import copy
import collections

from six import iteritems, string_types

from elasticsearch.helpers import scan
from elasticsearch.exceptions import TransportError

from .query import Q, Bool
from .aggs import A, AggBase
from .utils import DslBase, AttrDict
from .response import Response, Hit
from .connections import connections
from .exceptions import IllegalOperation

class QueryProxy(object):
    """
    Simple proxy around DSL objects (queries) that can be called
    (to add query/post_filter) and also allows attribute access which is proxied to
    the wrapped query.
    """
    def __init__(self, search, attr_name):
        self._search = search
        self._proxied = None
        self._attr_name = attr_name

    def __nonzero__(self):
        return self._proxied is not None
    __bool__ = __nonzero__

    def __call__(self, *args, **kwargs):
        s = self._search._clone()

        # we cannot use self._proxied since we just cloned self._search and
        # need to access the new self on the clone
        proxied = getattr(s, self._attr_name)
        if proxied._proxied is None:
            proxied._proxied = Q(*args, **kwargs)
        else:
            proxied._proxied &= Q(*args, **kwargs)

        # always return search to be chainable
        return s

    def __getattr__(self, attr_name):
        return getattr(self._proxied, attr_name)

    def __setattr__(self, attr_name, value):
        if not attr_name.startswith('_'):
            self._proxied = Q(self._proxied.to_dict())
            setattr(self._proxied, attr_name, value)
        super(QueryProxy, self).__setattr__(attr_name, value)

    def __getstate__(self):
        return (self._search, self._proxied, self._attr_name)

    def __setstate__(self, state):
        self._search, self._proxied, self._attr_name = state


class ProxyDescriptor(object):
    """
    Simple descriptor to enable setting of queries and filters as:

        s = Search()
        s.query = Q(...)

    """
    def __init__(self, name):
        self._attr_name = '_%s_proxy' % name

    def __get__(self, instance, owner):
        return getattr(instance, self._attr_name)

    def __set__(self, instance, value):
        proxy = getattr(instance, self._attr_name)
        proxy._proxied = Q(value)


class AggsProxy(AggBase, DslBase):
    name = 'aggs'
    def __init__(self, search):
        self._base = self._search = search
        self._params = {'aggs': {}}

    def to_dict(self):
        return super(AggsProxy, self).to_dict().get('aggs', {})

class Request(object):
    def __init__(self, using='default', index=None, doc_type=None, extra=None):
        self._using = using

        self._index = None
        if isinstance(index, (tuple, list)):
            self._index = list(index)
        elif index:
            self._index = [index]

        self._doc_type = []
        self._doc_type_map = {}
        if isinstance(doc_type, (tuple, list)):
            self._doc_type.extend(doc_type)
        elif isinstance(doc_type, collections.Mapping):
            self._doc_type.extend(doc_type.keys())
            self._doc_type_map.update(doc_type)
        elif doc_type:
            self._doc_type.append(doc_type)

        self._params = {}
        self._extra = extra or {}

    def __eq__(self, other):
        return (
            isinstance(other, Request) and
            other._params == self._params and
            other._index == self._index and
            other._doc_type == self._doc_type and
            other.to_dict() == self.to_dict()
        )

    def __copy__(self):
        return self._clone()

    def params(self, **kwargs):
        """
        Specify query params to be used when executing the search. All the
        keyword arguments will override the current values. See
        https://elasticsearch-py.readthedocs.io/en/master/api.html#elasticsearch.Elasticsearch.search
        for all available parameters.

        Example::

            s = Search()
            s = s.params(routing='user-1', preference='local')
        """
        s = self._clone()
        s._params.update(kwargs)
        return s

    def index(self, *index):
        """
        Set the index for the search. If called empty it will remove all information.

