# SPDX-License-Identifier: GPL-2.0-or-later

__all__ = (
    "batch_for_shader",
)


def batch_for_shader(shader, type, content, *, indices=None):
    """
    Return a batch already configured and compatible with the shader.

    :arg shader: shader for which a compatible format will be computed.
    :type shader: :class:`gpu.types.GPUShader`
    :arg type: "'POINTS', 'LINES', 'TRIS' or 'LINES_ADJ'".
    :type type: str
    :arg content: Maps the name of the shader attribute with the data to fill the vertex buffer.
    :type content: dict
    :return: compatible batch
    :rtype: :class:`gpu.types.Batch`
    """
    from gpu.types import (
        GPUBatch,
        GPUIndexBuf,
        GPUVertBuf,
    )

    for data in content.values():
        vbo_len = len(data)
        break
    else:
        raise ValueError("Empty 'content'")

    vbo_format = shader.format_calc()
    vbo = GPUVertBuf(vbo_format, vbo_len)

    for id, data in content.items():
        if len(data) != vbo_len:
            raise ValueError("Length mismatch for 'content' values")
        vbo.attr_fill(id, data)

    if indices is None:
        return GPUBatch(type=type, buf=vbo)
    else:
        ibo = GPUIndexBuf(type=type, seq=indices)
        return GPUBatch(type=type, buf=vbo, elem=ibo)