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# Source code for astropy.io.fits.hdu.streaming

    # Licensed under a 3-clause BSD style license - see PYFITS.rst

    import gzip
    import os

    from astropy.io.fits.file import _File
    from astropy.io.fits.header import _pad_length
    from astropy.io.fits.util import fileobj_name

    from .base import BITPIX2DTYPE, _BaseHDU
    from .hdulist import HDUList
    from .image import PrimaryHDU

    class StreamingHDU:
        """
        A class that provides the capability to stream data to a FITS file
        instead of requiring data to all be written at once.

        The following pseudocode illustrates its use::

            header = astropy.io.fits.Header()

            for all the cards you need in the header:
                header[key] = (value, comment)

            shdu = astropy.io.fits.StreamingHDU('filename.fits', header)

            for each piece of data:
                shdu.write(data)

            shdu.close()
        """

        def __init__(self, name, header):
            """
            Construct a `StreamingHDU` object given a file name and a header.

            Parameters
            ----------
            name : path-like or file-like
                The file to which the header and data will be streamed. If opened,
                the file object must be opened in a writeable binary mode such as
                'wb' or 'ab+'.

            header : `Header` instance
                The header object associated with the data to be written
                to the file.

            Notes
            -----
            The file will be opened and the header appended to the end of
            the file.  If the file does not already exist, it will be
            created, and if the header represents a Primary header, it
            will be written to the beginning of the file.  If the file
            does not exist and the provided header is not a Primary
            header, a default Primary HDU will be inserted at the
            beginning of the file and the provided header will be added as
            the first extension.  If the file does already exist, but the
            provided header represents a Primary header, the header will
            be modified to an image extension header and appended to the
            end of the file.
            """
            if isinstance(name, gzip.GzipFile):
                raise TypeError("StreamingHDU not supported for GzipFile objects.")

            self._header = header.copy()

            # handle a file object instead of a file name
            filename = fileobj_name(name) or ""

            filename = os.path.expanduser(filename)

            # Check if the file already exists.  If it does not, check to see
            # if we were provided with a Primary Header.  If not we will need
            # to prepend a default PrimaryHDU to the file before writing the
            # given header.

            newfile = False

            if filename:
                if not os.path.exists(filename) or os.path.getsize(filename) == 0:
                    newfile = True
            elif hasattr(name, "len") and name.len == 0:
                newfile = True

            if newfile:
                if "SIMPLE" not in self._header:
                    hdulist = HDUList([PrimaryHDU()])
                    hdulist.writeto(name, "exception")
            else:
                # This will not be the first extension in the file so we
                # must change the Primary header provided into an image
                # extension header.

                if "SIMPLE" in self._header:
                    self._header.set("XTENSION", "IMAGE", "Image extension", after="SIMPLE")
                    del self._header["SIMPLE"]

                    if "PCOUNT" not in self._header:
                        dim = self._header["NAXIS"]
                        dim = "" if dim == 0 else str(dim)
                        self._header.set(
                            "PCOUNT", 0, "number of parameters", after=f"NAXIS{dim}"
                        )

                    if "GCOUNT" not in self._header:
                        self._header.set("GCOUNT", 1, "number of groups", after="PCOUNT")

            self._ffo = _File(name, "append")

            # TODO : Fix this once the HDU writing API is cleaned up
            tmp_hdu = _BaseHDU()
            # Passing self._header as an argument to _BaseHDU() will cause its
            # values to be modified in undesired ways...need to have a better way
            # of doing this
            tmp_hdu._header = self._header
            self._header_offset = tmp_hdu._writeheader(self._ffo)[0]
            self._data_offset = self._ffo.tell()
            self._size = self.size

            if self._size != 0:
                self.writecomplete = False
            else:
                self.writecomplete = True

        # Support the 'with' statement
        def __enter__(self):
            return self

        def __exit__(self, type, value, traceback):
            self.close()

        def write(self, data):
            """
            Write the given data to the stream.

            Parameters
            ----------
            data : ndarray
                Data to stream to the file.

            Returns
            -------
            writecomplete : int
                Flag that when `True` indicates that all of the required
                data has been written to the stream.

            Notes
            -----
            Only the amount of data specified in the header provided to the class
            constructor may be written to the stream.  If the provided data would
            cause the stream to overflow, an `OSError` exception is
            raised and the data is not written. Once sufficient data has been
            written to the stream to satisfy the amount specified in the header,
            the stream is padded to fill a complete FITS block and no more data
            will be accepted. An attempt to write more data after the stream has
            been filled will raise an `OSError` exception. If the
            dtype of the input data does not match what is expected by the header,
            a `TypeError` exception is raised.
            """
            size = self._ffo.tell() - self._data_offset

            if self.writecomplete or size + data.nbytes > self._size:
                raise OSError(
                    "Attempt to write more data to the stream than the header specified."
                )

            if BITPIX2DTYPE[self._header["BITPIX"]] != data.dtype.name:
                raise TypeError(
                    "Supplied data does not match the type specified in the header."
                )

            if data.dtype.str[0] != ">":
                # byteswap little endian arrays before writing
                output = data.byteswap()
            else:
                output = data

            self._ffo.writearray(output)

            if self._ffo.tell() - self._data_offset == self._size:
                # the stream is full so pad the data to the next FITS block
                self._ffo.write(_pad_length(self._size) * "\0")
                self.writecomplete = True

            self._ffo.flush()

            return self.writecomplete

        @property
        def size(self):
            """
            Return the size (in bytes) of the data portion of the HDU.
            """
            size = 0
            naxis = self._header.get("NAXIS", 0)

            if naxis > 0:
                simple = self._header.get("SIMPLE", "F")
                random_groups = self._header.get("GROUPS", "F")

                if simple == "T" and random_groups == "T":
                    groups = 1
                else:
                    groups = 0

                size = 1

                for idx in range(groups, naxis):
                    size = size * self._header["NAXIS" + str(idx + 1)]
                bitpix = self._header["BITPIX"]
                gcount = self._header.get("GCOUNT", 1)
                pcount = self._header.get("PCOUNT", 0)
                size = abs(bitpix) * gcount * (pcount + size) // 8
            return size

        def close(self):
            """
            Close the physical FITS file.
            """
            self._ffo.close()