from __future__ import annotations

import logging
import random
from decimal import Decimal
from typing import Any, TypeVar

from django.conf import settings
from django.contrib.auth.models import AbstractBaseUser, Group
from django.db import models, router, transaction
from django.http import HttpRequest
from django.utils import timezone
from django.utils.translation import gettext_lazy as _

from waffle import (
    get_waffle_sample_model,
    get_waffle_switch_model,
    get_waffle_flag_model,
    managers,
)
from waffle.utils import get_setting, keyfmt, get_cache

logger = logging.getLogger('waffle')

CACHE_EMPTY = '-'


_BaseModelType = TypeVar("_BaseModelType", bound="BaseModel")


class BaseModel(models.Model):
    SINGLE_CACHE_KEY = ''
    ALL_CACHE_KEY = ''

    class Meta:
        abstract = True

    def __str__(self) -> str:
        return self.name

    def natural_key(self) -> tuple[str]:
        return (self.name,)

    @classmethod
    def _cache_key(cls, name: str) -> str:
        return keyfmt(get_setting(cls.SINGLE_CACHE_KEY), name)

    @classmethod
    def get(cls: type[_BaseModelType], name: str) -> _BaseModelType:
        cache = get_cache()
        cache_key = cls._cache_key(name)
        cached = cache.get(cache_key)
        if cached == CACHE_EMPTY:
            return cls(name=name)
        if cached:
            return cached

        try:
            obj = cls.get_from_db(name)
        except cls.DoesNotExist:
            cache.add(cache_key, CACHE_EMPTY)
            return cls(name=name)

        cache.add(cache_key, obj)
        return obj

    @classmethod
    def get_from_db(cls: type[_BaseModelType], name: str) -> _BaseModelType:
        objects = cls.objects
        if get_setting('READ_FROM_WRITE_DB'):
            objects = objects.using(router.db_for_write(cls))
        return objects.get(name=name)

    @classmethod
    def get_all(cls: type[_BaseModelType]) -> list[_BaseModelType]:
        cache = get_cache()
        cache_key = get_setting(cls.ALL_CACHE_KEY)
        cached = cache.get(cache_key)
        if cached == CACHE_EMPTY:
            return []
        if cached:
            return cached

        objs = cls.get_all_from_db()
        if not objs:
            cache.add(cache_key, CACHE_EMPTY)
            return []

        cache.add(cache_key, objs)
        return objs

    @classmethod
    def get_all_from_db(cls: type[_BaseModelType]) -> list[_BaseModelType]:
        objects = cls.objects
        if get_setting('READ_FROM_WRITE_DB'):
            objects = objects.using(router.db_for_write(cls))
        return list(objects.all())

    def flush(self) -> None:
        cache = get_cache()
        keys = [
            self._cache_key(self.name),
            get_setting(self.ALL_CACHE_KEY),
        ]
        cache.delete_many(keys)

    def save(self, *args: Any, **kwargs: Any) -> None:
        self.modified = timezone.now()
        ret = super().save(*args, **kwargs)
        if hasattr(transaction, 'on_commit'):
            transaction.on_commit(self.flush)
        else:
            self.flush()
        return ret

    def delete(self, *args: Any, **kwargs: Any) -> tuple[int, dict[str, int]]:
        ret = super().delete(*args, **kwargs)
        if hasattr(transaction, 'on_commit'):
            transaction.on_commit(self.flush)
        else:
            self.flush()
        return ret


def set_flag(request: HttpRequest, flag_name: str, active: bool | None = True, session_only: bool = False) -> None:
    """Set a flag value on a request object."""
    if not hasattr(request, 'waffles'):
        request.waffles = {}
    request.waffles[flag_name] = [active, session_only]


class AbstractBaseFlag(BaseModel):
    """A feature flag.

    Flags are active (or not) on a per-request basis.

