from collections import OrderedDict
from itertools import count, groupby

from django.conf import settings
from django.contrib.auth.models import User
from django.contrib.contenttypes.fields import GenericRelation
from django.contrib.postgres.fields import ArrayField
from django.core.exceptions import ValidationError
from django.core.validators import MaxValueValidator, MinValueValidator
from django.db import models
from django.db.models import Count, Sum
from django.urls import reverse
from mptt.models import MPTTModel, TreeForeignKey
from taggit.managers import TaggableManager

from dcim.choices import *
from dcim.constants import *
from dcim.elevations import RackElevationSVG
from extras.models import ChangeLoggedModel, CustomFieldModel, ObjectChange, TaggedItem
from extras.utils import extras_features
from utilities.choices import ColorChoices
from utilities.fields import ColorField, NaturalOrderingField
from utilities.querysets import RestrictedQuerySet
from utilities.mptt import TreeManager
from utilities.utils import serialize_object
from .devices import Device
from .power import PowerFeed

__all__ = (
    'Rack',
    'RackGroup',
    'RackReservation',
    'RackRole',
)


#
# Racks
#

@extras_features('export_templates')
class RackGroup(MPTTModel, ChangeLoggedModel):
    """
    Racks can be grouped as subsets within a Site. The scope of a group will depend on how Sites are defined. For
    example, if a Site spans a corporate campus, a RackGroup might be defined to represent each building within that
    campus. If a Site instead represents a single building, a RackGroup might represent a single room or floor.
    """
    name = models.CharField(
        max_length=50
    )
    slug = models.SlugField()
    site = models.ForeignKey(
        to='dcim.Site',
        on_delete=models.CASCADE,
        related_name='rack_groups'
    )
    parent = TreeForeignKey(
        to='self',
        on_delete=models.CASCADE,
        related_name='children',
        blank=True,
        null=True,
        db_index=True
    )
    description = models.CharField(
        max_length=200,
        blank=True
    )

    objects = TreeManager()

    csv_headers = ['site', 'parent', 'name', 'slug', 'description']

    class Meta:
        ordering = ['site', 'name']
        unique_together = [
            ['site', 'name'],
            ['site', 'slug'],
        ]

    class MPTTMeta:
        order_insertion_by = ['name']

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        return "{}?group_id={}".format(reverse('dcim:rack_list'), self.pk)

    def to_csv(self):
        return (
            self.site,
            self.parent.name if self.parent else '',
            self.name,
            self.slug,
            self.description,
        )

    def to_objectchange(self, action):
        # Remove MPTT-internal fields
        return ObjectChange(
            changed_object=self,
            object_repr=str(self),
            action=action,
            object_data=serialize_object(self, exclude=['level', 'lft', 'rght', 'tree_id'])
        )

    def clean(self):

        # Parent RackGroup (if any) must belong to the same Site
        if self.parent and self.parent.site != self.site:
            raise ValidationError(f"Parent rack group ({self.parent}) must belong to the same site ({self.site})")


class RackRole(ChangeLoggedModel):
    """
    Racks can be organized by functional role, similar to Devices.
    """
    name = models.CharField(
        max_length=50,
        unique=True
    )
    slug = models.SlugField(
        unique=True
    )
    color = ColorField(
        default=ColorChoices.COLOR_GREY
    )
    description = models.CharField(
        max_length=200,
        blank=True,
    )

    objects = RestrictedQuerySet.as_manager()

    csv_headers = ['name', 'slug', 'color', 'description']

    class Meta:
        ordering = ['name']

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        return "{}?role={}".format(reverse('dcim:rack_list'), self.slug)

    def to_csv(self):
        return (
            self.name,
            self.slug,
            self.color,
            self.description,
        )