        Example:

            s = Search()
            s = s.index('twitter-2015.01.01', 'twitter-2015.01.02')
            s = s.index(['twitter-2015.01.01', 'twitter-2015.01.02'])
        """
        # .index() resets
        s = self._clone()
        if not index:
            s._index = None
        else:
            indexes = []
            for i in index:
                if isinstance(i, string_types):
                    indexes.append(i)
                elif isinstance(i, list):
                    indexes += i
                elif isinstance(i, tuple):
                    indexes += list(i)

            s._index = (self._index or []) + indexes

        return s

    def _get_doc_type(self):
        """
        Return a list of doc_type names to be used
        """
        return list(set(dt._doc_type.name if hasattr(dt, '_doc_type') else dt for dt in self._doc_type))

    def _resolve_nested(self, hit, parent_class=None):
        doc_class = Hit
        nested_field = None

        nested_path = []
        nesting = hit['_nested']
        while nesting and 'field' in nesting:
            nested_path.append(nesting['field'])
            nesting = nesting.get('_nested')
        nested_path = '.'.join(nested_path)

        if hasattr(parent_class, '_index'):
            nested_field = parent_class._index.resolve_field(nested_path)
        else:
            for dt in self._doc_type:
                if not hasattr(dt, '_index'):
                    continue
                # TODO: verify that nested_field's parent is parent_class
                nested_field = dt._index.resolve_field(nested_path)
                if nested_field is not None:
                    break

        if nested_field is not None:
            return nested_field._doc_class

        return doc_class

    def _get_result(self, hit, parent_class=None):
        doc_class = Hit
        dt = hit.get('_type')

        if '_nested' in hit:
            doc_class = self._resolve_nested(hit, parent_class)

        elif dt in self._doc_type_map:
            doc_class = self._doc_type_map[dt]

        else:
            for doc_type in self._doc_type:
                if hasattr(doc_type, '_matches') and doc_type._matches(hit):
                    doc_class = doc_type
                    break

        for t in hit.get('inner_hits', ()):
            hit['inner_hits'][t] = Response(self, hit['inner_hits'][t], doc_class=doc_class)

        callback = getattr(doc_class, 'from_es', doc_class)
        return callback(hit)


    def doc_type(self, *doc_type, **kwargs):
        """
        Set the type to search through. You can supply a single value or
        multiple. Values can be strings or subclasses of ``Document``.

        You can also pass in any keyword arguments, mapping a doc_type to a
        callback that should be used instead of the Hit class.

        If no doc_type is supplied any information stored on the instance will
        be erased.

        Example:

            s = Search().doc_type('product', 'store', User, custom=my_callback)
        """
        # .doc_type() resets
        s = self._clone()
        if not doc_type and not kwargs:
            s._doc_type = []
            s._doc_type_map = {}
        else:
            s._doc_type.extend(doc_type)
            s._doc_type.extend(kwargs.keys())
            s._doc_type_map.update(kwargs)
        return s

    def using(self, client):
        """
        Associate the search request with an elasticsearch client. A fresh copy
        will be returned with current instance remaining unchanged.

        :arg client: an instance of ``elasticsearch.Elasticsearch`` to use or
            an alias to look up in ``elasticsearch_dsl.connections``

        """
        s = self._clone()
        s._using = client
        return s

    def extra(self, **kwargs):
        """
        Add extra keys to the request body. Mostly here for backwards
        compatibility.
        """
        s = self._clone()
        if 'from_' in kwargs:
            kwargs['from'] = kwargs.pop('from_')
        s._extra.update(kwargs)
        return s

    def _clone(self):
        s = self.__class__(using=self._using, index=self._index,
                           doc_type=self._doc_type)
        s._doc_type_map = self._doc_type_map.copy()
        s._extra = self._extra.copy()
        s._params = self._params.copy()
        return s


class Search(Request):
    query = ProxyDescriptor('query')
    post_filter = ProxyDescriptor('post_filter')

    def __init__(self, **kwargs):
        """
        Search request to elasticsearch.

        :arg using: `Elasticsearch` instance to use
        :arg index: limit the search to index
        :arg doc_type: only query this type.

        All the parameters supplied (or omitted) at creation type can be later
        overriden by methods (`using`, `index` and `doc_type` respectively).
        """
        super(Search, self).__init__(**kwargs)

        self.aggs = AggsProxy(self)
        self._sort = []
        self._source = None
        self._highlight = {}
        self._highlight_opts = {}
        self._suggest = {}
        self._script_fields = {}
        self._response_class = Response

        self._query_proxy = QueryProxy(self, 'query')
        self._post_filter_proxy = QueryProxy(self, 'post_filter')

    def filter(self, *args, **kwargs):
        return self.query(Bool(filter=[Q(*args, **kwargs)]))

    def exclude(self, *args, **kwargs):
        return self.query(Bool(filter=[~Q(*args, **kwargs)]))

    def __iter__(self):
        """
        Iterate over the hits.
        """
        return iter(self.execute())

    def __getitem__(self, n):
        """
        Support slicing the `Search` instance for pagination.

