from __future__ import annotations

from collections.abc import Awaitable, Callable
from typing import TypeVar

from pydantic_ai import messages as _messages
from pydantic_ai.tools import RunContext

DepsT = TypeVar('DepsT')

_HistoryProcessorSync = Callable[[list[_messages.ModelMessage]], list[_messages.ModelMessage]]
_HistoryProcessorAsync = Callable[[list[_messages.ModelMessage]], Awaitable[list[_messages.ModelMessage]]]
_HistoryProcessorSyncWithCtx = Callable[[RunContext[DepsT], list[_messages.ModelMessage]], list[_messages.ModelMessage]]
_HistoryProcessorAsyncWithCtx = Callable[
    [RunContext[DepsT], list[_messages.ModelMessage]], Awaitable[list[_messages.ModelMessage]]
]
HistoryProcessor = (
    _HistoryProcessorSync
    | _HistoryProcessorAsync
    | _HistoryProcessorSyncWithCtx[DepsT]
    | _HistoryProcessorAsyncWithCtx[DepsT]
)
"""A function that processes a list of model messages and returns a list of model messages.

Can optionally accept a `RunContext` as a parameter.
"""