"""
SQL functions reference lists:
https://web.archive.org/web/20130407175746/https://www.gaia-gis.it/gaia-sins/spatialite-sql-4.0.0.html
https://www.gaia-gis.it/gaia-sins/spatialite-sql-4.2.1.html
"""
import re

from django.contrib.gis.db.backends.base.operations import \
    BaseSpatialOperations
from django.contrib.gis.db.backends.spatialite.adapter import SpatiaLiteAdapter
from django.contrib.gis.db.backends.utils import SpatialOperator
from django.contrib.gis.db.models import aggregates
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.sqlite3.operations import DatabaseOperations
from django.utils.functional import cached_property


class SpatiaLiteDistanceOperator(SpatialOperator):
    def as_sql(self, connection, lookup, template_params, sql_params):
        if lookup.lhs.output_field.geodetic(connection):
            # SpatiaLite returns NULL instead of zero on geodetic coordinates
            sql_template = 'COALESCE(%(func)s(%(lhs)s, %(rhs)s, %%s), 0) %(op)s %(value)s'
            template_params.update({
                'op': self.op,
                'func': connection.ops.spatial_function_name('Distance'),
            })
            sql_params.insert(1, len(lookup.rhs) == 3 and lookup.rhs[-1] == 'spheroid')
            return sql_template % template_params, sql_params
        return super().as_sql(connection, lookup, template_params, sql_params)


class SpatiaLiteOperations(BaseSpatialOperations, DatabaseOperations):
    name = 'spatialite'
    spatialite = True
    version_regex = re.compile(r'^(?P<major>\d)\.(?P<minor1>\d)\.(?P<minor2>\d+)')

    Adapter = SpatiaLiteAdapter

    collect = 'Collect'
    extent = 'Extent'
    makeline = 'MakeLine'
    unionagg = 'GUnion'

    from_text = 'GeomFromText'
    from_wkb = 'GeomFromWKB'
    select = 'AsText(%s)'

    gis_operators = {
        # Binary predicates
        'equals': SpatialOperator(func='Equals'),
        'disjoint': SpatialOperator(func='Disjoint'),
        'touches': SpatialOperator(func='Touches'),
        'crosses': SpatialOperator(func='Crosses'),
        'within': SpatialOperator(func='Within'),
        'overlaps': SpatialOperator(func='Overlaps'),
        'contains': SpatialOperator(func='Contains'),
        'intersects': SpatialOperator(func='Intersects'),
        'relate': SpatialOperator(func='Relate'),
        # Returns true if B's bounding box completely contains A's bounding box.
        'contained': SpatialOperator(func='MbrWithin'),
        # Returns true if A's bounding box completely contains B's bounding box.
        'bbcontains': SpatialOperator(func='MbrContains'),
        # Returns true if A's bounding box overlaps B's bounding box.
        'bboverlaps': SpatialOperator(func='MbrOverlaps'),
        # These are implemented here as synonyms for Equals
        'same_as': SpatialOperator(func='Equals'),
        'exact': SpatialOperator(func='Equals'),
        # Distance predicates
        'dwithin': SpatialOperator(func='PtDistWithin'),
        'distance_gt': SpatiaLiteDistanceOperator(func='Distance', op='>'),
        'distance_gte': SpatiaLiteDistanceOperator(func='Distance', op='>='),
        'distance_lt': SpatiaLiteDistanceOperator(func='Distance', op='<'),
        'distance_lte': SpatiaLiteDistanceOperator(func='Distance', op='<='),
    }

    disallowed_aggregates = (aggregates.Extent3D,)

    @cached_property
    def function_names(self):
        return {
            'Length': 'ST_Length',
            'LineLocatePoint': 'ST_Line_Locate_Point',
            'NumPoints': 'ST_NPoints',
            'Reverse': 'ST_Reverse',
            'Scale': 'ScaleCoords',
            'Translate': 'ST_Translate',
            'Union': 'ST_Union',
        }

    @cached_property
    def unsupported_functions(self):
        unsupported = {'BoundingCircle', 'ForceRHR', 'MemSize'}
        if not self.lwgeom_version():
            unsupported |= {'Azimuth', 'GeoHash', 'IsValid', 'MakeValid'}
        return unsupported

    @cached_property
    def spatial_version(self):
        """Determine the version of the SpatiaLite library."""
        try:
            version = self.spatialite_version_tuple()[1:]
        except Exception as exc:
            raise ImproperlyConfigured(
                'Cannot determine the SpatiaLite version for the "%s" database. '
                'Was the SpatiaLite initialization SQL loaded on this database?' % (
                    self.connection.settings_dict['NAME'],
                )
            ) from exc
        if version < (4, 0, 0):
            raise ImproperlyConfigured('GeoDjango only supports SpatiaLite versions 4.0.0 and above.')
        return version

    def convert_extent(self, box):
        """
        Convert the polygon data received from SpatiaLite to min/max values.
        """
        if box is None:
            return None
        shell = Geometry(box).shell
        xmin, ymin = shell[0][:2]
        xmax, ymax = shell[2][:2]
        return (xmin, ymin, xmax, ymax)

    def geo_db_type(self, f):
        """
        Return None because geometry columns are added via the
        `AddGeometryColumn` stored procedure on SpatiaLite.
        """
        return None

    def get_distance(self, f, value, lookup_type):
        """
        Return the distance parameters for the given geometry field,
        lookup value, and lookup type.
        """
        if not value:
            return []
        value = value[0]
        if isinstance(value, Distance):
            if f.geodetic(self.connection):
                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:
            dist_param = value
        return [dist_param]

    def _get_spatialite_func(self, func):
        """
        Helper routine for calling SpatiaLite functions and returning
        their result.
        Any error occurring in this method should be handled by the caller.
        """
        cursor = self.connection._cursor()
        try:
            cursor.execute('SELECT %s' % func)
            row = cursor.fetchone()
        finally:
            cursor.close()
        return row[0]

    def geos_version(self):
        "Return the version of GEOS used by SpatiaLite as a string."
        return self._get_spatialite_func('geos_version()')

    def proj4_version(self):
        "Return the version of the PROJ.4 library used by SpatiaLite."
        return self._get_spatialite_func('proj4_version()')

    def lwgeom_version(self):
        """Return the version of LWGEOM library used by SpatiaLite."""
        return self._get_spatialite_func('lwgeom_version()')

    def spatialite_version(self):
        "Return the SpatiaLite library version as a string."
        return self._get_spatialite_func('spatialite_version()')

    def spatialite_version_tuple(self):
        """
        Return the SpatiaLite version as a tuple (version string, major,
        minor, subminor).
        """
        version = self.spatialite_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 SpatiaLite version string: %s' % version)

        return (version, major, minor1, minor2)

    def spatial_aggregate_name(self, agg_name):
        """
        Return the spatial aggregate SQL template and function for the
        given Aggregate instance.
        """
        agg_name = 'unionagg' if agg_name.lower() == 'union' else agg_name.lower()
        return getattr(self, agg_name)

    # Routines for getting the OGC-compliant models.
    def geometry_columns(self):
        from django.contrib.gis.db.backends.spatialite.models import SpatialiteGeometryColumns
        return SpatialiteGeometryColumns

    def spatial_ref_sys(self):
        from django.contrib.gis.db.backends.spatialite.models import SpatialiteSpatialRefSys
        return SpatialiteSpatialRefSys
