"""
Create SQL statements for QuerySets.

The code in here encapsulates all of the SQL construction so that QuerySets
themselves do not have to (and could be backed by things other than SQL
databases). The abstraction barrier only works one way: this module has to know
all about the internals of models in order to get the information it needs.
"""
import copy
import warnings
from collections import Counter, Iterator, Mapping, OrderedDict
from itertools import chain, count, product
from string import ascii_uppercase

from django.core.exceptions import FieldDoesNotExist, FieldError
from django.db import DEFAULT_DB_ALIAS, connections
from django.db.models.aggregates import Count
from django.db.models.constants import LOOKUP_SEP
from django.db.models.expressions import Col, Ref
from django.db.models.fields.related_lookups import MultiColSource
from django.db.models.query_utils import (
    PathInfo, Q, check_rel_lookup_compatibility, refs_expression,
)
from django.db.models.sql.constants import (
    INNER, LOUTER, ORDER_DIR, ORDER_PATTERN, QUERY_TERMS, SINGLE,
)
from django.db.models.sql.datastructures import (
    BaseTable, Empty, EmptyResultSet, Join, MultiJoin,
)
from django.db.models.sql.where import (
    AND, OR, ExtraWhere, NothingNode, WhereNode,
)
from django.utils import six
from django.utils.deprecation import RemovedInDjango110Warning
from django.utils.encoding import force_text
from django.utils.tree import Node

__all__ = ['Query', 'RawQuery']


def get_field_names_from_opts(opts):
    return set(chain.from_iterable(
        (f.name, f.attname) if f.concrete else (f.name,)
        for f in opts.get_fields()
    ))


class RawQuery(object):
    """
    A single raw SQL query
    """

    def __init__(self, sql, using, params=None, context=None):
        self.params = params or ()
        self.sql = sql
        self.using = using
        self.cursor = None

        # Mirror some properties of a normal query so that
        # the compiler can be used to process results.
        self.low_mark, self.high_mark = 0, None  # Used for offset/limit
        self.extra_select = {}
        self.annotation_select = {}
        self.context = context or {}

    def clone(self, using):
        return RawQuery(self.sql, using, params=self.params, context=self.context.copy())

    def get_columns(self):
        if self.cursor is None:
            self._execute_query()
        converter = connections[self.using].introspection.column_name_converter
        return [converter(column_meta[0])
                for column_meta in self.cursor.description]

    def __iter__(self):
        # Always execute a new query for a new iterator.
        # This could be optimized with a cache at the expense of RAM.
        self._execute_query()
        if not connections[self.using].features.can_use_chunked_reads:
            # If the database can't use chunked reads we need to make sure we
            # evaluate the entire query up front.
            result = list(self.cursor)
        else:
            result = self.cursor
        return iter(result)

    def __repr__(self):
        return "<RawQuery: %s>" % self

    @property
    def params_type(self):
        return dict if isinstance(self.params, Mapping) else tuple

    def __str__(self):
        return self.sql % self.params_type(self.params)

    def _execute_query(self):
        connection = connections[self.using]

        # Adapt parameters to the database, as much as possible considering
        # that the target type isn't known. See #17755.
        params_type = self.params_type
        adapter = connection.ops.adapt_unknown_value
        if params_type is tuple:
            params = tuple(adapter(val) for val in self.params)
        elif params_type is dict:
            params = dict((key, adapter(val)) for key, val in six.iteritems(self.params))
        else:
            raise RuntimeError("Unexpected params type: %s" % params_type)

        self.cursor = connection.cursor()
        self.cursor.execute(self.sql, params)


class Query(object):
    """
    A single SQL query.
    """

    alias_prefix = 'T'
    subq_aliases = frozenset([alias_prefix])
    query_terms = QUERY_TERMS

    compiler = 'SQLCompiler'

    def __init__(self, model, where=WhereNode):
        self.model = model
        self.alias_refcount = {}
        # alias_map is the most important data structure regarding joins.
        # It's used for recording which joins exist in the query and what
        # types they are. The key is the alias of the joined table (possibly
        # the table name) and the value is a Join-like object (see
        # sql.datastructures.Join for more information).
        self.alias_map = {}
        # Sometimes the query contains references to aliases in outer queries (as
        # a result of split_exclude). Correct alias quoting needs to know these
        # aliases too.
        self.external_aliases = set()
        self.table_map = {}     # Maps table names to list of aliases.
        self.default_cols = True
        self.default_ordering = True
        self.standard_ordering = True
        self.used_aliases = set()
        self.filter_is_sticky = False

        # SQL-related attributes
        # Select and related select clauses are expressions to use in the
        # SELECT clause of the query.
        # The select is used for cases where we want to set up the select
        # clause to contain other than default fields (values(), subqueries...)
        # Note that annotations go to annotations dictionary.
        self.select = []
        self.tables = []    # Aliases in the order they are created.
        self.where = where()
        self.where_class = where
        # The group_by attribute can have one of the following forms:
        #  - None: no group by at all in the query
        #  - A list of expressions: group by (at least) those expressions.
        #    String refs are also allowed for now.
        #  - True: group by all select fields of the model
        # See compiler.get_group_by() for details.
        self.group_by = None
        self.order_by = []
        self.low_mark, self.high_mark = 0, None  # Used for offset/limit
        self.distinct = False
        self.distinct_fields = []
        self.select_for_update = False
        self.select_for_update_nowait = False

        self.select_related = False
        # Arbitrary limit for select_related to prevents infinite recursion.
        self.max_depth = 5

        # Holds the selects defined by a call to values() or values_list()
        # excluding annotation_select and extra_select.
        self.values_select = []

