"""
话题门控模块 - 判断当前 query 是继续话题还是切换话题
"""

from typing import List, Tuple
from .anchor import AnchorExtractor


# 指代词列表
DEICTIC_WORDS = {
    '这个', '那个', '它', '她', '他', '上面', '刚才', '继续',
    '展开', '为什么会这样', '怎么改', '然后', '还有', '另外',
    '这样', '那样', '如此', '前一个', '这一', '那一'
}


class TopicGate:
    """话题门控：判断是继续当前话题还是切换到新话题"""

    # 阈值参数
    OVERLAP_CONTINUE_THRESHOLD = 0.45
    OVERLAP_SWITCH_THRESHOLD = 0.20
    NEW_RATIO_SWITCH_THRESHOLD = 0.70

    def __init__(self, anchor_extractor: AnchorExtractor = None):
        self.anchor_extractor = anchor_extractor or AnchorExtractor()
        self.active_topic_anchors: List[str] = []
        self.active_topic_idf: dict[str, float] = {}

    def update_active_topic(self, anchors: List[str], idf: dict[str, float]) -> None:
        """更新活跃话题的锚点集合"""
        self.active_topic_anchors = anchors
        self.active_topic_idf = idf

    def is_topic_switch(
        self, query: str, active_topic: Tuple[List[str], dict[str, float]] = None
    ) -> bool:
        """
        判断当前 query 是否切换了话题

        Returns:
            True  -> 切换到新话题
            False -> 继续当前话题
        """
        anchors, has_deictic = self.anchor_extractor.extract_with_deictic(query)

        if active_topic is None:
            self.active_topic_anchors = anchors
            return False

        topic_anchors, topic_idf = active_topic

        # 有指代词 → 强暗示继续
        if has_deictic:
            return False

        # 计算 overlap 和 new_ratio
        overlap = self._compute_overlap(anchors, topic_anchors, topic_idf)
        new_ratio = self._compute_new_ratio(anchors, topic_anchors, topic_idf)

        # 切换判断
        if overlap < self.OVERLAP_SWITCH_THRESHOLD and new_ratio > self.NEW_RATIO_SWITCH_THRESHOLD:
            return True

        # 继续判断
        if overlap > self.OVERLAP_CONTINUE_THRESHOLD:
            return False

        # 中间地带：默认继续
        return False

    def _compute_overlap(
        self, query_anchors: List[str], topic_anchors: List[str], topic_idf: dict[str, float]
    ) -> float:
        """计算加权重叠率"""
        if not query_anchors:
            return 0.0

        overlap_weight = sum(
            topic_idf.get(a, 1.0)
            for a in query_anchors
            if a in topic_anchors
        )
        total_weight = sum(topic_idf.get(a, 1.0) for a in query_anchors)

        return overlap_weight / total_weight if total_weight > 0 else 0.0

    def _compute_new_ratio(
        self, query_anchors: List[str], topic_anchors: List[str], topic_idf: dict[str, float]
    ) -> float:
        """计算新锚点比例"""
        if not query_anchors:
            return 1.0

        new_anchors = set(query_anchors) - set(topic_anchors)
        new_weight = sum(topic_idf.get(a, 1.0) for a in new_anchors)
        total_weight = sum(topic_idf.get(a, 1.0) for a in query_anchors)

        return new_weight / total_weight if total_weight > 0 else 1.0

    def compute_idf_for_anchors(self, anchors: List[str]) -> dict[str, float]:
        """为锚点集合计算 IDF 值（用于后续计算）"""
        idf = {}
        for a in anchors:
            idf[a] = self.anchor_extractor.idf(a)
        return idf