    """
    name = models.CharField(
        max_length=100,
        unique=True,
        help_text=_('The human/computer readable name.'),
        verbose_name=_('Name'),
    )
    everyone = models.BooleanField(
        blank=True,
        null=True,
        help_text=_(
            'Flip this flag on (Yes) or off (No) for everyone, overriding all '
            'other settings. Leave as Unknown to use normally.'),
        verbose_name=_('Everyone'),
    )
    percent = models.DecimalField(
        max_digits=3,
        decimal_places=1,
        null=True,
        blank=True,
        help_text=_('A number between 0.0 and 99.9 to indicate a percentage of '
                    'users for whom this flag will be active.'),
        verbose_name=_('Percent'),
    )
    testing = models.BooleanField(
        default=False,
        help_text=_('Allow this flag to be set for a session for user testing'),
        verbose_name=_('Testing'),
    )
    superusers = models.BooleanField(
        default=True,
        help_text=_('Flag always active for superusers?'),
        verbose_name=_('Superusers'),
    )
    staff = models.BooleanField(
        default=False,
        help_text=_('Flag always active for staff?'),
        verbose_name=_('Staff'),
    )
    authenticated = models.BooleanField(
        default=False,
        help_text=_('Flag always active for authenticated users?'),
        verbose_name=_('Authenticated'),
    )
    languages = models.TextField(
        blank=True,
        default='',
        help_text=_('Activate this flag for users with one of these languages (comma-separated list)'),
        verbose_name=_('Languages'),
    )
    rollout = models.BooleanField(
        default=False,
        help_text=_('Activate roll-out mode?'),
        verbose_name=_('Rollout'),
    )
    note = models.TextField(
        blank=True,
        help_text=_('Note where this Flag is used.'),
        verbose_name=_('Note'),
    )
    created = models.DateTimeField(
        default=timezone.now,
        db_index=True,
        help_text=_('Date when this Flag was created.'),
        verbose_name=_('Created'),
    )
    modified = models.DateTimeField(
        default=timezone.now,
        help_text=_('Date when this Flag was last modified.'),
        verbose_name=_('Modified'),
    )

    objects = managers.FlagManager()

    SINGLE_CACHE_KEY = 'FLAG_CACHE_KEY'
    ALL_CACHE_KEY = 'ALL_FLAGS_CACHE_KEY'

    class Meta:
        abstract = True
        verbose_name = _('Flag')
        verbose_name_plural = _('Flags')

    def flush(self) -> None:
        cache = get_cache()
        keys = self.get_flush_keys()
        cache.delete_many(keys)

    def get_flush_keys(self, flush_keys: list[str] | None = None) -> list[str]:
        flush_keys = flush_keys or []
        flush_keys.extend([
            self._cache_key(self.name),
            get_setting('ALL_FLAGS_CACHE_KEY'),
        ])
        return flush_keys

    def is_active_for_user(self, user: AbstractBaseUser) -> bool | None:
        if self.everyone:
            return True

        if self.authenticated and user.is_authenticated:
            return True

        if self.staff and getattr(user, 'is_staff', False):
            return True

        if self.superusers and getattr(user, 'is_superuser', False):
            return True

        return None

    def _is_active_for_user(self, request: HttpRequest) -> bool | None:
        user = getattr(request, "user", None)
        if user:
            return self.is_active_for_user(user)
        return False

    def _is_active_for_language(self, request: HttpRequest) -> bool | None:
        if self.languages:
            languages = [ln.strip() for ln in self.languages.split(',')]
            if (hasattr(request, 'LANGUAGE_CODE')
                    and request.LANGUAGE_CODE in languages):
                return True
        return None

    def is_active(self, request: HttpRequest, read_only: bool = False) -> bool | None:
        if not self.pk:
            log_level = get_setting('LOG_MISSING_FLAGS')
            if log_level:
                logger.log(log_level, 'Flag %s not found', self.name)
            if get_setting('CREATE_MISSING_FLAGS'):
                flag, _created = get_waffle_flag_model().objects.get_or_create(
                    name=self.name,
                    defaults={
                        'everyone': get_setting('FLAG_DEFAULT')
                    }
                )
                cache = get_cache()
                cache.set(self._cache_key(self.name), flag)

            return get_setting('FLAG_DEFAULT')

        if get_setting('OVERRIDE'):
            if self.name in request.GET:
                return request.GET[self.name] == '1'

        if self.everyone:
            return True
        elif self.everyone is False:
            return False

