import redis
from redis.connection import Connection, SSLConnection
from redis.sentinel import Sentinel


class RedisClientWrapper(redis.Redis):
    """
    A wrapper class for the Redis client that addresses the issue where the global
    `redis_client` variable cannot be updated when a new Redis instance is returned
    by Sentinel.

    This class allows for deferred initialization of the Redis client, enabling the
    client to be re-initialized with a new instance when necessary. This is particularly
    useful in scenarios where the Redis instance may change dynamically, such as during
    a failover in a Sentinel-managed Redis setup.

    Attributes:
        _client (redis.Redis): The actual Redis client instance. It remains None until
                               initialized with the `initialize` method.

    Methods:
        initialize(client): Initializes the Redis client if it hasn't been initialized already.
        __getattr__(item): Delegates attribute access to the Redis client, raising an error
                           if the client is not initialized.
    """

    def __init__(self):
        self._client = None

    def initialize(self, client):
        if self._client is None:
            self._client = client

    def __getattr__(self, item):
        if self._client is None:
            raise RuntimeError("Redis client is not initialized. Call init_app first.")
        return getattr(self._client, item)


redis_client = RedisClientWrapper()


def init_app(app):
    global redis_client
    connection_class = Connection
    if app.config.get("REDIS_USE_SSL"):
        connection_class = SSLConnection

    redis_params = {
        "username": app.config.get("REDIS_USERNAME"),
        "password": app.config.get("REDIS_PASSWORD"),
        "db": app.config.get("REDIS_DB"),
        "encoding": "utf-8",
        "encoding_errors": "strict",
        "decode_responses": False,
    }

    if app.config.get("REDIS_USE_SENTINEL"):
        sentinel_hosts = [
            (node.split(":")[0], int(node.split(":")[1])) for node in app.config.get("REDIS_SENTINELS").split(",")
        ]
        sentinel = Sentinel(
            sentinel_hosts,
            sentinel_kwargs={
                "socket_timeout": app.config.get("REDIS_SENTINEL_SOCKET_TIMEOUT", 0.1),
                "username": app.config.get("REDIS_SENTINEL_USERNAME"),
                "password": app.config.get("REDIS_SENTINEL_PASSWORD"),
            },
        )
        master = sentinel.master_for(app.config.get("REDIS_SENTINEL_SERVICE_NAME"), **redis_params)
        redis_client.initialize(master)
    else:
        redis_params.update(
            {
                "host": app.config.get("REDIS_HOST"),
                "port": app.config.get("REDIS_PORT"),
                "connection_class": connection_class,
            }
        )
        pool = redis.ConnectionPool(**redis_params)
        redis_client.initialize(redis.Redis(connection_pool=pool))

    app.extensions["redis"] = redis_client