"""
Redis Cache Adapter — Smart Layered Caching

Cache layers with different TTLs:
  Layer 1 — Intent cache       : 1 hour   (same query = same intent)
  Layer 2 — Live search cache  : 10 min   (DuckDuckGo/NewsAPI results)
  Layer 3 — Translation cache  : 1 hour   (LLM translation is expensive)
  Layer 4 — Full response cache: 5 min    (complete RAG answer)

Key naming convention:
  intent_v2:{query_hash}          → IntentResult dict
  live_search:{query_hash}        → list of live results
  translation:{query_hash}        → translation + expanded query dict
  rag_response:{query_hash}       → full RAG response dict

All keys use SHA-256 of the normalized query (lowercase, stripped).
"""

import json
import logging
import hashlib
import time
from typing import Optional, Dict, Any, List

import redis

from src.core.ports.cache_port import CachePort
from src.core.config import settings

logger = logging.getLogger(__name__)

# ── TTL constants (seconds) ───────────────────────────────────────────────────
TTL_INTENT      = 3600   # 1 hour  — intent rarely changes for same query
TTL_LIVE_SEARCH = 600    # 10 min  — live news stays fresh enough
TTL_TRANSLATION = 3600   # 1 hour  — translations don't change
TTL_RESPONSE    = 300    # 5 min   — full RAG response (temporal queries need freshness)
TTL_RESPONSE_HISTORICAL = 1800  # 30 min — historical answers change less often


class RedisAdapter(CachePort):
    """
    Redis cache adapter with smart layered caching.

    Falls back gracefully when Redis is unavailable — all methods
    return None/False instead of raising exceptions.
    """

    def __init__(self):
        self.client = None
        self._connect()

    def _connect(self):
        try:
            if hasattr(settings, "REDIS_URL") and settings.REDIS_URL:
                url = settings.REDIS_URL
                # Upstash requires TLS
                if url.startswith("redis://") and "upstash.io" in url:
                    url = "rediss://" + url[len("redis://"):]
                self.client = redis.from_url(url, decode_responses=True)
            else:
                pool = redis.ConnectionPool(
                    host=settings.REDIS_HOST,
                    port=settings.REDIS_PORT,
                    db=settings.REDIS_DB,
                    password=settings.REDIS_PASSWORD or None,
                    decode_responses=True,
                )
                self.client = redis.Redis(connection_pool=pool)
            self.client.ping()
            logger.info("✅ Connected to Redis cache.")
        except Exception as e:
            logger.warning(f"Redis unavailable: {e}. All cache operations will be no-ops.")
            self.client = None

    # ── CachePort interface ───────────────────────────────────────────────────

    def get(self, key: str) -> Optional[Any]:
        if not self.client:
            return None
        try:
            data = self.client.get(key)
            return json.loads(data) if data else None
        except Exception as e:
            logger.debug(f"Redis get error for key '{key}': {e}")
            return None

    def set(self, key: str, value: Any, expiration: int = 3600) -> bool:
        if not self.client:
            return False
        try:
            self.client.setex(key, expiration, json.dumps(value, default=str))
            return True
        except Exception as e:
            logger.debug(f"Redis set error for key '{key}': {e}")
            return False

    def delete(self, key: str) -> bool:
        if not self.client:
            return False
        try:
            self.client.delete(key)
            return True
        except Exception as e:
            logger.debug(f"Redis delete error for key '{key}': {e}")
            return False

    def search_similar(self, query_vector: list, threshold: float = 0.95) -> Optional[Dict[str, Any]]:
        """Vector similarity search — not implemented (requires RedisSearch module)."""
        return None

    # ── Key generation ────────────────────────────────────────────────────────

    def generate_exact_hash(self, text: str) -> str:
        """SHA-256 hash of normalized text for exact-match cache keys."""
        normalized = text.lower().strip()
        return hashlib.sha256(normalized.encode("utf-8")).hexdigest()

    def _make_key(self, prefix: str, query: str) -> str:
        """Build a namespaced cache key from query text."""
        return f"{prefix}:{self.generate_exact_hash(query)}"

    # ── Layer 1: Intent cache ─────────────────────────────────────────────────

    def get_intent(self, query: str) -> Optional[Dict[str, Any]]:
        """
        Retrieve cached intent result for a query.
        Returns dict with keys: intent, confidence, method
        """
        key = self._make_key("intent_v2", query)
        result = self.get(key)
        if result:
            logger.debug(f"[Cache] Intent HIT for '{query[:50]}'")
        return result

    def set_intent(self, query: str, intent_data: Dict[str, Any]) -> bool:
        """Cache intent result for 1 hour."""
        key = self._make_key("intent_v2", query)
        success = self.set(key, intent_data, expiration=TTL_INTENT)
        if success:
            logger.debug(f"[Cache] Intent SET for '{query[:50]}' (TTL={TTL_INTENT}s)")
        return success

