"""
Stripe-style version compatibility layer for browser-cli serve.

When a behaviour-breaking change ships in a new server version, add one entry
to _COMPAT below:

    ("X.Y.Z", request_fn, response_fn)

- ``request_fn(msg: dict) -> dict``
      Upgrade an incoming client message from a client older than X.Y.Z to the
      current format before forwarding it to the native host.
- ``response_fn(resp: bytes, command: str) -> bytes``
      Downgrade a native-host response to the format a client older than X.Y.Z
      expects before sending it back.

Either function may be ``None`` when only one direction needs adapting.

Entries must stay in ascending version order.  ``adapt_request`` walks forward
(oldest change first); ``adapt_response`` walks backward (newest change first)
so the transformations compose correctly.

Current baseline: 0.9.1  — no shims needed yet.
"""

from __future__ import annotations
from typing import Callable
from browser_cli.version_manager import parse_version

_COMPAT: list[tuple[str, Callable[[dict], dict] | None, Callable[[bytes, str], bytes] | None]] = [
    # ("1.0.0", _req_1_0_0, _resp_1_0_0),
]


def adapt_request(msg: dict, client_version: str) -> dict:
    """Upgrade a client message to the current server format."""
    cv = parse_version(client_version)
    for version, req_fn, _ in _COMPAT:
        if cv < parse_version(version) and req_fn is not None:
            msg = req_fn(msg)
    return msg


def adapt_response(resp: bytes, command: str, client_version: str) -> bytes:
    """Downgrade a server response to the format the client expects."""
    cv = parse_version(client_version)
    for version, _, resp_fn in reversed(_COMPAT):
        if cv < parse_version(version) and resp_fn is not None:
            resp = resp_fn(resp, command)
    return resp