"""Shared translation cache utilities."""
  
  from __future__ import annotations
  
  import hashlib
  import logging
  from typing import Mapping, Optional
  

  try:
      import redis
  except ImportError:  # pragma: no cover - runtime fallback for minimal envs
      redis = None  # type: ignore[assignment]

  from config.loader import get_app_config

  
  logger = logging.getLogger(__name__)
  
  
  class TranslationCache:
      """Redis-backed cache shared by all translation capabilities."""
  
      def __init__(self, config: Mapping[str, object]) -> None:
          self.ttl_seconds = int(config["ttl_seconds"])
          self.sliding_expiration = bool(config["sliding_expiration"])
          self.redis_client = self._init_redis_client()
  
      @property
      def available(self) -> bool:
          return self.redis_client is not None
  
      def build_key(self, *, model: str, target_lang: str, source_text: str) -> str:
          normalized_model = str(model or "").strip().lower()
          normalized_target_lang = str(target_lang or "").strip().lower()
          text = str(source_text or "")
          text_prefix = text[:4]
          digest = hashlib.sha256(text.encode("utf-8")).hexdigest()
          return f"trans:{normalized_model}:{normalized_target_lang}:{text_prefix}{digest}"
  

      def get(
          self,
          *,
          model: str,
          target_lang: str,
          source_text: str
      ) -> Optional[str]:

          if self.redis_client is None:
              return None
          key = self.build_key(model=model, target_lang=target_lang, source_text=source_text)
          try:
              value = self.redis_client.get(key)
              logger.info(

                  "Translation cache %s | text_len=%s key=%s",

                  "hit" if value is not None else "miss",

                  len(str(source_text or "")),
                  key,
              )
              if value and self.sliding_expiration:
                  self.redis_client.expire(key, self.ttl_seconds)
              return value
          except Exception as exc:
              logger.warning("Redis get translation cache failed: %s", exc)
              return None
  
      def set(self, *, model: str, target_lang: str, source_text: str, translated_text: str) -> None:
          if self.redis_client is None:
              return
          key = self.build_key(model=model, target_lang=target_lang, source_text=source_text)
          try:
              self.redis_client.setex(key, self.ttl_seconds, translated_text)
              logger.info(

                  "Translation cache write | text_len=%s result_len=%s ttl_seconds=%s key=%s",

                  len(str(source_text or "")),
                  len(str(translated_text or "")),
                  self.ttl_seconds,
                  key,
              )
          except Exception as exc:
              logger.warning("Redis set translation cache failed: %s", exc)
  
      @staticmethod
      def _init_redis_client() -> Optional[redis.Redis]:

          if redis is None:
              logger.warning("redis package is not installed; translation cache disabled")
              return None
          redis_config = get_app_config().infrastructure.redis

          try:
              client = redis.Redis(

                  host=redis_config.host,
                  port=redis_config.port,

                  db=redis_config.snapshot_db,

                  password=redis_config.password,

                  decode_responses=True,

                  socket_timeout=redis_config.socket_timeout,
                  socket_connect_timeout=redis_config.socket_connect_timeout,
                  retry_on_timeout=redis_config.retry_on_timeout,

                  health_check_interval=10,
              )
              client.ping()
              return client
          except Exception as exc:
              logger.warning("Failed to initialize translation redis cache: %s", exc)
              return None