from __future__ import annotations

import hashlib
import json
from collections.abc import Mapping, Sequence
from datetime import datetime
from typing import Any

from fastapi import Request, Response
from fastapi.encoders import jsonable_encoder


def _strip_keys(value: Any, excluded_keys: set[str]) -> Any:
    if isinstance(value, Mapping):
        return {
            key: _strip_keys(item, excluded_keys)
            for key, item in value.items()
            if key not in excluded_keys
        }
    if isinstance(value, Sequence) and not isinstance(value, (str, bytes, bytearray)):
        return [_strip_keys(item, excluded_keys) for item in value]
    return value


def build_etag(payload: Any, *, exclude_keys: set[str] | None = None) -> str:
    encoded = jsonable_encoder(payload)
    if exclude_keys:
        encoded = _strip_keys(encoded, exclude_keys)
    serialized = json.dumps(encoded, sort_keys=True, separators=(",", ":"), ensure_ascii=False)
    digest = hashlib.sha1(serialized.encode("utf-8")).hexdigest()
    return f'"{digest}"'


def is_matching_etag(request: Request, etag: str) -> bool:
    header = request.headers.get("if-none-match")
    if not header:
        return False

    for candidate in header.split(","):
        if candidate.strip() in {etag, "*"}:
            return True
    return False


def apply_cache_headers(
    response: Response,
    *,
    cache_control: str,
    etag: str | None = None,
    last_modified: datetime | None = None,
) -> None:
    response.headers["Cache-Control"] = cache_control
    response.headers["Vary"] = "Cookie, Authorization"
    if etag is not None:
        response.headers["ETag"] = etag
    if last_modified is not None:
        response.headers["Last-Modified"] = last_modified.strftime("%a, %d %b %Y %H:%M:%S GMT")


def set_no_store(response: Response) -> None:
    apply_cache_headers(response, cache_control="no-store")


def set_private_revalidate(response: Response, *, etag: str | None = None, last_modified: datetime | None = None) -> None:
    apply_cache_headers(
        response,
        cache_control="private, max-age=0, must-revalidate",
        etag=etag,
        last_modified=last_modified,
    )


def set_public_immutable(response: Response, *, etag: str | None = None, last_modified: datetime | None = None) -> None:
    apply_cache_headers(
        response,
        cache_control="public, max-age=31536000, immutable",
        etag=etag,
        last_modified=last_modified,
    )