# default_policy.py
# Built-in default policy for Berghain Challenge.
#
# Strategy:
#   - If all minimums are satisfied, admit freely.
#   - Admit creatives until quota met (they are rare).
#   - Admit Berlin locals until quota met (they are required in bulk).
#   - Otherwise admit if candidate helps at least one unmet need,
#     provided there is still enough capacity to meet all others.
#   - Reject if candidate does not help with unmet needs
#     or would make quotas infeasible.
#
# The policy records a human-readable reason string for each decision,
# retrievable via policy_reason(). Your UI can display this directly.

import sys

DEBUG = False
_last_reason: str | None = None


def _set_reason(msg: str) -> None:
    """Set the last decision reason (and echo to stderr if DEBUG)."""
    global _last_reason
    _last_reason = msg
    if DEBUG:
        print(msg, file=sys.stderr, flush=True)


def policy_reason() -> str | None:
    """Return the most recent decision reason string."""
    return _last_reason


def decide(attributes: dict[str, bool],
           tallies: dict[str, int],
           mins: dict[str, int],
           admitted_count: int,
           venue_cap: int,
           **_) -> bool:
    """Return True to admit, False to reject."""
    S = venue_cap - admitted_count
    need = {a: max(0, mins[a] - tallies.get(a, 0)) for a in mins}

    # 1. All quotas already met
    if sum(need.values()) == 0:
        _set_reason("Admit (all minimums satisfied)")
        return True

    # 2. Admit creatives until quota met
    if need.get("creative", 0) > 0 and attributes.get("creative", False):
        _set_reason("Admit creative (rare + still needed)")
        return True

    # 3. Admit locals until quota met
    if need.get("berlin_local", 0) > 0 and attributes.get("berlin_local", False):
        _set_reason("Admit berlin_local (large quota still unmet)")
        return True

    # 4. Admit if candidate helps an unmet need and feasibility is safe
    helps = [a for a in need if need[a] > 0 and attributes.get(a, False)]
    if helps:
        S_after = S - 1
        remaining_after = sum(
            max(0, need[a] - (1 if attributes.get(a, False) else 0))
            for a in need
        )
        if S_after >= remaining_after:
            _set_reason(f"Admit (helps {', '.join(helps)}, feasibility ok)")
            return True
        else:
            _set_reason("Reject (would break feasibility)")
            return False

    # 5. Reject if they don’t help
    _set_reason("Reject (no help to unmet needs)")
    return False