ciaovolo/flight-comparator/airports.py

"""
Airport data resolution by country.

Handles loading and filtering airport data from OpenFlights dataset.
"""

import json
import csv
from functools import lru_cache
from pathlib import Path
from typing import Optional
import urllib.request

# Try to import pycountry, fall back to manual mapping if not available
try:
    import pycountry
    HAS_PYCOUNTRY = True
except ImportError:
    HAS_PYCOUNTRY = False


AIRPORTS_JSON_PATH = Path(__file__).parent / "data" / "airports_by_country.json"
OPENFLIGHTS_URL = "https://raw.githubusercontent.com/jpatokal/openflights/master/data/airports.dat"

# Manual mapping for common countries (fallback if pycountry not available)
COUNTRY_NAME_TO_ISO = {
    "Germany": "DE",
    "United States": "US",
    "United Kingdom": "GB",
    "France": "FR",
    "Spain": "ES",
    "Italy": "IT",
    "Netherlands": "NL",
    "Belgium": "BE",
    "Austria": "AT",
    "Switzerland": "CH",
    "Poland": "PL",
    "Czech Republic": "CZ",
    "Denmark": "DK",
    "Sweden": "SE",
    "Norway": "NO",
    "Finland": "FI",
    "Ireland": "IE",
    "Portugal": "PT",
    "Greece": "GR",
    "Turkey": "TR",
    "Japan": "JP",
    "China": "CN",
    "South Korea": "KR",
    "India": "IN",
    "Australia": "AU",
    "New Zealand": "NZ",
    "Canada": "CA",
    "Mexico": "MX",
    "Brazil": "BR",
    "Argentina": "AR",
    "Chile": "CL",
    "Colombia": "CO",
    "Peru": "PE",
    "South Africa": "ZA",
    "Egypt": "EG",
    "United Arab Emirates": "AE",
    "Thailand": "TH",
    "Singapore": "SG",
    "Malaysia": "MY",
    "Indonesia": "ID",
    "Philippines": "PH",
    "Vietnam": "VN",
}


# Airports missing from the OpenFlights dataset (opened or renamed after dataset was last updated).
# Keyed by ISO country code; dicts match the airports_by_country.json schema (iata/name/city/icao).
_MISSING_AIRPORTS: dict[str, list[dict]] = {
    'DE': [{'iata': 'BER', 'name': 'Berlin Brandenburg Airport', 'city': 'Berlin', 'icao': 'EDDB'}],
}


def country_name_to_iso_code(country_name: str) -> Optional[str]:
    """
    Convert country name to ISO 2-letter code.

    Args:
        country_name: Full country name

    Returns:
        ISO 2-letter code or None if not found
    """
    if HAS_PYCOUNTRY:
        try:
            country = pycountry.countries.search_fuzzy(country_name)[0]
            return country.alpha_2
        except (LookupError, AttributeError):
            pass

    # Fallback to manual mapping
    return COUNTRY_NAME_TO_ISO.get(country_name)


def download_and_build_airport_data(force_rebuild: bool = False) -> None:
    """
    Download OpenFlights dataset and build airports_by_country.json.

    Filters to airports with valid IATA codes only.
    Groups by ISO 2-letter country code.

    Args:
        force_rebuild: If True, rebuild even if file exists
    """
    if AIRPORTS_JSON_PATH.exists() and not force_rebuild:
        return

    print(f"Downloading OpenFlights airport data from {OPENFLIGHTS_URL}...")

    # Download the data
    response = urllib.request.urlopen(OPENFLIGHTS_URL)
    data = response.read().decode('utf-8')

    # Parse CSV
    # Format: AirportID,Name,City,Country,IATA,ICAO,Lat,Lon,Alt,Timezone,DST,Tz,Type,Source
    airports_by_country = {}

    for line in data.strip().split('\n'):
        # Use csv reader to handle quoted fields properly
        row = next(csv.reader([line]))

        if len(row) < 5:
            continue

        airport_id = row[0]
        name = row[1]
        city = row[2]
        country_name = row[3]
        iata = row[4]
        icao = row[5] if len(row) > 5 else ""

