##############################################################################
# Copyright (c) 2013-2018, Lawrence Livermore National Security, LLC.
# Produced at the Lawrence Livermore National Laboratory.
#
# This file is part of Spack.
# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
# LLNL-CODE-647188
#
# For details, see https://github.com/spack/spack
# Please also see the NOTICE and LICENSE files for our notice and the LGPL.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License (as
# published by the Free Software Foundation) version 2.1, February 1999.
#
# This program 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 terms and
# conditions of the GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
##############################################################################
from __future__ import division

import os
import re
import functools
import collections
import inspect
from datetime import datetime, timedelta
from six import string_types

# Ignore emacs backups when listing modules
ignore_modules = [r'^\.#', '~$']


class classproperty(property):
    """classproperty decorator: like property but for classmethods."""
    def __get__(self, cls, owner):
        return self.fget.__get__(None, owner)()


def index_by(objects, *funcs):
    """Create a hierarchy of dictionaries by splitting the supplied
       set of objects on unique values of the supplied functions.
       Values are used as keys.  For example, suppose you have four
       objects with attributes that look like this::

          a = Spec(name="boost",    compiler="gcc",   arch="bgqos_0")
          b = Spec(name="mrnet",    compiler="intel", arch="chaos_5_x86_64_ib")
          c = Spec(name="libelf",   compiler="xlc",   arch="bgqos_0")
          d = Spec(name="libdwarf", compiler="intel", arch="chaos_5_x86_64_ib")

          list_of_specs = [a,b,c,d]
          index1 = index_by(list_of_specs, lambda s: s.arch,
                            lambda s: s.compiler)
          index2 = index_by(list_of_specs, lambda s: s.compiler)

       ``index1`` now has two levels of dicts, with lists at the
       leaves, like this::

           { 'bgqos_0'           : { 'gcc' : [a], 'xlc' : [c] },
             'chaos_5_x86_64_ib' : { 'intel' : [b, d] }
           }

       And ``index2`` is a single level dictionary of lists that looks
       like this::

           { 'gcc'    : [a],
             'intel'  : [b,d],
             'xlc'    : [c]
           }

       If any elemnts in funcs is a string, it is treated as the name
       of an attribute, and acts like getattr(object, name).  So
       shorthand for the above two indexes would be::

           index1 = index_by(list_of_specs, 'arch', 'compiler')
           index2 = index_by(list_of_specs, 'compiler')

       You can also index by tuples by passing tuples::

           index1 = index_by(list_of_specs, ('arch', 'compiler'))

       Keys in the resulting dict will look like ('gcc', 'bgqos_0').
    """
    if not funcs:
        return objects

    f = funcs[0]
    if isinstance(f, str):
        f = lambda x: getattr(x, funcs[0])
    elif isinstance(f, tuple):
        f = lambda x: tuple(getattr(x, p) for p in funcs[0])

    result = {}
    for o in objects:
        key = f(o)
        result.setdefault(key, []).append(o)

    for key, objects in result.items():
        result[key] = index_by(objects, *funcs[1:])

    return result


def caller_locals():
    """This will return the locals of the *parent* of the caller.
       This allows a function to insert variables into its caller's
       scope.  Yes, this is some black magic, and yes it's useful
       for implementing things like depends_on and provides.
    """
    # Passing zero here skips line context for speed.
    stack = inspect.stack(0)
    try:
        return stack[2][0].f_locals
    finally:
        del stack


def get_calling_module_name():
    """Make sure that the caller is a class definition, and return the
       enclosing module's name.
    """
    # Passing zero here skips line context for speed.
    stack = inspect.stack(0)
    try:
        # Make sure locals contain __module__
        caller_locals = stack[2][0].f_locals
    finally:
        del stack

    if '__module__' not in caller_locals:
        raise RuntimeError("Must invoke get_calling_module_name() "
                           "from inside a class definition!")

