import re

from django.conf import settings
from django.contrib.gis.db.backends.base.operations import \
    BaseSpatialOperations
from django.contrib.gis.db.backends.postgis.adapter import PostGISAdapter
from django.contrib.gis.db.backends.postgis.pgraster import (
    from_pgraster, to_pgraster,
)
from django.contrib.gis.db.backends.utils import SpatialOperator
from django.contrib.gis.geometry.backend import Geometry
from django.contrib.gis.measure import Distance
from django.core.exceptions import ImproperlyConfigured
from django.db.backends.postgresql.operations import DatabaseOperations
from django.db.utils import ProgrammingError
from django.utils.functional import cached_property

from .models import PostGISGeometryColumns, PostGISSpatialRefSys
from .pgraster import get_pgraster_srid


class PostGISOperator(SpatialOperator):
    def __init__(self, geography=False, **kwargs):
        # Only a subset of the operators and functions are available
        # for the geography type.
        self.geography = geography
        super(PostGISOperator, self).__init__(**kwargs)

    def as_sql(self, connection, lookup, *args):
        if lookup.lhs.output_field.geography and not self.geography:
            raise ValueError('PostGIS geography does not support the "%s" '
                             'function/operator.' % (self.func or self.op,))
        return super(PostGISOperator, self).as_sql(connection, lookup, *args)


class PostGISDistanceOperator(PostGISOperator):
    sql_template = '%(func)s(%(lhs)s, %(rhs)s) %(op)s %%s'

    def as_sql(self, connection, lookup, template_params, sql_params):
        if not lookup.lhs.output_field.geography and lookup.lhs.output_field.geodetic(connection):
            sql_template = self.sql_template
            if len(lookup.rhs) == 3 and lookup.rhs[-1] == 'spheroid':
                template_params.update({'op': self.op, 'func': 'ST_Distance_Spheroid'})
                sql_template = '%(func)s(%(lhs)s, %(rhs)s, %%s) %(op)s %%s'
            else:
                template_params.update({'op': self.op, 'func': 'ST_Distance_Sphere'})
            return sql_template % template_params, sql_params
        return super(PostGISDistanceOperator, self).as_sql(connection, lookup, template_params, sql_params)


class PostGISOperations(BaseSpatialOperations, DatabaseOperations):
    name = 'postgis'
    postgis = True
    geography = True
    geom_func_prefix = 'ST_'
    version_regex = re.compile(r'^(?P<major>\d)\.(?P<minor1>\d)\.(?P<minor2>\d+)')

    Adapter = PostGISAdapter
    Adaptor = Adapter  # Backwards-compatibility alias.

    gis_operators = {
        'bbcontains': PostGISOperator(op='~'),
        'bboverlaps': PostGISOperator(op='&&', geography=True),
        'contained': PostGISOperator(op='@'),
        'contains': PostGISOperator(func='ST_Contains'),
        'overlaps_left': PostGISOperator(op='&<'),
        'overlaps_right': PostGISOperator(op='&>'),
        'overlaps_below': PostGISOperator(op='&<|'),
        'overlaps_above': PostGISOperator(op='|&>'),
        'left': PostGISOperator(op='<<'),
        'right': PostGISOperator(op='>>'),
        'strictly_below': PostGISOperator(op='<<|'),
        'strictly_above': PostGISOperator(op='|>>'),
        'same_as': PostGISOperator(op='~='),
        'exact': PostGISOperator(op='~='),  # alias of same_as
        'contains_properly': PostGISOperator(func='ST_ContainsProperly'),
        'coveredby': PostGISOperator(func='ST_CoveredBy', geography=True),
        'covers': PostGISOperator(func='ST_Covers', geography=True),
        'crosses': PostGISOperator(func='ST_Crosses'),
        'disjoint': PostGISOperator(func='ST_Disjoint'),
        'equals': PostGISOperator(func='ST_Equals'),
        'intersects': PostGISOperator(func='ST_Intersects', geography=True),
        'overlaps': PostGISOperator(func='ST_Overlaps'),
        'relate': PostGISOperator(func='ST_Relate'),
        'touches': PostGISOperator(func='ST_Touches'),
        'within': PostGISOperator(func='ST_Within'),
        'dwithin': PostGISOperator(func='ST_DWithin', geography=True),
        'distance_gt': PostGISDistanceOperator(func='ST_Distance', op='>', geography=True),
        'distance_gte': PostGISDistanceOperator(func='ST_Distance', op='>=', geography=True),
        'distance_lt': PostGISDistanceOperator(func='ST_Distance', op='<', geography=True),
        'distance_lte': PostGISDistanceOperator(func='ST_Distance', op='<=', geography=True),
    }

    unsupported_functions = set()
    function_names = {
        'BoundingCircle': 'ST_MinimumBoundingCircle',
        'MemSize': 'ST_Mem_Size',
        'NumPoints': 'ST_NPoints',
    }

    def __init__(self, connection):
        super(PostGISOperations, self).__init__(connection)

