import ast
import re
import warnings
from datetime import datetime, timedelta

from django.conf import settings
from django.core.exceptions import ImproperlyConfigured

import haystack
from haystack.backends import BaseEngine, BaseSearchBackend, BaseSearchQuery, log_query
from haystack.constants import (
    ALL_FIELD,
    DEFAULT_OPERATOR,
    DJANGO_CT,
    DJANGO_ID,
    FUZZY_MAX_EXPANSIONS,
    FUZZY_MIN_SIM,
    ID,
)
from haystack.exceptions import MissingDependency, MoreLikeThisError, SkipDocument
from haystack.inputs import Clean, Exact, PythonData, Raw
from haystack.models import SearchResult
from haystack.utils import get_identifier, get_model_ct
from haystack.utils import log as logging
from haystack.utils.app_loading import haystack_get_model

try:
    import elasticsearch

    if (1, 0, 0) <= elasticsearch.__version__ < (2, 0, 0):
        warnings.warn(
            "ElasticSearch 1.x support deprecated, will be removed in 4.0",
            DeprecationWarning,
        )

    try:
        # let's try this, for elasticsearch > 1.7.0
        from elasticsearch.helpers import bulk
    except ImportError:
        # let's try this, for elasticsearch <= 1.7.0
        from elasticsearch.helpers import bulk_index as bulk
    from elasticsearch.exceptions import NotFoundError
except ImportError:
    raise MissingDependency(
        "The 'elasticsearch' backend requires the installation of 'elasticsearch'. Please refer to the documentation."
    )


DATETIME_REGEX = re.compile(
    r"^(?P<year>\d{4})-(?P<month>\d{2})-(?P<day>\d{2})T"
    r"(?P<hour>\d{2}):(?P<minute>\d{2}):(?P<second>\d{2})(\.\d+)?$"
)


class ElasticsearchSearchBackend(BaseSearchBackend):
    # Word reserved by Elasticsearch for special use.
    RESERVED_WORDS = ("AND", "NOT", "OR", "TO")

    # Characters reserved by Elasticsearch for special use.
    # The '\\' must come first, so as not to overwrite the other slash replacements.
    RESERVED_CHARACTERS = (
        "\\",
        "+",
        "-",
        "&&",
        "||",
        "!",
        "(",
        ")",
        "{",
        "}",
        "[",
        "]",
        "^",
        '"',
        "~",
        "*",
        "?",
        ":",
        "/",
    )

    # Settings to add an n-gram & edge n-gram analyzer.
    DEFAULT_SETTINGS = {
        "settings": {
            "analysis": {
                "analyzer": {
                    "ngram_analyzer": {
                        "type": "custom",
                        "tokenizer": "standard",
                        "filter": ["haystack_ngram", "lowercase"],
                    },
                    "edgengram_analyzer": {
                        "type": "custom",
                        "tokenizer": "standard",
                        "filter": ["haystack_edgengram", "lowercase"],
                    },
                },
                "tokenizer": {
                    "haystack_ngram_tokenizer": {
                        "type": "nGram",
                        "min_gram": 3,
                        "max_gram": 15,
                    },
                    "haystack_edgengram_tokenizer": {
                        "type": "edgeNGram",
                        "min_gram": 2,
                        "max_gram": 15,
                        "side": "front",
                    },
                },
                "filter": {
                    "haystack_ngram": {"type": "nGram", "min_gram": 3, "max_gram": 15},
                    "haystack_edgengram": {
                        "type": "edgeNGram",
                        "min_gram": 2,
                        "max_gram": 15,
                    },
                },
            }
        }
    }

    def __init__(self, connection_alias, **connection_options):
        super().__init__(connection_alias, **connection_options)

        if "URL" not in connection_options:
            raise ImproperlyConfigured(
                "You must specify a 'URL' in your settings for connection '%s'."
                % connection_alias
            )

        if "INDEX_NAME" not in connection_options:
            raise ImproperlyConfigured(
                "You must specify a 'INDEX_NAME' in your settings for connection '%s'."
                % connection_alias
            )

