"""RRF 融合与截断的单元测试"""

import pytest
from qdrant_client import models

from app.core.ranker import finalize, rrf_fuse


def _point(pid: str, score: float = 1.0) -> models.ScoredPoint:
    return models.ScoredPoint(id=pid, version=0, score=score, payload={}, vector=None)


class TestRrfFuse:
    """rrf_fuse 的排序 / 去重 / 空输入 / k 参数行为"""

    def test_empty_input(self):
        """空列表输入返回 []"""
        assert rrf_fuse([]) == []
        assert rrf_fuse([[], []]) == []

    def test_single_list_fused_scores(self):
        """单路结果按 rank 计算 1/(k+rank) 融合分并降序返回"""
        fused = rrf_fuse([[_point("a"), _point("b"), _point("c")]], k=60)
        assert [p.id for p in fused] == ["a", "b", "c"]
        assert fused[0].score == pytest.approx(1 / 61)
        assert fused[1].score == pytest.approx(1 / 62)
        assert fused[2].score == pytest.approx(1 / 63)

    def test_dedup_merges_scores(self):
        """同一 point id 出现在多路结果中，只保留一条且分数累加"""
        list1 = [_point("a"), _point("b")]
        list2 = [_point("b"), _point("c")]
        fused = rrf_fuse([list1, list2], k=60)
        # b 在两路中分别 rank2/rank1，融合分最高；a 与 c 各 1/61
        assert [p.id for p in fused] == ["b", "a", "c"]
        assert fused[0].score == pytest.approx(1 / 62 + 1 / 61)
        assert fused[1].score == pytest.approx(1 / 61)
        assert fused[2].score == pytest.approx(1 / 62)

    def test_k_affects_ranking(self):
        """k 参数改变融合权重，可改变最终排序

        A 排名 [1, 10]，B 排名 [5, 5]：
        - k=60 时 B 总分更高（两路均衡占优）
        - k=1 时 A 总分更高（头部 rank 权重被放大）
        """
        l1 = [_point("a"), *[_point(f"n{i}") for i in range(3)], _point("b"), *[_point(f"m{i}") for i in range(5)]]
        l2 = [*[_point(f"x{i}") for i in range(4)], _point("b"), *[_point(f"y{i}") for i in range(4)], _point("a")]
        # l1：a rank1，b rank5；l2：b rank5，a rank10

        fused_k60 = rrf_fuse([l1, l2], k=60)
        assert fused_k60[0].id == "b"

        fused_k1 = rrf_fuse([l1, l2], k=1)
        assert fused_k1[0].id == "a"

    def test_result_is_new_objects(self):
        """返回的是写回融合分的新对象，不修改原 point"""
        original = _point("a", score=0.99)
        fused = rrf_fuse([[original]], k=60)
        assert fused[0].score != 0.99
        assert original.score == 0.99


class TestFinalize:
    """finalize 截断行为"""

    def test_truncate(self):
        points = [_point(str(i)) for i in range(10)]
        result = finalize(points, 5)
        assert [p.id for p in result] == ["0", "1", "2", "3", "4"]

    def test_truncate_larger_than_input(self):
        """final_k 大于列表长度时返回全部"""
        points = [_point("a"), _point("b")]
        assert finalize(points, 5) == points

    def test_empty(self):
        assert finalize([], 5) == []