miles_tables.py

"""Miles accrual tables for CX Marco Polo and SQ KrisFlyer."""

from __future__ import annotations

# ---------------------------------------------------------------------------
# Fare class earn multipliers
# ---------------------------------------------------------------------------

# CX Marco Polo Club — tier miles multiplier per fare class
# Source: Cathay Pacific Marco Polo Club earning table
MARCO_POLO_MULTIPLIERS: dict[str, float] = {
    "F": 1.5,   # First
    "A": 1.5,   # First (promo)
    "J": 1.25,  # Business
    "C": 1.25,  # Business
    "D": 1.25,  # Business
    "I": 1.0,   # Business (lower)
    "W": 0.0,   # Premium Economy (no tier miles)
    "R": 0.0,   # Premium Economy (no tier miles)
    "E": 0.0,   # Premium Economy (no tier miles)
    "Y": 1.0,   # Economy full fare
    "B": 1.0,   # Economy
    "H": 0.75,  # Economy
    "K": 0.5,   # Economy
    "M": 0.5,   # Economy
    "L": 0.25,  # Economy
    "V": 0.0,   # Economy (no tier miles)
    "G": 0.0,   # Economy (no tier miles)
    "S": 0.0,   # Economy (no tier miles)
    "O": 0.0,   # Economy (no tier miles)
    "Q": 0.25,  # Economy
    "N": 0.25,  # Economy
    "T": 0.0,   # Economy (no tier miles)
    "X": 0.0,   # Economy (no tier miles)
    "P": 0.0,   # Economy (no tier miles)
}

# SQ KrisFlyer — tier miles (PPS Value) multiplier per fare class
# Source: Singapore Airlines KrisFlyer earning table
KRISFLYER_MULTIPLIERS: dict[str, float] = {
    "F": 1.5,   # First / Suites
    "P": 1.5,   # First (promo)
    "J": 1.25,  # Business
    "C": 1.25,  # Business
    "D": 1.25,  # Business
    "U": 1.0,   # Business (lower)
    "Z": 1.0,   # Business (lower)
    "W": 0.75,  # Premium Economy
    "R": 0.75,  # Premium Economy
    "E": 0.75,  # Premium Economy
    "T": 0.75,  # Premium Economy
    "Y": 1.0,   # Economy full fare
    "B": 1.0,   # Economy
    "G": 0.75,  # Economy
    "S": 0.75,  # Economy
    "H": 0.75,  # Economy
    "Q": 0.5,   # Economy
    "K": 0.5,   # Economy
    "M": 0.5,   # Economy
    "L": 0.25,  # Economy
    "V": 0.25,  # Economy
    "A": 0.0,   # Economy (no tier miles)
    "N": 0.0,   # Economy (no tier miles)
    "O": 0.0,   # Economy (no tier miles)
}

# ---------------------------------------------------------------------------
# Route distances (air miles, statute miles)
# ---------------------------------------------------------------------------

ROUTE_DISTANCES_MI: dict[frozenset[str], int] = {
    frozenset({"HKG", "NRT"}): 2894,
    frozenset({"HKG", "TYO"}): 2894,  # alias
    frozenset({"HKG", "SIN"}): 1597,
    frozenset({"HKG", "LHR"}): 5986,
    frozenset({"HKG", "LAX"}): 7260,
    frozenset({"HKG", "SFO"}): 6905,
    frozenset({"HKG", "SYD"}): 4587,
    frozenset({"HKG", "ICN"}): 1309,
    frozenset({"HKG", "BKK"}): 1072,
    frozenset({"SIN", "LHR"}): 6764,
    frozenset({"SIN", "NRT"}): 3321,
    frozenset({"SIN", "SYD"}): 3908,
    frozenset({"SIN", "LAX"}): 8753,
    frozenset({"HKG", "SFO"}): 6905,
    frozenset({"HKG", "ORD"}): 7797,
    frozenset({"HKG", "JFK"}): 8054,
    frozenset({"HKG", "CDG"}): 5980,
    frozenset({"HKG", "FRA"}): 5737,
}

# ---------------------------------------------------------------------------
# Multiplier table lookup by airline
# ---------------------------------------------------------------------------

_AIRLINE_MULTIPLIER_TABLES: dict[str, dict[str, float]] = {
    "CX": MARCO_POLO_MULTIPLIERS,
    "SQ": KRISFLYER_MULTIPLIERS,
}


def calculate_miles(airline: str, fare_class: str, origin: str, dest: str) -> int | None:
    """Calculate estimated tier miles for a given flight.

    Returns None if:
    - Airline not in supported tables
    - Route not in distance table
    - fare_class earns 0 multiplier (still returns 0, not None)

    Returns None only for unknown route or unsupported airline.
    """
    table = _AIRLINE_MULTIPLIER_TABLES.get(airline.upper())
    if table is None:
        return None

    route_key = frozenset({origin.upper(), dest.upper()})
    distance = ROUTE_DISTANCES_MI.get(route_key)
    if distance is None:
        return None

    multiplier = table.get(fare_class.upper(), None)
    if multiplier is None:
        return None

    return round(distance * multiplier)