        self.conn = elasticsearch.Elasticsearch(
            connection_options["URL"],
            timeout=self.timeout,
            **connection_options.get("KWARGS", {}),
        )
        self.index_name = connection_options["INDEX_NAME"]
        self.log = logging.getLogger("haystack")
        self.setup_complete = False
        self.existing_mapping = {}

    def _get_doc_type_option(self):
        return {
            "doc_type": "modelresult",
        }

    def _get_current_mapping(self, field_mapping):
        return {"modelresult": {"properties": field_mapping}}

    def setup(self):
        """
        Defers loading until needed.
        """
        # Get the existing mapping & cache it. We'll compare it
        # during the ``update`` & if it doesn't match, we'll put the new
        # mapping.
        try:
            self.existing_mapping = self.conn.indices.get_mapping(index=self.index_name)
        except NotFoundError:
            pass
        except Exception:
            if not self.silently_fail:
                raise

        unified_index = haystack.connections[self.connection_alias].get_unified_index()
        self.content_field_name, field_mapping = self.build_schema(
            unified_index.all_searchfields()
        )
        current_mapping = self._get_current_mapping(field_mapping)

        if current_mapping != self.existing_mapping:
            try:
                # Make sure the index is there first.
                self.conn.indices.create(
                    index=self.index_name, body=self.DEFAULT_SETTINGS, ignore=400
                )
                self.conn.indices.put_mapping(
                    index=self.index_name,
                    body=current_mapping,
                    **self._get_doc_type_option(),
                )
                self.existing_mapping = current_mapping
            except Exception:
                if not self.silently_fail:
                    raise

        self.setup_complete = True

    def _prepare_object(self, index, obj):
        return index.full_prepare(obj)

    def update(self, index, iterable, commit=True):
        if not self.setup_complete:
            try:
                self.setup()
            except elasticsearch.TransportError:
                if not self.silently_fail:
                    raise

                self.log.exception("Failed to add documents to Elasticsearch")
                return

        prepped_docs = []

        for obj in iterable:
            try:
                prepped_data = self._prepare_object(index, obj)
                final_data = {}

                # Convert the data to make sure it's happy.
                for key, value in prepped_data.items():
                    final_data[key] = self._from_python(value)
                final_data["_id"] = final_data[ID]

                prepped_docs.append(final_data)
            except SkipDocument:
                self.log.debug("Indexing for object `%s` skipped", obj)
            except elasticsearch.TransportError:
                if not self.silently_fail:
                    raise

                # We'll log the object identifier but won't include the actual object
                # to avoid the possibility of that generating encoding errors while
                # processing the log message:
                self.log.exception(
                    "Preparing object for update",
                    extra={"data": {"index": index, "object": get_identifier(obj)}},
                )

        bulk(
            self.conn,
            prepped_docs,
            index=self.index_name,
            **self._get_doc_type_option(),
        )

        if commit:
            self.conn.indices.refresh(index=self.index_name)

    def remove(self, obj_or_string, commit=True):
        doc_id = get_identifier(obj_or_string)

        if not self.setup_complete:
            try:
                self.setup()
            except elasticsearch.TransportError:
                if not self.silently_fail:
                    raise

                self.log.exception(
                    "Failed to remove document '%s' from Elasticsearch",
                    doc_id,
                )
                return

        try:
            self.conn.delete(
                index=self.index_name,
                id=doc_id,
                ignore=404,
                **self._get_doc_type_option(),
            )

            if commit:
                self.conn.indices.refresh(index=self.index_name)
        except elasticsearch.TransportError:
            if not self.silently_fail:
                raise

            self.log.exception(
                "Failed to remove document '%s' from Elasticsearch",
                doc_id,
            )

    def clear(self, models=None, commit=True):
        # We actually don't want to do this here, as mappings could be
        # very different.
        # if not self.setup_complete:
        #     self.setup()

        if models is not None:
            assert isinstance(models, (list, tuple))

        try:
            if models is None:
                self.conn.indices.delete(index=self.index_name, ignore=404)
                self.setup_complete = False
                self.existing_mapping = {}
            else:
                models_to_delete = []

                for model in models:
                    models_to_delete.append("%s:%s" % (DJANGO_CT, get_model_ct(model)))