        # SQL annotation-related attributes
        # The _annotations will be an OrderedDict when used. Due to the cost
        # of creating OrderedDict this attribute is created lazily (in
        # self.annotations property).
        self._annotations = None  # Maps alias -> Annotation Expression
        self.annotation_select_mask = None
        self._annotation_select_cache = None

        # These are for extensions. The contents are more or less appended
        # verbatim to the appropriate clause.
        # The _extra attribute is an OrderedDict, lazily created similarly to
        # .annotations
        self._extra = None  # Maps col_alias -> (col_sql, params).
        self.extra_select_mask = None
        self._extra_select_cache = None

        self.extra_tables = ()
        self.extra_order_by = ()

        # A tuple that is a set of model field names and either True, if these
        # are the fields to defer, or False if these are the only fields to
        # load.
        self.deferred_loading = (set(), True)

        self.context = {}

    @property
    def extra(self):
        if self._extra is None:
            self._extra = OrderedDict()
        return self._extra

    @property
    def annotations(self):
        if self._annotations is None:
            self._annotations = OrderedDict()
        return self._annotations

    @property
    def aggregates(self):
        warnings.warn(
            "The aggregates property is deprecated. Use annotations instead.",
            RemovedInDjango110Warning, stacklevel=2)
        return self.annotations

    def __str__(self):
        """
        Returns the query as a string of SQL with the parameter values
        substituted in (use sql_with_params() to see the unsubstituted string).

        Parameter values won't necessarily be quoted correctly, since that is
        done by the database interface at execution time.
        """
        sql, params = self.sql_with_params()
        return sql % params

    def sql_with_params(self):
        """
        Returns the query as an SQL string and the parameters that will be
        substituted into the query.
        """
        return self.get_compiler(DEFAULT_DB_ALIAS).as_sql()

    def __deepcopy__(self, memo):
        result = self.clone(memo=memo)
        memo[id(self)] = result
        return result

    def _prepare(self, field):
        return self

    def get_compiler(self, using=None, connection=None):
        if using is None and connection is None:
            raise ValueError("Need either using or connection")
        if using:
            connection = connections[using]
        return connection.ops.compiler(self.compiler)(self, connection, using)

    def get_meta(self):
        """
        Returns the Options instance (the model._meta) from which to start
        processing. Normally, this is self.model._meta, but it can be changed
        by subclasses.
        """
        return self.model._meta

    def clone(self, klass=None, memo=None, **kwargs):
        """
        Creates a copy of the current instance. The 'kwargs' parameter can be
        used by clients to update attributes after copying has taken place.
        """
        obj = Empty()
        obj.__class__ = klass or self.__class__
        obj.model = self.model
        obj.alias_refcount = self.alias_refcount.copy()
        obj.alias_map = self.alias_map.copy()
        obj.external_aliases = self.external_aliases.copy()
        obj.table_map = self.table_map.copy()
        obj.default_cols = self.default_cols
        obj.default_ordering = self.default_ordering
        obj.standard_ordering = self.standard_ordering
        obj.select = self.select[:]
        obj.tables = self.tables[:]
        obj.where = self.where.clone()
        obj.where_class = self.where_class
        if self.group_by is None:
            obj.group_by = None
        elif self.group_by is True:
            obj.group_by = True
        else:
            obj.group_by = self.group_by[:]
        obj.order_by = self.order_by[:]
        obj.low_mark, obj.high_mark = self.low_mark, self.high_mark
        obj.distinct = self.distinct
        obj.distinct_fields = self.distinct_fields[:]
        obj.select_for_update = self.select_for_update
        obj.select_for_update_nowait = self.select_for_update_nowait
        obj.select_related = self.select_related
        obj.values_select = self.values_select[:]
        obj._annotations = self._annotations.copy() if self._annotations is not None else None
        if self.annotation_select_mask is None:
            obj.annotation_select_mask = None
        else:
            obj.annotation_select_mask = self.annotation_select_mask.copy()
        # _annotation_select_cache cannot be copied, as doing so breaks the
        # (necessary) state in which both annotations and
        # _annotation_select_cache point to the same underlying objects.
        # It will get re-populated in the cloned queryset the next time it's
        # used.
        obj._annotation_select_cache = None
        obj.max_depth = self.max_depth
        obj._extra = self._extra.copy() if self._extra is not None else None
        if self.extra_select_mask is None:
            obj.extra_select_mask = None
        else:
            obj.extra_select_mask = self.extra_select_mask.copy()
        if self._extra_select_cache is None:
            obj._extra_select_cache = None
        else:
            obj._extra_select_cache = self._extra_select_cache.copy()
        obj.extra_tables = self.extra_tables
        obj.extra_order_by = self.extra_order_by
        obj.deferred_loading = copy.copy(self.deferred_loading[0]), self.deferred_loading[1]
        if self.filter_is_sticky and self.used_aliases:
            obj.used_aliases = self.used_aliases.copy()
        else:
            obj.used_aliases = set()
        obj.filter_is_sticky = False
        if 'alias_prefix' in self.__dict__:
            obj.alias_prefix = self.alias_prefix
        if 'subq_aliases' in self.__dict__:
            obj.subq_aliases = self.subq_aliases.copy()

        obj.__dict__.update(kwargs)
        if hasattr(obj, '_setup_query'):
            obj._setup_query()
        obj.context = self.context.copy()
        return obj

    def add_context(self, key, value):
        self.context[key] = value

    def get_context(self, key, default=None):
        return self.context.get(key, default)

    def relabeled_clone(self, change_map):
        clone = self.clone()