routesapi/app/services/__init__.py

"""Services package."""

from __future__ import annotations

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

try:
    import redis  # type: ignore
except Exception:  # pragma: no cover
    redis = None  # type: ignore

logger = logging.getLogger(__name__)


def _redis_url_from_parts() -> Optional[str]:
    """
    Build a redis:// URL from discrete env vars, percent-encoding the credentials.

    A hand-written REDIS_URL breaks the moment the password contains a reserved
    character: an '@' splits the authority section early, so the client silently
    dials a garbage host instead of failing loudly. Assembling the URL here with
    quote() removes that whole class of bug - callers set REDIS_HOST/REDIS_PASSWORD
    and never have to think about escaping.

    Returns None when REDIS_HOST is unset, so an explicit REDIS_URL still wins.
    """
    host = os.getenv("REDIS_HOST")
    if not host:
        return None
    from urllib.parse import quote

    user = os.getenv("REDIS_USERNAME", "")
    pwd = os.getenv("REDIS_PASSWORD", "")
    port = os.getenv("REDIS_PORT", "6379")
    db = os.getenv("REDIS_DB", "0")
    auth = f"{quote(user, safe='')}:{quote(pwd, safe='')}@" if pwd else ""
    return f"redis://{auth}{host}:{port}/{db}"


class RedisCache:
    """Lightweight Redis cache wrapper with graceful in-memory fallback."""

    def __init__(self, url_env: str = "REDIS_URL", default_ttl_seconds: Optional[int] = None) -> None:
        import threading
        self._lock = threading.Lock()
        self._memory_cache: Dict[str, tuple[float, str]] = {}  # key -> (expire_time, serialized_value)
        
        # Allow TTL to be configurable via env var (default 300s = 5 min, or 86400 = 24h)
        ttl_env = os.getenv("REDIS_CACHE_TTL_SECONDS")
        if default_ttl_seconds is None:
            default_ttl_seconds = int(ttl_env) if ttl_env else 300
        
        self.default_ttl_seconds = default_ttl_seconds
        self._enabled = False
        self._client = None
        self._stats = {"hits": 0, "misses": 0, "sets": 0}

        url = os.getenv(url_env) or _redis_url_from_parts()
        if not url or redis is None:
            _why = "redis client not installed" if redis is None else "no REDIS_URL/REDIS_HOST"
            logger.warning(f"Redis not configured or client unavailable ({_why}); falling back to local thread-safe in-memory cache")
            return
        try:
            self._client = redis.Redis.from_url(url, decode_responses=True)
            self._client.ping()
            self._enabled = True
            logger.info(f"Redis cache connected (TTL: {self.default_ttl_seconds}s)")
        except Exception as exc:
            logger.warning(f"Redis connection failed: {exc}; falling back to local thread-safe in-memory cache")
            self._enabled = False
            self._client = None

    @property
    def enabled(self) -> bool:
        return self._enabled and self._client is not None

    def get_json(self, key: str) -> Optional[Any]:
        if self.enabled:
            try:
                raw = self._client.get(key)  # type: ignore[union-attr]
                if raw:
                    self._stats["hits"] += 1
                    return json.loads(raw)
                else:
                    self._stats["misses"] += 1
                    return None
            except Exception as exc:
                logger.debug(f"Redis get_json error for key={key}: {exc}")
                self._stats["misses"] += 1
                return None
        else:
            import time
            with self._lock:
                if key in self._memory_cache:
                    expire_time, raw = self._memory_cache[key]
                    if expire_time < 0 or expire_time > time.time():
                        self._stats["hits"] += 1
                        return json.loads(raw)
                    else:
                        del self._memory_cache[key]
                self._stats["misses"] += 1
                return None

    def set_json(self, key: str, value: Any, ttl_seconds: Optional[int] = None) -> None:
        payload = json.dumps(value, default=lambda o: getattr(o, "model_dump", lambda: o)())
        ttl = ttl_seconds if ttl_seconds is not None else self.default_ttl_seconds
        
        if self.enabled:
            try:
                if ttl > 0:
                    self._client.setex(key, ttl, payload)  # type: ignore[union-attr]
                else:
                    self._client.set(key, payload)  # type: ignore[union-attr]
                self._stats["sets"] += 1
            except Exception as exc:
                logger.debug(f"Redis set_json error for key={key}: {exc}")
        else:
            import time
            expire_time = (time.time() + ttl) if ttl > 0 else -1.0
            with self._lock:
                # Evict oldest keys if cache grows too large to prevent leak
                if len(self._memory_cache) >= 2000:
                    now = time.time()
                    expired_keys = [k for k, (exp, _) in self._memory_cache.items() if exp > 0 and exp < now]
                    for k in expired_keys:
                        del self._memory_cache[k]
                    if len(self._memory_cache) >= 2000:
                        first_key = next(iter(self._memory_cache))
                        del self._memory_cache[first_key]
                self._memory_cache[key] = (expire_time, payload)
                self._stats["sets"] += 1

    def delete(self, pattern: str) -> int:
        """Delete keys matching pattern (e.g., 'routes:*'). Returns count deleted."""
        if self.enabled:
            try:
                keys = list(self._client.scan_iter(match=pattern))  # type: ignore[union-attr]
                if keys:
                    return self._client.delete(*keys)  # type: ignore[union-attr]
                return 0
            except Exception as exc:
                logger.error(f"Redis delete error for pattern={pattern}: {exc}")
                return 0
        else:
            import fnmatch
            deleted = 0
            with self._lock:
                keys_to_del = [k for k in self._memory_cache.keys() if fnmatch.fnmatchcase(k, pattern)]
                for k in keys_to_del:
                    del self._memory_cache[k]
                    deleted += 1
            return deleted

    def get_stats(self) -> Dict[str, Any]:
        """Get cache statistics."""
        stats = self._stats.copy()
        if self.enabled:
            try:
                # Count cache keys
                route_keys = list(self._client.scan_iter(match="routes:*"))  # type: ignore[union-attr]
                stats["total_keys"] = len(route_keys)
                stats["enabled"] = True
                stats["type"] = "Redis"
            except Exception:
                stats["total_keys"] = 0
                stats["enabled"] = True
                stats["type"] = "Redis"
        else:
            import time
            now = time.time()
            with self._lock:
                active_keys = [k for k, (exp, _) in self._memory_cache.items() if exp < 0 or exp > now]
                stats["total_keys"] = len(active_keys)
                stats["enabled"] = True
                stats["type"] = "In-Memory Fallback"
        return stats

    def get_keys(self, pattern: str = "routes:*") -> list[str]:
        """Get list of cache keys matching pattern."""
        if self.enabled:
            try:
                return list(self._client.scan_iter(match=pattern))  # type: ignore[union-attr]
            except Exception as exc:
                logger.error(f"Redis get_keys error for pattern={pattern}: {exc}")
                return []
        else:
            import fnmatch
            import time
            now = time.time()
            with self._lock:
                return [
                    k for k, (exp, _) in self._memory_cache.items()
                    if (exp < 0 or exp > now) and fnmatch.fnmatchcase(k, pattern)
                ]


# Singleton cache instance for app
cache = RedisCache()