                # Delete by query in Elasticsearch assumes you're dealing with
                # a ``query`` root object. :/
                query = {
                    "query": {"query_string": {"query": " OR ".join(models_to_delete)}}
                }
                self.conn.delete_by_query(
                    index=self.index_name,
                    body=query,
                    **self._get_doc_type_option(),
                )
        except elasticsearch.TransportError:
            if not self.silently_fail:
                raise

            if models is not None:
                self.log.exception(
                    "Failed to clear Elasticsearch index of models '%s'",
                    ",".join(models_to_delete),
                )
            else:
                self.log.exception("Failed to clear Elasticsearch index")

    def build_search_kwargs(
        self,
        query_string,
        sort_by=None,
        start_offset=0,
        end_offset=None,
        fields="",
        highlight=False,
        facets=None,
        date_facets=None,
        query_facets=None,
        narrow_queries=None,
        spelling_query=None,
        within=None,
        dwithin=None,
        distance_point=None,
        models=None,
        limit_to_registered_models=None,
        result_class=None,
        **extra_kwargs,
    ):
        index = haystack.connections[self.connection_alias].get_unified_index()
        content_field = index.document_field

        if query_string == "*:*":
            kwargs = {"query": {"match_all": {}}}
        else:
            kwargs = {
                "query": {
                    "query_string": {
                        "default_field": content_field,
                        "default_operator": DEFAULT_OPERATOR,
                        "query": query_string,
                        "analyze_wildcard": True,
                        "auto_generate_phrase_queries": True,
                        "fuzzy_min_sim": FUZZY_MIN_SIM,
                        "fuzzy_max_expansions": FUZZY_MAX_EXPANSIONS,
                    }
                }
            }

        # so far, no filters
        filters = []

        if fields:
            if isinstance(fields, (list, set)):
                fields = " ".join(fields)

            kwargs["fields"] = fields

        if sort_by is not None:
            order_list = []
            for field, direction in sort_by:
                if field == "distance" and distance_point:
                    # Do the geo-enabled sort.
                    lng, lat = distance_point["point"].coords
                    sort_kwargs = {
                        "_geo_distance": {
                            distance_point["field"]: [lng, lat],
                            "order": direction,
                            "unit": "km",
                        }
                    }
                else:
                    if field == "distance":
                        warnings.warn(
                            "In order to sort by distance, you must call the '.distance(...)' method."
                        )

                    # Regular sorting.
                    sort_kwargs = {field: {"order": direction}}

                order_list.append(sort_kwargs)

            kwargs["sort"] = order_list

        # From/size offsets don't seem to work right in Elasticsearch's DSL. :/
        # if start_offset is not None:
        #     kwargs['from'] = start_offset

        # if end_offset is not None:
        #     kwargs['size'] = end_offset - start_offset

        if highlight:
            # `highlight` can either be True or a dictionary containing custom parameters
            # which will be passed to the backend and may override our default settings:

            kwargs["highlight"] = {"fields": {content_field: {"store": "yes"}}}

            if isinstance(highlight, dict):
                kwargs["highlight"].update(highlight)

        if self.include_spelling:
            kwargs["suggest"] = {
                "suggest": {
                    "text": spelling_query or query_string,
                    "term": {
                        # Using content_field here will result in suggestions of stemmed words.
                        "field": ALL_FIELD,
                    },
                }
            }

        if narrow_queries is None:
            narrow_queries = set()

        if facets is not None:
            kwargs.setdefault("facets", {})

            for facet_fieldname, extra_options in facets.items():
                facet_options = {"terms": {"field": facet_fieldname, "size": 100}}
                # Special cases for options applied at the facet level (not the terms level).
                if extra_options.pop("global_scope", False):
                    # Renamed "global_scope" since "global" is a python keyword.
                    facet_options["global"] = True
                if "facet_filter" in extra_options:
                    facet_options["facet_filter"] = extra_options.pop("facet_filter")
                facet_options["terms"].update(extra_options)
                kwargs["facets"][facet_fieldname] = facet_options

        if date_facets is not None:
            kwargs.setdefault("facets", {})

            for facet_fieldname, value in date_facets.items():
                # Need to detect on gap_by & only add amount if it's more than one.
                interval = value.get("gap_by").lower()

