#
# The Python Imaging Library
# $Id$
#
# GRIB stub adapter
#
# Copyright (c) 1996-2003 by Fredrik Lundh
#
# See the README file for information on usage and redistribution.
#
from __future__ import annotations

import os

from . import Image, ImageFile

TYPE_CHECKING = False
if TYPE_CHECKING:
    from typing import IO


def register_handler(handler: ImageFile.StubHandler | None) -> None:
    """
    Install application-specific GRIB image handler.

    :param handler: Handler object.
    """
    GribStubImageFile._handler = handler


# --------------------------------------------------------------------
# Image adapter


def _accept(prefix: bytes) -> bool:
    return len(prefix) >= 8 and prefix.startswith(b"GRIB") and prefix[7] == 1


class GribStubImageFile(ImageFile.StubImageFile):
    format = "GRIB"
    format_description = "GRIB"

    def _open(self) -> None:
        assert self.fp is not None
        if not _accept(self.fp.read(8)):
            msg = "Not a GRIB file"
            raise SyntaxError(msg)

        self.fp.seek(-8, os.SEEK_CUR)

        # make something up
        self._mode = "F"


def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
    if GribStubImageFile._handler is None or not hasattr(
        GribStubImageFile._handler, "save"
    ):
        msg = "GRIB save handler not installed"
        raise OSError(msg)
    GribStubImageFile._handler.save(im, fp, filename)


# --------------------------------------------------------------------
# Registry

Image.register_open(GribStubImageFile.format, GribStubImageFile, _accept)
Image.register_save(GribStubImageFile.format, _save)

Image.register_extension(GribStubImageFile.format, ".grib")