"""

 This overrides the traditional `inspectdb` command so that geographic databases

 may be introspected.

"""

from django.core.management.commands.inspectdb import Command as InspectCommand

from django.contrib.gis.db.backend import SpatialBackend

class Command(InspectCommand):

    # Mapping from lower-case OGC type to the corresponding GeoDjango field.

    geofield_mapping = {'point' : 'PointField',

                        'linestring' : 'LineStringField',

                        'polygon' : 'PolygonField',

                        'multipoint' : 'MultiPointField',

                        'multilinestring' : 'MultiLineStringField',

                        'multipolygon' : 'MultiPolygonField',

                        'geometrycollection' : 'GeometryCollectionField',

                        'geometry' : 'GeometryField',

                        }

    def geometry_columns(self):

        """

        Returns a datastructure of metadata information associated with the

        `geometry_columns` (or equivalent) table.

        """

        # The `geo_cols` is a dictionary data structure that holds information

        # about any geographic columns in the database.

        geo_cols = {}

        def add_col(table, column, coldata):

            if table in geo_cols:

                # If table already has a geometry column.

                geo_cols[table][column] = coldata

            else:

                # Otherwise, create a dictionary indexed by column.

                geo_cols[table] = { column : coldata }

        if SpatialBackend.name == 'postgis':

            # PostGIS holds all geographic column information in the `geometry_columns` table.

            from django.contrib.gis.models import GeometryColumns

            for geo_col in GeometryColumns.objects.all():

                table = geo_col.f_table_name

                column = geo_col.f_geometry_column

                coldata = {'type' : geo_col.type, 'srid' : geo_col.srid, 'dim' : geo_col.coord_dimension}

                add_col(table, column, coldata)

            return geo_cols

        elif SpatialBackend.name == 'mysql':

            # On MySQL have to get all table metadata before hand; this means walking through

            # each table and seeing if any column types are spatial.  Can't detect this with

            # `cursor.description` (what the introspection module does) because all spatial types

            # have the same integer type (255 for GEOMETRY).

            from django.db import connection

            cursor = connection.cursor()

            cursor.execute('SHOW TABLES')

            tables = cursor.fetchall();

            for table_tup in tables:

                table = table_tup[0]

                table_desc = cursor.execute('DESCRIBE `%s`' % table)

                col_info = cursor.fetchall()

                for column, typ, null, key, default, extra in col_info:

                    if typ in self.geofield_mapping: add_col(table, column, {'type' : typ})

            return geo_cols

        else:

            # TODO: Oracle (has incomplete `geometry_columns` -- have to parse

            #  SDO SQL to get specific type, SRID, and other information).

            raise NotImplementedError('Geographic database inspection not available.')

    def handle_inspection(self):

        "Overloaded from Django's version to handle geographic database tables."

        from django.db import connection

        import keyword

        geo_cols = self.geometry_columns()

        table2model = lambda table_name: table_name.title().replace('_', '')

        cursor = connection.cursor()

        yield "# This is an auto-generated Django model module."

        yield "# You'll have to do the following manually to clean this up:"

        yield "#     * Rearrange models' order"

        yield "#     * Make sure each model has one field with primary_key=True"

        yield "# Feel free to rename the models, but don't rename db_table values or field names."

        yield "#"

        yield "# Also note: You'll have to insert the output of 'django-admin.py sqlcustom [appname]'"

        yield "# into your database."

        yield ''

        yield 'from django.contrib.gis.db import models'

        yield ''

        for table_name in connection.introspection.get_table_list(cursor):

            # Getting the geographic table dictionary.

            geo_table = geo_cols.get(table_name, {})

            yield 'class %s(models.Model):' % table2model(table_name)

            try:

                relations = connection.introspection.get_relations(cursor, table_name)

            except NotImplementedError:

                relations = {}

            try:

                indexes = connection.introspection.get_indexes(cursor, table_name)

            except NotImplementedError:

                indexes = {}

            for i, row in enumerate(connection.introspection.get_table_description(cursor, table_name)):

                att_name, iatt_name = row[0].lower(), row[0]

                comment_notes = [] # Holds Field notes, to be displayed in a Python comment.

                extra_params = {}  # Holds Field parameters such as 'db_column'.

                if ' ' in att_name:

                    extra_params['db_column'] = att_name

                    att_name = att_name.replace(' ', '')

                    comment_notes.append('Field renamed to remove spaces.')

                if keyword.iskeyword(att_name):

                    extra_params['db_column'] = att_name

                    att_name += '_field'

                    comment_notes.append('Field renamed because it was a Python reserved word.')

                if i in relations:

                    rel_to = relations[i][1] == table_name and "'self'" or table2model(relations[i][1])

                    field_type = 'ForeignKey(%s' % rel_to

                    if att_name.endswith('_id'):

                        att_name = att_name[:-3]

                    else:

                        extra_params['db_column'] = att_name

                else:

                    if iatt_name in geo_table:

                        ## Customization for Geographic Columns ##

                        geo_col = geo_table[iatt_name]

                        field_type = self.geofield_mapping[geo_col['type'].lower()]

                        # Adding extra keyword arguments for the SRID and dimension (if not defaults).

                        dim, srid = geo_col.get('dim', 2), geo_col.get('srid', 4326)

                        if dim != 2: extra_params['dim'] = dim

                        if srid != 4326: extra_params['srid'] = srid

                    else:

                        try:

                            field_type = connection.introspection.get_field_type(row[1], row)

                        except KeyError:

                            field_type = 'TextField'

                            comment_notes.append('This field type is a guess.')

                    # This is a hook for data_types_reverse to return a tuple of

                    # (field_type, extra_params_dict).

                    if type(field_type) is tuple:

                        field_type, new_params = field_type

                        extra_params.update(new_params)

                    # Add max_length for all CharFields.

                    if field_type == 'CharField' and row[3]:

                        extra_params['max_length'] = row[3]

                    if field_type == 'DecimalField':

                        extra_params['max_digits'] = row[4]

                        extra_params['decimal_places'] = row[5]

                    # Add primary_key and unique, if necessary.

                    column_name = extra_params.get('db_column', att_name)

                    if column_name in indexes:

                        if indexes[column_name]['primary_key']:

                            extra_params['primary_key'] = True

                        elif indexes[column_name]['unique']:

                            extra_params['unique'] = True

                    field_type += '('

                # Don't output 'id = meta.AutoField(primary_key=True)', because

                # that's assumed if it doesn't exist.

                if att_name == 'id' and field_type == 'AutoField(' and extra_params == {'primary_key': True}:

                    continue

                # Add 'null' and 'blank', if the 'null_ok' flag was present in the

                # table description.

                if row[6]: # If it's NULL...

                    extra_params['blank'] = True

                    if not field_type in ('TextField(', 'CharField('):

                        extra_params['null'] = True

                field_desc = '%s = models.%s' % (att_name, field_type)

                if extra_params:

                    if not field_desc.endswith('('):

                        field_desc += ', '

                    field_desc += ', '.join(['%s=%r' % (k, v) for k, v in extra_params.items()])

                field_desc += ')'

                if comment_notes:

                    field_desc += ' # ' + ' '.join(comment_notes)

                yield '    %s' % field_desc

            if table_name in geo_cols:

                yield '    objects = models.GeoManager()'

            yield '    class Meta:'

            yield '        db_table = %r' % table_name

            yield ''