                # Need to detect on amount (can't be applied on months or years).
                if value.get("gap_amount", 1) != 1 and interval not in (
                    "month",
                    "year",
                ):
                    # Just the first character is valid for use.
                    interval = "%s%s" % (value["gap_amount"], interval[:1])

                kwargs["facets"][facet_fieldname] = {
                    "date_histogram": {"field": facet_fieldname, "interval": interval},
                    "facet_filter": {
                        "range": {
                            facet_fieldname: {
                                "from": self._from_python(value.get("start_date")),
                                "to": self._from_python(value.get("end_date")),
                            }
                        }
                    },
                }

        if query_facets is not None:
            kwargs.setdefault("facets", {})

            for facet_fieldname, value in query_facets:
                kwargs["facets"][facet_fieldname] = {
                    "query": {"query_string": {"query": value}}
                }

        if limit_to_registered_models is None:
            limit_to_registered_models = getattr(
                settings, "HAYSTACK_LIMIT_TO_REGISTERED_MODELS", True
            )

        if models and len(models):
            model_choices = sorted(get_model_ct(model) for model in models)
        elif limit_to_registered_models:
            # Using narrow queries, limit the results to only models handled
            # with the current routers.
            model_choices = self.build_models_list()
        else:
            model_choices = []

        if len(model_choices) > 0:
            filters.append({"terms": {DJANGO_CT: model_choices}})

        for q in narrow_queries:
            filters.append(
                {"fquery": {"query": {"query_string": {"query": q}}, "_cache": True}}
            )

        if within is not None:
            from haystack.utils.geo import generate_bounding_box

            (south, west), (north, east) = generate_bounding_box(
                within["point_1"], within["point_2"]
            )
            within_filter = {
                "geo_bounding_box": {
                    within["field"]: {
                        "top_left": {"lat": north, "lon": west},
                        "bottom_right": {"lat": south, "lon": east},
                    }
                }
            }
            filters.append(within_filter)

        if dwithin is not None:
            lng, lat = dwithin["point"].coords

            # NB: the 1.0.0 release of elasticsearch introduce an
            #     incompatible change on the distance filter formating
            if elasticsearch.VERSION >= (1, 0, 0):
                distance = "%(dist).6f%(unit)s" % {
                    "dist": dwithin["distance"].km,
                    "unit": "km",
                }
            else:
                distance = dwithin["distance"].km

            dwithin_filter = {
                "geo_distance": {
                    "distance": distance,
                    dwithin["field"]: {"lat": lat, "lon": lng},
                }
            }
            filters.append(dwithin_filter)

        # if we want to filter, change the query type to filteres
        if filters:
            kwargs["query"] = {"filtered": {"query": kwargs.pop("query")}}
            if len(filters) == 1:
                kwargs["query"]["filtered"]["filter"] = filters[0]
            else:
                kwargs["query"]["filtered"]["filter"] = {"bool": {"must": filters}}

        if extra_kwargs:
            kwargs.update(extra_kwargs)

        return kwargs

    @log_query
    def search(self, query_string, **kwargs):
        if len(query_string) == 0:
            return {"results": [], "hits": 0}

        if not self.setup_complete:
            self.setup()

        search_kwargs = self.build_search_kwargs(query_string, **kwargs)
        search_kwargs["from"] = kwargs.get("start_offset", 0)

        order_fields = set()
        for order in search_kwargs.get("sort", []):
            for key in order.keys():
                order_fields.add(key)