        Slicing equates to the from/size parameters. E.g.::

            s = Search().query(...)[0:25]

        is equivalent to::

            s = Search().query(...).extra(from_=0, size=25)

        """
        s = self._clone()

        if isinstance(n, slice):
            # If negative slicing, abort.
            if n.start and n.start < 0 or n.stop and n.stop < 0:
                raise ValueError("Search does not support negative slicing.")
            # Elasticsearch won't get all results so we default to size: 10 if
            # stop not given.
            s._extra['from'] = n.start or 0
            s._extra['size'] = n.stop - (n.start or 0) if n.stop is not None else 10
            return s
        else:  # This is an index lookup, equivalent to slicing by [n:n+1].
            # If negative index, abort.
            if n < 0:
                raise ValueError("Search does not support negative indexing.")
            s._extra['from'] = n
            s._extra['size'] = 1
            return s

    @classmethod
    def from_dict(cls, d):
        """
        Construct a new `Search` instance from a raw dict containing the search
        body. Useful when migrating from raw dictionaries.

        Example::

            s = Search.from_dict({
                "query": {
                    "bool": {
                        "must": [...]
                    }
                },
                "aggs": {...}
            })
            s = s.filter('term', published=True)
        """
        s = cls()
        s.update_from_dict(d)
        return s

    def _clone(self):
        """
        Return a clone of the current search request. Performs a shallow copy
        of all the underlying objects. Used internally by most state modifying
        APIs.
        """
        s = super(Search, self)._clone()

        s._response_class = self._response_class
        s._sort = self._sort[:]
        s._source = copy.copy(self._source) \
            if self._source is not None else None
        s._highlight = self._highlight.copy()
        s._highlight_opts = self._highlight_opts.copy()
        s._suggest = self._suggest.copy()
        s._script_fields = self._script_fields.copy()
        for x in ('query', 'post_filter'):
            getattr(s, x)._proxied = getattr(self, x)._proxied

        # copy top-level bucket definitions
        if self.aggs._params.get('aggs'):
            s.aggs._params = {'aggs': self.aggs._params['aggs'].copy()}
        return s

    def response_class(self, cls):
        """
        Override the default wrapper used for the response.
        """
        s = self._clone()
        s._response_class = cls
        return s

    def update_from_dict(self, d):
        """
        Apply options from a serialized body to the current instance. Modifies
        the object in-place. Used mostly by ``from_dict``.
        """
        d = d.copy()
        if 'query' in d:
            self.query._proxied = Q(d.pop('query'))
        if 'post_filter' in d:
            self.post_filter._proxied = Q(d.pop('post_filter'))

        aggs = d.pop('aggs', d.pop('aggregations', {}))
        if aggs:
            self.aggs._params = {
                'aggs': dict(
                    (name, A(value)) for (name, value) in iteritems(aggs))
            }
        if 'sort' in d:
            self._sort = d.pop('sort')
        if '_source' in d:
            self._source = d.pop('_source')
        if 'highlight' in d:
            high = d.pop('highlight').copy()
            self._highlight = high.pop('fields')
            self._highlight_opts = high
        if 'suggest' in d:
            self._suggest = d.pop('suggest')
            if 'text' in self._suggest:
                text = self._suggest.pop('text')
                for s in self._suggest.values():
                    s.setdefault('text', text)
        if 'script_fields' in d:
            self._script_fields = d.pop('script_fields')
        self._extra = d
        return self

    def script_fields(self, **kwargs):
        """
        Define script fields to be calculated on hits. See
        https://www.elastic.co/guide/en/elasticsearch/reference/current/search-request-script-fields.html
        for more details.

