import functools
import logging
import re
import sys

import formencode.validators

import ckan.model as model
import ckan.new_authz as new_authz
import ckan.lib.navl.dictization_functions as df
import ckan.plugins as p

from ckan.common import _, c

log = logging.getLogger(__name__)
_validate = df.validate


class NameConflict(Exception):
    pass


class AttributeDict(dict):
    def __getattr__(self, name):
        try:
            return self[name]
        except KeyError:
            raise AttributeError('No such attribute %r' % name)

    def __setattr__(self, name, value):
        raise AttributeError(
            'You cannot set attributes of this object directly'
        )


class ActionError(Exception):
    pass

class NotFound(ActionError):
    '''Exception raised by logic functions when a given object is not found.

    For example :py:func:`~ckan.logic.action.get.package_show` raises
    :py:exc:`~ckan.plugins.toolkit.ObjectNotFound` if no package with the
    given ``id`` exists.

    '''
    pass


class NotAuthorized(ActionError):
    '''Exception raised when the user is not authorized to call the action.

    For example :py:func:`~ckan.logic.action.create.package_create` raises
    :py:exc:`~ckan.plugins.toolkit.NotAuthorized` if the user is not authorized
    to create packages.

    '''
    pass


class ValidationError(ActionError):
    '''Exception raised by action functions when validating their given
    ``data_dict`` fails.

    '''
    def __init__(self, error_dict, error_summary=None, extra_msg=None):
        if not isinstance(error_dict, dict):
            error_dict = {'message': error_dict}
        # tags errors are a mess so let's clean them up
        if 'tags' in error_dict:
            tag_errors = []
            for error in error_dict['tags']:
                try:
                    tag_errors.append(', '.join(error['name']))
                except KeyError:
                    pass
            error_dict['tags'] = tag_errors
        self.error_dict = error_dict
        self._error_summary = error_summary
        super(ValidationError, self).__init__(extra_msg)

    @property
    def error_summary(self):
        ''' autogenerate the summary if not supplied '''
        def summarise(error_dict):
            ''' Do some i18n stuff on the error_dict keys '''

            def prettify(field_name):
                field_name = re.sub('(?<!\w)[Uu]rl(?!\w)', 'URL',
                                    field_name.replace('_', ' ').capitalize())
                return _(field_name.replace('_', ' '))

            summary = {}

            for key, error in error_dict.iteritems():
                if key == 'resources':
                    summary[_('Resources')] = _('Package resource(s) invalid')
                elif key == 'extras':
                    errors_extras = []
                    for item in error:
                        if (item.get('key')
                                and item['key'][0] not in errors_extras):
                            errors_extras.append(item.get('key')[0])
                    summary[_('Extras')] = ', '.join(errors_extras)
                elif key == 'extras_validation':
                    summary[_('Extras')] = error[0]
                elif key == 'tags':
                    summary[_('Tags')] = error[0]
                else:
                    summary[_(prettify(key))] = error[0]
            return summary

        if self._error_summary:
            return self._error_summary
        return summarise(self.error_dict)

    def __str__(self):
        err_msgs = (super(ValidationError, self).__str__(),
                    self.error_dict)
        return ' - '.join([str(err_msg) for err_msg in err_msgs if err_msg])

log = logging.getLogger(__name__)


def parse_params(params, ignore_keys=None):
    '''Takes a dict and returns it with some values standardised.
    This is done on a dict before calling tuplize_dict on it.
    '''
    parsed = {}
    for key in params:
        if ignore_keys and key in ignore_keys:
            continue
        value = params.getall(key)
        # Blank values become ''
        if not value:
            value = ''
        # A list with only one item is stripped of being a list
        if len(value) == 1:
            value = value[0]
        parsed[key] = value
    return parsed


def clean_dict(data_dict):
    '''Takes a dict and if any of the values are lists of dicts,
    the empty dicts are stripped from the lists (recursive).