        geo_sort = "_geo_distance" in order_fields

        end_offset = kwargs.get("end_offset")
        start_offset = kwargs.get("start_offset", 0)
        if end_offset is not None and end_offset > start_offset:
            search_kwargs["size"] = end_offset - start_offset

        try:
            raw_results = self.conn.search(
                body=search_kwargs,
                index=self.index_name,
                _source=True,
                **self._get_doc_type_option(),
            )
        except elasticsearch.TransportError:
            if not self.silently_fail:
                raise

            self.log.exception(
                "Failed to query Elasticsearch using '%s'",
                query_string,
            )
            raw_results = {}

        return self._process_results(
            raw_results,
            highlight=kwargs.get("highlight"),
            result_class=kwargs.get("result_class", SearchResult),
            distance_point=kwargs.get("distance_point"),
            geo_sort=geo_sort,
        )

    def more_like_this(
        self,
        model_instance,
        additional_query_string=None,
        start_offset=0,
        end_offset=None,
        models=None,
        limit_to_registered_models=None,
        result_class=None,
        **kwargs,
    ):
        from haystack import connections

        if not self.setup_complete:
            self.setup()

        # Deferred models will have a different class ("RealClass_Deferred_fieldname")
        # which won't be in our registry:
        model_klass = model_instance._meta.concrete_model

        index = (
            connections[self.connection_alias]
            .get_unified_index()
            .get_index(model_klass)
        )
        field_name = index.get_content_field()
        params = {}

        if start_offset is not None:
            params["search_from"] = start_offset

        if end_offset is not None:
            params["search_size"] = end_offset - start_offset

        doc_id = get_identifier(model_instance)

        try:
            raw_results = self.conn.mlt(
                index=self.index_name,
                id=doc_id,
                mlt_fields=[field_name],
                **self._get_doc_type_option(),
                **params,
            )
        except elasticsearch.TransportError:
            if not self.silently_fail:
                raise

            self.log.exception(
                "Failed to fetch More Like This from Elasticsearch for document '%s'",
                doc_id,
            )
            raw_results = {}

        return self._process_results(raw_results, result_class=result_class)

    def _process_hits(self, raw_results):
        return raw_results.get("hits", {}).get("total", 0)

    def _process_results(
        self,
        raw_results,
        highlight=False,
        result_class=None,
        distance_point=None,
        geo_sort=False,
    ):
        from haystack import connections

        results = []
        hits = self._process_hits(raw_results)
        facets = {}
        spelling_suggestion = None

        if result_class is None:
            result_class = SearchResult

        if self.include_spelling and "suggest" in raw_results:
            raw_suggest = raw_results["suggest"].get("suggest")
            if raw_suggest:
                spelling_suggestion = " ".join(
                    [
                        (
                            word["text"]
                            if len(word["options"]) == 0
                            else word["options"][0]["text"]
                        )
                        for word in raw_suggest
                    ]
                )

        if "facets" in raw_results:
            facets = {"fields": {}, "dates": {}, "queries": {}}

            # ES can return negative timestamps for pre-1970 data. Handle it.
            def from_timestamp(tm):
                if tm >= 0:
                    return datetime.utcfromtimestamp(tm)
                else:
                    return datetime(1970, 1, 1) + timedelta(seconds=tm)

            for facet_fieldname, facet_info in raw_results["facets"].items():
                if facet_info.get("_type", "terms") == "terms":
                    facets["fields"][facet_fieldname] = [
                        (individual["term"], individual["count"])
                        for individual in facet_info["terms"]
                    ]
                elif facet_info.get("_type", "terms") == "date_histogram":
                    # Elasticsearch provides UTC timestamps with an extra three
                    # decimals of precision, which datetime barfs on.
                    facets["dates"][facet_fieldname] = [
                        (from_timestamp(individual["time"] / 1000), individual["count"])
                        for individual in facet_info["entries"]
                    ]
                elif facet_info.get("_type", "terms") == "query":
                    facets["queries"][facet_fieldname] = facet_info["count"]

