import json
import os
from typing import Any, Dict, Optional

from config import Config
from services.cache import NoopCache, RedisCache


class SqlPromptManager:
    """按表名读取 SQL 提示词"""

    def __init__(self, base_dir: Optional[str] = None):
        root_dir = os.path.dirname(os.path.dirname(__file__))
        self._base_dir = base_dir or os.path.join(root_dir, "config", "sql_gen_prompts")
        self._cache = self._init_cache()
        self._cache_ttl = self._get_cache_ttl()

    @staticmethod
    def _get_cache_ttl() -> int:
        redis_cfg = Config.get_section("redis")
        try:
            return int(redis_cfg.get("sql_prompt_ttl", 600))
        except Exception:
            return 600

    @staticmethod
    def _init_cache():
        redis_cfg = Config.get_section("redis")
        enabled = str(redis_cfg.get("enabled", "false")).lower() in ("1", "true", "yes")
        if not enabled:
            return NoopCache()

        # 优先使用完整 URL；否则使用 host/port/password/database 拼接
        url = redis_cfg.get("url")
        db = int(redis_cfg.get("db", redis_cfg.get("database", 0)))
        if not url:
            host = redis_cfg.get("host")
            port = redis_cfg.get("port", "6379")
            password = redis_cfg.get("password", "")
            database = redis_cfg.get("database", str(db))
            if host:
                auth = f":{password}@" if password else ""
                url = f"redis://{auth}{host}:{port}/{database}"

        if not url:
            return NoopCache()
        try:
            return RedisCache(url=url, db=db)
        except Exception:
            return NoopCache()

    @staticmethod
    def _safe_filename(name: str) -> str:
        return name.replace("..", "").replace("/", "_").replace("\\", "_")

    @staticmethod
    def _cache_key(table_name: str, mtime: float) -> str:
        return f"sql_prompt:{table_name}:{int(mtime)}"

    def get_prompt(self, table_name: str) -> Optional[Dict[str, Any]]:
        """读取指定表的提示词 JSON"""
        if not table_name:
            return None
        safe_name = self._safe_filename(table_name)
        filename = safe_name + ".json"
        path = os.path.join(self._base_dir, filename)
        if not os.path.exists(path):
            return None

        mtime = os.path.getmtime(path)
        key = self._cache_key(safe_name, mtime)
        cached = self._cache.get(key)
        if cached:
            try:
                return json.loads(cached)
            except Exception:
                pass

        with open(path, "r", encoding="utf-8") as f:
            prompt = json.load(f)

        self._cache.set(key, json.dumps(prompt, ensure_ascii=False), self._cache_ttl)
        return prompt


_GLOBAL_SQL_PROMPT_MANAGER: Optional[SqlPromptManager] = None


def get_sql_prompt_manager(base_dir: Optional[str] = None) -> SqlPromptManager:
    """获取全局 SqlPromptManager（单例）"""
    global _GLOBAL_SQL_PROMPT_MANAGER
    if _GLOBAL_SQL_PROMPT_MANAGER is None:
        _GLOBAL_SQL_PROMPT_MANAGER = SqlPromptManager(base_dir=base_dir)
    return _GLOBAL_SQL_PROMPT_MANAGER