import datetime
import json

from psycopg2.extras import DateRange, DateTimeTZRange, NumericRange, Range

from django.contrib.postgres import forms, lookups
from django.db import models

from .utils import AttributeSetter

__all__ = [
    'RangeField', 'IntegerRangeField', 'BigIntegerRangeField',
    'FloatRangeField', 'DateTimeRangeField', 'DateRangeField',
]


class RangeField(models.Field):
    empty_strings_allowed = False

    def __init__(self, *args, **kwargs):
        # Initializing base_field here ensures that its model matches the model for self.
        if hasattr(self, 'base_field'):
            self.base_field = self.base_field()
        super().__init__(*args, **kwargs)

    @property
    def model(self):
        try:
            return self.__dict__['model']
        except KeyError:
            raise AttributeError("'%s' object has no attribute 'model'" % self.__class__.__name__)

    @model.setter
    def model(self, model):
        self.__dict__['model'] = model
        self.base_field.model = model

    def get_prep_value(self, value):
        if value is None:
            return None
        elif isinstance(value, Range):
            return value
        elif isinstance(value, (list, tuple)):
            return self.range_type(value[0], value[1])
        return value

    def to_python(self, value):
        if isinstance(value, str):
            # Assume we're deserializing
            vals = json.loads(value)
            for end in ('lower', 'upper'):
                if end in vals:
                    vals[end] = self.base_field.to_python(vals[end])
            value = self.range_type(**vals)
        elif isinstance(value, (list, tuple)):
            value = self.range_type(value[0], value[1])
        return value

    def set_attributes_from_name(self, name):
        super().set_attributes_from_name(name)
        self.base_field.set_attributes_from_name(name)

    def value_to_string(self, obj):
        value = self.value_from_object(obj)
        if value is None:
            return None
        if value.isempty:
            return json.dumps({"empty": True})
        base_field = self.base_field
        result = {"bounds": value._bounds}
        for end in ('lower', 'upper'):
            val = getattr(value, end)
            if val is None:
                result[end] = None
            else:
                obj = AttributeSetter(base_field.attname, val)
                result[end] = base_field.value_to_string(obj)
        return json.dumps(result)

    def formfield(self, **kwargs):
        kwargs.setdefault('form_class', self.form_field)
        return super().formfield(**kwargs)


class IntegerRangeField(RangeField):
    base_field = models.IntegerField
    range_type = NumericRange
    form_field = forms.IntegerRangeField

    def db_type(self, connection):
        return 'int4range'


class BigIntegerRangeField(RangeField):
    base_field = models.BigIntegerField
    range_type = NumericRange
    form_field = forms.IntegerRangeField

    def db_type(self, connection):
        return 'int8range'


class FloatRangeField(RangeField):
    base_field = models.FloatField
    range_type = NumericRange
    form_field = forms.FloatRangeField

    def db_type(self, connection):
        return 'numrange'


class DateTimeRangeField(RangeField):
    base_field = models.DateTimeField
    range_type = DateTimeTZRange
    form_field = forms.DateTimeRangeField

    def db_type(self, connection):
        return 'tstzrange'


class DateRangeField(RangeField):
    base_field = models.DateField
    range_type = DateRange
    form_field = forms.DateRangeField

    def db_type(self, connection):
        return 'daterange'


RangeField.register_lookup(lookups.DataContains)
RangeField.register_lookup(lookups.ContainedBy)
RangeField.register_lookup(lookups.Overlap)


class DateTimeRangeContains(models.Lookup):
    """
    Lookup for Date/DateTimeRange containment to cast the rhs to the correct
    type.
    """
    lookup_name = 'contains'

    def process_rhs(self, compiler, connection):
        # Transform rhs value for db lookup.
        if isinstance(self.rhs, datetime.date):
            output_field = models.DateTimeField() if isinstance(self.rhs, datetime.datetime) else models.DateField()
            value = models.Value(self.rhs, output_field=output_field)
            self.rhs = value.resolve_expression(compiler.query)
        return super().process_rhs(compiler, connection)

    def as_sql(self, compiler, connection):
        lhs, lhs_params = self.process_lhs(compiler, connection)
        rhs, rhs_params = self.process_rhs(compiler, connection)
        params = lhs_params + rhs_params
        # Cast the rhs if needed.
        cast_sql = ''
        if isinstance(self.rhs, models.Expression) and self.rhs._output_field_or_none:
            cast_internal_type = self.lhs.output_field.base_field.get_internal_type()
            cast_sql = '::{}'.format(connection.data_types.get(cast_internal_type))
        return '%s @> %s%s' % (lhs, rhs, cast_sql), params


DateRangeField.register_lookup(DateTimeRangeContains)
DateTimeRangeField.register_lookup(DateTimeRangeContains)


class RangeContainedBy(models.Lookup):
    lookup_name = 'contained_by'
    type_mapping = {
        'integer': 'int4range',
        'bigint': 'int8range',
        'double precision': 'numrange',
        'date': 'daterange',
        'timestamp with time zone': 'tstzrange',
    }

    def as_sql(self, qn, connection):
        field = self.lhs.output_field
        if isinstance(field, models.FloatField):
            sql = '%s::numeric <@ %s::{}'.format(self.type_mapping[field.db_type(connection)])
        else:
            sql = '%s <@ %s::{}'.format(self.type_mapping[field.db_type(connection)])
        lhs, lhs_params = self.process_lhs(qn, connection)
        rhs, rhs_params = self.process_rhs(qn, connection)
        params = lhs_params + rhs_params
        return sql % (lhs, rhs), params

    def get_prep_lookup(self):
        return RangeField().get_prep_value(self.rhs)


models.DateField.register_lookup(RangeContainedBy)
models.DateTimeField.register_lookup(RangeContainedBy)
models.IntegerField.register_lookup(RangeContainedBy)
models.BigIntegerField.register_lookup(RangeContainedBy)
models.FloatField.register_lookup(RangeContainedBy)


@RangeField.register_lookup
class FullyLessThan(lookups.PostgresSimpleLookup):
    lookup_name = 'fully_lt'
    operator = '<<'


@RangeField.register_lookup
class FullGreaterThan(lookups.PostgresSimpleLookup):
    lookup_name = 'fully_gt'
    operator = '>>'


@RangeField.register_lookup
class NotLessThan(lookups.PostgresSimpleLookup):
    lookup_name = 'not_lt'
    operator = '&>'


@RangeField.register_lookup
class NotGreaterThan(lookups.PostgresSimpleLookup):
    lookup_name = 'not_gt'
    operator = '&<'


@RangeField.register_lookup
class AdjacentToLookup(lookups.PostgresSimpleLookup):
    lookup_name = 'adjacent_to'
    operator = '-|-'


@RangeField.register_lookup
class RangeStartsWith(models.Transform):
    lookup_name = 'startswith'
    function = 'lower'

    @property
    def output_field(self):
        return self.lhs.output_field.base_field


@RangeField.register_lookup
class RangeEndsWith(models.Transform):
    lookup_name = 'endswith'
    function = 'upper'

    @property
    def output_field(self):
        return self.lhs.output_field.base_field


@RangeField.register_lookup
class IsEmpty(models.Transform):
    lookup_name = 'isempty'
    function = 'isempty'
    output_field = models.BooleanField()
