# Authors: Alexandre Gramfort <alexandre.gramfort@inria.fr>
#          Matti Hämäläinen <msh@nmr.mgh.harvard.edu>
#
# License: BSD-3-Clause

from contextlib import contextmanager
from gzip import GzipFile
import os.path as op
import re
import time
import uuid

import numpy as np

from .constants import FIFF
from ..utils import logger, _file_like
from ..utils.numerics import _cal_to_julian

# We choose a "magic" date to store (because meas_date is obligatory)
# to treat as meas_date=None. This one should be impossible for systems
# to write -- the second field is microseconds, so anything >= 1e6
# should be moved into the first field (seconds).
DATE_NONE = (0, 2 ** 31 - 1)


def _write(fid, data, kind, data_size, FIFFT_TYPE, dtype):
    """Write data."""
    if isinstance(data, np.ndarray):
        data_size *= data.size

    # XXX for string types the data size is used as
    # computed in ``write_string``.

    fid.write(np.array(kind, dtype='>i4').tobytes())
    fid.write(np.array(FIFFT_TYPE, dtype='>i4').tobytes())
    fid.write(np.array(data_size, dtype='>i4').tobytes())
    fid.write(np.array(FIFF.FIFFV_NEXT_SEQ, dtype='>i4').tobytes())
    fid.write(np.array(data, dtype=dtype).tobytes())


def _get_split_size(split_size):
    """Convert human-readable bytes to machine-readable bytes."""
    if isinstance(split_size, str):
        exp = dict(MB=20, GB=30).get(split_size[-2:], None)
        if exp is None:
            raise ValueError('split_size has to end with either'
                             '"MB" or "GB"')
        split_size = int(float(split_size[:-2]) * 2 ** exp)

    if split_size > 2147483648:
        raise ValueError('split_size cannot be larger than 2GB')
    return split_size


_NEXT_FILE_BUFFER = 1048576  # 2 ** 20 extra cushion for last post-data tags


def write_nop(fid, last=False):
    """Write a FIFF_NOP."""
    fid.write(np.array(FIFF.FIFF_NOP, dtype='>i4').tobytes())
    fid.write(np.array(FIFF.FIFFT_VOID, dtype='>i4').tobytes())
    fid.write(np.array(0, dtype='>i4').tobytes())
    next_ = FIFF.FIFFV_NEXT_NONE if last else FIFF.FIFFV_NEXT_SEQ
    fid.write(np.array(next_, dtype='>i4').tobytes())


INT32_MAX = 2147483647


def write_int(fid, kind, data):
    """Write a 32-bit integer tag to a fif file."""
    data_size = 4
    data = np.asarray(data)
    if data.dtype.kind not in 'uib' and data.size > 0:
        raise TypeError(
            f'Cannot safely write data with dtype {data.dtype} as int')
    max_val = data.max() if data.size > 0 else 0
    if max_val > INT32_MAX:
        raise TypeError(
            f'Value {max_val} exceeds maximum allowed ({INT32_MAX}) for '
            f'tag {kind}')
    data = data.astype('>i4').T
    _write(fid, data, kind, data_size, FIFF.FIFFT_INT, '>i4')


def write_double(fid, kind, data):
    """Write a double-precision floating point tag to a fif file."""
    data_size = 8
    data = np.array(data, dtype='>f8').T
    _write(fid, data, kind, data_size, FIFF.FIFFT_DOUBLE, '>f8')


def write_float(fid, kind, data):
    """Write a single-precision floating point tag to a fif file."""
    data_size = 4
    data = np.array(data, dtype='>f4').T
    _write(fid, data, kind, data_size, FIFF.FIFFT_FLOAT, '>f4')


def write_dau_pack16(fid, kind, data):
    """Write a dau_pack16 tag to a fif file."""
    data_size = 2
    data = np.array(data, dtype='>i2').T
    _write(fid, data, kind, data_size, FIFF.FIFFT_DAU_PACK16, '>i2')


def write_complex64(fid, kind, data):
    """Write a 64 bit complex floating point tag to a fif file."""
    data_size = 8
    data = np.array(data, dtype='>c8').T
    _write(fid, data, kind, data_size, FIFF.FIFFT_COMPLEX_FLOAT, '>c8')


