"""GPS data reader for adacam-api.
Primary source: /data/recording/odc-api.db framekms table (confirmed schema from live device).
Fallback: Redis (keys may appear when device has outdoor GPS fix post-liberation).

Confirmed field names from live device:
  latitude, longitude, altitude, hdop, satellites_used, speed, heading, time
"""
import json
import os
import sqlite3
import time

ODC_DB = '/data/recording/odc-api.db'
GNSS_REDIS_KEYS = ['GNSSFusion30Hz', 'GnssData', 'GnssPvt', 'GnssPosition']

_redis_client = None


def _get_redis():
    global _redis_client
    try:
        import redis
        if _redis_client is None:
            _redis_client = redis.Redis(host='localhost', port=6379, decode_responses=True)
        _redis_client.ping()
        return _redis_client
    except Exception:
        _redis_client = None
        return None


def get_latest_gnss():
    """Get latest GPS fix. Returns dict with keys: lat_deg, lon_deg, alt_m, hdop, num_satellites.
    Field names kept compatible with original API response format."""

    # Primary: SQLite framekms (confirmed live device schema)
    if os.path.exists(ODC_DB):
        try:
            conn = sqlite3.connect(ODC_DB)
            row = conn.execute(
                'SELECT latitude, longitude, altitude, hdop, satellites_used, time '
                'FROM framekms WHERE latitude IS NOT NULL AND latitude != 0 '
                'ORDER BY time DESC LIMIT 1'
            ).fetchone()
            conn.close()
            if row:
                return {
                    'lat_deg': row[0],
                    'lon_deg': row[1],
                    'alt_m': row[2],
                    'hdop': row[3],
                    'num_satellites': row[4],
                    'unix_milliseconds': int(row[5]) if row[5] else int(time.time() * 1000),
                }
        except Exception:
            pass

    # Fallback: Redis (may appear post-liberation with outdoor GPS fix)
    r = _get_redis()
    if r:
        for key in GNSS_REDIS_KEYS:
            try:
                for getter in [lambda k: r.zrevrange(k, 0, 0), lambda k: [r.get(k)]]:
                    items = getter(key)
                    item = items[0] if items else None
                    if item:
                        data = json.loads(item)
                        lat = data.get('latitude') or data.get('lat_deg')
                        lon = data.get('longitude') or data.get('lon_deg')
                        if lat and lon:
                            return {
                                'lat_deg': lat,
                                'lon_deg': lon,
                                'alt_m': data.get('altitude') or data.get('alt_m', 0),
                                'hdop': data.get('hdop', 99),
                                'num_satellites': data.get('satellites_used') or data.get('num_satellites', 0),
                                'unix_milliseconds': int(data.get('unix_milliseconds', time.time() * 1000)),
                            }
            except Exception:
                continue
    return None


def has_gps_lock():
    """Check if we have a valid GPS lock."""
    gnss = get_latest_gnss()
    return gnss is not None and gnss.get('num_satellites', 0) >= 4