"""Repeated-run finding stability metrics."""

from __future__ import annotations

from collections.abc import Iterable, Sequence
from typing import Any

from .metrics import distribution_summary


def jaccard(left: set[str], right: set[str]) -> float:
    union = left | right
    return len(left & right) / len(union) if union else 1.0


def stability_summary(runs: Sequence[Iterable[str]]) -> dict[str, Any]:
    sets = [set(run) for run in runs]
    if not sets:
        return {
            "run_count": 0,
            "exact": False,
            "intersection_count": 0,
            "union_count": 0,
            "churn_count": 0,
            "per_run_counts": [],
            "pairwise_jaccard": distribution_summary([]),
        }

    intersection = set.intersection(*sets)
    union = set.union(*sets)
    pairwise = [
        jaccard(sets[left], sets[right])
        for left in range(len(sets))
        for right in range(left + 1, len(sets))
    ]
    if len(sets) == 1:
        pairwise = [1.0]
    return {
        "run_count": len(sets),
        "exact": all(current == sets[0] for current in sets[1:]),
        "intersection_count": len(intersection),
        "union_count": len(union),
        "churn_count": len(union - intersection),
        "per_run_counts": [len(current) for current in sets],
        "pairwise_jaccard": distribution_summary(pairwise),
    }