# -*- coding: utf-8 -*-
# Copyright (C) Duncan Macleod (2014-2019)
#
# This file is part of GWpy.
#
# GWpy is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# GWpy is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with GWpy.  If not, see <http://www.gnu.org/licenses/>.

"""Fetch registration for database queries
"""

import re

from six import string_types

from astropy.io import registry as io_registry
try:
    from astropy.io.registry import IORegistryError
except ImportError:  # astropy < 1.2.1
    IORegistryError = Exception
from astropy.table import Table

_FETCHERS = {}

__author__ = 'Duncan Macleod <duncan.macleod@ligo.org>'


def register_fetcher(data_format, data_class, function, force=False,
                     usage=None):
    """Register a new method to EventTable.fetch() for a given format

    Parameters
    ----------
    data_format : `str`
        name of the format to be registered

    data_class : `type`
        the class that the fetcher returns

    function : `callable`
        the method to call from :meth:`EventTable.fetch`

    force : `bool`, optional
        overwrite existing registration for ``data_format`` if found,
        default: `False`
    """
    key = (data_format, data_class)
    if key not in _FETCHERS or force:
        _FETCHERS[key] = (function, usage)
    else:
        raise IORegistryError("Fetcher for format '{0}' and class '{1}' "
                              "has already been " "defined".format(
                                  data_format, data_class))
    _update__doc__(data_class)


def get_fetcher(data_format, data_class):
    """Return the :meth:`~EventTable.fetch` function for the given format

    Parameters
    ----------
    data_format : `str`
        name of the format

    data_class : `type`
        the class that the fetcher returns

    Raises
    ------
    astropy.io.registry.IORegistryError
        if not registration is found matching ``data_format``
    """
    # this is a copy of astropy.io.regsitry.get_reader
    fetchers = [(fmt, cls) for fmt, cls in _FETCHERS if fmt == data_format]
    for fetch_fmt, fetch_cls in fetchers:
        if io_registry._is_best_match(data_class, fetch_cls, fetchers):
            return _FETCHERS[(fetch_fmt, fetch_cls)][0]
    else:
        formats = [fmt for fmt, cls in _FETCHERS if
                   io_registry._is_best_match(fmt, cls, fetchers)]
        formatstr = '\n'.join(sorted(formats))
        raise IORegistryError(
            "No fetcher definer for format '{0}' and class '{1}'.\n"
            "The available formats are:\n{2}".format(
                data_format, data_class.__name__, formatstr))


def _update__doc__(data_class):
    header = "The available named formats are:"
    fetch = data_class.fetch

    # if __doc__ isn't a string, bail-out now
    if not isinstance(fetch.__doc__, string_types):
        return

    # remove the old format list
    lines = fetch.__doc__.splitlines()
    try:
        pos = [i for i, line in enumerate(lines) if header in line][0]
    except IndexError:
        pass
    else:
        lines = lines[:pos]

    # work out the indentation
    matches = [re.search(r'(\S)', line) for line in lines[1:]]
    indent = min(match.start() for match in matches if match)

    # now re-write the format list
    formats = []
    for fmt, cls in sorted(_FETCHERS, key=lambda x: x[0]):
        if cls is not data_class:
            continue
        usage = _FETCHERS[(fmt, cls)][1]
        formats.append((
            fmt, '``fetch(%r, %s)``' % (fmt, usage)))
    format_str = Table(rows=formats, names=['Format', 'Basic usage']).pformat(
        max_lines=-1, max_width=80, align=('>', '<'))
    format_str[1] = format_str[1].replace('-', '=')
    format_str.insert(0, format_str[1])
    format_str.append(format_str[0])

    lines.extend([' ' * indent + line for line in [header, ''] + format_str])
    # and overwrite the docstring
    try:
        fetch.__doc__ = '\n'.join(lines)
    except AttributeError:
        fetch.__func__.__doc__ = '\n'.join(lines)
