"""Packing a frame as std/media/v1/Image.

The struct is respelled here rather than imported from the viewer: node
repositories share no source package, so the manifest and this schema are the
whole contract between them.
"""

import numpy as np
import pyarrow as pa

IMAGE_TYPE = pa.struct([
    ("width", pa.uint32()),
    ("height", pa.uint32()),
    ("encoding", pa.utf8()),
    ("data", pa.large_binary()),
])


def pack(frame: np.ndarray, encoding: str, width: int, height: int) -> pa.Array:
    """Pack encoded frame bytes as a single-row std/media/v1/Image array.

    Parameters
    ----------
    frame : np.ndarray
        The bytes to send. Either a raw pixel buffer or the output of an
        encoder; either way only its bytes are read.
    encoding : str
        Name of the encoding the bytes are in, e.g. ``bgr8`` or ``jpeg``.
    width, height : int
        Dimensions of the *image*, which for a compressed encoding are not the
        shape of ``frame``. They are recorded so a receiver can size a buffer
        without decoding first.

    Returns
    -------
    pa.Array
        One-row struct array matching ``IMAGE_TYPE``.

    """
    return pa.array(
        [{
            "width": width,
            "height": height,
            "encoding": encoding,
            "data": frame.tobytes(),
        }],
        type=IMAGE_TYPE,
    )