# ========= Copyright 2026 @ Strukto.AI All Rights Reserved. =========
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ========= Copyright 2026 @ Strukto.AI All Rights Reserved. =========

from collections.abc import AsyncIterator


async def _read_stdin_async(
        stdin: AsyncIterator[bytes] | bytes | None) -> bytes | None:
    if stdin is None:
        return None
    if isinstance(stdin, bytes):
        return stdin
    chunks: list[bytes] = []
    async for chunk in stdin:
        chunks.append(chunk)
    return b"".join(chunks)


async def _wrap_bytes(data: bytes) -> AsyncIterator[bytes]:
    yield data


def _resolve_source(
    stdin: AsyncIterator[bytes] | bytes | None,
    error_msg: str | None = None,
    error_cls: type[Exception] = ValueError,
) -> AsyncIterator[bytes]:
    if stdin is not None:
        if isinstance(stdin, bytes):
            return _wrap_bytes(stdin)
        return stdin
    if error_msg is not None:
        # error_cls picks the severity: UsageError for usage errors (exit 2),
        # the ValueError default for data/operand errors (exit 1).
        raise error_cls(error_msg)
    # GNU semantics: no stdin behaves like empty input (/dev/null)
    return _wrap_bytes(b"")