>> pending_, inView_;
    std::map<int, std::set<int>> used_;  // per constellation, from GSA
};

}  // namespace roro::gnss