    e.g.
    >>> clean_dict(
        {'name': u'testgrp4',
         'title': u'',
         'description': u'',
         'packages': [{'name': u'testpkg'}, {'name': u'testpkg'}],
         'extras': [{'key': u'packages', 'value': u'["testpkg"]'},
                    {'key': u'', 'value': u''},
                    {'key': u'', 'value': u''}],
         'state': u'active'}
    {'name': u'testgrp4',
     'title': u'',
     'description': u'',
     'packages': [{'name': u'testpkg'}, {'name': u'testpkg'}],
     'extras': [{'key': u'packages', 'value': u'["testpkg"]'}],
     'state': u'active'}

    '''
    for key, value in data_dict.items():
        if not isinstance(value, list):
            continue
        for inner_dict in value[:]:
            if isinstance(inner_dict, basestring):
                break
            if not any(inner_dict.values()):
                value.remove(inner_dict)
            else:
                clean_dict(inner_dict)
    return data_dict


def tuplize_dict(data_dict):
    '''Takes a dict with keys of the form 'table__0__key' and converts them
    to a tuple like ('table', 0, 'key').

    Dict should be put through parse_dict before this function, to have
    values standardized.

    May raise a DataError if the format of the key is incorrect.
    '''
    tuplized_dict = {}
    for key, value in data_dict.iteritems():
        key_list = key.split('__')
        for num, key in enumerate(key_list):
            if num % 2 == 1:
                try:
                    key_list[num] = int(key)
                except ValueError:
                    raise df.DataError('Bad key')
        tuplized_dict[tuple(key_list)] = value
    return tuplized_dict


def untuplize_dict(tuplized_dict):

    data_dict = {}
    for key, value in tuplized_dict.iteritems():
        new_key = '__'.join([str(item) for item in key])
        data_dict[new_key] = value
    return data_dict


def flatten_to_string_key(dict):

    flattented = df.flatten_dict(dict)
    return untuplize_dict(flattented)


def _prepopulate_context(context):
    if context is None:
        context = {}
    context.setdefault('model', model)
    context.setdefault('session', model.Session)
    try:
        context.setdefault('user', c.user or c.author)
    except TypeError:
        # c not registered
        pass
    return context


def check_access(action, context, data_dict=None):
    '''Calls the authorization function for the provided action

    This is the only function that should be called to determine whether a
    user (or an anonymous request) is allowed to perform a particular action.

    The function accepts a context object, which should contain a 'user' key
    with the name of the user performing the action, and optionally a
    dictionary with extra data to be passed to the authorization function.

    For example::

        check_access('package_update', context, data_dict)

    If not already there, the function will add an `auth_user_obj` key to the
    context object with the actual User object (in case it exists in the
    database). This check is only performed once per context object.

    Raise :py:exc:`~ckan.plugins.toolkit.NotAuthorized` if the user is not
    authorized to call the named action function.

    If the user *is* authorized to call the action, return ``True``.

    :param action: the name of the action function, eg. ``'package_create'``
    :type action: string

    :param context:
    :type context: dict

    :param data_dict:
    :type data_dict: dict

    :raises: :py:exc:`~ckan.plugins.toolkit.NotAuthorized` if the user is not
        authorized to call the named action

    '''

    # Auth Auditing.  We remove this call from the __auth_audit stack to show
    # we have called the auth function
    try:
        audit = context.get('__auth_audit', [])[-1]
    except IndexError:
        audit = ''
    if audit and audit[0] == action:
        context['__auth_audit'].pop()

    user = context.get('user')

    try:
        if not 'auth_user_obj' in context:
            context['auth_user_obj'] = None

        if not context.get('ignore_auth'):
            if not context.get('__auth_user_obj_checked'):
                if context.get('user') and not context.get('auth_user_obj'):
                    context['auth_user_obj'] = \
                        model.User.by_name(context['user'])
                context['__auth_user_obj_checked'] = True

        context = _prepopulate_context(context)

        logic_authorization = new_authz.is_authorized(action, context,
                                                      data_dict)
        if not logic_authorization['success']:
            msg = logic_authorization.get('msg', '')
            raise NotAuthorized(msg)
    except NotAuthorized, e:
        log.debug(u'check access NotAuthorized - %s user=%s "%s"',
                  action, user, unicode(e))
        raise

    log.debug('check access OK - %s user=%s', action, user)
    return True


_actions = {}
def clear_actions_cache():
    _actions.clear()


def get_action(action):
    '''Return the named :py:mod:`ckan.logic.action` function.