        prefix = self.geom_func_prefix

        self.area = prefix + 'Area'
        self.bounding_circle = prefix + 'MinimumBoundingCircle'
        self.centroid = prefix + 'Centroid'
        self.collect = prefix + 'Collect'
        self.difference = prefix + 'Difference'
        self.distance = prefix + 'Distance'
        self.distance_sphere = prefix + 'distance_sphere'
        self.distance_spheroid = prefix + 'distance_spheroid'
        self.envelope = prefix + 'Envelope'
        self.extent = prefix + 'Extent'
        self.extent3d = prefix + '3DExtent'
        self.force_rhr = prefix + 'ForceRHR'
        self.geohash = prefix + 'GeoHash'
        self.geojson = prefix + 'AsGeoJson'
        self.gml = prefix + 'AsGML'
        self.intersection = prefix + 'Intersection'
        self.kml = prefix + 'AsKML'
        self.length = prefix + 'Length'
        self.length3d = prefix + '3DLength'
        self.length_spheroid = prefix + 'length_spheroid'
        self.makeline = prefix + 'MakeLine'
        self.mem_size = prefix + 'mem_size'
        self.num_geom = prefix + 'NumGeometries'
        self.num_points = prefix + 'npoints'
        self.perimeter = prefix + 'Perimeter'
        self.perimeter3d = prefix + '3DPerimeter'
        self.point_on_surface = prefix + 'PointOnSurface'
        self.polygonize = prefix + 'Polygonize'
        self.reverse = prefix + 'Reverse'
        self.scale = prefix + 'Scale'
        self.snap_to_grid = prefix + 'SnapToGrid'
        self.svg = prefix + 'AsSVG'
        self.sym_difference = prefix + 'SymDifference'
        self.transform = prefix + 'Transform'
        self.translate = prefix + 'Translate'
        self.union = prefix + 'Union'
        self.unionagg = prefix + 'Union'

    @cached_property
    def spatial_version(self):
        """Determine the version of the PostGIS library."""
        # Trying to get the PostGIS version because the function
        # signatures will depend on the version used.  The cost
        # here is a database query to determine the version, which
        # can be mitigated by setting `POSTGIS_VERSION` with a 3-tuple
        # comprising user-supplied values for the major, minor, and
        # subminor revision of PostGIS.
        if hasattr(settings, 'POSTGIS_VERSION'):
            version = settings.POSTGIS_VERSION
        else:
            # Run a basic query to check the status of the connection so we're
            # sure we only raise the error below if the problem comes from
            # PostGIS and not from PostgreSQL itself (see #24862).
            self._get_postgis_func('version')

            try:
                vtup = self.postgis_version_tuple()
            except ProgrammingError:
                raise ImproperlyConfigured(
                    'Cannot determine PostGIS version for database "%s" '
                    'using command "SELECT postgis_lib_version()". '
                    'GeoDjango requires at least PostGIS version 2.0. '
                    'Was the database created from a spatial database '
                    'template?' % self.connection.settings_dict['NAME']
                )
            version = vtup[1:]
        return version

    def convert_extent(self, box, srid):
        """
        Returns a 4-tuple extent for the `Extent` aggregate by converting
        the bounding box text returned by PostGIS (`box` argument), for
        example: "BOX(-90.0 30.0, -85.0 40.0)".
        """
        if box is None:
            return None
        ll, ur = box[4:-1].split(',')
        xmin, ymin = map(float, ll.split())
        xmax, ymax = map(float, ur.split())
        return (xmin, ymin, xmax, ymax)

    def convert_extent3d(self, box3d, srid):
        """
        Returns a 6-tuple extent for the `Extent3D` aggregate by converting
        the 3d bounding-box text returned by PostGIS (`box3d` argument), for
        example: "BOX3D(-90.0 30.0 1, -85.0 40.0 2)".
        """
        if box3d is None:
            return None
        ll, ur = box3d[6:-1].split(',')
        xmin, ymin, zmin = map(float, ll.split())
        xmax, ymax, zmax = map(float, ur.split())
        return (xmin, ymin, zmin, xmax, ymax, zmax)

    def convert_geom(self, hex, geo_field):
        """
        Converts the geometry returned from PostGIS aggregates.
        """
        if hex:
            return Geometry(hex, srid=geo_field.srid)
        else:
            return None

    def geo_db_type(self, f):
        """
        Return the database field type for the given spatial field.
        """
        if f.geom_type == 'RASTER':
            return 'raster'
        elif f.geography:
            if f.srid != 4326:
                raise NotImplementedError('PostGIS only supports geography columns with an SRID of 4326.')

            return 'geography(%s,%d)' % (f.geom_type, f.srid)
        else:
            # Type-based geometries.
            # TODO: Support 'M' extension.
            if f.dim == 3:
                geom_type = f.geom_type + 'Z'
            else:
                geom_type = f.geom_type
            return 'geometry(%s,%d)' % (geom_type, f.srid)

    def get_distance(self, f, dist_val, lookup_type):
        """
        Retrieve the distance parameters for the given geometry field,
        distance lookup value, and the distance lookup type.

