from itertools import izip

from django.db.backends.util import truncate_name

from django.db.models.sql import compiler

from django.db.models.sql.constants import TABLE_NAME

from django.db.models.sql.query import get_proxied_model

SQLCompiler = compiler.SQLCompiler

class GeoSQLCompiler(compiler.SQLCompiler):

    def get_columns(self, with_aliases=False):

        """

        Return the list of columns to use in the select statement. If no

        columns have been specified, returns all columns relating to fields in

        the model.

        If 'with_aliases' is true, any column names that are duplicated

        (without the table names) are given unique aliases. This is needed in

        some cases to avoid ambiguitity with nested queries.

        This routine is overridden from Query to handle customized selection of

        geometry columns.

        """

        qn = self.quote_name_unless_alias

        qn2 = self.connection.ops.quote_name

        result = ['(%s) AS %s' % (self.get_extra_select_format(alias) % col[0], qn2(alias))

                  for alias, col in self.query.extra_select.iteritems()]

        aliases = set(self.query.extra_select.keys())

        if with_aliases:

            col_aliases = aliases.copy()

        else:

            col_aliases = set()

        if self.query.select:

            only_load = self.deferred_to_columns()

            # This loop customized for GeoQuery.

            for col, field in izip(self.query.select, self.query.select_fields):

                if isinstance(col, (list, tuple)):

                    alias, column = col

                    table = self.query.alias_map[alias][TABLE_NAME]

                    if table in only_load and col not in only_load[table]:

                        continue

                    r = self.get_field_select(field, alias, column)

                    if with_aliases:

                        if col[1] in col_aliases:

                            c_alias = 'Col%d' % len(col_aliases)

                            result.append('%s AS %s' % (r, c_alias))

                            aliases.add(c_alias)

                            col_aliases.add(c_alias)

                        else:

                            result.append('%s AS %s' % (r, qn2(col[1])))

                            aliases.add(r)

                            col_aliases.add(col[1])

                    else:

                        result.append(r)

                        aliases.add(r)

                        col_aliases.add(col[1])

                else:

                    result.append(col.as_sql(qn, self.connection))

                    if hasattr(col, 'alias'):

                        aliases.add(col.alias)

                        col_aliases.add(col.alias)

        elif self.query.default_cols:

            cols, new_aliases = self.get_default_columns(with_aliases,

                    col_aliases)

            result.extend(cols)

            aliases.update(new_aliases)

        max_name_length = self.connection.ops.max_name_length()

        result.extend([

                '%s%s' % (

                    self.get_extra_select_format(alias) % aggregate.as_sql(qn, self.connection),

                    alias is not None

                        and ' AS %s' % qn(truncate_name(alias, max_name_length))

                        or ''

                    )

                for alias, aggregate in self.query.aggregate_select.items()

        ])

        # This loop customized for GeoQuery.

        for (table, col), field in izip(self.query.related_select_cols, self.query.related_select_fields):

            r = self.get_field_select(field, table, col)

            if with_aliases and col in col_aliases:

                c_alias = 'Col%d' % len(col_aliases)

                result.append('%s AS %s' % (r, c_alias))

                aliases.add(c_alias)

                col_aliases.add(c_alias)

            else:

                result.append(r)

                aliases.add(r)

                col_aliases.add(col)

        self._select_aliases = aliases

        return result

    def get_default_columns(self, with_aliases=False, col_aliases=None,

                            start_alias=None, opts=None, as_pairs=False):

        """

        Computes the default columns for selecting every field in the base

        model. Will sometimes be called to pull in related models (e.g. via

        select_related), in which case "opts" and "start_alias" will be given

        to provide a starting point for the traversal.

        Returns a list of strings, quoted appropriately for use in SQL

        directly, as well as a set of aliases used in the select statement (if

        'as_pairs' is True, returns a list of (alias, col_name) pairs instead

        of strings as the first component and None as the second component).

        This routine is overridden from Query to handle customized selection of

        geometry columns.

        """

        result = []

        if opts is None:

            opts = self.query.model._meta

        aliases = set()

        only_load = self.deferred_to_columns()

        # Skip all proxy to the root proxied model

        proxied_model = get_proxied_model(opts)

        if start_alias:

            seen = {None: start_alias}

        for field, model in opts.get_fields_with_model():

            if start_alias:

                try:

                    alias = seen[model]

                except KeyError:

                    if model is proxied_model:

                        alias = start_alias

                    else:

                        link_field = opts.get_ancestor_link(model)

                        alias = self.query.join((start_alias, model._meta.db_table,

                                link_field.column, model._meta.pk.column))

                    seen[model] = alias

            else:

                # If we're starting from the base model of the queryset, the

                # aliases will have already been set up in pre_sql_setup(), so

                # we can save time here.

                alias = self.query.included_inherited_models[model]

            table = self.query.alias_map[alias][TABLE_NAME]

            if table in only_load and field.column not in only_load[table]:

                continue

            if as_pairs:

                result.append((alias, field.column))

                aliases.add(alias)

                continue

            # This part of the function is customized for GeoQuery. We

            # see if there was any custom selection specified in the

            # dictionary, and set up the selection format appropriately.

            field_sel = self.get_field_select(field, alias)

            if with_aliases and field.column in col_aliases:

                c_alias = 'Col%d' % len(col_aliases)

                result.append('%s AS %s' % (field_sel, c_alias))

                col_aliases.add(c_alias)

                aliases.add(c_alias)

            else:

                r = field_sel

                result.append(r)

                aliases.add(r)

                if with_aliases:

                    col_aliases.add(field.column)

        return result, aliases

    def resolve_columns(self, row, fields=()):

        """

        This routine is necessary so that distances and geometries returned

        from extra selection SQL get resolved appropriately into Python

        objects.