    For example ``get_action('package_create')`` will normally return the
    :py:func:`ckan.logic.action.create.package_create()` function.

    For documentation of the available action functions, see
    :ref:`api-reference`.

    You should always use ``get_action()`` instead of importing an action
    function directly, because :py:class:`~ckan.plugins.interfaces.IActions`
    plugins can override action functions, causing ``get_action()`` to return a
    plugin-provided function instead of the default one.

    Usage::

        import ckan.plugins.toolkit as toolkit

        # Call the package_create action function:
        toolkit.get_action('package_create')(context, data_dict)

    As the context parameter passed to an action function is commonly::

        context = {'model': ckan.model, 'session': ckan.model.Session,
                   'user': pylons.c.user or pylons.c.author}

    an action function returned by ``get_action()`` will automatically add
    these parameters to the context if they are not defined.  This is
    especially useful for plugins as they should not really be importing parts
    of ckan eg :py:mod:`ckan.model` and as such do not have access to ``model``
    or ``model.Session``.

    If a ``context`` of ``None`` is passed to the action function then the
    default context dict will be created.

    :param action: name of the action function to return,
        eg. ``'package_create'``
    :type action: string

    :returns: the named action function
    :rtype: callable

    '''

    if _actions:
        if not action in _actions:
            raise KeyError("Action '%s' not found" % action)
        return _actions.get(action)
    # Otherwise look in all the plugins to resolve all possible
    # First get the default ones in the ckan/logic/action directory
    # Rather than writing them out in full will use __import__
    # to load anything from ckan.logic.action that looks like it might
    # be an action
    for action_module_name in ['get', 'create', 'update', 'delete', 'patch']:
        module_path = 'ckan.logic.action.' + action_module_name
        module = __import__(module_path)
        for part in module_path.split('.')[1:]:
            module = getattr(module, part)
        for k, v in module.__dict__.items():
            if not k.startswith('_'):
                # Only load functions from the action module or already
                # replaced functions.
                if (hasattr(v, '__call__')
                        and (v.__module__ == module_path
                             or hasattr(v, '__replaced'))):
                    _actions[k] = v

                    # Whitelist all actions defined in logic/action/get.py as
                    # being side-effect free.
                    if action_module_name == 'get' and \
                       not hasattr(v, 'side_effect_free'):
                        v.side_effect_free = True


    # Then overwrite them with any specific ones in the plugins:
    resolved_action_plugins = {}
    fetched_actions = {}
    for plugin in p.PluginImplementations(p.IActions):
        for name, auth_function in plugin.get_actions().items():
            if name in resolved_action_plugins:
                raise NameConflict(
                    'The action %r is already implemented in %r' % (
                        name,
                        resolved_action_plugins[name]
                    )
                )
            resolved_action_plugins[name] = plugin.name
            # Extensions are exempted from the auth audit for now
            # This needs to be resolved later
            auth_function.auth_audit_exempt = True
            fetched_actions[name] = auth_function
    # Use the updated ones in preference to the originals.
    _actions.update(fetched_actions)

    # wrap the functions
    for action_name, _action in _actions.items():
        def make_wrapped(_action, action_name):
            def wrapped(context=None, data_dict=None, **kw):
                if kw:
                    log.critical('%s was passed extra keywords %r'
                                 % (_action.__name__, kw))

                context = _prepopulate_context(context)

