"""RAG 适配层 — 查询已由 rag_jrxml 子项目构建好的 ChromaDB 向量知识库。

rag_jrxml 独立运行产出向量库后，主项目通过此模块进行语义搜索。

用法:
    from backend.rag_adapter import search_chunks
    context = search_chunks("如何添加饼图", k=5)
"""

import os
import logging
from pathlib import Path
from typing import Optional

from dotenv import load_dotenv

load_dotenv()

logger = logging.getLogger(__name__)

_PROJECT_ROOT = Path(__file__).resolve().parent.parent


def _resolve(path: str) -> Path:
    p = Path(path)
    if not p.is_absolute():
        p = _PROJECT_ROOT / p
    return p


class RAGSearcher:
    """连接预构建的 ChromaDB，提供语义搜索。"""

    def __init__(
        self,
        chroma_path: Optional[str] = None,
        collection_name: Optional[str] = None,
        model_name: Optional[str] = None,
        use_gpu: Optional[bool] = None,
        use_fp16: Optional[bool] = None,
    ):
        self.chroma_path = _resolve(chroma_path or os.getenv("RAG_CHROMA_PATH", "./db/chroma"))
        self.collection_name = collection_name or os.getenv("RAG_COLLECTION_NAME", "jrxml_chunks")
        model_path = model_name or os.getenv("RAG_EMBED_MODEL", "./rag/models/paraphrase-multilingual-MiniLM-L12-v2")
        # 如果本地路径存在则使用本地，否则当 Hub 模型名使用
        resolved = _resolve(model_path)
        self.model_name = str(resolved) if resolved.exists() else model_path
        self.use_gpu = use_gpu if use_gpu is not None else os.getenv("RAG_USE_GPU", "true").lower() in ("true", "1")
        self.use_fp16 = use_fp16 if use_fp16 is not None else os.getenv("RAG_USE_FP16", "true").lower() in ("true", "1")

        self._model = None
        self._client = None
        self._collection = None

    # ---- 模型懒加载 ----
    @property
    def model(self):
        if self._model is None:
            import torch
            from sentence_transformers import SentenceTransformer

            device = "cuda" if (self.use_gpu and torch.cuda.is_available()) else "cpu"
            logger.info("加载嵌入模型: %s (device=%s)", self.model_name, device)
            model = SentenceTransformer(self.model_name, device=device)
            if device == "cuda" and self.use_fp16:
                model = model.half()
            self._model = model
        return self._model

    # ---- ChromaDB 懒连接 ----
    @property
    def client(self):
        if self._client is None:
            import chromadb
            self._client = chromadb.PersistentClient(path=str(self.chroma_path))
        return self._client

    @property
    def collection(self):
        if self._collection is None:
            self._collection = self.client.get_collection(self.collection_name)
        return self._collection

    def is_ready(self) -> bool:
        try:
            self.client.get_collection(self.collection_name)
            return True
        except Exception:
            return False

    # ---- 语义搜索 ----
    def search(self, query: str, k: int = 5, threshold: Optional[float] = None) -> list[dict]:
        """搜索相关 JRXML chunks，返回 [{id, content, metadata, distance}, ...]."""
        if not self.is_ready():
            logger.warning("ChromaDB 集合 '%s' 不存在，请先在 rag/ 子项目中运行管线", self.collection_name)
            return []

        query_embedding = self.model.encode(
            query, normalize_embeddings=True, show_progress_bar=False
        )

        results = self.collection.query(
            query_embeddings=[query_embedding.tolist()],
            n_results=k,
            include=["documents", "metadatas", "distances"],
        )

        output = []
        if not results["ids"] or not results["ids"][0]:
            return output

        for i, doc_id in enumerate(results["ids"][0]):
            dist = results["distances"][0][i]
            if threshold is not None and dist > threshold:
                continue
            output.append({
                "id": doc_id,
                "content": results["documents"][0][i],
                "metadata": results["metadatas"][0][i],
                "distance": dist,
            })
        return output

    def search_as_context(self, query: str, k: int = 5) -> str:
        """搜索并返回拼接好的上下文字符串，可直接注入 LLM prompt。"""
        results = self.search(query, k=k)
        if not results:
            return ""

        parts = []
        for r in results:
            meta = r["metadata"]
            header = f"[类型:{meta.get('chunk_type', 'N/A')}]"
            if meta.get("report_name"):
                header += f" [报表:{meta['report_name']}]"
            if meta.get("band_name"):
                header += f" [区域:{meta['band_name']}]"
            parts.append(f"{header}\n{r['content']}")
        return "\n\n---\n\n".join(parts)


# 全局单例，避免重复加载模型
_searcher: Optional[RAGSearcher] = None


def _get_searcher() -> RAGSearcher:
    global _searcher
    if _searcher is None:
        _searcher = RAGSearcher()
    return _searcher


def search_chunks(query: str, k: int = 5, kb_id: str = "") -> str:
    """搜索知识库并返回拼接后的上下文文本。

    若指定 kb_id，使用该 KB 专属 ChromaDB；否则使用全局默认库。
    """
    if kb_id:
        from backend.kb_searcher import search_kb
        return search_kb(kb_id, query, k=k)
    return _get_searcher().search_as_context(query, k=k)