"""检索结果重排：RRF 融合与最终截断"""

from qdrant_client import models


def rrf_fuse(result_lists: list[list[models.ScoredPoint]], k: int = 60) -> list[models.ScoredPoint]:
    """标准 RRF（Reciprocal Rank Fusion）融合

    融合分 = Σ 1/(k + rank)（rank 从 1 开始），按 point id 去重合并，
    返回按融合分降序的列表，score 字段写回融合分。空输入返回 []。
    """
    scores: dict[str | int, float] = {}
    points: dict[str | int, models.ScoredPoint] = {}
    for results in result_lists:
        for rank, point in enumerate(results, start=1):
            scores[point.id] = scores.get(point.id, 0.0) + 1.0 / (k + rank)
            points.setdefault(point.id, point)
    ordered = sorted(points, key=lambda pid: scores[pid], reverse=True)
    return [points[pid].model_copy(update={"score": scores[pid]}) for pid in ordered]


def finalize(points: list[models.ScoredPoint], final_k: int) -> list[models.ScoredPoint]:
    """截断为最终返回的 top final_k"""
    return points[:final_k]