// api_v1/scanner/parsers/parseFit.js
const { execFile } = require("child_process");

// FIT position_lat / position_long sono in semicircles.
// Conversione ufficiale: degrees = semicircles * 180 / 2^31
function fitSemicirclesToDegrees(value) {
  if (value == null) return null;

  const n = Number(value);
  if (!Number.isFinite(n)) return null;

  return n * (180 / 2147483648);
}

function buildTrackPreviewFromFitRecords(records, maxPoints = 300) {
  if (!Array.isArray(records)) return [];

  const points = [];

  for (const r of records) {
    const f = r.fields || {};

    const rawLat =
      f.position_lat ??
      f.latitude ??
      f.lat;

    const rawLng =
      f.position_long ??
      f.position_lon ??
      f.longitude ??
      f.lng ??
      f.lon;

    const lat = fitSemicirclesToDegrees(rawLat);
    const lng = fitSemicirclesToDegrees(rawLng);

    const altRaw =
      f.altitude ??
      f.enhanced_altitude;

    const alt = altRaw != null ? Number(altRaw) : null;

    if (!Number.isFinite(lat) || !Number.isFinite(lng)) continue;

    const point = { lat, lng };

    if (Number.isFinite(alt)) {
      point.alt = alt;
    }

    points.push(point);
  }

  if (points.length <= maxPoints) return points;

  const step = Math.ceil(points.length / maxPoints);
  const preview = [];

  for (let i = 0; i < points.length; i += step) {
    preview.push(points[i]);
  }

  const last = points[points.length - 1];
  const currentLast = preview[preview.length - 1];

  if (
    !currentLast ||
    currentLast.lat !== last.lat ||
    currentLast.lng !== last.lng
  ) {
    preview.push(last);
  }

  return preview;
}

async function parseFit(absPath) {
  const frames = await new Promise((resolve, reject) => {
    execFile(
      "/home/orangepi/.local/pipx/venvs/fitdecode/bin/python",
      ["api_v1/scanner/parsers/parse_fit.py", absPath],
      { maxBuffer: 1024 * 1024 * 50 },
      (err, stdout) => {
        if (err) return reject(err);

        try {
          resolve(JSON.parse(stdout));
        } catch (e) {
          reject(new Error("Errore nel parsing JSON FIT: " + e.message));
        }
      }
    );
  });

  // -------------------------------
  // 1. Trova i frame principali
  // -------------------------------
  const sessions = frames.filter(f => f.name === "session");
  const laps = frames.filter(f => f.name === "lap");
  const records = frames.filter(f => f.name === "record");
  const fileId = frames.find(f => f.name === "file_id");

  const session = sessions[0]?.fields || {};
  const file = fileId?.fields || {};

  // -------------------------------
  // 2. Tempi
  // -------------------------------
  const startTime = session.start_time || session.start_time_local || null;

  const endTime = session.total_timer_time && startTime
    ? new Date(new Date(startTime).getTime() + session.total_timer_time * 1000)
    : null;

  const startMillis = startTime ? new Date(startTime).getTime() : null;
  const endMillis = endTime ? endTime.getTime() : null;

  const durationMillis = session.total_timer_time
    ? session.total_timer_time * 1000
    : endMillis && startMillis
      ? endMillis - startMillis
      : null;

  // -------------------------------
  // 3. Distanza / Elevazione
  // -------------------------------
  const distance = session.total_distance || null;
  const elevGain = session.total_ascent || null;
  const elevLoss = session.total_descent || null;

  // -------------------------------
  // 4. HR / Cadenza / Velocità
  // -------------------------------
  const avgHr = session.avg_heart_rate || null;
  const maxHr = session.max_heart_rate || null;

  const avgCad = session.avg_cadence || null;
  const maxCad = session.max_cadence || null;

  const avgSpeed = session.avg_speed || null;
  const maxSpeed = session.max_speed || null;

  // -------------------------------
  // 5. Bounding box GPS
  // -------------------------------
  let minLat = null;
  let maxLat = null;
  let minLon = null;
  let maxLon = null;
  let minElev = null;
  let maxElev = null;

  for (const r of records) {
    const f = r.fields || {};

    const lat = fitSemicirclesToDegrees(f.position_lat);
    const lon = fitSemicirclesToDegrees(f.position_long);

    const eleRaw =
      f.altitude ??
      f.enhanced_altitude;

    const ele = eleRaw != null ? Number(eleRaw) : null;

    if (Number.isFinite(lat) && Number.isFinite(lon)) {
      minLat = minLat == null ? lat : Math.min(minLat, lat);
      maxLat = maxLat == null ? lat : Math.max(maxLat, lat);
      minLon = minLon == null ? lon : Math.min(minLon, lon);
      maxLon = maxLon == null ? lon : Math.max(maxLon, lon);
    }

    if (Number.isFinite(ele)) {
      minElev = minElev == null ? ele : Math.min(minElev, ele);
      maxElev = maxElev == null ? ele : Math.max(maxElev, ele);
    }
  }

  const centerLat =
    minLat != null && maxLat != null ? (minLat + maxLat) / 2 : null;

  const centerLon =
    minLon != null && maxLon != null ? (minLon + maxLon) / 2 : null;

  // -------------------------------
  // 6. Track preview per gallery
  // -------------------------------
  const trackPreview = buildTrackPreviewFromFitRecords(records, 300);

  // Log utile temporaneo. Puoi rimuoverlo dopo il test.
  console.log("[parseFit] track preview", {
    file: absPath,
    records: records.length,
    preview: trackPreview.length,
    first: trackPreview[0],
    minLat,
    maxLat,
    minLon,
    maxLon,
  });

  // -------------------------------
  // 7. Costruzione oggetto attività finale
  // -------------------------------
  return {
    format: "FIT",

    display_name: session.sport || null,
    route_name: session.sport || null,
    title: session.sport || null,
    description: null,
    notes: null,

    sport: session.sport || null,
    activity_type: session.sub_sport || null,
    device_manufacturer: file.manufacturer || null,
    device_model: file.product || null,
    source_app: null,

    start_time_millis: startMillis,
    end_time_millis: endMillis,
    duration_millis: durationMillis,

    distance_meters: distance,
    elevation_gain_meters: elevGain,
    elevation_loss_meters: elevLoss,

    min_elevation_meters: minElev,
    max_elevation_meters: maxElev,

    file_distance_meters: distance,
    file_elevation_gain_meters: elevGain,

    computed_distance_meters: distance,
    computed_elevation_gain_meters: elevGain,

    average_speed_mps: avgSpeed,
    max_speed_mps: maxSpeed,
    average_pace_sec_per_km: avgSpeed ? 1000 / avgSpeed : null,

    average_heart_rate: avgHr,
    max_heart_rate: maxHr,
    average_cadence: avgCad,
    max_cadence: maxCad,

    calories: session.total_calories || null,
    power_avg: session.avg_power || null,
    power_max: session.max_power || null,

    point_count: records.length,
    segment_count: laps.length,
    lap_count: laps.length,

    min_latitude: minLat,
    max_latitude: maxLat,
    min_longitude: minLon,
    max_longitude: maxLon,
    center_latitude: centerLat,
    center_longitude: centerLon,

    // Preview ridotta del percorso per i thumb della gallery
    track_preview: trackPreview,

    tags: [],

    diagnostics: {
      source: "FIT",
      sessions: sessions.length,
      laps: laps.length,
      records: records.length,
      track_preview_points: trackPreview.length,
      coordinates_converted_from_semicircles: true,
    },
  };
}

module.exports = parseFit;