def write_complex128(fid, kind, data):
    """Write a 128 bit complex floating point tag to a fif file."""
    data_size = 16
    data = np.array(data, dtype='>c16').T
    _write(fid, data, kind, data_size, FIFF.FIFFT_COMPLEX_FLOAT, '>c16')


def write_julian(fid, kind, data):
    """Write a Julian-formatted date to a FIF file."""
    assert len(data) == 3
    data_size = 4
    jd = np.sum(_cal_to_julian(*data))
    data = np.array(jd, dtype='>i4')
    _write(fid, data, kind, data_size, FIFF.FIFFT_JULIAN, '>i4')


def write_string(fid, kind, data):
    """Write a string tag."""
    str_data = data.encode('latin1')
    data_size = len(str_data)  # therefore compute size here
    my_dtype = '>a'  # py2/3 compatible on writing -- don't ask me why
    if data_size > 0:
        _write(fid, str_data, kind, data_size, FIFF.FIFFT_STRING, my_dtype)


def write_name_list(fid, kind, data):
    """Write a colon-separated list of names.

    Parameters
    ----------
    data : list of strings
    """
    write_string(fid, kind, ':'.join(data))


def write_float_matrix(fid, kind, mat):
    """Write a single-precision floating-point matrix tag."""
    FIFFT_MATRIX = 1 << 30
    FIFFT_MATRIX_FLOAT = FIFF.FIFFT_FLOAT | FIFFT_MATRIX

    data_size = 4 * mat.size + 4 * (mat.ndim + 1)

    fid.write(np.array(kind, dtype='>i4').tobytes())
    fid.write(np.array(FIFFT_MATRIX_FLOAT, dtype='>i4').tobytes())
    fid.write(np.array(data_size, dtype='>i4').tobytes())
    fid.write(np.array(FIFF.FIFFV_NEXT_SEQ, dtype='>i4').tobytes())
    fid.write(np.array(mat, dtype='>f4').tobytes())

    dims = np.empty(mat.ndim + 1, dtype=np.int32)
    dims[:mat.ndim] = mat.shape[::-1]
    dims[-1] = mat.ndim
    fid.write(np.array(dims, dtype='>i4').tobytes())
    check_fiff_length(fid)


def write_double_matrix(fid, kind, mat):
    """Write a double-precision floating-point matrix tag."""
    FIFFT_MATRIX = 1 << 30
    FIFFT_MATRIX_DOUBLE = FIFF.FIFFT_DOUBLE | FIFFT_MATRIX

    data_size = 8 * mat.size + 4 * (mat.ndim + 1)

    fid.write(np.array(kind, dtype='>i4').tobytes())
    fid.write(np.array(FIFFT_MATRIX_DOUBLE, dtype='>i4').tobytes())
    fid.write(np.array(data_size, dtype='>i4').tobytes())
    fid.write(np.array(FIFF.FIFFV_NEXT_SEQ, dtype='>i4').tobytes())
    fid.write(np.array(mat, dtype='>f8').tobytes())

    dims = np.empty(mat.ndim + 1, dtype=np.int32)
    dims[:mat.ndim] = mat.shape[::-1]
    dims[-1] = mat.ndim
    fid.write(np.array(dims, dtype='>i4').tobytes())
    check_fiff_length(fid)


def write_int_matrix(fid, kind, mat):
    """Write integer 32 matrix tag."""
    FIFFT_MATRIX = 1 << 30
    FIFFT_MATRIX_INT = FIFF.FIFFT_INT | FIFFT_MATRIX

    data_size = 4 * mat.size + 4 * 3

    fid.write(np.array(kind, dtype='>i4').tobytes())
    fid.write(np.array(FIFFT_MATRIX_INT, dtype='>i4').tobytes())
    fid.write(np.array(data_size, dtype='>i4').tobytes())
    fid.write(np.array(FIFF.FIFFV_NEXT_SEQ, dtype='>i4').tobytes())
    fid.write(np.array(mat, dtype='>i4').tobytes())

    dims = np.empty(3, dtype=np.int32)
    dims[0] = mat.shape[1]
    dims[1] = mat.shape[0]
    dims[2] = 2
    fid.write(np.array(dims, dtype='>i4').tobytes())
    check_fiff_length(fid)


