"""
My own variation on function-specific inspect-like features.
"""

# Author: Gael Varoquaux <gael dot varoquaux at normalesup dot org>
# Copyright (c) 2009 Gael Varoquaux
# License: BSD Style, 3 clauses.

from itertools import islice
import inspect
import warnings
import re
import os
import collections

from ._compat import _basestring
from .logger import pformat
from ._memory_helpers import open_py_source
from ._compat import PY3_OR_LATER

full_argspec_fields = ('args varargs varkw defaults kwonlyargs '
                       'kwonlydefaults annotations')
full_argspec_type = collections.namedtuple('FullArgSpec', full_argspec_fields)


def get_func_code(func):
    """ Attempts to retrieve a reliable function code hash.

        The reason we don't use inspect.getsource is that it caches the
        source, whereas we want this to be modified on the fly when the
        function is modified.

        Returns
        -------
        func_code: string
            The function code
        source_file: string
            The path to the file in which the function is defined.
        first_line: int
            The first line of the code in the source file.

        Notes
        ------
        This function does a bit more magic than inspect, and is thus
        more robust.
    """
    source_file = None
    try:
        code = func.__code__
        source_file = code.co_filename
        if not os.path.exists(source_file):
            # Use inspect for lambda functions and functions defined in an
            # interactive shell, or in doctests
            source_code = ''.join(inspect.getsourcelines(func)[0])
            line_no = 1
            if source_file.startswith('<doctest '):
                source_file, line_no = re.match(
                    r'\<doctest (.*\.rst)\[(.*)\]\>', source_file).groups()
                line_no = int(line_no)
                source_file = '<doctest %s>' % source_file
            return source_code, source_file, line_no
        # Try to retrieve the source code.
        with open_py_source(source_file) as source_file_obj:
            first_line = code.co_firstlineno
            # All the lines after the function definition:
            source_lines = list(islice(source_file_obj, first_line - 1, None))
        return ''.join(inspect.getblock(source_lines)), source_file, first_line
    except:
        # If the source code fails, we use the hash. This is fragile and
        # might change from one session to another.
        if hasattr(func, '__code__'):
            # Python 3.X
            return str(func.__code__.__hash__()), source_file, -1
        else:
            # Weird objects like numpy ufunc don't have __code__
            # This is fragile, as quite often the id of the object is
            # in the repr, so it might not persist across sessions,
            # however it will work for ufuncs.
            return repr(func), source_file, -1


def _clean_win_chars(string):
    """Windows cannot encode some characters in filename."""
    import urllib
    if hasattr(urllib, 'quote'):
        quote = urllib.quote
    else:
        # In Python 3, quote is elsewhere
        import urllib.parse
        quote = urllib.parse.quote
    for char in ('<', '>', '!', ':', '\\'):
        string = string.replace(char, quote(char))
    return string


def get_func_name(func, resolv_alias=True, win_characters=True):
    """ Return the function import path (as a list of module names), and
        a name for the function.

        Parameters
        ----------
        func: callable
            The func to inspect
        resolv_alias: boolean, optional
            If true, possible local aliases are indicated.
        win_characters: boolean, optional
            If true, substitute special characters using urllib.quote
            This is useful in Windows, as it cannot encode some filenames
    """
    if hasattr(func, '__module__'):
        module = func.__module__
    else:
        try:
            module = inspect.getmodule(func)
        except TypeError:
            if hasattr(func, '__class__'):
                module = func.__class__.__module__
            else:
                module = 'unknown'
    if module is None:
        # Happens in doctests, eg
        module = ''
    if module == '__main__':
        try:
            filename = os.path.abspath(inspect.getsourcefile(func))
        except:
            filename = None
        if filename is not None:
            # mangling of full path to filename
            parts = filename.split(os.sep)
            if parts[-1].startswith('<ipython-input'):
                # function is defined in an IPython session. The filename
                # will change with every new kernel instance. This hack
                # always returns the same filename
                parts[-1] = '__ipython-input__'
            filename = '-'.join(parts)
            if filename.endswith('.py'):
                filename = filename[:-3]
            module = module + '-' + filename
    module = module.split('.')
    if hasattr(func, 'func_name'):
        name = func.func_name
    elif hasattr(func, '__name__'):
        name = func.__name__
    else:
        name = 'unknown'
    # Hack to detect functions not defined at the module-level
    if resolv_alias:
        # TODO: Maybe add a warning here?
        if hasattr(func, 'func_globals') and name in func.func_globals:
            if not func.func_globals[name] is func:
                name = '%s-alias' % name
    if inspect.ismethod(func):
        # We need to add the name of the class
        if hasattr(func, 'im_class'):
            klass = func.im_class
            module.append(klass.__name__)
    if os.name == 'nt' and win_characters:
        # Stupid windows can't encode certain characters in filenames
        name = _clean_win_chars(name)
        module = [_clean_win_chars(s) for s in module]
    return module, name


def getfullargspec(func):
    """Compatibility function to provide inspect.getfullargspec in Python 2