                # Auth Auditing - checks that the action function did call
                # check_access (unless there is no accompanying auth function).
                # We push the action name and id onto the __auth_audit stack
                # before calling the action, and check_access removes it.
                # (We need the id of the action in case the action is wrapped
                # inside an action of the same name, which happens in the
                # datastore)
                context.setdefault('__auth_audit', [])
                context['__auth_audit'].append((action_name, id(_action)))

                # check_access(action_name, context, data_dict=None)
                result = _action(context, data_dict, **kw)
                try:
                    audit = context['__auth_audit'][-1]
                    if audit[0] == action_name and audit[1] == id(_action):
                        if action_name not in new_authz.auth_functions_list():
                            log.debug('No auth function for %s' % action_name)
                        elif not getattr(_action, 'auth_audit_exempt', False):
                            raise Exception(
                                'Action function {0} did not call its auth function'
                                .format(action_name))
                        # remove from audit stack
                        context['__auth_audit'].pop()
                except IndexError:
                    pass
                return result
            return wrapped

        # If we have been called multiple times for example during tests then
        # we need to make sure that we do not rewrap the actions.
        if hasattr(_action, '__replaced'):
            _actions[action_name] = _action.__replaced
            continue

        fn = make_wrapped(_action, action_name)
        # we need to mirror the docstring
        fn.__doc__ = _action.__doc__
        # we need to retain the side effect free behaviour
        if getattr(_action, 'side_effect_free', False):
            fn.side_effect_free = True
        _actions[action_name] = fn

    return _actions.get(action)


def get_or_bust(data_dict, keys):
    '''Return the value(s) from the given data_dict for the given key(s).

    Usage::

        single_value = get_or_bust(data_dict, 'a_key')
        value_1, value_2 = get_or_bust(data_dict, ['key1', 'key2'])

    :param data_dict: the dictionary to return the values from
    :type data_dict: dictionary

    :param keys: the key(s) for the value(s) to return
    :type keys: either a string or a list

    :returns: a single value from the dict if a single key was given,
        or a tuple of values if a list of keys was given

    :raises: :py:exc:`ckan.logic.ValidationError` if one of the given keys is
        not in the given dictionary

    '''
    if isinstance(keys, basestring):
        keys = [keys]

    import ckan.logic.schema as schema
    schema = schema.create_schema_for_required_keys(keys)

    data_dict, errors = _validate(data_dict, schema)

    if errors:
        raise ValidationError(errors)

    # preserve original key order
    values = [data_dict[key] for key in keys]
    if len(values) == 1:
        return values[0]
    return tuple(values)

def validate(schema_func, can_skip_validator=False):
    ''' A decorator that validates an action function against a given schema
    '''
    def action_decorator(action):
        @functools.wraps(action)
        def wrapper(context, data_dict):
            if can_skip_validator:
                if context.get('skip_validation'):
                    return action(context, data_dict)

            schema = context.get('schema', schema_func())
            data_dict, errors = _validate(data_dict, schema, context)
            if errors:
                raise ValidationError(errors)
            return action(context, data_dict)
        return wrapper
    return action_decorator

def side_effect_free(action):
    '''A decorator that marks the given action function as side-effect-free.

    Action functions decorated with this decorator can be called with an HTTP
    GET request to the :doc:`Action API </api/index>`. Action functions that
    don't have this decorator must be called with a POST request.

    If your CKAN extension defines its own action functions using the
    :py:class:`~ckan.plugins.interfaces.IActions` plugin interface, you can use
    this decorator to make your actions available with GET requests instead of
    just with POST requests.

    Example::

        import ckan.plugins.toolkit as toolkit

        @toolkit.side_effect_free
        def my_custom_action_function(context, data_dict):
            ...

    (Then implement :py:class:`~ckan.plugins.interfaces.IActions` to register
    your action function with CKAN.)

    '''
    @functools.wraps(action)
    def wrapper(context, data_dict):
        return action(context, data_dict)
    wrapper.side_effect_free = True

    return wrapper


def auth_sysadmins_check(action):
    '''A decorator that prevents sysadmins from being automatically authorized
    to call an action function.

