import uuid

from django.db import models
from django.contrib.auth import get_user_model

# Uncomment if you override model's clean method
# from django.core.exceptions import ValidationError

from uncloud_pay.models import Product, RecurringPeriod
import uncloud_pay.models as pay_models
import uncloud_storage.models

STATUS_CHOICES = (
    ('pending', 'Pending'),   # Initial state
    ('creating', 'Creating'),  # Creating VM/image/etc.
    ('active', 'Active'),      # Is usable / active
    ('disabled', 'Disabled'),  # Is usable, but cannot be used for new things
    ('unusable', 'Unusable'),  # Has some kind of error
    ('deleted', 'Deleted'),   # Does not exist anymore, only DB entry as a log
)

STATUS_DEFAULT = 'pending'


class VMHost(models.Model):
    uuid = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)

    # 253 is the maximum DNS name length
    hostname = models.CharField(max_length=253, unique=True)

    # indirectly gives a maximum number of cores / VM - f.i. 32
    physical_cores = models.IntegerField(default=0)

    # determines the maximum usable cores - f.i. 320 if you overbook by a factor of 10
    usable_cores = models.IntegerField(default=0)

    # ram that can be used of the server
    usable_ram_in_gb = models.FloatField(default=0)

    status = models.CharField(
        max_length=32, choices=STATUS_CHOICES, default=STATUS_DEFAULT
    )

    @property
    def vms(self):
        return VMProduct.objects.filter(vmhost=self)

    @property
    def used_ram_in_gb(self):
        return sum([vm.ram_in_gb for vm in VMProduct.objects.filter(vmhost=self)])

    @property
    def available_ram_in_gb(self):
        return self.usable_ram_in_gb - sum([vm.ram_in_gb for vm in self.vms ])

    @property
    def available_cores(self):
        return self.usable_cores - sum([vm.cores for vm in self.vms ])


class VMProduct(Product):
    vmhost = models.ForeignKey(
        VMHost, on_delete=models.CASCADE, editable=False, blank=True, null=True
    )

    # VM-specific. The name is only intended for customers: it's a pain to
    # remember IDs (speaking from experience as ungleich customer)!
    name = models.CharField(max_length=32, blank=True, null=True)
    cores = models.IntegerField()
    ram_in_gb = models.FloatField()


    def recurring_price(self, recurring_period=RecurringPeriod.PER_MONTH):
        # TODO: move magic numbers in variables
        if recurring_period == RecurringPeriod.PER_MONTH:
            return self.cores * 3 + self.ram_in_gb * 4
        elif recurring_period == RecurringPeriod.PER_HOUR:
            return self.cores * 4.0/(30 * 24) + self.ram_in_gb * 4.5/(30* 24)
        else:
            raise Exception('Invalid recurring period for VM Product pricing.')

    def __str__(self):
        return "VM {} ({}): {} cores {} gb ram".format(self.uuid,
                                                       self.name,
                                                       self.cores,
                                                       self.ram_in_gb)
    @property
    def description(self):
        return "Virtual machine '{}': {} core(s), {}GB memory".format(
                self.name, self.cores, self.ram_in_gb)

    @staticmethod
    def allowed_recurring_periods():
        return list(filter(
            lambda pair: pair[0] in [RecurringPeriod.PER_MONTH, RecurringPeriod.PER_HOUR],
            RecurringPeriod.choices))

class VMWithOSProduct(VMProduct):
    pass


class VMDiskImageProduct(models.Model):
    """
    Images are used for cloning/linking.

    They are the base for images.

    """

    uuid = models.UUIDField(
        primary_key=True, default=uuid.uuid4, editable=False
    )
    owner = models.ForeignKey(
        get_user_model(), on_delete=models.CASCADE, editable=False
    )

    name = models.CharField(max_length=256)
    is_os_image = models.BooleanField(default=False)
    is_public = models.BooleanField(default=False)

    size_in_gb = models.FloatField(null=True, blank=True)
    import_url = models.URLField(null=True, blank=True)
    image_source = models.CharField(max_length=128, null=True)
    image_source_type = models.CharField(max_length=128, null=True)

    storage_class = models.CharField(max_length=32,
                                     choices = uncloud_storage.models.StorageClass.choices,
                                     default = uncloud_storage.models.StorageClass.SSD)

    status = models.CharField(
        max_length=32, choices=STATUS_CHOICES, default=STATUS_DEFAULT
    )

    def __str__(self):
        return "VMDiskImage {} ({}): {} gb".format(self.uuid,
                                                   self.name,
                                                   self.size_in_gb)



class VMDiskProduct(models.Model):
    """
    The VMDiskProduct is attached to a VM.

    It is based on a VMDiskImageProduct that will be used as a basis.

    It can be enlarged, but not shrinked compared to the VMDiskImageProduct.
    """

    uuid = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    owner = models.ForeignKey(get_user_model(),
                              on_delete=models.CASCADE,
                              editable=False)

    vm = models.ForeignKey(VMProduct, on_delete=models.CASCADE)
    image = models.ForeignKey(VMDiskImageProduct, on_delete=models.CASCADE)

    size_in_gb = models.FloatField(blank=True)

    # Sample code for clean method

    # Ensures that a VMDiskProduct can only be created from a VMDiskImageProduct
    # that is in status 'active'

    # def clean(self):
    #     if self.image.status != 'active':
    #         raise ValidationError({
    #             'image': 'VM Disk must be created from an active disk image.'
    #         })

    def save(self, *args, **kwargs):
        self.full_clean()
        super().save(*args, **kwargs)


class VMNetworkCard(models.Model):
    vm = models.ForeignKey(VMProduct, on_delete=models.CASCADE)

    mac_address = models.BigIntegerField()

    ip_address = models.GenericIPAddressField(blank=True,
                                              null=True)


class VMSnapshotProduct(Product):
    gb_ssd = models.FloatField(editable=False)
    gb_hdd = models.FloatField(editable=False)

    vm = models.ForeignKey(VMProduct,
                           related_name='snapshots',
                           on_delete=models.CASCADE)