    This should be rewritten using a backport of Python 3 signature
    once we drop support for Python 2.6. We went for a simpler
    approach at the time of writing because signature uses OrderedDict
    which is not available in Python 2.6.
    """
    try:
        return inspect.getfullargspec(func)
    except AttributeError:
        arg_spec = inspect.getargspec(func)
        return full_argspec_type(args=arg_spec.args,
                                 varargs=arg_spec.varargs,
                                 varkw=arg_spec.keywords,
                                 defaults=arg_spec.defaults,
                                 kwonlyargs=[],
                                 kwonlydefaults=None,
                                 annotations={})


def _signature_str(function_name, arg_spec):
    """Helper function to output a function signature"""
    # inspect.formatargspec can not deal with the same
    # number of arguments in python 2 and 3
    arg_spec_for_format = arg_spec[:7 if PY3_OR_LATER else 4]

    arg_spec_str = inspect.formatargspec(*arg_spec_for_format)
    return '{}{}'.format(function_name, arg_spec_str)


def _function_called_str(function_name, args, kwargs):
    """Helper function to output a function call"""
    template_str = '{0}({1}, {2})'

    args_str = repr(args)[1:-1]
    kwargs_str = ', '.join('%s=%s' % (k, v)
                           for k, v in kwargs.items())
    return template_str.format(function_name, args_str,
                               kwargs_str)


def filter_args(func, ignore_lst, args=(), kwargs=dict()):
    """ Filters the given args and kwargs using a list of arguments to
        ignore, and a function specification.

        Parameters
        ----------
        func: callable
            Function giving the argument specification
        ignore_lst: list of strings
            List of arguments to ignore (either a name of an argument
            in the function spec, or '*', or '**')
        *args: list
            Positional arguments passed to the function.
        **kwargs: dict
            Keyword arguments passed to the function

        Returns
        -------
        filtered_args: list
            List of filtered positional and keyword arguments.
    """
    args = list(args)
    if isinstance(ignore_lst, _basestring):
        # Catch a common mistake
        raise ValueError(
            'ignore_lst must be a list of parameters to ignore '
            '%s (type %s) was given' % (ignore_lst, type(ignore_lst)))
    # Special case for functools.partial objects
    if (not inspect.ismethod(func) and not inspect.isfunction(func)):
        if ignore_lst:
            warnings.warn('Cannot inspect object %s, ignore list will '
                          'not work.' % func, stacklevel=2)
        return {'*': args, '**': kwargs}
    arg_spec = getfullargspec(func)
    arg_names = arg_spec.args + arg_spec.kwonlyargs
    arg_defaults = arg_spec.defaults or ()
    if arg_spec.kwonlydefaults:
        arg_defaults = arg_defaults + tuple(arg_spec.kwonlydefaults[k]
                                            for k in arg_spec.kwonlyargs
                                            if k in arg_spec.kwonlydefaults)
    arg_varargs = arg_spec.varargs
    arg_varkw = arg_spec.varkw

    if inspect.ismethod(func):
        # First argument is 'self', it has been removed by Python
        # we need to add it back:
        args = [func.__self__, ] + args
    # XXX: Maybe I need an inspect.isbuiltin to detect C-level methods, such
    # as on ndarrays.

    _, name = get_func_name(func, resolv_alias=False)
    arg_dict = dict()
    arg_position = -1
    for arg_position, arg_name in enumerate(arg_names):
        if arg_position < len(args):
            # Positional argument or keyword argument given as positional
            if arg_name not in arg_spec.kwonlyargs:
                arg_dict[arg_name] = args[arg_position]
            else:
                raise ValueError(
                    "Keyword-only parameter '%s' was passed as "
                    'positional parameter for %s:\n'
                    '     %s was called.'
                    % (arg_name,
                       _signature_str(name, arg_spec),
                       _function_called_str(name, args, kwargs))
                )

        else:
            position = arg_position - len(arg_names)
            if arg_name in kwargs:
                arg_dict[arg_name] = kwargs[arg_name]
            else:
                try:
                    arg_dict[arg_name] = arg_defaults[position]
                except (IndexError, KeyError):
                    # Missing argument
                    raise ValueError(
                        'Wrong number of arguments for %s:\n'
                        '     %s was called.'
                        % (_signature_str(name, arg_spec),
                           _function_called_str(name, args, kwargs))
                    )

    varkwargs = dict()
    for arg_name, arg_value in sorted(kwargs.items()):
        if arg_name in arg_dict:
            arg_dict[arg_name] = arg_value
        elif arg_varkw is not None:
            varkwargs[arg_name] = arg_value
        else:
            raise TypeError("Ignore list for %s() contains an unexpected "
                            "keyword argument '%s'" % (name, arg_name))

    if arg_varkw is not None:
        arg_dict['**'] = varkwargs
    if arg_varargs is not None:
        varargs = args[arg_position + 1:]
        arg_dict['*'] = varargs

    # Now remove the arguments to be ignored
    for item in ignore_lst:
        if item in arg_dict:
            arg_dict.pop(item)
        else:
            raise ValueError("Ignore list: argument '%s' is not defined for "
                             "function %s"
                             % (item,
                                _signature_str(name, arg_spec))
                             )
    # XXX: Return a sorted list of pairs?
    return arg_dict


def _format_arg(arg):
    formatted_arg = pformat(arg, indent=2)
    if len(formatted_arg) > 1500:
        formatted_arg = '%s...' % formatted_arg[:700]
    return formatted_arg


def format_signature(func, *args, **kwargs):
    # XXX: Should this use inspect.formatargvalues/formatargspec?
    module, name = get_func_name(func)
    module = [m for m in module if m]
    if module:
        module.append(name)
        module_path = '.'.join(module)
    else:
        module_path = name
    arg_str = list()
    previous_length = 0
    for arg in args:
        formatted_arg = _format_arg(arg)
        if previous_length > 80:
            formatted_arg = '\n%s' % formatted_arg
        previous_length = len(formatted_arg)
        arg_str.append(formatted_arg)
    arg_str.extend(['%s=%s' % (v, _format_arg(i)) for v, i in kwargs.items()])