@extras_features('custom_fields', 'custom_links', 'export_templates', 'webhooks')
class Rack(ChangeLoggedModel, CustomFieldModel):
    """
    Devices are housed within Racks. Each rack has a defined height measured in rack units, and a front and rear face.
    Each Rack is assigned to a Site and (optionally) a RackGroup.
    """
    name = models.CharField(
        max_length=50
    )
    _name = NaturalOrderingField(
        target_field='name',
        max_length=100,
        blank=True
    )
    facility_id = models.CharField(
        max_length=50,
        blank=True,
        null=True,
        verbose_name='Facility ID',
        help_text='Locally-assigned identifier'
    )
    site = models.ForeignKey(
        to='dcim.Site',
        on_delete=models.PROTECT,
        related_name='racks'
    )
    group = models.ForeignKey(
        to='dcim.RackGroup',
        on_delete=models.SET_NULL,
        related_name='racks',
        blank=True,
        null=True,
        help_text='Assigned group'
    )
    tenant = models.ForeignKey(
        to='tenancy.Tenant',
        on_delete=models.PROTECT,
        related_name='racks',
        blank=True,
        null=True
    )
    status = models.CharField(
        max_length=50,
        choices=RackStatusChoices,
        default=RackStatusChoices.STATUS_ACTIVE
    )
    role = models.ForeignKey(
        to='dcim.RackRole',
        on_delete=models.PROTECT,
        related_name='racks',
        blank=True,
        null=True,
        help_text='Functional role'
    )
    serial = models.CharField(
        max_length=50,
        blank=True,
        verbose_name='Serial number'
    )
    asset_tag = models.CharField(
        max_length=50,
        blank=True,
        null=True,
        unique=True,
        verbose_name='Asset tag',
        help_text='A unique tag used to identify this rack'
    )
    type = models.CharField(
        choices=RackTypeChoices,
        max_length=50,
        blank=True,
        verbose_name='Type'
    )
    width = models.PositiveSmallIntegerField(
        choices=RackWidthChoices,
        default=RackWidthChoices.WIDTH_19IN,
        verbose_name='Width',
        help_text='Rail-to-rail width'
    )
    u_height = models.PositiveSmallIntegerField(
        default=RACK_U_HEIGHT_DEFAULT,
        verbose_name='Height (U)',
        validators=[MinValueValidator(1), MaxValueValidator(100)],
        help_text='Height in rack units'
    )
    desc_units = models.BooleanField(
        default=False,
        verbose_name='Descending units',
        help_text='Units are numbered top-to-bottom'
    )
    outer_width = models.PositiveSmallIntegerField(
        blank=True,
        null=True,
        help_text='Outer dimension of rack (width)'
    )
    outer_depth = models.PositiveSmallIntegerField(
        blank=True,
        null=True,
        help_text='Outer dimension of rack (depth)'
    )
    outer_unit = models.CharField(
        max_length=50,
        choices=RackDimensionUnitChoices,
        blank=True,
    )
    comments = models.TextField(
        blank=True
    )
    custom_field_values = GenericRelation(
        to='extras.CustomFieldValue',
        content_type_field='obj_type',
        object_id_field='obj_id'
    )
    images = GenericRelation(
        to='extras.ImageAttachment'
    )
    tags = TaggableManager(through=TaggedItem)

    objects = RestrictedQuerySet.as_manager()

    csv_headers = [
        'site', 'group', 'name', 'facility_id', 'tenant', 'status', 'role', 'type', 'serial', 'asset_tag', 'width',
        'u_height', 'desc_units', 'outer_width', 'outer_depth', 'outer_unit', 'comments',
    ]
    clone_fields = [
        'site', 'group', 'tenant', 'status', 'role', 'type', 'width', 'u_height', 'desc_units', 'outer_width',
        'outer_depth', 'outer_unit',
    ]