    # ── Layer 2: Live search cache ────────────────────────────────────────────

    def get_live_search(self, query: str) -> Optional[List[Dict[str, Any]]]:
        """
        Retrieve cached live search results (DuckDuckGo + NewsAPI).
        Returns list of result dicts or None if not cached.
        """
        key = self._make_key("live_search", query)
        result = self.get(key)
        if result:
            age = result.get("_cached_at", 0)
            elapsed = int(time.time()) - age if age else 0
            logger.info(f"[Cache] Live search HIT for '{query[:50]}' (age={elapsed}s)")
            return result.get("results", [])
        return None

    def set_live_search(self, query: str, results: List[Dict[str, Any]]) -> bool:
        """Cache live search results for 10 minutes."""
        key = self._make_key("live_search", query)
        payload = {
            "results": results,
            "_cached_at": int(time.time()),
            "_query": query[:100],
        }
        success = self.set(key, payload, expiration=TTL_LIVE_SEARCH)
        if success:
            logger.info(f"[Cache] Live search SET for '{query[:50]}' ({len(results)} results, TTL={TTL_LIVE_SEARCH}s)")
        return success

    # ── Layer 3: Translation cache ────────────────────────────────────────────

    def get_translation(self, query: str) -> Optional[Dict[str, Any]]:
        """
        Retrieve cached translation + query expansion result.
        Returns dict with keys: expanded_query, translations, days_back, etc.
        """
        key = self._make_key("translation", query)
        result = self.get(key)
        if result:
            logger.debug(f"[Cache] Translation HIT for '{query[:50]}'")
        return result

    def set_translation(self, query: str, translation_data: Dict[str, Any]) -> bool:
        """Cache translation result for 1 hour."""
        key = self._make_key("translation", query)
        success = self.set(key, translation_data, expiration=TTL_TRANSLATION)
        if success:
            logger.debug(f"[Cache] Translation SET for '{query[:50]}' (TTL={TTL_TRANSLATION}s)")
        return success

    # ── Layer 4: Full response cache ──────────────────────────────────────────

    def get_response(self, query: str) -> Optional[Dict[str, Any]]:
        """
        Retrieve cached full RAG response.
        Returns complete response dict or None if not cached.
        """
        key = self._make_key("rag_response", query)
        result = self.get(key)
        if result:
            age = result.get("_cached_at", 0)
            elapsed = int(time.time()) - age if age else 0
            logger.info(f"[Cache] Response HIT for '{query[:50]}' (age={elapsed}s)")
        return result

    def set_response(
        self,
        query: str,
        response: Dict[str, Any],
        intent: str = "NEWS_GENERAL"
    ) -> bool:
        """
        Cache full RAG response.
        TTL depends on intent:
          - NEWS_TEMPORAL   → 5 min  (fresh news changes fast)
          - NEWS_HISTORICAL → 30 min (historical facts are stable)
          - NEWS_GENERAL    → 5 min  (default)
        """
        key = self._make_key("rag_response", query)
        ttl = TTL_RESPONSE_HISTORICAL if intent == "NEWS_HISTORICAL" else TTL_RESPONSE
        payload = {
            **response,
            "_cached_at": int(time.time()),
            "_intent": intent,
        }
        success = self.set(key, payload, expiration=ttl)
        if success:
            logger.info(f"[Cache] Response SET for '{query[:50]}' (intent={intent}, TTL={ttl}s)")
        return success

    # ── Cache stats ───────────────────────────────────────────────────────────

    def get_stats(self) -> Dict[str, Any]:
        """Return cache statistics."""
        if not self.client:
            return {"status": "disconnected"}
        try:
            info = self.client.info("stats")
            keyspace = self.client.info("keyspace")
            return {
                "status": "connected",
                "hits": info.get("keyspace_hits", 0),
                "misses": info.get("keyspace_misses", 0),
                "hit_rate": round(
                    info.get("keyspace_hits", 0) /
                    max(1, info.get("keyspace_hits", 0) + info.get("keyspace_misses", 0))
                    * 100, 1
                ),
                "total_keys": sum(
                    v.get("keys", 0) for v in keyspace.values()
                    if isinstance(v, dict)
                ),
                "memory_used": self.client.info("memory").get("used_memory_human", "?"),
            }
        except Exception as e:
            return {"status": "error", "error": str(e)}

    def is_available(self) -> bool:
        """Check if Redis is connected."""
        if not self.client:
            return False
        try:
            self.client.ping()
            return True
        except Exception:
            return False