        unified_index = connections[self.connection_alias].get_unified_index()
        indexed_models = unified_index.get_indexed_models()
        content_field = unified_index.document_field

        for raw_result in raw_results.get("hits", {}).get("hits", []):
            source = raw_result["_source"]
            app_label, model_name = source[DJANGO_CT].split(".")
            additional_fields = {}
            model = haystack_get_model(app_label, model_name)

            if model and model in indexed_models:
                index = source and unified_index.get_index(model)
                for key, value in source.items():
                    string_key = str(key)

                    if string_key in index.fields and hasattr(
                        index.fields[string_key], "convert"
                    ):
                        additional_fields[string_key] = index.fields[
                            string_key
                        ].convert(value)
                    else:
                        additional_fields[string_key] = self._to_python(value)

                del additional_fields[DJANGO_CT]
                del additional_fields[DJANGO_ID]

                if "highlight" in raw_result:
                    additional_fields["highlighted"] = raw_result["highlight"].get(
                        content_field, ""
                    )

                if distance_point:
                    additional_fields["_point_of_origin"] = distance_point

                    if geo_sort and raw_result.get("sort"):
                        from django.contrib.gis.measure import Distance

                        additional_fields["_distance"] = Distance(
                            km=float(raw_result["sort"][0])
                        )
                    else:
                        additional_fields["_distance"] = None

                result = result_class(
                    app_label,
                    model_name,
                    source[DJANGO_ID],
                    raw_result["_score"],
                    **additional_fields,
                )
                results.append(result)
            else:
                hits -= 1

        return {
            "results": results,
            "hits": hits,
            "facets": facets,
            "spelling_suggestion": spelling_suggestion,
        }

    def _get_common_mapping(self):
        return {
            DJANGO_CT: {
                "type": "string",
                "index": "not_analyzed",
                "include_in_all": False,
            },
            DJANGO_ID: {
                "type": "string",
                "index": "not_analyzed",
                "include_in_all": False,
            },
        }

    def build_schema(self, fields):
        content_field_name = ""
        mapping = self._get_common_mapping()

        for _, field_class in fields.items():
            field_mapping = FIELD_MAPPINGS.get(
                field_class.field_type, DEFAULT_FIELD_MAPPING
            ).copy()
            if field_class.boost != 1.0:
                field_mapping["boost"] = field_class.boost

            if field_class.document is True:
                content_field_name = field_class.index_fieldname

            # Do this last to override `text` fields.
            if field_mapping["type"] == "string":
                if field_class.indexed is False or hasattr(field_class, "facet_for"):
                    field_mapping["index"] = "not_analyzed"
                    del field_mapping["analyzer"]

            mapping[field_class.index_fieldname] = field_mapping

        return (content_field_name, mapping)

    def _iso_datetime(self, value):
        """
        If value appears to be something datetime-like, return it in ISO format.

        Otherwise, return None.
        """
        if hasattr(value, "strftime"):
            if hasattr(value, "hour"):
                return value.isoformat()
            else:
                return "%sT00:00:00" % value.isoformat()

    def _from_python(self, value):
        """Convert more Python data types to ES-understandable JSON."""
        iso = self._iso_datetime(value)
        if iso:
            return iso
        elif isinstance(value, bytes):
            # TODO: Be stricter.
            return str(value, errors="replace")
        elif isinstance(value, set):
            return list(value)
        return value

    def _to_python(self, value):
        """Convert values from ElasticSearch to native Python values."""
        if isinstance(value, (int, float, complex, list, tuple, bool)):
            return value

        if isinstance(value, str):
            possible_datetime = DATETIME_REGEX.search(value)

            if possible_datetime:
                date_values = possible_datetime.groupdict()

                for dk, dv in date_values.items():
                    date_values[dk] = int(dv)

                return datetime(
                    date_values["year"],
                    date_values["month"],
                    date_values["day"],
                    date_values["hour"],
                    date_values["minute"],
                    date_values["second"],
                )

        try:
            # This is slightly gross but it's hard to tell otherwise what the
            # string's original type might have been. Be careful who you trust.
            converted_value = ast.literal_eval(value)