        if self.testing:  # Testing mode is on.
            tc = get_setting('TEST_COOKIE') % self.name
            th = tc.replace('_', '-')
            on = None
            if tc in request.GET:
                on = request.GET[tc] == '1'
            elif th in request.headers:
                on = request.headers[th] == '1'
            if on is not None:
                if not hasattr(request, 'waffle_tests'):
                    request.waffle_tests = {}
                request.waffle_tests[self.name] = on
                return on
            if tc in request.COOKIES:
                return request.COOKIES[tc] == 'True'

        active_for_language = self._is_active_for_language(request)
        if active_for_language is not None:
            return active_for_language

        active_for_user = self._is_active_for_user(request)
        if active_for_user is not None:
            return active_for_user

        if self.percent and self.percent > 0:
            if not hasattr(request, 'waffles'):
                request.waffles = {}
            elif self.name in request.waffles:
                return request.waffles[self.name][0]

            cookie = get_setting('COOKIE') % self.name
            if cookie in request.COOKIES:
                flag_active = request.COOKIES[cookie] == 'True'
                if not read_only:
                    set_flag(request, self.name, flag_active, self.rollout)
                return flag_active

            if not read_only:
                if Decimal(str(random.uniform(0, 100))) <= self.percent:
                    set_flag(request, self.name, True, self.rollout)
                    return True
                set_flag(request, self.name, False, self.rollout)

            else:
                return None

        return False


class AbstractUserFlag(AbstractBaseFlag):
    groups = models.ManyToManyField(
        Group,
        blank=True,
        help_text=_('Activate this flag for these user groups.'),
        verbose_name=_('Groups'),
    )
    users = models.ManyToManyField(
        settings.AUTH_USER_MODEL,
        blank=True,
        help_text=_('Activate this flag for these users.'),
        verbose_name=_('Users'),
    )

    class Meta(AbstractBaseFlag.Meta):
        abstract = True
        verbose_name = _('Flag')
        verbose_name_plural = _('Flags')

    def get_flush_keys(self, flush_keys: list[str] | None = None) -> list[str]:
        flush_keys = super().get_flush_keys(flush_keys)
        flush_keys.extend([
            keyfmt(get_setting('FLAG_USERS_CACHE_KEY'), self.name),
            keyfmt(get_setting('FLAG_GROUPS_CACHE_KEY'), self.name),
        ])
        return flush_keys

    def _get_user_ids(self) -> set[Any]:
        cache = get_cache()
        cache_key = keyfmt(get_setting('FLAG_USERS_CACHE_KEY'), self.name)
        cached = cache.get(cache_key)
        if cached == CACHE_EMPTY:
            return set()
        if cached:
            return cached

        user_ids = set(self.users.all().values_list('pk', flat=True))
        if not user_ids:
            cache.add(cache_key, CACHE_EMPTY)
            return set()

        cache.add(cache_key, user_ids)
        return user_ids

    def _get_group_ids(self) -> set[Any]:
        cache = get_cache()
        cache_key = keyfmt(get_setting('FLAG_GROUPS_CACHE_KEY'), self.name)
        cached = cache.get(cache_key)
        if cached == CACHE_EMPTY:
            return set()
        if cached:
            return cached

        group_ids = set(self.groups.all().values_list('pk', flat=True))
        if not group_ids:
            cache.add(cache_key, CACHE_EMPTY)
            return set()

        cache.add(cache_key, group_ids)
        return group_ids

    def is_active_for_user(self, user: AbstractBaseUser) -> bool | None:
        is_active = super().is_active_for_user(user)
        if is_active:
            return is_active

        user_ids = self._get_user_ids()
        if hasattr(user, 'pk') and user.pk in user_ids:
            return True

        if hasattr(user, 'groups'):
            group_ids = self._get_group_ids()
            if group_ids:
                user_groups = set(user.groups.all().values_list('pk', flat=True))
                if group_ids.intersection(user_groups):
                    return True

        return None


class Flag(AbstractUserFlag):
    """A feature flag.

    Flags are active (or not) on a per-request basis.

    """
    class Meta(AbstractUserFlag.Meta):
        swappable = 'WAFFLE_FLAG_MODEL'
        verbose_name = _('Flag')
        verbose_name_plural = _('Flags')


class AbstractBaseSwitch(BaseModel):
    """A feature switch.

    Switches are active, or inactive, globally.