        """

        values = []

        aliases = self.query.extra_select.keys()

        if self.query.aggregates:

            # If we have an aggregate annotation, must extend the aliases

            # so their corresponding row values are included.

            aliases.extend([None for i in xrange(len(self.query.aggregates))])

        # Have to set a starting row number offset that is used for

        # determining the correct starting row index -- needed for

        # doing pagination with Oracle.

        rn_offset = 0

        if self.connection.ops.oracle:

            if self.query.high_mark is not None or self.query.low_mark: rn_offset = 1

        index_start = rn_offset + len(aliases)

        # Converting any extra selection values (e.g., geometries and

        # distance objects added by GeoQuerySet methods).

        values = [self.query.convert_values(v,

                               self.query.extra_select_fields.get(a, None),

                               self.connection)

                  for v, a in izip(row[rn_offset:index_start], aliases)]

        if self.connection.ops.oracle or getattr(self.query, 'geo_values', False):

            # We resolve the rest of the columns if we're on Oracle or if

            # the `geo_values` attribute is defined.

            for value, field in map(None, row[index_start:], fields):

                values.append(self.query.convert_values(value, field, connection=self.connection))

        else:

            values.extend(row[index_start:])

        return tuple(values)

    #### Routines unique to GeoQuery ####

    def get_extra_select_format(self, alias):

        sel_fmt = '%s'

        if alias in self.query.custom_select:

            sel_fmt = sel_fmt % self.query.custom_select[alias]

        return sel_fmt

    def get_field_select(self, field, alias=None, column=None):

        """

        Returns the SELECT SQL string for the given field.  Figures out

        if any custom selection SQL is needed for the column  The `alias`

        keyword may be used to manually specify the database table where

        the column exists, if not in the model associated with this

        `GeoQuery`.  Similarly, `column` may be used to specify the exact

        column name, rather than using the `column` attribute on `field`.

        """

        sel_fmt = self.get_select_format(field)

        if field in self.query.custom_select:

            field_sel = sel_fmt % self.query.custom_select[field]

        else:

            field_sel = sel_fmt % self._field_column(field, alias, column)

        return field_sel

    def get_select_format(self, fld):

        """

        Returns the selection format string, depending on the requirements

        of the spatial backend.  For example, Oracle and MySQL require custom

        selection formats in order to retrieve geometries in OGC WKT. For all

        other fields a simple '%s' format string is returned.

        """

        if self.connection.ops.select and hasattr(fld, 'geom_type'):

            # This allows operations to be done on fields in the SELECT,

            # overriding their values -- used by the Oracle and MySQL

            # spatial backends to get database values as WKT, and by the

            # `transform` method.

            sel_fmt = self.connection.ops.select

            # Because WKT doesn't contain spatial reference information,

            # the SRID is prefixed to the returned WKT to ensure that the

            # transformed geometries have an SRID different than that of the

            # field -- this is only used by `transform` for Oracle and

            # SpatiaLite backends.

            if self.query.transformed_srid and ( self.connection.ops.oracle or

                                                 self.connection.ops.spatialite ):

                sel_fmt = "'SRID=%d;'||%s" % (self.query.transformed_srid, sel_fmt)

        else:

            sel_fmt = '%s'

        return sel_fmt

    # Private API utilities, subject to change.

    def _field_column(self, field, table_alias=None, column=None):

        """

        Helper function that returns the database column for the given field.

        The table and column are returned (quoted) in the proper format, e.g.,

        `"geoapp_city"."point"`.  If `table_alias` is not specified, the

        database table associated with the model of this `GeoQuery` will be

        used.  If `column` is specified, it will be used instead of the value

        in `field.column`.

        """

        if table_alias is None: table_alias = self.query.model._meta.db_table

        return "%s.%s" % (self.quote_name_unless_alias(table_alias),

                          self.connection.ops.quote_name(column or field.column))

class SQLInsertCompiler(compiler.SQLInsertCompiler, GeoSQLCompiler):

    pass

class SQLDeleteCompiler(compiler.SQLDeleteCompiler, GeoSQLCompiler):

    pass

class SQLUpdateCompiler(compiler.SQLUpdateCompiler, GeoSQLCompiler):

    pass

class SQLAggregateCompiler(compiler.SQLAggregateCompiler, GeoSQLCompiler):

    pass

class SQLDateCompiler(compiler.SQLDateCompiler, GeoSQLCompiler):

    pass