            # Try to handle most built-in types.
            if isinstance(
                converted_value, (int, list, tuple, set, dict, float, complex)
            ):
                return converted_value
        except Exception:
            # If it fails (SyntaxError or its ilk) or we don't trust it,
            # continue on.
            pass

        return value


# DRL_FIXME: Perhaps move to something where, if none of these
#            match, call a custom method on the form that returns, per-backend,
#            the right type of storage?
DEFAULT_FIELD_MAPPING = {"type": "string", "analyzer": "snowball"}
FIELD_MAPPINGS = {
    "edge_ngram": {"type": "string", "analyzer": "edgengram_analyzer"},
    "ngram": {"type": "string", "analyzer": "ngram_analyzer"},
    "date": {"type": "date"},
    "datetime": {"type": "date"},
    "location": {"type": "geo_point"},
    "boolean": {"type": "boolean"},
    "float": {"type": "float"},
    "long": {"type": "long"},
    "integer": {"type": "long"},
}


# Sucks that this is almost an exact copy of what's in the Solr backend,
# but we can't import due to dependencies.
class ElasticsearchSearchQuery(BaseSearchQuery):
    def matching_all_fragment(self):
        return "*:*"

    def build_query_fragment(self, field, filter_type, value):
        from haystack import connections

        query_frag = ""

        if not hasattr(value, "input_type_name"):
            # Handle when we've got a ``ValuesListQuerySet``...
            if hasattr(value, "values_list"):
                value = list(value)

            if isinstance(value, str):
                # It's not an ``InputType``. Assume ``Clean``.
                value = Clean(value)
            else:
                value = PythonData(value)

        # Prepare the query using the InputType.
        prepared_value = value.prepare(self)

        if not isinstance(prepared_value, (set, list, tuple)):
            # Then convert whatever we get back to what pysolr wants if needed.
            prepared_value = self.backend._from_python(prepared_value)

        # 'content' is a special reserved word, much like 'pk' in
        # Django's ORM layer. It indicates 'no special field'.
        if field == "content":
            index_fieldname = ""
        else:
            index_fieldname = "%s:" % connections[
                self._using
            ].get_unified_index().get_index_fieldname(field)

        filter_types = {
            "content": "%s",
            "contains": "*%s*",
            "endswith": "*%s",
            "startswith": "%s*",
            "exact": "%s",
            "gt": "{%s TO *}",
            "gte": "[%s TO *]",
            "lt": "{* TO %s}",
            "lte": "[* TO %s]",
            "fuzzy": "%s~",
        }

        if value.post_process is False:
            query_frag = prepared_value
        else:
            if filter_type in [
                "content",
                "contains",
                "startswith",
                "endswith",
                "fuzzy",
            ]:
                if value.input_type_name == "exact":
                    query_frag = prepared_value
                else:
                    # Iterate over terms & incorporate the converted form of each into the query.
                    terms = []

                    if isinstance(prepared_value, str):
                        for possible_value in prepared_value.split(" "):
                            terms.append(
                                filter_types[filter_type]
                                % self.backend._from_python(possible_value)
                            )
                    else:
                        terms.append(
                            filter_types[filter_type]
                            % self.backend._from_python(prepared_value)
                        )

                    if len(terms) == 1:
                        query_frag = terms[0]
                    else:
                        query_frag = "(%s)" % " AND ".join(terms)
            elif filter_type == "in":
                in_options = []

                if not prepared_value:
                    query_frag = "(!*:*)"
                else:
                    for possible_value in prepared_value:
                        in_options.append(
                            '"%s"' % self.backend._from_python(possible_value)
                        )
                    query_frag = "(%s)" % " OR ".join(in_options)