    """

    name = models.CharField(
        max_length=100,
        unique=True,
        help_text=_('The human/computer readable name.'),
        verbose_name=_('Name'),
    )
    active = models.BooleanField(
        default=False,
        help_text=_('Is this switch active?'),
        verbose_name=_('Active'),
    )
    note = models.TextField(
        blank=True,
        help_text=_('Note where this Switch is used.'),
        verbose_name=_('Note'),
    )
    created = models.DateTimeField(
        default=timezone.now,
        db_index=True,
        help_text=_('Date when this Switch was created.'),
        verbose_name=_('Created'),
    )
    modified = models.DateTimeField(
        default=timezone.now,
        help_text=_('Date when this Switch was last modified.'),
        verbose_name=_('Modified'),
    )

    objects = managers.SwitchManager()

    SINGLE_CACHE_KEY = 'SWITCH_CACHE_KEY'
    ALL_CACHE_KEY = 'ALL_SWITCHES_CACHE_KEY'

    class Meta:
        abstract = True
        verbose_name = _('Switch')
        verbose_name_plural = _('Switches')

    def is_active(self) -> bool:
        if not self.pk:
            log_level = get_setting('LOG_MISSING_SWITCHES')
            if log_level:
                logger.log(log_level, 'Switch %s not found', self.name)
            if get_setting('CREATE_MISSING_SWITCHES'):
                switch, _created = get_waffle_switch_model().objects.get_or_create(
                    name=self.name, defaults={"active": get_setting("SWITCH_DEFAULT")}
                )
                cache = get_cache()
                cache.set(self._cache_key(self.name), switch)

            return get_setting('SWITCH_DEFAULT')

        return self.active


class AbstractBaseSample(BaseModel):
    """A sample of users.

    A sample is true some percentage of the time, but is not connected
    to users or requests.

    """

    name = models.CharField(
        max_length=100,
        unique=True,
        help_text=_('The human/computer readable name.'),
        verbose_name=_('Name'),
    )
    percent = models.DecimalField(
        max_digits=4,
        decimal_places=1,
        help_text=_('A number between 0.0 and 100.0 to indicate a percentage of the time '
                    'this sample will be active.'),
        verbose_name=_('Percent'),
    )
    note = models.TextField(
        blank=True,
        help_text=_('Note where this Sample is used.'),
        verbose_name=_('Note'),
    )
    created = models.DateTimeField(
        default=timezone.now,
        db_index=True,
        help_text=_('Date when this Sample was created.'),
        verbose_name=_('Created'),
    )
    modified = models.DateTimeField(
        default=timezone.now,
        help_text=_('Date when this Sample was last modified.'),
        verbose_name=_('Modified'),
    )

    objects = managers.SampleManager()

    SINGLE_CACHE_KEY = 'SAMPLE_CACHE_KEY'
    ALL_CACHE_KEY = 'ALL_SAMPLES_CACHE_KEY'

    class Meta:
        abstract = True
        verbose_name = _('Sample')
        verbose_name_plural = _('Samples')

    def is_active(self) -> bool:
        if not self.pk:
            log_level = get_setting('LOG_MISSING_SAMPLES')
            if log_level:
                logger.log(log_level, 'Sample %s not found', self.name)
            if get_setting('CREATE_MISSING_SAMPLES'):

                default_percent = 100 if get_setting('SAMPLE_DEFAULT') else 0

                sample, _created = get_waffle_sample_model().objects.get_or_create(
                    name=self.name, defaults={"percent": default_percent}
                )
                cache = get_cache()
                cache.set(self._cache_key(self.name), sample)

            return get_setting('SAMPLE_DEFAULT')
        return Decimal(str(random.uniform(0, 100))) <= self.percent


class Switch(AbstractBaseSwitch):
    """A feature switch.

    Switches are active, or inactive, globally.

    """
    class Meta(AbstractBaseSwitch.Meta):
        swappable = 'WAFFLE_SWITCH_MODEL'
        verbose_name = _('Switch')
        verbose_name_plural = _('Switches')


class Sample(AbstractBaseSample):
    """A sample of users.

    A sample is true some percentage of the time, but is not connected
    to users or requests.

    """
    class Meta(AbstractBaseSample.Meta):
        swappable = 'WAFFLE_SAMPLE_MODEL'
        verbose_name = _('Sample')
        verbose_name_plural = _('Samples')