import json
from decimal import Decimal, InvalidOperation

from django.contrib import messages
from django.conf import settings
from django.core.exceptions import ValidationError
from django.db import transaction
from django.db.models import Count
from django.http import HttpResponseForbidden, JsonResponse
from django.shortcuts import get_object_or_404, redirect, render
from django.urls import reverse
from django.utils.translation import gettext as _
from django.views.generic import View

from dcim.models import Rack
from netbox.views import generic
from utilities.views import ObjectPermissionRequiredMixin, ViewTab, register_model_view

from . import deploy, filtersets, forms, tables
from .elevation import get_elevations
from .models import ConceptDevice, RackConcept

__all__ = (
    'ConceptDeviceView',
    'MergeConceptsView',
    'MergeRacksToConceptView',
    'RackConceptView',
)


#
# Rack concepts
#

@register_model_view(RackConcept, 'list', path='', detail=False)
class RackConceptListView(generic.ObjectListView):
    queryset = RackConcept.objects.annotate(
        device_count=Count('devices')
    ).select_related('tenant', 'tenant_group', 'rack_type')
    table = tables.RackConceptTable
    filterset = filtersets.RackConceptFilterSet
    filterset_form = forms.RackConceptFilterForm


@register_model_view(RackConcept)
class RackConceptView(generic.ObjectView):
    queryset = RackConcept.objects.select_related('tenant', 'tenant_group', 'rack_type', 'source_rack')
    template_name = 'netbox_rack_concept/rackconcept.html'

    def get_extra_context(self, request, instance):
        front, rear = get_elevations(instance)
        deployments = tables.ConceptDeploymentTable(
            instance.deployments.select_related('rack', 'user')
        )
        return {
            'front_elevation': front,
            'rear_elevation': rear,
            'deployments_table': deployments,
        }


@register_model_view(RackConcept, 'devices')
class RackConceptDevicesView(generic.ObjectChildrenView):
    queryset = RackConcept.objects.all()
    child_model = ConceptDevice
    table = tables.ConceptDeviceElevationTable
    filterset = filtersets.ConceptDeviceFilterSet
    template_name = 'netbox_rack_concept/rackconcept_devices.html'
    tab = ViewTab(
        label=_('Devices'),
        badge=lambda obj: obj.devices.count(),
        permission='netbox_rack_concept.view_conceptdevice',
        weight=500
    )

    def get_children(self, request, parent):
        return parent.devices.select_related('device_type', 'device_type__manufacturer', 'role', 'platform', 'tenant')


@register_model_view(RackConcept, 'add', detail=False)
@register_model_view(RackConcept, 'edit')
class RackConceptEditView(generic.ObjectEditView):
    queryset = RackConcept.objects.all()
    form = forms.RackConceptForm

    def alter_object(self, obj, request, url_args, url_kwargs):
        if not obj.pk:
            config = settings.PLUGINS_CONFIG.get('netbox_rack_concept', {})
            obj.u_height = config.get('default_u_height', 42)
            obj.width = config.get('default_width', 19)
        return obj


@register_model_view(RackConcept, 'delete')
class RackConceptDeleteView(generic.ObjectDeleteView):
    queryset = RackConcept.objects.all()


@register_model_view(RackConcept, 'bulk_import', path='import', detail=False)
class RackConceptBulkImportView(generic.BulkImportView):
    queryset = RackConcept.objects.all()
    model_form = forms.RackConceptImportForm


@register_model_view(RackConcept, 'bulk_edit', path='edit', detail=False)
class RackConceptBulkEditView(generic.BulkEditView):
    queryset = RackConcept.objects.annotate(device_count=Count('devices'))
    filterset = filtersets.RackConceptFilterSet
    table = tables.RackConceptTable
    form = forms.RackConceptBulkEditForm


@register_model_view(RackConcept, 'bulk_delete', path='delete', detail=False)
class RackConceptBulkDeleteView(generic.BulkDeleteView):
    queryset = RackConcept.objects.annotate(device_count=Count('devices'))
    filterset = filtersets.RackConceptFilterSet
    table = tables.RackConceptTable


#
# Concept devices
#

@register_model_view(ConceptDevice, 'list', path='', detail=False)
class ConceptDeviceListView(generic.ObjectListView):
    queryset = ConceptDevice.objects.select_related(
        'concept', 'device_type', 'device_type__manufacturer', 'role', 'platform', 'tenant'
    )
    table = tables.ConceptDeviceTable
    filterset = filtersets.ConceptDeviceFilterSet
    filterset_form = forms.ConceptDeviceFilterForm


