#include "track.h"

#include <cmath>
#include <cstdio>
#include <ctime>

namespace roro::gnss {

namespace {

constexpr double kEarthRadiusM = 6371000.0;

double radians(double degrees) { return degrees * M_PI / 180.0; }

// UTC fields from seconds since 1970 (gmtime_r works on the device and the PC alike).
struct tm utc(int64_t seconds) {
    time_t t = static_cast<time_t>(seconds);
    struct tm out;
    gmtime_r(&t, &out);
    return out;
}

}  // namespace

double distanceMeters(double lat1, double lon1, double lat2, double lon2) {
    double dLat = radians(lat2 - lat1), dLon = radians(lon2 - lon1);
    double h = std::sin(dLat / 2) * std::sin(dLat / 2) +
               std::cos(radians(lat1)) * std::cos(radians(lat2)) * std::sin(dLon / 2) * std::sin(dLon / 2);
    return 2 * kEarthRadiusM * std::asin(std::sqrt(h));
}

bool TrackRule::due(uint32_t nowMs, double lat, double lon) {
    if (any_ && (nowMs - lastMs_ < kEveryMs || distanceMeters(lat_, lon_, lat, lon) < kMinMeters)) return false;
    any_ = true;
    lastMs_ = nowMs;
    lat_ = lat;
    lon_ = lon;
    return true;
}

std::string trackPath(int64_t utcSeconds) {
    struct tm t = utc(utcSeconds);
    char buf[48];
    std::snprintf(buf, sizeof buf, "/gnss/tracks/%04d%02d%02d-%02d%02d%02d.gpx", t.tm_year + 1900, t.tm_mon + 1,
                  t.tm_mday, t.tm_hour, t.tm_min, t.tm_sec);
    return buf;
}

namespace gpx {

std::string header(const std::string& name) {
    return "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
           "<gpx version=\"1.1\" creator=\"roro9stack\" xmlns=\"http://www.topografix.com/GPX/1/1\">\n"
           "<trk><name>" + name + "</name><trkseg>";
}

std::string point(double lat, double lon, bool hasElevation, float elevationM, int64_t utcSeconds) {
    struct tm t = utc(utcSeconds);
    char buf[160], ele[32] = "";
    if (hasElevation) std::snprintf(ele, sizeof ele, "<ele>%.1f</ele>", elevationM);
    std::snprintf(buf, sizeof buf,
                  "<trkpt lat=\"%.7f\" lon=\"%.7f\">%s<time>%04d-%02d-%02dT%02d:%02d:%02dZ</time></trkpt>", lat, lon,
                  ele, t.tm_year + 1900, t.tm_mon + 1, t.tm_mday, t.tm_hour, t.tm_min, t.tm_sec);
    return buf;
}

std::string footer() { return "</trkseg></trk></gpx>"; }

bool finished(const std::string& tail) {
    size_t end = tail.find_last_not_of(" \r\n\t");
    return end != std::string::npos && end + 1 >= 6 && tail.compare(end + 1 - 6, 6, "</gpx>") == 0;
}

}  // namespace gpx

}  // namespace roro::gnss