from __future__ import annotations

from pathlib import Path
from PIL import Image, ExifTags
import csv
import argparse


def _to_deg(value):
    """Convert EXIF GPS coordinates to float degrees."""
    try:
        def to_float(x):
            try:
                if isinstance(x, tuple) and len(x) == 2:
                    return x[0] / x[1]
            except Exception:
                pass
            return float(x)

        d = to_float(value[0])
        m = to_float(value[1])
        s = to_float(value[2])
        return d + (m / 60.0) + (s / 3600.0)
    except Exception:
        return None


def exif_latlon(img_path: Path):
    """Read (lat, lon) from image EXIF. Returns tuple or None if missing."""
    try:
        with Image.open(img_path) as img:
            exif = img._getexif() or {}
    except Exception:
        return None

    if not exif:
        return None

    exif_dict = {ExifTags.TAGS.get(k, k): v for k, v in exif.items()}
    gps_tag = exif_dict.get('GPSInfo')
    if not gps_tag:
        return None

    gps = {ExifTags.GPSTAGS.get(k, k): v for k, v in gps_tag.items()}
    lat_raw = gps.get('GPSLatitude')
    lon_raw = gps.get('GPSLongitude')
    if lat_raw is None or lon_raw is None:
        return None

    lat = _to_deg(lat_raw)
    lon = _to_deg(lon_raw)
    if lat is None or lon is None:
        return None

    if gps.get('GPSLatitudeRef', 'N') in ('S', b'S'):
        lat = -lat
    if gps.get('GPSLongitudeRef', 'E') in ('W', b'W'):
        lon = -lon

    return lat, lon


def extract_split(split_dir: Path) -> Path:
    """Scan a split directory for images and write metadata.csv with
    columns: file_name, Latitude, Longitude (as per notebook).
    Returns path to the written CSV.
    """
    exts = {'.jpg', '.jpeg', '.JPG', '.JPEG'}
    rows = []
    total = 0

    for p in split_dir.rglob('*'):
        if p.is_file() and p.suffix in exts:
            total += 1
            ll = exif_latlon(p)
            if ll:
                # store path relative to split directory to keep it portable
                rel = p.relative_to(split_dir)
                rows.append([str(rel).replace('\\\\', '/'), ll[0], ll[1]])

    out_csv = split_dir / 'metadata.csv'
    with out_csv.open('w', newline='', encoding='utf-8') as f:
        w = csv.writer(f)
        w.writerow(['file_name', 'Latitude', 'Longitude'])
        w.writerows(rows)

    print(f"Split: {split_dir}")
    print(f"Scanned {total} images; extracted {len(rows)} with GPS.")
    print(f"Wrote: {out_csv}")
    return out_csv


def main():
    ap = argparse.ArgumentParser(description='Extract metadata.csv for a split directory (Route B).')
    ap.add_argument('split_dir', type=Path, help='Path to a split directory (e.g., data/train)')
    args = ap.parse_args()

    if not args.split_dir.exists() or not args.split_dir.is_dir():
        raise SystemExit(f"Split directory not found: {args.split_dir}")

    extract_split(args.split_dir)


if __name__ == '__main__':
    main()