        Example::

            s = Search()
            s = s.script_fields(times_two="doc['field'].value * 2")
            s = s.script_fields(
                times_three={
                    'script': {
                        'inline': "doc['field'].value * params.n",
                        'params': {'n': 3}
                    }
                }
            )

        """
        s = self._clone()
        for name in kwargs:
            if isinstance(kwargs[name], string_types):
                kwargs[name] = {'script': kwargs[name]}
        s._script_fields.update(kwargs)
        return s

    def source(self, fields=None, **kwargs):
        """
        Selectively control how the _source field is returned.

        :arg source: wildcard string, array of wildcards, or dictionary of includes and excludes

        If ``source`` is None, the entire document will be returned for
        each hit.  If source is a dictionary with keys of 'include' and/or
        'exclude' the fields will be either included or excluded appropriately.

        Calling this multiple times with the same named parameter will override the
        previous values with the new ones.

        Example::

            s = Search()
            s = s.source(include=['obj1.*'], exclude=["*.description"])

            s = Search()
            s = s.source(include=['obj1.*']).source(exclude=["*.description"])

        """
        s = self._clone()

        if fields and kwargs:
            raise ValueError("You cannot specify fields and kwargs at the same time.")

        if fields is not None:
            s._source = fields
            return s

        if kwargs and not isinstance(s._source, dict):
            s._source = {}

        for key, value in kwargs.items():
            if value is None:
                try:
                    del s._source[key]
                except KeyError:
                    pass
            else:
                s._source[key] = value

        return s

    def sort(self, *keys):
        """
        Add sorting information to the search request. If called without
        arguments it will remove all sort requirements. Otherwise it will
        replace them. Acceptable arguments are::

            'some.field'
            '-some.other.field'
            {'different.field': {'any': 'dict'}}

        so for example::

            s = Search().sort(
                'category',
                '-title',
                {"price" : {"order" : "asc", "mode" : "avg"}}
            )

        will sort by ``category``, ``title`` (in descending order) and
        ``price`` in ascending order using the ``avg`` mode.

        The API returns a copy of the Search object and can thus be chained.
        """
        s = self._clone()
        s._sort = []
        for k in keys:
            if isinstance(k, string_types) and k.startswith('-'):
                if k[1:] == '_score':
                    raise IllegalOperation('Sorting by `-_score` is not allowed.')
                k = {k[1:]: {"order": "desc"}}
            s._sort.append(k)
        return s

    def highlight_options(self, **kwargs):
        """
        Update the global highlighting options used for this request. For
        example::

            s = Search()
            s = s.highlight_options(order='score')
        """
        s = self._clone()
        s._highlight_opts.update(kwargs)
        return s

    def highlight(self, *fields, **kwargs):
        """
        Request highlighting of some fields. All keyword arguments passed in will be
        used as parameters for all the fields in the ``fields`` parameter. Example::

            Search().highlight('title', 'body', fragment_size=50)

        will produce the equivalent of::

            {
                "highlight": {
                    "fields": {
                        "body": {"fragment_size": 50},
                        "title": {"fragment_size": 50}
                    }
                }
            }

        If you want to have different options for different fields you can call ``highlight`` twice::

            Search().highlight('title', fragment_size=50).highlight('body', fragment_size=100)

        which will produce::

            {
                "highlight": {
                    "fields": {
                        "body": {"fragment_size": 100},
                        "title": {"fragment_size": 50}
                    }
                }
            }

        """
        s = self._clone()
        for f in fields:
            s._highlight[f] = kwargs
        return s

    def suggest(self, name, text, **kwargs):
        """
        Add a suggestions request to the search.

        :arg name: name of the suggestion
        :arg text: text to suggest on

        All keyword arguments will be added to the suggestions body. For example::

            s = Search()
            s = s.suggest('suggestion-1', 'Elasticsearch', term={'field': 'body'})
        """
        s = self._clone()
        s._suggest[name] = {'text': text}
        s._suggest[name].update(kwargs)
        return s

    def to_dict(self, count=False, **kwargs):
        """
        Serialize the search into the dictionary that will be sent over as the
        request's body.

        :arg count: a flag to specify we are interested in a body for count -
            no aggregations, no pagination bounds etc.