            elif filter_type == "range":
                start = self.backend._from_python(prepared_value[0])
                end = self.backend._from_python(prepared_value[1])
                query_frag = '["%s" TO "%s"]' % (start, end)
            elif filter_type == "exact":
                if value.input_type_name == "exact":
                    query_frag = prepared_value
                else:
                    prepared_value = Exact(prepared_value).prepare(self)
                    query_frag = filter_types[filter_type] % prepared_value
            else:
                if value.input_type_name != "exact":
                    prepared_value = Exact(prepared_value).prepare(self)

                query_frag = filter_types[filter_type] % prepared_value

        if len(query_frag) and not isinstance(value, Raw):
            if not query_frag.startswith("(") and not query_frag.endswith(")"):
                query_frag = "(%s)" % query_frag

        return "%s%s" % (index_fieldname, query_frag)

    def build_alt_parser_query(self, parser_name, query_string="", **kwargs):
        if query_string:
            kwargs["v"] = query_string

        kwarg_bits = []

        for key in sorted(kwargs.keys()):
            if isinstance(kwargs[key], str) and " " in kwargs[key]:
                kwarg_bits.append("%s='%s'" % (key, kwargs[key]))
            else:
                kwarg_bits.append("%s=%s" % (key, kwargs[key]))

        return "{!%s %s}" % (parser_name, " ".join(kwarg_bits))

    def build_params(self, spelling_query=None, **kwargs):
        search_kwargs = {
            "start_offset": self.start_offset,
            "result_class": self.result_class,
        }
        order_by_list = None

        if self.order_by:
            if order_by_list is None:
                order_by_list = []

            for field in self.order_by:
                direction = "asc"
                if field.startswith("-"):
                    direction = "desc"
                    field = field[1:]
                order_by_list.append((field, direction))

            search_kwargs["sort_by"] = order_by_list

        if self.date_facets:
            search_kwargs["date_facets"] = self.date_facets

        if self.distance_point:
            search_kwargs["distance_point"] = self.distance_point

        if self.dwithin:
            search_kwargs["dwithin"] = self.dwithin

        if self.end_offset is not None:
            search_kwargs["end_offset"] = self.end_offset

        if self.facets:
            search_kwargs["facets"] = self.facets

        if self.fields:
            search_kwargs["fields"] = self.fields

        if self.highlight:
            search_kwargs["highlight"] = self.highlight

        if self.models:
            search_kwargs["models"] = self.models

        if self.narrow_queries:
            search_kwargs["narrow_queries"] = self.narrow_queries

        if self.query_facets:
            search_kwargs["query_facets"] = self.query_facets

        if self.within:
            search_kwargs["within"] = self.within

        if spelling_query:
            search_kwargs["spelling_query"] = spelling_query
        elif self.spelling_query:
            search_kwargs["spelling_query"] = self.spelling_query

        return search_kwargs

    def run(self, spelling_query=None, **kwargs):
        """Builds and executes the query. Returns a list of search results."""
        final_query = self.build_query()
        search_kwargs = self.build_params(spelling_query, **kwargs)

        if kwargs:
            search_kwargs.update(kwargs)

        results = self.backend.search(final_query, **search_kwargs)
        self._results = results.get("results", [])
        self._hit_count = results.get("hits", 0)
        self._facet_counts = self.post_process_facets(results)
        self._spelling_suggestion = results.get("spelling_suggestion", None)

    def run_mlt(self, **kwargs):
        """Builds and executes the query. Returns a list of search results."""
        if self._more_like_this is False or self._mlt_instance is None:
            raise MoreLikeThisError(
                "No instance was provided to determine 'More Like This' results."
            )

        additional_query_string = self.build_query()
        search_kwargs = {
            "start_offset": self.start_offset,
            "result_class": self.result_class,
            "models": self.models,
        }

        if self.end_offset is not None:
            search_kwargs["end_offset"] = self.end_offset - self.start_offset

        results = self.backend.more_like_this(
            self._mlt_instance, additional_query_string, **search_kwargs
        )
        self._results = results.get("results", [])
        self._hit_count = results.get("hits", 0)


class ElasticsearchSearchEngine(BaseEngine):
    backend = ElasticsearchSearchBackend
    query = ElasticsearchSearchQuery