        # Skip if no valid IATA code
        if not iata or iata == "\\N" or len(iata) != 3:
            continue

        # Skip if country name is missing
        if not country_name or country_name == "\\N":
            continue

        # Convert country name to ISO code
        country_code = country_name_to_iso_code(country_name)
        if not country_code:
            # Skip if we can't map the country
            continue

        # Build airport entry
        airport = {
            "iata": iata,
            "name": name,
            "city": city,
            "icao": icao if icao != "\\N" else ""
        }

        # Group by country ISO code
        if country_code not in airports_by_country:
            airports_by_country[country_code] = []

        airports_by_country[country_code].append(airport)

    # Ensure data directory exists
    AIRPORTS_JSON_PATH.parent.mkdir(parents=True, exist_ok=True)

    # Write to JSON file
    with open(AIRPORTS_JSON_PATH, 'w', encoding='utf-8') as f:
        json.dump(airports_by_country, f, indent=2, ensure_ascii=False)

    total_airports = sum(len(v) for v in airports_by_country.values())
    print(f"✓ Built airport data: {len(airports_by_country)} countries, {total_airports} airports")


def get_airports_for_country(country_code: str) -> list[dict]:
    """
    Get list of airports for a given country code.

    Args:
        country_code: ISO 2-letter country code (e.g., "DE", "US")

    Returns:
        List of airport dicts with keys: iata, name, city, icao

    Raises:
        FileNotFoundError: If airports data file doesn't exist
        ValueError: If country code not found
    """
    # Ensure data file exists
    if not AIRPORTS_JSON_PATH.exists():
        download_and_build_airport_data()

    # Load from JSON
    with open(AIRPORTS_JSON_PATH, 'r', encoding='utf-8') as f:
        airports_by_country = json.load(f)

    country_code = country_code.upper()

    if country_code not in airports_by_country:
        available = sorted(airports_by_country.keys())[:10]
        raise ValueError(
            f"Country code '{country_code}' not found. "
            f"Available codes (sample): {', '.join(available)}..."
        )

    result = list(airports_by_country[country_code])
    existing_iatas = {a['iata'] for a in result}
    for extra in _MISSING_AIRPORTS.get(country_code, []):
        if extra['iata'] not in existing_iatas:
            result.append(extra)
    return result


def resolve_airport_list(country: Optional[str], from_airports: Optional[str]) -> list[dict]:
    """
    Resolve the final list of origin airports to scan.

    Args:
        country: ISO 2-letter country code (if --from not provided)
        from_airports: Comma-separated IATA codes (overrides country)

    Returns:
        List of airport dicts with keys: iata, name, city

    Raises:
        ValueError: If neither country nor from_airports provided, or if invalid
    """
    if from_airports:
        # Parse custom airport list
        iata_codes = [code.strip().upper() for code in from_airports.split(',')]
        # Create minimal airport dicts
        return [{"iata": code, "name": code, "city": ""} for code in iata_codes]

    if country:
        return get_airports_for_country(country)

    raise ValueError("Either --country or --from must be provided")


@lru_cache(maxsize=1)
def _all_airports_by_iata() -> dict:
    """Return {iata: airport_dict} for every airport. Cached after first load."""
    if not AIRPORTS_JSON_PATH.exists():
        download_and_build_airport_data()
    with open(AIRPORTS_JSON_PATH, 'r', encoding='utf-8') as f:
        airports_by_country = json.load(f)
    result = {
        a['iata']: a
        for airports in airports_by_country.values()
        for a in airports
    }
    for extras in _MISSING_AIRPORTS.values():
        for extra in extras:
            if extra['iata'] not in result:
                result[extra['iata']] = extra
    return result


def lookup_airport(iata: str) -> dict | None:
    """Look up a single airport by IATA code. Returns None if not found."""
    return _all_airports_by_iata().get(iata.upper())


if __name__ == "__main__":
    # Build the dataset if run directly
    download_and_build_airport_data(force_rebuild=True)
    print("\nSample data for Germany (DE):")
    de_airports = get_airports_for_country("DE")
    for airport in de_airports[:5]:
        print(f"  {airport['iata']} - {airport['name']} ({airport['city']})")
    print(f"  ... and {len(de_airports) - 5} more")