        This is the most complex implementation of the spatial backends due to
        what is supported on geodetic geometry columns vs. what's available on
        projected geometry columns.  In addition, it has to take into account
        the geography column type.
        """
        # Getting the distance parameter and any options.
        if len(dist_val) == 1:
            value, option = dist_val[0], None
        else:
            value, option = dist_val

        # Shorthand boolean flags.
        geodetic = f.geodetic(self.connection)
        geography = f.geography

        if isinstance(value, Distance):
            if geography:
                dist_param = value.m
            elif geodetic:
                if lookup_type == 'dwithin':
                    raise ValueError('Only numeric values of degree units are '
                                     'allowed on geographic DWithin queries.')
                dist_param = value.m
            else:
                dist_param = getattr(value, Distance.unit_attname(f.units_name(self.connection)))
        else:
            # Assuming the distance is in the units of the field.
            dist_param = value

        if (not geography and geodetic and lookup_type != 'dwithin'
                and option == 'spheroid'):
            # using distance_spheroid requires the spheroid of the field as
            # a parameter.
            return [f._spheroid, dist_param]
        else:
            return [dist_param]

    def get_geom_placeholder(self, f, value, compiler):
        """
        Provides a proper substitution value for Geometries that are not in the
        SRID of the field.  Specifically, this routine will substitute in the
        ST_Transform() function call.
        """
        # Get the srid for this object
        if value is None:
            value_srid = None
        elif f.geom_type == 'RASTER':
            value_srid = get_pgraster_srid(value)
        else:
            value_srid = value.srid

        # Adding Transform() to the SQL placeholder if the value srid
        # is not equal to the field srid.
        if value_srid is None or value_srid == f.srid:
            placeholder = '%s'
        elif f.geom_type == 'RASTER':
            placeholder = '%s((%%s)::raster, %s)' % (self.transform, f.srid)
        else:
            placeholder = '%s(%%s, %s)' % (self.transform, f.srid)

        if hasattr(value, 'as_sql'):
            # If this is an F expression, then we don't really want
            # a placeholder and instead substitute in the column
            # of the expression.
            sql, _ = compiler.compile(value)
            placeholder = placeholder % sql

        return placeholder

    def _get_postgis_func(self, func):
        """
        Helper routine for calling PostGIS functions and returning their result.
        """
        # Close out the connection.  See #9437.
        with self.connection.temporary_connection() as cursor:
            cursor.execute('SELECT %s()' % func)
            return cursor.fetchone()[0]

    def postgis_geos_version(self):
        "Returns the version of the GEOS library used with PostGIS."
        return self._get_postgis_func('postgis_geos_version')

    def postgis_lib_version(self):
        "Returns the version number of the PostGIS library used with PostgreSQL."
        return self._get_postgis_func('postgis_lib_version')

    def postgis_proj_version(self):
        "Returns the version of the PROJ.4 library used with PostGIS."
        return self._get_postgis_func('postgis_proj_version')

    def postgis_version(self):
        "Returns PostGIS version number and compile-time options."
        return self._get_postgis_func('postgis_version')

    def postgis_full_version(self):
        "Returns PostGIS version number and compile-time options."
        return self._get_postgis_func('postgis_full_version')

    def postgis_version_tuple(self):
        """
        Returns the PostGIS version as a tuple (version string, major,
        minor, subminor).
        """
        # Getting the PostGIS version
        version = self.postgis_lib_version()
        m = self.version_regex.match(version)

        if m:
            major = int(m.group('major'))
            minor1 = int(m.group('minor1'))
            minor2 = int(m.group('minor2'))
        else:
            raise Exception('Could not parse PostGIS version string: %s' % version)

        return (version, major, minor1, minor2)

    def proj_version_tuple(self):
        """
        Return the version of PROJ.4 used by PostGIS as a tuple of the
        major, minor, and subminor release numbers.
        """
        proj_regex = re.compile(r'(\d+)\.(\d+)\.(\d+)')
        proj_ver_str = self.postgis_proj_version()
        m = proj_regex.search(proj_ver_str)
        if m:
            return tuple(map(int, [m.group(1), m.group(2), m.group(3)]))
        else:
            raise Exception('Could not determine PROJ.4 version from PostGIS.')

    def spatial_aggregate_name(self, agg_name):
        if agg_name == 'Extent3D':
            return self.extent3d
        else:
            return self.geom_func_prefix + agg_name

    # Routines for getting the OGC-compliant models.
    def geometry_columns(self):
        return PostGISGeometryColumns

    def spatial_ref_sys(self):
        return PostGISSpatialRefSys

    # Methods to convert between PostGIS rasters and dicts that are
    # readable by GDALRaster.
    def parse_raster(self, value):
        return from_pgraster(value)

    def deconstruct_raster(self, value):
        return to_pgraster(value)