    module_name = caller_locals['__module__']
    base_name = module_name.split('.')[-1]
    return base_name


def attr_required(obj, attr_name):
    """Ensure that a class has a required attribute."""
    if not hasattr(obj, attr_name):
        raise RequiredAttributeError(
            "No required attribute '%s' in class '%s'"
            % (attr_name, obj.__class__.__name__))


def attr_setdefault(obj, name, value):
    """Like dict.setdefault, but for objects."""
    if not hasattr(obj, name):
        setattr(obj, name, value)
    return getattr(obj, name)


def has_method(cls, name):
    for base in inspect.getmro(cls):
        if base is object:
            continue
        if name in base.__dict__:
            return True
    return False


class memoized(object):
    """Decorator that caches the results of a function, storing them
       in an attribute of that function."""

    def __init__(self, func):
        self.func = func
        self.cache = {}

    def __call__(self, *args):
        if not isinstance(args, collections.Hashable):
            # Not hashable, so just call the function.
            return self.func(*args)

        if args not in self.cache:
            self.cache[args] = self.func(*args)
        return self.cache[args]

    def __get__(self, obj, objtype):
        """Support instance methods."""
        return functools.partial(self.__call__, obj)

    def clear(self):
        """Expunge cache so that self.func will be called again."""
        self.cache.clear()


def list_modules(directory, **kwargs):
    """Lists all of the modules, excluding ``__init__.py``, in a
       particular directory.  Listed packages have no particular
       order."""
    list_directories = kwargs.setdefault('directories', True)

    for name in os.listdir(directory):
        if name == '__init__.py':
            continue

        path = os.path.join(directory, name)
        if list_directories and os.path.isdir(path):
            init_py = os.path.join(path, '__init__.py')
            if os.path.isfile(init_py):
                yield name

        elif name.endswith('.py'):
            if not any(re.search(pattern, name) for pattern in ignore_modules):
                yield re.sub('.py$', '', name)


def key_ordering(cls):
    """Decorates a class with extra methods that implement rich comparison
       operations and ``__hash__``.  The decorator assumes that the class
       implements a function called ``_cmp_key()``.  The rich comparison
       operations will compare objects using this key, and the ``__hash__``
       function will return the hash of this key.

       If a class already has ``__eq__``, ``__ne__``, ``__lt__``, ``__le__``,
       ``__gt__``, or ``__ge__`` defined, this decorator will overwrite them.

       Raises:
           TypeError: If the class does not have a ``_cmp_key`` method
    """
    def setter(name, value):
        value.__name__ = name
        setattr(cls, name, value)

    if not has_method(cls, '_cmp_key'):
        raise TypeError("'%s' doesn't define _cmp_key()." % cls.__name__)

    setter('__eq__',
           lambda s, o:
           (s is o) or (o is not None and s._cmp_key() == o._cmp_key()))
    setter('__lt__',
           lambda s, o: o is not None and s._cmp_key() < o._cmp_key())
    setter('__le__',
           lambda s, o: o is not None and s._cmp_key() <= o._cmp_key())

    setter('__ne__',
           lambda s, o:
           (s is not o) and (o is None or s._cmp_key() != o._cmp_key()))
    setter('__gt__',
           lambda s, o: o is None or s._cmp_key() > o._cmp_key())
    setter('__ge__',
           lambda s, o: o is None or s._cmp_key() >= o._cmp_key())

    setter('__hash__', lambda self: hash(self._cmp_key()))

    return cls


@key_ordering
class HashableMap(collections.MutableMapping):
    """This is a hashable, comparable dictionary.  Hash is performed on
       a tuple of the values in the dictionary."""

    def __init__(self):
        self.dict = {}

    def __getitem__(self, key):
        return self.dict[key]

    def __setitem__(self, key, value):
        self.dict[key] = value

    def __iter__(self):
        return iter(self.dict)

    def __len__(self):
        return len(self.dict)

    def __delitem__(self, key):
        del self.dict[key]

    def _cmp_key(self):
        return tuple(sorted(self.values()))

    def copy(self):
        """Type-agnostic clone method.  Preserves subclass type."""
        # Construct a new dict of my type
        self_type = type(self)
        clone = self_type()

        # Copy everything from this dict into it.
        for key in self:
            clone[key] = self[key].copy()
        return clone


def in_function(function_name):
    """True if the caller was called from some function with
       the supplied Name, False otherwise."""
    stack = inspect.stack()
    try:
        for elt in stack[2:]:
            if elt[3] == function_name:
                return True
        return False
    finally:
        del stack


def check_kwargs(kwargs, fun):
    """Helper for making functions with kwargs.  Checks whether the kwargs
       are empty after all of them have been popped off.  If they're
       not, raises an error describing which kwargs are invalid.

