import six
import json
import copy
import warnings
from collections import MutableMapping
from importlib import import_module
from pprint import pformat

from scrapy.utils.deprecate import create_deprecated_class
from scrapy.exceptions import ScrapyDeprecationWarning

from . import default_settings


SETTINGS_PRIORITIES = {
    'default': 0,
    'command': 10,
    'project': 20,
    'spider': 30,
    'cmdline': 40,
}


def get_settings_priority(priority):
    """
    Small helper function that looks up a given string priority in the
    :attr:`~scrapy.settings.SETTINGS_PRIORITIES` dictionary and returns its
    numerical value, or directly returns a given numerical priority.
    """
    if isinstance(priority, six.string_types):
        return SETTINGS_PRIORITIES[priority]
    else:
        return priority


class SettingsAttribute(object):

    """Class for storing data related to settings attributes.

    This class is intended for internal usage, you should try Settings class
    for settings configuration, not this one.
    """

    def __init__(self, value, priority):
        self.value = value
        if isinstance(self.value, BaseSettings):
            self.priority = max(self.value.maxpriority(), priority)
        else:
            self.priority = priority

    def set(self, value, priority):
        """Sets value if priority is higher or equal than current priority."""
        if priority >= self.priority:
            if isinstance(self.value, BaseSettings):
                value = BaseSettings(value, priority=priority)
            self.value = value
            self.priority = priority

    def __str__(self):
        return "<SettingsAttribute value={self.value!r} " \
               "priority={self.priority}>".format(self=self)

    __repr__ = __str__


class BaseSettings(MutableMapping):
    """
    Instances of this class behave like dictionaries, but store priorities
    along with their ``(key, value)`` pairs, and can be frozen (i.e. marked
    immutable).

    Key-value entries can be passed on initialization with the ``values``
    argument, and they would take the ``priority`` level (unless ``values`` is
    already an instance of :class:`~scrapy.settings.BaseSettings`, in which
    case the existing priority levels will be kept).  If the ``priority``
    argument is a string, the priority name will be looked up in
    :attr:`~scrapy.settings.SETTINGS_PRIORITIES`. Otherwise, a specific integer
    should be provided.

    Once the object is created, new settings can be loaded or updated with the
    :meth:`~scrapy.settings.BaseSettings.set` method, and can be accessed with
    the square bracket notation of dictionaries, or with the
    :meth:`~scrapy.settings.BaseSettings.get` method of the instance and its
    value conversion variants. When requesting a stored key, the value with the
    highest priority will be retrieved.
    """

    def __init__(self, values=None, priority='project'):
        self.frozen = False
        self.attributes = {}
        self.update(values, priority)

    def __getitem__(self, opt_name):
        if opt_name not in self:
            return None
        return self.attributes[opt_name].value

    def __contains__(self, name):
        return name in self.attributes

    def get(self, name, default=None):
        """
        Get a setting value without affecting its original type.

        :param name: the setting name
        :type name: string

        :param default: the value to return if no setting is found
        :type default: any
        """
        return self[name] if self[name] is not None else default

    def getbool(self, name, default=False):
        """
        Get a setting value as a boolean.

        ``1``, ``'1'``, and ``True`` return ``True``, while ``0``, ``'0'``,
        ``False`` and ``None`` return ``False``.

        For example, settings populated through environment variables set to
        ``'0'`` will return ``False`` when using this method.

        :param name: the setting name
        :type name: string

        :param default: the value to return if no setting is found
        :type default: any
        """
        return bool(int(self.get(name, default)))

    def getint(self, name, default=0):
        """
        Get a setting value as an int.

        :param name: the setting name
        :type name: string

        :param default: the value to return if no setting is found
        :type default: any
        """
        return int(self.get(name, default))

    def getfloat(self, name, default=0.0):
        """
        Get a setting value as a float.

        :param name: the setting name
        :type name: string

        :param default: the value to return if no setting is found
        :type default: any
        """
        return float(self.get(name, default))

    def getlist(self, name, default=None):
        """
        Get a setting value as a list. If the setting original type is a list, a
        copy of it will be returned. If it's a string it will be split by ",".

        For example, settings populated through environment variables set to
        ``'one,two'`` will return a list ['one', 'two'] when using this method.

        :param name: the setting name
        :type name: string

        :param default: the value to return if no setting is found
        :type default: any
        """
        value = self.get(name, default or [])
        if isinstance(value, six.string_types):
            value = value.split(',')
        return list(value)

    def getdict(self, name, default=None):
        """
        Get a setting value as a dictionary. If the setting original type is a
        dictionary, a copy of it will be returned. If it is a string it will be
        evaluated as a JSON dictionary. In the case that it is a
        :class:`~scrapy.settings.BaseSettings` instance itself, it will be
        converted to a dictionary, containing all its current settings values
        as they would be returned by :meth:`~scrapy.settings.BaseSettings.get`,
        and losing all information about priority and mutability.