    STATUS_CLASS_MAP = {
        RackStatusChoices.STATUS_RESERVED: 'warning',
        RackStatusChoices.STATUS_AVAILABLE: 'success',
        RackStatusChoices.STATUS_PLANNED: 'info',
        RackStatusChoices.STATUS_ACTIVE: 'primary',
        RackStatusChoices.STATUS_DEPRECATED: 'danger',
    }

    class Meta:
        ordering = ('site', 'group', '_name', 'pk')  # (site, group, name) may be non-unique
        unique_together = (
            # Name and facility_id must be unique *only* within a RackGroup
            ('group', 'name'),
            ('group', 'facility_id'),
        )

    def __str__(self):
        return self.display_name or super().__str__()

    def get_absolute_url(self):
        return reverse('dcim:rack', args=[self.pk])

    def clean(self):

        # Validate outer dimensions and unit
        if (self.outer_width is not None or self.outer_depth is not None) and not self.outer_unit:
            raise ValidationError("Must specify a unit when setting an outer width/depth")
        elif self.outer_width is None and self.outer_depth is None:
            self.outer_unit = ''

        if self.pk:
            # Validate that Rack is tall enough to house the installed Devices
            top_device = Device.objects.filter(
                rack=self
            ).exclude(
                position__isnull=True
            ).order_by('-position').first()
            if top_device:
                min_height = top_device.position + top_device.device_type.u_height - 1
                if self.u_height < min_height:
                    raise ValidationError({
                        'u_height': "Rack must be at least {}U tall to house currently installed devices.".format(
                            min_height
                        )
                    })
            # Validate that Rack was assigned a group of its same site, if applicable
            if self.group:
                if self.group.site != self.site:
                    raise ValidationError({
                        'group': "Rack group must be from the same site, {}.".format(self.site)
                    })

    def save(self, *args, **kwargs):

        # Record the original site assignment for this rack.
        _site_id = None
        if self.pk:
            _site_id = Rack.objects.get(pk=self.pk).site_id

        super().save(*args, **kwargs)

        # Update racked devices if the assigned Site has been changed.
        if _site_id is not None and self.site_id != _site_id:
            devices = Device.objects.filter(rack=self)
            for device in devices:
                device.site = self.site
                device.save()

    def to_csv(self):
        return (
            self.site.name,
            self.group.name if self.group else None,
            self.name,
            self.facility_id,
            self.tenant.name if self.tenant else None,
            self.get_status_display(),
            self.role.name if self.role else None,
            self.get_type_display() if self.type else None,
            self.serial,
            self.asset_tag,
            self.width,
            self.u_height,
            self.desc_units,
            self.outer_width,
            self.outer_depth,
            self.outer_unit,
            self.comments,
        )

    @property
    def units(self):
        if self.desc_units:
            return range(1, self.u_height + 1)
        else:
            return reversed(range(1, self.u_height + 1))

    @property
    def display_name(self):
        if self.facility_id:
            return f'{self.name} ({self.facility_id})'
        return self.name

    def get_status_class(self):
        return self.STATUS_CLASS_MAP.get(self.status)

    def get_rack_units(self, user=None, face=DeviceFaceChoices.FACE_FRONT, exclude=None, expand_devices=True):
        """
        Return a list of rack units as dictionaries. Example: {'device': None, 'face': 0, 'id': 48, 'name': 'U48'}
        Each key 'device' is either a Device or None. By default, multi-U devices are repeated for each U they occupy.

        :param face: Rack face (front or rear)
        :param user: User instance to be used for evaluating device view permissions. If None, all devices
            will be included.
        :param exclude: PK of a Device to exclude (optional); helpful when relocating a Device within a Rack
        :param expand_devices: When True, all units that a device occupies will be listed with each containing a
            reference to the device. When False, only the bottom most unit for a device is included and that unit
            contains a height attribute for the device
        """

        elevation = OrderedDict()
        for u in self.units:
            elevation[u] = {
                'id': u,
                'name': f'U{u}',
                'face': face,
                'device': None,
                'occupied': False
            }

