from dataclasses import dataclass
from typing import List, Literal, Optional, Sequence, Tuple

PhoneKind = Literal["mobile", "telephone"]


@dataclass(frozen=True)
class PhoneEntry:
    """One phone number as Abri lists it for a tenant, in document order."""

    kind: PhoneKind
    number: str
    priority: Optional[str] = None


@dataclass(frozen=True)
class SelectedPhoneNumbers:
    """The numbers a contact carries: best of each kind plus the runner-up."""

    mobile: Optional[str]
    telephone: Optional[str]
    secondary: Optional[str]


# TODO(#1474): confirm the priority ordering with Abri — this assumes the
# lowest numeric priority marks the preferred number, and that entries with
# a missing or non-numeric priority rank last (ties keep document order).
def _priority_sort_key(entry: PhoneEntry) -> Tuple[int, int]:
    """Sort key: lowest numeric priority first; unusable priorities last."""
    try:
        return (0, int((entry.priority or "").strip()))
    except ValueError:
        return (1, 0)


def _best(entries: List[PhoneEntry]) -> Optional[PhoneEntry]:
    ranked = sorted(entries, key=_priority_sort_key)  # stable: ties keep document order
    return ranked[0] if ranked else None


def _number(entry: Optional[PhoneEntry]) -> Optional[str]:
    return entry.number.strip() if entry is not None else None


def select_phone_numbers(entries: Sequence[PhoneEntry]) -> SelectedPhoneNumbers:
    """Best mobile, best landline, then the best of the leftovers of both kinds.

    All three picks use the same rule: lowest numeric priority wins, entries
    without a usable priority sort last, ties break by document order, blank
    numbers are ignored.
    """
    usable = [entry for entry in entries if entry.number.strip()]

    best_mobile = _best([e for e in usable if e.kind == "mobile"])
    best_telephone = _best([e for e in usable if e.kind == "telephone"])
    runner_up = _best(
        [e for e in usable if e is not best_mobile and e is not best_telephone]
    )

    return SelectedPhoneNumbers(
        mobile=_number(best_mobile),
        telephone=_number(best_telephone),
        secondary=_number(runner_up),
    )