       Example::

          def foo(self, **kwargs):
              x = kwargs.pop('x', None)
              y = kwargs.pop('y', None)
              z = kwargs.pop('z', None)
              check_kwargs(kwargs, self.foo)

          # This raises a TypeError:
          foo(w='bad kwarg')
    """
    if kwargs:
        raise TypeError(
            "'%s' is an invalid keyword argument for function %s()."
            % (next(kwargs.iterkeys()), fun.__name__))


def match_predicate(*args):
    """Utility function for making string matching predicates.

    Each arg can be a:
    * regex
    * list or tuple of regexes
    * predicate that takes a string.

    This returns a predicate that is true if:
    * any arg regex matches
    * any regex in a list or tuple of regexes matches.
    * any predicate in args matches.
    """
    def match(string):
        for arg in args:
            if isinstance(arg, string_types):
                if re.search(arg, string):
                    return True
            elif isinstance(arg, list) or isinstance(arg, tuple):
                if any(re.search(i, string) for i in arg):
                    return True
            elif callable(arg):
                if arg(string):
                    return True
            else:
                raise ValueError("args to match_predicate must be regex, "
                                 "list of regexes, or callable.")
        return False
    return match


def dedupe(sequence):
    """Yields a stable de-duplication of an hashable sequence

    Args:
        sequence: hashable sequence to be de-duplicated

    Returns:
        stable de-duplication of the sequence
    """
    seen = set()
    for x in sequence:
        if x not in seen:
            yield x
            seen.add(x)


def pretty_date(time, now=None):
    """Convert a datetime or timestamp to a pretty, relative date.

    Args:
        time (datetime or int): date to print prettily
        now (datetime): dateimte for 'now', i.e. the date the pretty date
            is relative to (default is datetime.now())

    Returns:
        (str): pretty string like 'an hour ago', 'Yesterday',
            '3 months ago', 'just now', etc.

    Adapted from https://stackoverflow.com/questions/1551382.

    """
    if now is None:
        now = datetime.now()

    if type(time) is int:
        diff = now - datetime.fromtimestamp(time)
    elif isinstance(time, datetime):
        diff = now - time
    else:
        raise ValueError("pretty_date requires a timestamp or datetime")

    second_diff = diff.seconds
    day_diff = diff.days

    if day_diff < 0:
        return ''

    if day_diff == 0:
        if second_diff < 10:
            return "just now"
        if second_diff < 60:
            return str(second_diff) + " seconds ago"
        if second_diff < 120:
            return "a minute ago"
        if second_diff < 3600:
            return str(second_diff // 60) + " minutes ago"
        if second_diff < 7200:
            return "an hour ago"
        if second_diff < 86400:
            return str(second_diff // 3600) + " hours ago"
    if day_diff == 1:
        return "yesterday"
    if day_diff < 7:
        return str(day_diff) + " days ago"
    if day_diff < 28:
        weeks = day_diff // 7
        if weeks == 1:
            return "a week ago"
        else:
            return str(day_diff // 7) + " weeks ago"
    if day_diff < 365:
        months = day_diff // 30
        if months == 1:
            return "a month ago"
        elif months == 12:
            months -= 1
        return str(months) + " months ago"

    diff = day_diff // 365
    if diff == 1:
        return "a year ago"
    else:
        return str(diff) + " years ago"


def pretty_string_to_date(date_str, now=None):
    """Parses a string representing a date and returns a datetime object.