        # Add devices to rack units list
        if self.pk:

            # Retrieve all devices installed within the rack
            queryset = Device.objects.prefetch_related(
                'device_type',
                'device_type__manufacturer',
                'device_role'
            ).annotate(
                devicebay_count=Count('devicebays')
            ).exclude(
                pk=exclude
            ).filter(
                rack=self,
                position__gt=0,
                device_type__u_height__gt=0
            ).filter(
                Q(face=face) | Q(device_type__is_full_depth=True)
            )

            # Determine which devices the user has permission to view
            permitted_device_ids = []
            if user is not None:
                permitted_device_ids = self.devices.restrict(user, 'view').values_list('pk', flat=True)

            for device in queryset:
                if expand_devices:
                    for u in range(device.position, device.position + device.device_type.u_height):
                        if user is None or device.pk in permitted_device_ids:
                            elevation[u]['device'] = device
                        elevation[u]['occupied'] = True
                else:
                    if user is None or device.pk in permitted_device_ids:
                        elevation[device.position]['device'] = device
                    elevation[device.position]['occupied'] = True
                    elevation[device.position]['height'] = device.device_type.u_height
                    for u in range(device.position + 1, device.position + device.device_type.u_height):
                        elevation.pop(u, None)

        return [u for u in elevation.values()]

    def get_available_units(self, u_height=1, rack_face=None, exclude=None):
        """
        Return a list of units within the rack available to accommodate a device of a given U height (default 1).
        Optionally exclude one or more devices when calculating empty units (needed when moving a device from one
        position to another within a rack).

        :param u_height: Minimum number of contiguous free units required
        :param rack_face: The face of the rack (front or rear) required; 'None' if device is full depth
        :param exclude: List of devices IDs to exclude (useful when moving a device within a rack)
        """
        # Gather all devices which consume U space within the rack
        devices = self.devices.prefetch_related('device_type').filter(position__gte=1)
        if exclude is not None:
            devices = devices.exclude(pk__in=exclude)

        # Initialize the rack unit skeleton
        units = list(range(1, self.u_height + 1))

        # Remove units consumed by installed devices
        for d in devices:
            if rack_face is None or d.face == rack_face or d.device_type.is_full_depth:
                for u in range(d.position, d.position + d.device_type.u_height):
                    try:
                        units.remove(u)
                    except ValueError:
                        # Found overlapping devices in the rack!
                        pass

        # Remove units without enough space above them to accommodate a device of the specified height
        available_units = []
        for u in units:
            if set(range(u, u + u_height)).issubset(units):
                available_units.append(u)

        return list(reversed(available_units))

    def get_reserved_units(self):
        """
        Return a dictionary mapping all reserved units within the rack to their reservation.
        """
        reserved_units = {}
        for r in self.reservations.all():
            for u in r.units:
                reserved_units[u] = r
        return reserved_units

    def get_elevation_svg(
            self,
            face=DeviceFaceChoices.FACE_FRONT,
            user=None,
            unit_width=settings.RACK_ELEVATION_DEFAULT_UNIT_WIDTH,
            unit_height=settings.RACK_ELEVATION_DEFAULT_UNIT_HEIGHT,
            legend_width=RACK_ELEVATION_LEGEND_WIDTH_DEFAULT,
            include_images=True,
            base_url=None
    ):
        """
        Return an SVG of the rack elevation

        :param face: Enum of [front, rear] representing the desired side of the rack elevation to render
        :param user: User instance to be used for evaluating device view permissions. If None, all devices
            will be included.
        :param unit_width: Width in pixels for the rendered drawing
        :param unit_height: Height of each rack unit for the rendered drawing. Note this is not the total
            height of the elevation
        :param legend_width: Width of the unit legend, in pixels
        :param include_images: Embed front/rear device images where available
        :param base_url: Base URL for links and images. If none, URLs will be relative.
        """
        elevation = RackElevationSVG(self, user=user, include_images=include_images, base_url=base_url)

        return elevation.render(face, unit_width, unit_height, legend_width)

    def get_0u_devices(self):
        return self.devices.filter(position=0)

    def get_utilization(self):
        """
        Determine the utilization rate of the rack and return it as a percentage. Occupied and reserved units both count
        as utilized.
        """
        # Determine unoccupied units
        available_units = self.get_available_units()

