import inspect
from base64 import urlsafe_b64encode
from collections.abc import Callable
from dataclasses import dataclass
from functools import wraps
from itertools import chain
from typing import Iterable, ParamSpec, TypeVar

from redis import Redis


@dataclass(frozen=True, kw_only=True, slots=True)
class Config:
    redis: Redis
    prefix: str | None = "cache"
    ttl_fresh: int = 600
    ttl_stale: int | None = None


def qualified_name(callable_obj) -> str:
    # callable classes/instances
    if hasattr(callable_obj, "__call__") and not inspect.isroutine(callable_obj):
        # callable instance: use its class
        cls = callable_obj.__class__
        module = getattr(cls, "__module__", None)
        qual = getattr(cls, "__qualname__", cls.__name__)
        return f"{module}.{qual}" if module else qual

    # functions, methods, builtins
    # unwrap descriptors like staticmethod/classmethod
    if isinstance(callable_obj, staticmethod | classmethod):
        callable_obj = callable_obj.__func__

    # bound method
    if inspect.ismethod(callable_obj):
        func = callable_obj.__func__
        owner = getattr(func, "__qualname__", func.__name__).rsplit(".", 1)[0]
        module = getattr(func, "__module__", None)
        qual = f"{owner}.{func.__name__}"
        return f"{module}.{qual}" if module else qual

    # regular function or builtin
    if inspect.isfunction(callable_obj) or inspect.isbuiltin(callable_obj):
        module = getattr(callable_obj, "__module__", None)
        qual = getattr(callable_obj, "__qualname__", callable_obj.__name__)
        return f"{module}.{qual}" if module else qual

    # fallback for other callables (functors, functools.partial, etc.)
    try:
        module = getattr(callable_obj, "__module__", None)
        qual = getattr(callable_obj, "__qualname__", None) or getattr(
            callable_obj, "__name__", type(callable_obj).__name__
        )
        return f"{module}.{qual}" if module else qual

    except Exception:
        return urlsafe_b64encode(repr(callable_obj).encode("utf-8")).decode("utf-8")


P = ParamSpec("P")
R = TypeVar("R")


def args_slice(func: Callable[P, R], *args: Iterable) -> tuple:
    if hasattr(func, "__call__") and not inspect.isroutine(func):
        return args[1:]

    if isinstance(func, staticmethod | classmethod):
        func = func.__func__

    if inspect.ismethod(func):
        return args[1:]

    return tuple(*args)


def cache_key(func: Callable[P, R], *args: P.args, **kwargs: P.kwargs) -> str:
    """Return a cache key for use with cached methods."""

    kwargs_by_key = sorted(kwargs.items(), key=lambda kv: kv[0])

    parts = chain(
        (qualified_name(func),),
        # positional args
        (repr(arg) for arg in args_slice(func, args)),
        # keyword args
        (f"{k}={v!r}" for k, v in kwargs_by_key),
    )

    return ":".join(parts)


def redis_cached(cfg: Config) -> Callable[[Callable[P, R]], Callable[P, R]]:
    """ """

    def decorator(func: Callable[P, R]) -> Callable[P, R]:
        """ """

        @wraps(func)
        def wrapper(*args: P.args, **kwargs: P.kwargs) -> R:
            key = cache_key(func, *args, **kwargs)

            if cfg.prefix is not None:
                key = f"{cfg.prefix}:{key}"

            # pre-hook
            result = func(*args, **kwargs)
            # post-hook
            return result

        return wrapper

    return decorator