def write_complex_float_matrix(fid, kind, mat):
    """Write complex 64 matrix tag."""
    FIFFT_MATRIX = 1 << 30
    FIFFT_MATRIX_COMPLEX_FLOAT = FIFF.FIFFT_COMPLEX_FLOAT | FIFFT_MATRIX

    data_size = 4 * 2 * mat.size + 4 * (mat.ndim + 1)

    fid.write(np.array(kind, dtype='>i4').tobytes())
    fid.write(np.array(FIFFT_MATRIX_COMPLEX_FLOAT, dtype='>i4').tobytes())
    fid.write(np.array(data_size, dtype='>i4').tobytes())
    fid.write(np.array(FIFF.FIFFV_NEXT_SEQ, dtype='>i4').tobytes())
    fid.write(np.array(mat, dtype='>c8').tobytes())

    dims = np.empty(mat.ndim + 1, dtype=np.int32)
    dims[:mat.ndim] = mat.shape[::-1]
    dims[-1] = mat.ndim
    fid.write(np.array(dims, dtype='>i4').tobytes())
    check_fiff_length(fid)


def write_complex_double_matrix(fid, kind, mat):
    """Write complex 128 matrix tag."""
    FIFFT_MATRIX = 1 << 30
    FIFFT_MATRIX_COMPLEX_DOUBLE = FIFF.FIFFT_COMPLEX_DOUBLE | FIFFT_MATRIX

    data_size = 8 * 2 * mat.size + 4 * (mat.ndim + 1)

    fid.write(np.array(kind, dtype='>i4').tobytes())
    fid.write(np.array(FIFFT_MATRIX_COMPLEX_DOUBLE, dtype='>i4').tobytes())
    fid.write(np.array(data_size, dtype='>i4').tobytes())
    fid.write(np.array(FIFF.FIFFV_NEXT_SEQ, dtype='>i4').tobytes())
    fid.write(np.array(mat, dtype='>c16').tobytes())

    dims = np.empty(mat.ndim + 1, dtype=np.int32)
    dims[:mat.ndim] = mat.shape[::-1]
    dims[-1] = mat.ndim
    fid.write(np.array(dims, dtype='>i4').tobytes())
    check_fiff_length(fid)


def get_machid():
    """Get (mostly) unique machine ID.

    Returns
    -------
    ids : array (length 2, int32)
        The machine identifier used in MNE.
    """
    mac = b'%012x' % uuid.getnode()  # byte conversion for Py3
    mac = re.findall(b'..', mac)  # split string
    mac += [b'00', b'00']  # add two more fields

    # Convert to integer in reverse-order (for some reason)
    from codecs import encode
    mac = b''.join([encode(h, 'hex_codec') for h in mac[::-1]])
    ids = np.flipud(np.frombuffer(mac, np.int32, count=2))
    return ids


def get_new_file_id():
    """Create a new file ID tag."""
    secs, usecs = divmod(time.time(), 1.)
    secs, usecs = int(secs), int(usecs * 1e6)
    return {'machid': get_machid(), 'version': FIFF.FIFFC_VERSION,
            'secs': secs, 'usecs': usecs}


def write_id(fid, kind, id_=None):
    """Write fiff id."""
    id_ = _generate_meas_id() if id_ is None else id_

    data_size = 5 * 4                       # The id comprises five integers
    fid.write(np.array(kind, dtype='>i4').tobytes())
    fid.write(np.array(FIFF.FIFFT_ID_STRUCT, dtype='>i4').tobytes())
    fid.write(np.array(data_size, dtype='>i4').tobytes())
    fid.write(np.array(FIFF.FIFFV_NEXT_SEQ, dtype='>i4').tobytes())

    # Collect the bits together for one write
    arr = np.array([id_['version'],
                    id_['machid'][0], id_['machid'][1],
                    id_['secs'], id_['usecs']], dtype='>i4')
    fid.write(arr.tobytes())


def start_block(fid, kind):
    """Write a FIFF_BLOCK_START tag."""
    write_int(fid, FIFF.FIFF_BLOCK_START, kind)


def end_block(fid, kind):
    """Write a FIFF_BLOCK_END tag."""
    write_int(fid, FIFF.FIFF_BLOCK_END, kind)


def start_file(fname, id_=None):
    """Open a fif file for writing and writes the compulsory header tags.