    Args:
        date_str (str): string representing a date. This string might be
            in different format (like ``YYYY``, ``YYYY-MM``, ``YYYY-MM-DD``)
            or be a *pretty date* (like ``yesterday`` or ``two months ago``)

    Returns:
        (datetime): datetime object corresponding to ``date_str``
    """

    pattern = {}

    now = now or datetime.now()

    # datetime formats
    pattern[re.compile('^\d{4}$')] = lambda x: datetime.strptime(x, '%Y')
    pattern[re.compile('^\d{4}-\d{2}$')] = lambda x: datetime.strptime(
        x, '%Y-%m'
    )
    pattern[re.compile('^\d{4}-\d{2}-\d{2}$')] = lambda x: datetime.strptime(
        x, '%Y-%m-%d'
    )

    pretty_regex = re.compile(
        r'(a|\d+)\s*(year|month|week|day|hour|minute|second)s?\s*ago')

    def _n_xxx_ago(x):
        how_many, time_period = pretty_regex.search(x).groups()

        how_many = 1 if how_many == 'a' else int(how_many)

        # timedelta natively supports time periods up to 'weeks'.
        # To apply month or year we convert to 30 and 365 days
        if time_period == 'month':
            how_many *= 30
            time_period = 'day'
        elif time_period == 'year':
            how_many *= 365
            time_period = 'day'

        kwargs = {(time_period + 's'): how_many}
        return now - timedelta(**kwargs)

    pattern[pretty_regex] = _n_xxx_ago

    # yesterday
    callback = lambda x: now - timedelta(days=1)
    pattern[re.compile('^yesterday$')] = callback

    for regexp, parser in pattern.items():
        if bool(regexp.match(date_str)):
            return parser(date_str)

    msg = 'date "{0}" does not match any valid format'.format(date_str)
    raise ValueError(msg)


class RequiredAttributeError(ValueError):

    def __init__(self, message):
        super(RequiredAttributeError, self).__init__(message)


class ObjectWrapper(object):
    """Base class that wraps an object. Derived classes can add new behavior
    while staying undercover.

    This class is modeled after the stackoverflow answer:
    * http://stackoverflow.com/a/1445289/771663
    """
    def __init__(self, wrapped_object):
        wrapped_cls = type(wrapped_object)
        wrapped_name = wrapped_cls.__name__

        # If the wrapped object is already an ObjectWrapper, or a derived class
        # of it, adding type(self) in front of type(wrapped_object)
        # results in an inconsistent MRO.
        #
        # TODO: the implementation below doesn't account for the case where we
        # TODO: have different base classes of ObjectWrapper, say A and B, and
        # TODO: we want to wrap an instance of A with B.
        if type(self) not in wrapped_cls.__mro__:
            self.__class__ = type(wrapped_name, (type(self), wrapped_cls), {})
        else:
            self.__class__ = type(wrapped_name, (wrapped_cls,), {})

        self.__dict__ = wrapped_object.__dict__


class Singleton(object):
    """Simple wrapper for lazily initialized singleton objects."""

    def __init__(self, factory):
        """Create a new singleton to be inited with the factory function.

        Args:
            factory (function): function taking no arguments that
                creates the singleton instance.
        """
        self.factory = factory
        self._instance = None

    @property
    def instance(self):
        if self._instance is None:
            self._instance = self.factory()
        return self._instance

    def __getattr__(self, name):
        return getattr(self.instance, name)

    def __getitem__(self, name):
        return self.instance[name]

    def __contains__(self, element):
        return element in self.instance

    def __iter__(self):
        return iter(self.instance)

    def __str__(self):
        return str(self.instance)

    def __repr__(self):
        return repr(self.instance)


class LazyReference(object):
    """Lazily evaluated reference to part of a singleton."""

    def __init__(self, ref_function):
        self.ref_function = ref_function

    def __getattr__(self, name):
        return getattr(self.ref_function(), name)

    def __getitem__(self, name):
        return self.ref_function()[name]

    def __str__(self):
        return str(self.ref_function())

    def __repr__(self):
        return repr(self.ref_function())
