"""
锚点提取模块 - 用规则从文本中提取有代表性的锚点
"""

import re
from collections import Counter
from typing import List, Tuple


class AnchorExtractor:
    """提取文本中的锚点，用于话题判断和检索"""

    def __init__(self):
        # IDF 字典，用于权重计算（简单起见用内部默认值，可扩展）
        self._idf_cache: dict[str, float] = {}
        self._doc_count = 0

    def extract(self, text: str) -> List[str]:
        """从文本中提取锚点列表"""
        anchors = []

        # 中文 2-gram / 3-gram（转小写以便匹配）
        chinese_chars = re.findall(r'[\u4e00-\u9fff]+', text)
        for chunk in chinese_chars:
            if len(chunk) >= 2:
                for i in range(len(chunk) - 1):
                    anchors.append(chunk[i:i+2].lower())
            if len(chunk) >= 3:
                for i in range(len(chunk) - 2):
                    anchors.append(chunk[i:i+3].lower())

        # 英文单词
        english_words = re.findall(r'[a-zA-Z_][a-zA-Z0-9_-]*', text)
        anchors.extend([w.lower() for w in english_words if len(w) >= 2])

        # 代码标识符（反引号内）
        code_segments = re.findall(r'`([^`]+)`', text)
        for seg in code_segments:
            anchors.extend(re.findall(r'[a-zA-Z_][a-zA-Z0-9_-]*', seg))

        # 引号内的短语
        quoted_phrases = re.findall(r'["\u201c\u201d]([^"\u201c\u201d]+)["\u201c\u201d]', text)
        anchors.extend(quoted_phrases)

        # 数字、版本号
        versions = re.findall(r'v?\d+(\.\d+)*', text)
        anchors.extend(versions)

        return anchors

    def extract_with_deictic(self, text: str) -> Tuple[List[str], bool]:
        """提取锚点，并检测是否有指代词"""
        anchors = self.extract(text)
        deictic_patterns = [
            '这个', '那个', '它', '上面', '刚才', '继续', '展开',
            '为什么会这样', '怎么改', '然后', '还有', '另外'
        ]
        has_deictic = any(p in text for p in deictic_patterns)
        return anchors, has_deictic

    def compute_idf(self, all_doc_anchors: List[List[str]]) -> None:
        """根据一批文档计算 IDF 值"""
        self._doc_count = len(all_doc_anchors)
        doc_freq = Counter()
        for anchors in all_doc_anchors:
            unique_anchors = set(anchors)
            for a in unique_anchors:
                doc_freq[a] += 1

        for anchor, df in doc_freq.items():
            self._idf_cache[anchor] = self._doc_count / df

    def idf(self, anchor: str) -> float:
        """获取锚点的 IDF 值，默认 1.0"""
        return self._idf_cache.get(anchor, 1.0)