        All additional keyword arguments will be included into the dictionary.
        """
        d = {}

        if self.query:
            d["query"] = self.query.to_dict()

        # count request doesn't care for sorting and other things
        if not count:
            if self.post_filter:
                d['post_filter'] = self.post_filter.to_dict()

            if self.aggs.aggs:
                d.update(self.aggs.to_dict())

            if self._sort:
                d['sort'] = self._sort

            d.update(self._extra)

            if self._source not in (None, {}):
                d['_source'] = self._source

            if self._highlight:
                d['highlight'] = {'fields': self._highlight}
                d['highlight'].update(self._highlight_opts)

            if self._suggest:
                d['suggest'] = self._suggest

            if self._script_fields:
                d['script_fields'] = self._script_fields

        d.update(kwargs)
        return d

    def count(self):
        """
        Return the number of hits matching the query and filters. Note that
        only the actual number is returned.
        """
        if hasattr(self, '_response'):
            return self._response.hits.total

        es = connections.get_connection(self._using)

        d = self.to_dict(count=True)
        # TODO: failed shards detection
        return es.count(
            index=self._index,
            doc_type=self._get_doc_type(),
            body=d,
            **self._params
        )['count']

    def execute(self, ignore_cache=False):
        """
        Execute the search and return an instance of ``Response`` wrapping all
        the data.

        :arg response_class: optional subclass of ``Response`` to use instead.
        """
        if ignore_cache or not hasattr(self, '_response'):
            es = connections.get_connection(self._using)

            self._response = self._response_class(
                self,
                es.search(
                    index=self._index,
                    doc_type=self._get_doc_type(),
                    body=self.to_dict(),
                    **self._params
                )
            )
        return self._response

    def scan(self):
        """
        Turn the search into a scan search and return a generator that will
        iterate over all the documents matching the query.

        Use ``params`` method to specify any additional arguments you with to
        pass to the underlying ``scan`` helper from ``elasticsearch-py`` -
        https://elasticsearch-py.readthedocs.io/en/master/helpers.html#elasticsearch.helpers.scan

        """
        es = connections.get_connection(self._using)

        for hit in scan(
                es,
                query=self.to_dict(),
                index=self._index,
                doc_type=self._get_doc_type(),
                **self._params
        ):
            yield self._get_result(hit)

    def delete(self):
        """
        delete() executes the query by delegating to delete_by_query()
        """

        es = connections.get_connection(self._using)

        return AttrDict(
            es.delete_by_query(
                index=self._index,
                body=self.to_dict(),
                doc_type=self._get_doc_type(),
                **self._params
            )
        )


class MultiSearch(Request):
    """
    Combine multiple :class:`~elasticsearch_dsl.Search` objects into a single
    request.
    """
    def __init__(self, **kwargs):
        super(MultiSearch, self).__init__(**kwargs)
        self._searches = []

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

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

    def _clone(self):
        ms = super(MultiSearch, self)._clone()
        ms._searches = self._searches[:]
        return ms

    def add(self, search):
        """
        Adds a new :class:`~elasticsearch_dsl.Search` object to the request::

            ms = MultiSearch(index='my-index')
            ms = ms.add(Search(doc_type=Category).filter('term', category='python'))
            ms = ms.add(Search(doc_type=Blog))
        """
        ms = self._clone()
        ms._searches.append(search)
        return ms

    def to_dict(self):
        out = []
        for s in self._searches:
            meta = {}
            if s._index:
                meta['index'] = s._index
            if s._doc_type:
                meta['type'] = s._get_doc_type()
            meta.update(s._params)

            out.append(meta)
            out.append(s.to_dict())

        return out

    def execute(self, ignore_cache=False, raise_on_error=True):
        """
        Execute the multi search request and return a list of search results.
        """
        if ignore_cache or not hasattr(self, '_response'):
            es = connections.get_connection(self._using)

            responses = es.msearch(
                index=self._index,
                doc_type=self._get_doc_type(),
                body=self.to_dict(),
                **self._params
            )

            out = []
            for s, r in zip(self._searches, responses['responses']):
                if r.get('error', False):
                    if raise_on_error:
                        raise TransportError('N/A', r['error']['type'], r['error'])
                    r = None
                else:
                    r = Response(s, r)
                out.append(r)

            self._response = out

        return self._response