    Parameters
    ----------
    fname : string | fid
        The name of the file to open. It is recommended
        that the name ends with .fif or .fif.gz. Can also be an
        already opened file.
    id_ : dict | None
        ID to use for the FIFF_FILE_ID.
    """
    if _file_like(fname):
        logger.debug('Writing using %s I/O' % type(fname))
        fid = fname
        fid.seek(0)
    else:
        fname = str(fname)
        if op.splitext(fname)[1].lower() == '.gz':
            logger.debug('Writing using gzip')
            # defaults to compression level 9, which is barely smaller but much
            # slower. 2 offers a good compromise.
            fid = GzipFile(fname, "wb", compresslevel=2)
        else:
            logger.debug('Writing using normal I/O')
            fid = open(fname, "wb")
    #   Write the compulsory items
    write_id(fid, FIFF.FIFF_FILE_ID, id_)
    write_int(fid, FIFF.FIFF_DIR_POINTER, -1)
    write_int(fid, FIFF.FIFF_FREE_LIST, -1)
    return fid


@contextmanager
def start_and_end_file(fname, id_=None):
    """Start and (if successfully written) close the file."""
    with start_file(fname, id_=id_) as fid:
        yield fid
        end_file(fid)  # we only hit this line if the yield does not err


def check_fiff_length(fid, close=True):
    """Ensure our file hasn't grown too large to work properly."""
    if fid.tell() > 2147483648:  # 2 ** 31, FIFF uses signed 32-bit locations
        if close:
            fid.close()
        raise IOError('FIFF file exceeded 2GB limit, please split file, reduce'
                      ' split_size (if possible), or save to a different '
                      'format')


def end_file(fid):
    """Write the closing tags to a fif file and closes the file."""
    write_nop(fid, last=True)
    check_fiff_length(fid)
    fid.close()


def write_coord_trans(fid, trans):
    """Write a coordinate transformation structure."""
    data_size = 4 * 2 * 12 + 4 * 2
    fid.write(np.array(FIFF.FIFF_COORD_TRANS, dtype='>i4').tobytes())
    fid.write(np.array(FIFF.FIFFT_COORD_TRANS_STRUCT, dtype='>i4').tobytes())
    fid.write(np.array(data_size, dtype='>i4').tobytes())
    fid.write(np.array(FIFF.FIFFV_NEXT_SEQ, dtype='>i4').tobytes())
    fid.write(np.array(trans['from'], dtype='>i4').tobytes())
    fid.write(np.array(trans['to'], dtype='>i4').tobytes())

    #   The transform...
    rot = trans['trans'][:3, :3]
    move = trans['trans'][:3, 3]
    fid.write(np.array(rot, dtype='>f4').tobytes())
    fid.write(np.array(move, dtype='>f4').tobytes())

    #   ...and its inverse
    trans_inv = np.linalg.inv(trans['trans'])
    rot = trans_inv[:3, :3]
    move = trans_inv[:3, 3]
    fid.write(np.array(rot, dtype='>f4').tobytes())
    fid.write(np.array(move, dtype='>f4').tobytes())


def write_ch_info(fid, ch):
    """Write a channel information record to a fif file."""
    data_size = 4 * 13 + 4 * 7 + 16

    fid.write(np.array(FIFF.FIFF_CH_INFO, dtype='>i4').tobytes())
    fid.write(np.array(FIFF.FIFFT_CH_INFO_STRUCT, dtype='>i4').tobytes())
    fid.write(np.array(data_size, dtype='>i4').tobytes())
    fid.write(np.array(FIFF.FIFFV_NEXT_SEQ, dtype='>i4').tobytes())

    #   Start writing fiffChInfoRec
    fid.write(np.array(ch['scanno'], dtype='>i4').tobytes())
    fid.write(np.array(ch['logno'], dtype='>i4').tobytes())
    fid.write(np.array(ch['kind'], dtype='>i4').tobytes())
    fid.write(np.array(ch['range'], dtype='>f4').tobytes())
    fid.write(np.array(ch['cal'], dtype='>f4').tobytes())
    fid.write(np.array(ch['coil_type'], dtype='>i4').tobytes())
    fid.write(np.array(ch['loc'], dtype='>f4').tobytes())  # writing 12 values

