"""session.py — the two-photo safety policy that sits over the resolver.

The core safety rule, stated plainly:

    You are never shown an edible verdict on the strength of a single photo.

A single photo can show DEADLY (over-warning is always safe) or abstain. A
SAFE/CAUTION identification is only surfaced when a SECOND photo agrees with the
first (geometric-mean fusion + consensus, in infer.identify_many). So the second
photo is requested exactly, and only, when the system is leaning toward telling
you something is edible — the one moment extra rigor is worth the friction.

This is what closes the ~1% single-shot deadly-shown-edible residual to 0.00%
(scripts/multiview_smoketest.py).
"""

from PIL import Image

from .convergence import ForagerResult, build_result
from .infer import Pipeline

# There is no confidence bar that lets one photo commit edible. A 0.85 bar used to:
# the val sets had put every single-photo deadly-as-edible miss at <= 0.772. Over
# the full val sets, two toxic mushroom photos commit as SAFE above it (lion's
# mane at 0.91, chanterelle at 0.87), and val is the optimistic case. A confident
# wrong answer looks exactly like a confident right one, so no threshold on one
# photo's confidence can hold; only a second look can.


def resolve_session(pipe: Pipeline, images: list[Image.Image]) -> ForagerResult:
    """Run the K-photo pipeline and apply the single-photo edible gate.

    - 0 photos -> abstain.
    - DEADLY (any photo count) -> surface it. Over-warning is safe.
    - 1 photo, SAFE/CAUTION, at any confidence -> withhold; ask for a second photo.
    - 2+ photos -> the fused/consensus verdict from identify_many stands.
    """
    result = build_result(pipe.identify_many(images))

    if (len(images) == 1
            and not result.abstained
            and result.safety in ("SAFE", "CAUTION")):
        return _need_second_photo(result)
    return result


def _need_second_photo(provisional: ForagerResult) -> ForagerResult:
    """Turn a single-photo edible lean into a 'add a second photo' refusal,
    carrying the provisional species so the UI can say what it's leaning toward
    without committing to it."""
    return ForagerResult(
        domain=provisional.domain,
        species="unknown",
        scientific_name=provisional.scientific_name,
        confidence=provisional.confidence,
        safety="UNKNOWN",
        lookalike=provisional.lookalike,
        key_diff=(f"Leaning {provisional.species.replace('_', ' ')}, but an edible call "
                  f"needs a second photo from a different angle to confirm."),
        low_confidence=True,
        expert_model=provisional.expert_model,
        abstained=True,
        reason="need_second_photo",
    )