import inspect
import os
import re
import subprocess
import sys
from functools import partial
from operator import attrgetter

orig = inspect.isfunction


# See https://opendreamkit.org/2017/06/09/CythonSphinx/
def isfunction(obj):

    orig_val = orig(obj)

    new_val = hasattr(type(obj), "__code__")

    if (orig_val != new_val):
        return new_val

    return orig_val


inspect.isfunction = isfunction

REVISION_CMD = 'git rev-parse --short HEAD'

source_regex = re.compile(r"^File: (.*?) \(starting at line ([0-9]*?)\)$",
                          re.MULTILINE)


def _get_git_revision():
    try:
        revision = subprocess.check_output(REVISION_CMD.split()).strip()
    except (subprocess.CalledProcessError, OSError):
        print('Failed to execute git to get revision')
        return None
    return revision.decode('utf-8')


def _linkcode_resolve(domain, info, package, url_fmt, revision):
    """Determine a link to online source for a class/method/function

    This is called by sphinx.ext.linkcode

    An example with a long-untouched module that everyone has
    >>> _linkcode_resolve('py', {'module': 'tty',
    ...                          'fullname': 'setraw'},
    ...                   package='tty',
    ...                   url_fmt='http://hg.python.org/cpython/file/'
    ...                           '{revision}/Lib/{package}/{path}#L{lineno}',
    ...                   revision='xxxx')
    'http://hg.python.org/cpython/file/xxxx/Lib/tty/tty.py#L18'
    """

    if revision is None:
        return
    if domain not in ('py', 'pyx'):
        return
    if not info.get('module') or not info.get('fullname'):
        return

    class_name = info['fullname'].split('.')[0]
    module = __import__(info['module'], fromlist=[class_name])
    obj = attrgetter(info['fullname'])(module)

    # Unwrap the object to get the correct source
    # file in case that is wrapped by a decorator
    obj = inspect.unwrap(obj)

    fn: str = None
    lineno: str = None

    try:
        fn = inspect.getsourcefile(obj)
    except Exception:
        fn = None
    if not fn:
        try:
            fn = inspect.getsourcefile(sys.modules[obj.__module__])
        except Exception:
            fn = None

    if not fn:
        # Possibly Cython code. Search docstring for source
        m = source_regex.search(obj.__doc__)

        if (m is not None):
            source_file = m.group(1)
            lineno = m.group(2)

            # fn is expected to be the absolute path.
            fn = os.path.relpath(source_file, start=package)
            print("{}:{}".format(
                os.path.abspath(os.path.join("..", "python", "cuml", fn)),
                lineno))
        else:
            return
    else:
        # Test if we are absolute or not (pyx are relative)
        if (not os.path.isabs(fn)):
            # Should be relative to docs right now
            fn = os.path.abspath(os.path.join("..", "python", fn))

        # Convert to relative from module root
        fn = os.path.relpath(fn,
                             start=os.path.dirname(
                                 __import__(package).__file__))

    # Get the line number if we need it. (Can work without it)
    if (lineno is None):
        try:
            lineno = inspect.getsourcelines(obj)[1]
        except Exception:

            # Can happen if its a cyfunction. See if it has `__code__`
            if (hasattr(obj, "__code__")):
                lineno = obj.__code__.co_firstlineno
            else:
                lineno = ''
    return url_fmt.format(revision=revision,
                          package=package,
                          path=fn,
                          lineno=lineno)


def make_linkcode_resolve(package, url_fmt):
    """Returns a linkcode_resolve function for the given URL format

    revision is a git commit reference (hash or name)

    package is the name of the root module of the package

    url_fmt is along the lines of ('https://github.com/USER/PROJECT/'
                                   'blob/{revision}/{package}/'
                                   '{path}#L{lineno}')
    """
    revision = _get_git_revision()
    return partial(_linkcode_resolve,
                   revision=revision,
                   package=package,
                   url_fmt=url_fmt)