    Normally sysadmins are allowed to call any action function (for example
    when they're using the :doc:`Action API </api/index>` or the web
    interface), if the user is a sysadmin the action function's authorization
    function will not even be called.

    If an action function is decorated with this decorator, then its
    authorization function will always be called, even if the user is a
    sysadmin.

    '''
    @functools.wraps(action)
    def wrapper(context, data_dict):
        return action(context, data_dict)
    wrapper.auth_sysadmins_check = True
    return wrapper


def auth_audit_exempt(action):
    ''' Dirty hack to stop auth audit being done '''
    @functools.wraps(action)
    def wrapper(context, data_dict):
        return action(context, data_dict)
    wrapper.auth_audit_exempt = True
    return wrapper

def auth_allow_anonymous_access(action):
    ''' Flag an auth function as not requiring a logged in user

    This means that check_access won't automatically raise a NotAuthorized
    exception if an authenticated user is not provided in the context. (The
    auth function can still return False if for some reason access is not
    granted).
    '''
    @functools.wraps(action)
    def wrapper(context, data_dict):
        return action(context, data_dict)
    wrapper.auth_allow_anonymous_access = True
    return wrapper

def auth_disallow_anonymous_access(action):
    ''' Flag an auth function as requiring a logged in user

    This means that check_access will automatically raise a NotAuthorized
    exception if an authenticated user is not provided in the context, without
    calling the actual auth function.
    '''
    @functools.wraps(action)
    def wrapper(context, data_dict):
        return action(context, data_dict)
    wrapper.auth_allow_anonymous_access = False
    return wrapper

class UnknownValidator(Exception):
    '''Exception raised when a requested validator function cannot be found.

    '''
    pass


_validators_cache = {}

def clear_validators_cache():
    _validators_cache.clear()


# This function exists mainly so that validators can be made available to
# extensions via ckan.plugins.toolkit.
def get_validator(validator):
    '''Return a validator function by name.

    :param validator: the name of the validator function to return,
        eg. ``'package_name_exists'``
    :type validator: string

    :raises: :py:exc:`~ckan.plugins.toolkit.UnknownValidator` if the named
        validator is not found

    :returns: the named validator function
    :rtype: ``types.FunctionType``

    '''
    if  not _validators_cache:
        validators = _import_module_functions('ckan.lib.navl.validators')
        _validators_cache.update(validators)
        validators = _import_module_functions('ckan.logic.validators')
        _validators_cache.update(validators)
        _validators_cache.update({'OneOf': formencode.validators.OneOf})
        converters = _import_module_functions('ckan.logic.converters')
        _validators_cache.update(converters)

        for plugin in p.PluginImplementations(p.IValidators):
            for name, fn in plugin.get_validators().items():
                if name in _validators_cache:
                    raise NameConflict(
                        'The validator %r is already defined' % (name,)
                    )
                log.debug('Validator function {0} from plugin {1} was inserted'.format(name, plugin.name))
                _validators_cache[name] = fn
    try:
        return _validators_cache[validator]
    except KeyError:
        raise UnknownValidator('Validator `%s` does not exist' % validator)


def model_name_to_class(model_module, model_name):
    '''Return the class in model_module that has the same name as the received string.

    Raises AttributeError if there's no model in model_module named model_name.
    '''
    try:
        model_class_name = model_name.title()
        return getattr(model_module, model_class_name)
    except AttributeError:
        raise ValidationError("%s isn't a valid model" % model_class_name)

def _import_module_functions(module_path):
    '''Import a module and get the functions and return them in a dict'''
    functions_dict = {}
    module = __import__(module_path)
    for part in module_path.split('.')[1:]:
        module = getattr(module, part)
    for k, v in module.__dict__.items():

        try:
            if v.__module__ != module_path:
                continue
            functions_dict[k] = v
        except AttributeError:
            pass
    return functions_dict
