"""FastAPI 依赖注入 — 集中管理应用状态, 替代模块级全局变量."""
import logging
import os
import threading

from src.core.config import load_config
from src.core.db import VectorDB
from src.core.embedder import create_embedder
from src.core.ingest import DocumentIngestor
from src.core.search import Searcher

logger = logging.getLogger("md-vector-db")


class AppState:
    """应用级共享状态 — db 和 embedder 全局共享, searcher/ingestor 按 collection 懒创建."""

    def __init__(self):
        config_path = os.environ.get("MD_VECTOR_CONFIG", "config.yaml")
        self.config = load_config(config_path)

        data_dir = os.environ.get(
            "MD_VECTOR_DB_DATA_DIR", self.config.chroma.persist_dir
        )
        self.db = VectorDB(persist_dir=data_dir)
        self.embedder = create_embedder(self.config.embed)

        self.default_collection = os.environ.get(
            "MD_VECTOR_DB_COLLECTION", self.config.chroma.collection_name
        )

        # 按 collection 懒加载 searcher / ingestor
        self._searchers: dict[str, Searcher] = {}
        self._ingestors: dict[str, DocumentIngestor] = {}
        self._cache_lock = threading.Lock()

    def get_searcher(self, collection: str | None = None) -> Searcher:
        name = collection or self.default_collection
        with self._cache_lock:
            if name not in self._searchers:
                self._searchers[name] = Searcher(
                    self.db, self.embedder, name,
                    search_config=self.config.search,
                )
            return self._searchers[name]

    def get_ingestor(self, collection: str | None = None) -> DocumentIngestor:
        name = collection or self.default_collection
        with self._cache_lock:
            if name not in self._ingestors:
                self._ingestors[name] = DocumentIngestor(
                    self.db, self.embedder, name,
                    chunk_config=self.config.chunk,
                )
            return self._ingestors[name]

    def list_collections_with_stats(self) -> list[dict]:
        """列出所有 collection 及其统计（直接从 ChromaDB 查询）."""
        result = []
        for coll in self.db.list_collections():
            result.append({"name": coll.name, "count": coll.count()})
        return result

    def is_healthy(self) -> dict:
        """真实健康检查: 验证 ChromaDB 和 Embedder 是否可用.

        对外仅返回 ok/degraded 状态，详细信息记入日志，不泄露内部路径.
        """
        status = {"status": "ok", "checks": {}}
        try:
            count = self.db.get_or_create_collection(
                self.default_collection
            ).count()
            status["checks"]["chromadb"] = {"status": "ok", "count": count}
        except Exception as e:
            logger.error("ChromaDB 健康检查失败: %s", e)
            status["checks"]["chromadb"] = {"status": "error", "detail": "unavailable"}
            status["status"] = "degraded"
        try:
            dim = self.embedder.dimension
            status["checks"]["embedder"] = {"status": "ok", "dimension": dim}
        except Exception as e:
            logger.error("Embedder 健康检查失败: %s", e)
            status["checks"]["embedder"] = {"status": "error", "detail": "unavailable"}
            status["status"] = "degraded"
        return status


_state: AppState | None = None
_state_lock = threading.Lock()


def get_state() -> AppState:
    """获取应用状态单例 (懒初始化, 线程安全)."""
    global _state
    if _state is None:
        with _state_lock:
            if _state is None:
                logger.info("初始化应用状态...")
                _state = AppState()
    return _state


def get_default_collection() -> str:
    """获取默认 collection 名, 供 CLI 等非 HTTP 场景使用."""
    return get_state().default_collection