        # Remove reserved units
        for u in self.get_reserved_units():
            if u in available_units:
                available_units.remove(u)

        occupied_unit_count = self.u_height - len(available_units)
        percentage = int(float(occupied_unit_count) / self.u_height * 100)

        return percentage

    def get_power_utilization(self):
        """
        Determine the utilization rate of power in the rack and return it as a percentage.
        """
        power_stats = PowerFeed.objects.filter(
            rack=self
        ).annotate(
            allocated_draw_total=Sum('connected_endpoint__poweroutlets__connected_endpoint__allocated_draw'),
        ).values(
            'allocated_draw_total',
            'available_power'
        )

        if power_stats:
            allocated_draw_total = sum(x['allocated_draw_total'] or 0 for x in power_stats)
            available_power_total = sum(x['available_power'] for x in power_stats)
            return int(allocated_draw_total / available_power_total * 100) or 0
        return 0


@extras_features('custom_links', 'export_templates', 'webhooks')
class RackReservation(ChangeLoggedModel):
    """
    One or more reserved units within a Rack.
    """
    rack = models.ForeignKey(
        to='dcim.Rack',
        on_delete=models.CASCADE,
        related_name='reservations'
    )
    units = ArrayField(
        base_field=models.PositiveSmallIntegerField()
    )
    tenant = models.ForeignKey(
        to='tenancy.Tenant',
        on_delete=models.PROTECT,
        related_name='rackreservations',
        blank=True,
        null=True
    )
    user = models.ForeignKey(
        to=User,
        on_delete=models.PROTECT
    )
    description = models.CharField(
        max_length=200
    )
    tags = TaggableManager(through=TaggedItem)

    objects = RestrictedQuerySet.as_manager()

    csv_headers = ['site', 'rack_group', 'rack', 'units', 'tenant', 'user', 'description']

    class Meta:
        ordering = ['created', 'pk']

    def __str__(self):
        return "Reservation for rack {}".format(self.rack)

    def get_absolute_url(self):
        return reverse('dcim:rackreservation', args=[self.pk])

    def clean(self):

        if hasattr(self, 'rack') and self.units:

            # Validate that all specified units exist in the Rack.
            invalid_units = [u for u in self.units if u not in self.rack.units]
            if invalid_units:
                raise ValidationError({
                    'units': "Invalid unit(s) for {}U rack: {}".format(
                        self.rack.u_height,
                        ', '.join([str(u) for u in invalid_units]),
                    ),
                })

            # Check that none of the units has already been reserved for this Rack.
            reserved_units = []
            for resv in self.rack.reservations.exclude(pk=self.pk):
                reserved_units += resv.units
            conflicting_units = [u for u in self.units if u in reserved_units]
            if conflicting_units:
                raise ValidationError({
                    'units': 'The following units have already been reserved: {}'.format(
                        ', '.join([str(u) for u in conflicting_units]),
                    )
                })

    def to_csv(self):
        return (
            self.rack.site.name,
            self.rack.group if self.rack.group else None,
            self.rack.name,
            ','.join([str(u) for u in self.units]),
            self.tenant.name if self.tenant else None,
            self.user.username,
            self.description
        )

    @property
    def unit_list(self):
        """
        Express the assigned units as a string of summarized ranges. For example:
            [0, 1, 2, 10, 14, 15, 16] => "0-2, 10, 14-16"
        """
        group = (list(x) for _, x in groupby(sorted(self.units), lambda x, c=count(): next(c) - x))
        return ', '.join('-'.join(map(str, (g[0], g[-1])[:len(g)])) for g in group)
