import sys
from ctypes.util import find_library
from django.conf import settings

from django.core.exceptions import ImproperlyConfigured
from django.db.backends.sqlite3.base import (Database,
    DatabaseWrapper as SQLiteDatabaseWrapper, SQLiteCursorWrapper)
from django.contrib.gis.db.backends.spatialite.client import SpatiaLiteClient
from django.contrib.gis.db.backends.spatialite.creation import SpatiaLiteCreation
from django.contrib.gis.db.backends.spatialite.introspection import SpatiaLiteIntrospection
from django.contrib.gis.db.backends.spatialite.operations import SpatiaLiteOperations
from django.contrib.gis.db.backends.spatialite.schema import SpatialiteSchemaEditor
from django.utils import six


class DatabaseWrapper(SQLiteDatabaseWrapper):
    def __init__(self, *args, **kwargs):
        # Before we get too far, make sure pysqlite 2.5+ is installed.
        if Database.version_info < (2, 5, 0):
            raise ImproperlyConfigured('Only versions of pysqlite 2.5+ are '
                                       'compatible with SpatiaLite and GeoDjango.')

        # Trying to find the location of the SpatiaLite library.
        # Here we are figuring out the path to the SpatiaLite library
        # (`libspatialite`). If it's not in the system library path (e.g., it
        # cannot be found by `ctypes.util.find_library`), then it may be set
        # manually in the settings via the `SPATIALITE_LIBRARY_PATH` setting.
        self.spatialite_lib = getattr(settings, 'SPATIALITE_LIBRARY_PATH',
                                      find_library('spatialite'))
        if not self.spatialite_lib:
            raise ImproperlyConfigured('Unable to locate the SpatiaLite library. '
                                       'Make sure it is in your library path, or set '
                                       'SPATIALITE_LIBRARY_PATH in your settings.'
                                       )
        super(DatabaseWrapper, self).__init__(*args, **kwargs)
        self.ops = SpatiaLiteOperations(self)
        self.client = SpatiaLiteClient(self)
        self.creation = SpatiaLiteCreation(self)
        self.introspection = SpatiaLiteIntrospection(self)

    def schema_editor(self, *args, **kwargs):
        "Returns a new instance of this backend's SchemaEditor"
        return SpatialiteSchemaEditor(self, *args, **kwargs)

    def get_new_connection(self, conn_params):
        conn = super(DatabaseWrapper, self).get_new_connection(conn_params)
        # Enabling extension loading on the SQLite connection.
        try:
            conn.enable_load_extension(True)
        except AttributeError:
            raise ImproperlyConfigured(
                'The pysqlite library does not support C extension loading. '
                'Both SQLite and pysqlite must be configured to allow '
                'the loading of extensions to use SpatiaLite.')
        # Loading the SpatiaLite library extension on the connection, and returning
        # the created cursor.
        cur = conn.cursor(factory=SQLiteCursorWrapper)
        try:
            cur.execute("SELECT load_extension(%s)", (self.spatialite_lib,))
        except Exception as msg:
            new_msg = (
                'Unable to load the SpatiaLite library extension '
                '"%s" because: %s') % (self.spatialite_lib, msg)
            six.reraise(ImproperlyConfigured, ImproperlyConfigured(new_msg), sys.exc_info()[2])
        cur.close()
        return conn