// Pure EXIF GPS helpers — tolerant of the varied shapes EXIF parsers return:
// numbers (37.7749), arrays ([d, m, s]), rational strings ("37/1", "46/1", "26964/1000")
// and arrays of rational strings.

export function parseRational(value: unknown): number | null {
  if (typeof value === 'number') {
    return Number.isFinite(value) ? value : null;
  }
  if (typeof value === 'string') {
    const parts = value.trim().split('/');
    if (parts.length === 2) {
      const num = Number(parts[0]);
      const den = Number(parts[1]);
      if (Number.isFinite(num) && Number.isFinite(den) && den !== 0) return num / den;
    }
    const n = Number(value);
    return Number.isFinite(n) ? n : null;
  }
  return null;
}

function toDecimal(value: unknown, ref: string): number | null {
  // value: single decimal (number|string) OR array [deg, min, sec]
  if (Array.isArray(value)) {
    const d = parseRational(value[0]);
    const m = parseRational(value[1]);
    const s = value.length > 2 ? parseRational(value[2]) : 0;
    if (d === null || m === null || s === null || d < 0 || m < 0 || s < 0) return null;
    return d + m / 60 + s / 3600;
  }
  const n = parseRational(value);
  return n === null || n < 0 ? null : n;
}

export function parseExifCoordinate(
  raw: unknown,
  ref: unknown
): number | null {
  const absolute = toDecimal(raw, String(ref));
  if (absolute === null || absolute === 0) return null; // ignore 0,0 placeholders
  const negative = ref === 'S' || ref === 'W';
  return negative ? -absolute : absolute;
}

export interface ExifLike {
  GPSLatitude?: unknown;
  GPSLatitudeRef?: unknown;
  GPSLongitude?: unknown;
  GPSLongitudeRef?: unknown;
  GPSDateStamp?: unknown;
  GPSTimeStamp?: unknown;
  DateTimeOriginal?: unknown;
}

export function parseExifGPS(exif: ExifLike | null | undefined): { latitude: number; longitude: number } | null {
  if (!exif) return null;
  const lat = parseExifCoordinate(exif.GPSLatitude, exif.GPSLatitudeRef);
  const lon = parseExifCoordinate(exif.GPSLongitude, exif.GPSLongitudeRef);
  if (lat === null || lon === null) return null;
  if (Math.abs(lat) > 90 || Math.abs(lon) > 180) return null; // invalid ranges
  if (lat === 0 && lon === 0) return null;
  return { latitude: lat, longitude: lon };
}

const parseTimeStamp = (value: unknown): [number, number, number] | null => {
  if (!Array.isArray(value)) return null;
  const h = parseRational(value[0]);
  const m = parseRational(value[1]);
  const s = value.length > 2 ? parseRational(value[2]) : 0;
  if (h === null || m === null || s === null) return null;
  if (h > 23 || m > 59 || s > 61) return null;
  return [h, m, s];
};

// EXIF stores dates as "2023:01:02 15:04:05" — colons, not dashes.
export function parseExifTimestamp(exif: ExifLike | null | undefined): number | null {
  if (!exif) return null;
  const raw = typeof exif.DateTimeOriginal === 'string' ? exif.DateTimeOriginal : '';
  let dateText = raw.trim();
  if (!dateText && typeof exif.GPSDateStamp === 'string') {
    const gpsDate = (exif.GPSDateStamp as string).trim();
    const gpsTime = parseTimeStamp(exif.GPSTimeStamp);
    if (gpsTime) {
      dateText = `${gpsDate} ${gpsTime[0]}:${gpsTime[1]}:${gpsTime[2]}`;
    } else if (gpsDate) {
      dateText = `${gpsDate} 00:00:00`;
    }
  }
  if (!dateText) return null;
  // Normalize "2023:1:2 15:4:5" (any of : / - separators, unpadded parts)
  // into an ISO string "2023-01-02T15:04:05" before parsing.
  const m = dateText.match(/^(\d{4})[:/-](\d{1,2})[:/-](\d{1,2})(?:[ T]+(\d{1,2}):(\d{1,2})(?::(\d{1,2}))?)?/);
  if (!m) return null;
  const two = (v: string) => v.padStart(2, '0');
  const [, y, mo, d, h = '0', mi = '0', s = '0'] = m;
  const time = Date.parse(`${y}-${two(mo)}-${two(d)}T${two(h)}:${two(mi)}:${two(s)}`);
  return Number.isFinite(time) ? time : null;
}