strukto-ai--mirage/python/mirage/commands/builtin/databricks_volume/head.py

# ========= 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

from mirage.accessor.databricks_volume import DatabricksVolumeAccessor
from mirage.cache.index import IndexCacheStore
from mirage.cache.read_through import cached_prefix_bytes
from mirage.commands.builtin.generic.head import head as generic_head
from mirage.commands.builtin.generic.head import head_multi
from mirage.commands.builtin.utils.stream import _resolve_source
from mirage.commands.registry import command
from mirage.commands.spec import SPECS
from mirage.core.databricks_volume.glob import resolve_glob
from mirage.core.databricks_volume.stream import range_read, read_stream
from mirage.io.stream import yield_bytes
from mirage.io.types import ByteSource, IOResult
from mirage.types import PathSpec


@command("head", resource="databricks_volume", spec=SPECS["head"])
async def head(
    accessor: DatabricksVolumeAccessor,
    paths: list[PathSpec],
    *texts: str,
    stdin: AsyncIterator[bytes] | bytes | None = None,
    n: str | None = None,
    c: str | None = None,
    q: bool = False,
    v: bool = False,
    index: IndexCacheStore = None,
    **_extra: object,
) -> tuple[ByteSource | None, IOResult]:
    n_int = int(n) if n is not None else None
    c_int = int(c) if c is not None else None
    if paths:
        paths = await resolve_glob(accessor, paths, index)
        # Single file with -c >= 0: serve the first c_int bytes from the
        # cache when warm, otherwise fetch only those bytes via a range
        # request instead of streaming the whole file. A negative -c (all but
        # the last N bytes) cannot be a prefix fetch, so fall through to the
        # generic head, which reads the whole object.
        if len(paths) == 1 and c_int is not None and c_int >= 0:
            data = await cached_prefix_bytes(paths[0], c_int)
            if data is None:
                data = await range_read(accessor, paths[0], 0, c_int)
            return yield_bytes(data), IOResult()
        return head_multi(paths,
                          read=read_stream,
                          accessor=accessor,
                          index=index,
                          n=n_int,
                          c=c_int,
                          show_headers=(v or len(paths) > 1)
                          and not q), IOResult()
    source = _resolve_source(stdin, "head: missing operand")
    return generic_head(source, n=n_int, c=c_int), IOResult()