    #   unit and unit multiplier
    fid.write(np.array(ch['unit'], dtype='>i4').tobytes())
    fid.write(np.array(ch['unit_mul'], dtype='>i4').tobytes())

    #   Finally channel name
    ch_name = ch['ch_name'][:15]
    fid.write(np.array(ch_name, dtype='>c').tobytes())
    fid.write(b'\0' * (16 - len(ch_name)))


def write_dig_points(fid, dig, block=False, coord_frame=None):
    """Write a set of digitizer data points into a fif file."""
    if dig is not None:
        data_size = 5 * 4
        if block:
            start_block(fid, FIFF.FIFFB_ISOTRAK)
        if coord_frame is not None:
            write_int(fid, FIFF.FIFF_MNE_COORD_FRAME, coord_frame)
        for d in dig:
            fid.write(np.array(FIFF.FIFF_DIG_POINT, '>i4').tobytes())
            fid.write(np.array(FIFF.FIFFT_DIG_POINT_STRUCT, '>i4').tobytes())
            fid.write(np.array(data_size, dtype='>i4').tobytes())
            fid.write(np.array(FIFF.FIFFV_NEXT_SEQ, '>i4').tobytes())
            #   Start writing fiffDigPointRec
            fid.write(np.array(d['kind'], '>i4').tobytes())
            fid.write(np.array(d['ident'], '>i4').tobytes())
            fid.write(np.array(d['r'][:3], '>f4').tobytes())
        if block:
            end_block(fid, FIFF.FIFFB_ISOTRAK)


def write_float_sparse_rcs(fid, kind, mat):
    """Write a single-precision sparse compressed row matrix tag."""
    return write_float_sparse(fid, kind, mat, fmt='csr')


def write_float_sparse_ccs(fid, kind, mat):
    """Write a single-precision sparse compressed column matrix tag."""
    return write_float_sparse(fid, kind, mat, fmt='csc')


def write_float_sparse(fid, kind, mat, fmt='auto'):
    """Write a single-precision floating-point sparse matrix tag."""
    from scipy import sparse
    from .tag import _matrix_coding_CCS, _matrix_coding_RCS
    if fmt == 'auto':
        fmt = 'csr' if isinstance(mat, sparse.csr_matrix) else 'csc'
    if fmt == 'csr':
        need = sparse.csr_matrix
        bits = _matrix_coding_RCS
    else:
        need = sparse.csc_matrix
        bits = _matrix_coding_CCS
    if not isinstance(mat, need):
        raise TypeError('Must write %s, got %s' % (fmt.upper(), type(mat),))
    FIFFT_MATRIX = bits << 16
    FIFFT_MATRIX_FLOAT_RCS = FIFF.FIFFT_FLOAT | FIFFT_MATRIX

    nnzm = mat.nnz
    nrow = mat.shape[0]
    data_size = 4 * nnzm + 4 * nnzm + 4 * (nrow + 1) + 4 * 4

    fid.write(np.array(kind, dtype='>i4').tobytes())
    fid.write(np.array(FIFFT_MATRIX_FLOAT_RCS, dtype='>i4').tobytes())
    fid.write(np.array(data_size, dtype='>i4').tobytes())
    fid.write(np.array(FIFF.FIFFV_NEXT_SEQ, dtype='>i4').tobytes())

    fid.write(np.array(mat.data, dtype='>f4').tobytes())
    fid.write(np.array(mat.indices, dtype='>i4').tobytes())
    fid.write(np.array(mat.indptr, dtype='>i4').tobytes())

    dims = [nnzm, mat.shape[0], mat.shape[1], 2]
    fid.write(np.array(dims, dtype='>i4').tobytes())
    check_fiff_length(fid)


def _generate_meas_id():
    """Generate a new meas_id dict."""
    id_ = dict()
    id_['version'] = FIFF.FIFFC_VERSION
    id_['machid'] = get_machid()
    id_['secs'], id_['usecs'] = DATE_NONE
    return id_