        :param name: the setting name
        :type name: string

        :param default: the value to return if no setting is found
        :type default: any
        """
        value = self.get(name, default or {})
        if isinstance(value, six.string_types):
            value = json.loads(value)
        return dict(value)

    def getwithbase(self, name):
        """Get a composition of a dictionary-like setting and its `_BASE`
        counterpart.

        :param name: name of the dictionary-like setting
        :type name: string
        """
        compbs = BaseSettings()
        compbs.update(self[name + '_BASE'])
        compbs.update(self[name])
        return compbs

    def getpriority(self, name):
        """
        Return the current numerical priority value of a setting, or ``None`` if
        the given ``name`` does not exist.

        :param name: the setting name
        :type name: string
        """
        if name not in self:
            return None
        return self.attributes[name].priority

    def maxpriority(self):
        """
        Return the numerical value of the highest priority present throughout
        all settings, or the numerical value for ``default`` from
        :attr:`~scrapy.settings.SETTINGS_PRIORITIES` if there are no settings
        stored.
        """
        if len(self) > 0:
            return max(self.getpriority(name) for name in self)
        else:
            return get_settings_priority('default')

    def __setitem__(self, name, value):
        self.set(name, value)

    def set(self, name, value, priority='project'):
        """
        Store a key/value attribute with a given priority.

        Settings should be populated *before* configuring the Crawler object
        (through the :meth:`~scrapy.crawler.Crawler.configure` method),
        otherwise they won't have any effect.

        :param name: the setting name
        :type name: string

        :param value: the value to associate with the setting
        :type value: any

        :param priority: the priority of the setting. Should be a key of
            :attr:`~scrapy.settings.SETTINGS_PRIORITIES` or an integer
        :type priority: string or int
        """
        self._assert_mutability()
        priority = get_settings_priority(priority)
        if name not in self:
            if isinstance(value, SettingsAttribute):
                self.attributes[name] = value
            else:
                self.attributes[name] = SettingsAttribute(value, priority)
        else:
            self.attributes[name].set(value, priority)

    def setdict(self, values, priority='project'):
        self.update(values, priority)

    def setmodule(self, module, priority='project'):
        """
        Store settings from a module with a given priority.

        This is a helper function that calls
        :meth:`~scrapy.settings.BaseSettings.set` for every globally declared
        uppercase variable of ``module`` with the provided ``priority``.

        :param module: the module or the path of the module
        :type module: module object or string

        :param priority: the priority of the settings. Should be a key of
            :attr:`~scrapy.settings.SETTINGS_PRIORITIES` or an integer
        :type priority: string or int
        """
        self._assert_mutability()
        if isinstance(module, six.string_types):
            module = import_module(module)
        for key in dir(module):
            if key.isupper():
                self.set(key, getattr(module, key), priority)

    def update(self, values, priority='project'):
        """
        Store key/value pairs with a given priority.

        This is a helper function that calls
        :meth:`~scrapy.settings.BaseSettings.set` for every item of ``values``
        with the provided ``priority``.

        If ``values`` is a string, it is assumed to be JSON-encoded and parsed
        into a dict with ``json.loads()`` first. If it is a
        :class:`~scrapy.settings.BaseSettings` instance, the per-key priorities
        will be used and the ``priority`` parameter ignored. This allows
        inserting/updating settings with different priorities with a single
        command.

        :param values: the settings names and values
        :type values: dict or string or :class:`~scrapy.settings.BaseSettings`

        :param priority: the priority of the settings. Should be a key of
            :attr:`~scrapy.settings.SETTINGS_PRIORITIES` or an integer
        :type priority: string or int
        """
        self._assert_mutability()
        if isinstance(values, six.string_types):
            values = json.loads(values)
        if values is not None:
            if isinstance(values, BaseSettings):
                for name, value in six.iteritems(values):
                    self.set(name, value, values.getpriority(name))
            else:
                for name, value in six.iteritems(values):
                    self.set(name, value, priority)

    def delete(self, name, priority='project'):
        self._assert_mutability()
        priority = get_settings_priority(priority)
        if priority >= self.getpriority(name):
            del self.attributes[name]

    def __delitem__(self, name):
        self._assert_mutability()
        del self.attributes[name]

    def _assert_mutability(self):
        if self.frozen:
            raise TypeError("Trying to modify an immutable Settings object")

    def copy(self):
        """
        Make a deep copy of current settings.

        This method returns a new instance of the :class:`Settings` class,
        populated with the same values and their priorities.

        Modifications to the new object won't be reflected on the original
        settings.
        """
        return copy.deepcopy(self)