# -*- coding: utf-8 -*-
"""Hybrid Search RAG - combines semantic and keyword (BM25) retrieval."""
import numpy as np
from .base import BaseRAG


class HybridSearchRAG(BaseRAG):
    def __init__(self, bm25_weight=0.3, semantic_weight=0.7, **kwargs):
        super().__init__(**kwargs)
        self.bm25_weight = bm25_weight
        self.semantic_weight = semantic_weight
        self.bm25 = None
        self._all_texts = []
        self._all_documents = []

    def index_documents(self, documents):
        texts = [doc.page_content for doc in documents]
        embeddings = self.embedding_model.embed_documents(texts)
        self.vector_store.add_documents(documents, embeddings)
        
        self._all_documents = documents
        self._all_texts = [text.split() for text in texts]
        
        from rank_bm25 import BM25Okapi
        self.bm25 = BM25Okapi(self._all_texts)

    def retrieve(self, query, k=10):
        query_embedding = self.embedding_model.embed_query(query)
        semantic_results = self.vector_store.similarity_search(query_embedding, k * 2)
        
        bm25_scores = np.zeros(len(self._all_documents))
        query_tokens = query.split()
        bm25_scores = self.bm25.get_scores(query_tokens)
        
        semantic_scores = np.zeros(len(self._all_documents))
        for doc, score in semantic_results:
            for i, ref_doc in enumerate(self._all_documents):
                if doc.page_content == ref_doc.page_content:
                    semantic_scores[i] = score
                    break
        
        hybrid_scores = self.semantic_weight * semantic_scores + self.bm25_weight * bm25_scores
        
        top_indices = np.argsort(hybrid_scores)[::-1][:k]
        results = []
        for idx in top_indices:
            if hybrid_scores[idx] > 0:
                results.append((self._all_documents[idx], float(hybrid_scores[idx])))
        
        return self._deduplicate_results(results, k)

    def generate(self, query, context):
        prompt = (
            "根据以下混合检索（语义+关键词）的参考文档，回答问题。\n\n"
            "参考文档：\n{}\n\n"
            "问题：{}\n\n"
            "请详细回答。".format(context, query)
        )
        return self._call_llm(prompt)