@register_model_view(ConceptDevice)
class ConceptDeviceView(generic.ObjectView):
    queryset = ConceptDevice.objects.select_related(
        'concept', 'device_type', 'device_type__manufacturer', 'role', 'platform', 'tenant', 'source_device'
    )
    template_name = 'netbox_rack_concept/conceptdevice.html'


@register_model_view(ConceptDevice, 'add', detail=False)
@register_model_view(ConceptDevice, 'edit')
class ConceptDeviceEditView(generic.ObjectEditView):
    queryset = ConceptDevice.objects.all()
    form = forms.ConceptDeviceForm


@register_model_view(ConceptDevice, 'delete')
class ConceptDeviceDeleteView(generic.ObjectDeleteView):
    queryset = ConceptDevice.objects.all()


@register_model_view(ConceptDevice, 'bulk_import', path='import', detail=False)
class ConceptDeviceBulkImportView(generic.BulkImportView):
    queryset = ConceptDevice.objects.all()
    model_form = forms.ConceptDeviceImportForm


@register_model_view(ConceptDevice, 'bulk_edit', path='edit', detail=False)
class ConceptDeviceBulkEditView(generic.BulkEditView):
    queryset = ConceptDevice.objects.select_related('concept', 'device_type', 'role')
    filterset = filtersets.ConceptDeviceFilterSet
    table = tables.ConceptDeviceTable
    form = forms.ConceptDeviceBulkEditForm


@register_model_view(ConceptDevice, 'bulk_delete', path='delete', detail=False)
class ConceptDeviceBulkDeleteView(generic.BulkDeleteView):
    queryset = ConceptDevice.objects.select_related('concept', 'device_type', 'role')
    filterset = filtersets.ConceptDeviceFilterSet
    table = tables.ConceptDeviceTable


#
# Actions: copy, clone, deploy, reorder
#

class RackCopyView(ObjectPermissionRequiredMixin, View):
    """Copy a real rack into a new concept. Reached from the rack detail page."""
    queryset = RackConcept.objects.all()

    def get_required_permission(self):
        return 'netbox_rack_concept.add_rackconcept'

    def get(self, request, pk):
        rack = get_object_or_404(Rack.objects.restrict(request.user, 'view'), pk=pk)
        form = forms.RackCopyForm(initial={
            'name': _('%(rack)s (concept)') % {'rack': rack.name},
            'tenant': rack.tenant_id,
            'tenant_group': rack.tenant.group_id if rack.tenant else None,
        })
        return render(request, 'netbox_rack_concept/rack_copy.html', {
            'rack': rack,
            'form': form,
            'device_count': rack.devices.filter(position__isnull=False).count(),
            'return_url': rack.get_absolute_url(),
        })

    def post(self, request, pk):
        rack = get_object_or_404(Rack.objects.restrict(request.user, 'view'), pk=pk)
        form = forms.RackCopyForm(request.POST)

        if form.is_valid():
            try:
                concept, warnings = deploy.copy_rack_to_concept(
                    rack=rack,
                    name=form.cleaned_data['name'],
                    status=form.cleaned_data['status'],
                    tenant=form.cleaned_data['tenant'],
                    tenant_group=form.cleaned_data['tenant_group'],
                    description=form.cleaned_data['description'],
                    include_devices=form.cleaned_data['include_devices'],
                    include_device_names=form.cleaned_data['include_device_names'],
                    override_width=form.cleaned_data['override_width'],
                    override_u_height=form.cleaned_data['override_u_height'],
                    override_starting_unit=form.cleaned_data['override_starting_unit'],
                )
            except ValidationError as exc:
                form.add_error(None, exc)
            else:
                for warning in warnings:
                    messages.warning(request, warning)
                messages.success(request, _('Created concept %(concept)s from rack %(rack)s.') % {
                    'concept': concept, 'rack': rack
                })
                return redirect(concept.get_absolute_url())

        return render(request, 'netbox_rack_concept/rack_copy.html', {
            'rack': rack,
            'form': form,
            'device_count': rack.devices.filter(position__isnull=False).count(),
            'return_url': rack.get_absolute_url(),
        })


class MergeConceptsView(ObjectPermissionRequiredMixin, View):
    """Stack two blueprints (e.g. two half-height racks) into one taller concept."""
    queryset = RackConcept.objects.all()

    def get_required_permission(self):
        return 'netbox_rack_concept.add_rackconcept'

    def get(self, request):
        form = forms.MergeConceptsForm(initial={
            'concept_bottom': request.GET.get('concept_bottom'),
            'concept_top': request.GET.get('concept_top'),
        })
        return render(request, 'netbox_rack_concept/concept_merge.html', {
            'form': form,
            'return_url': reverse('plugins:netbox_rack_concept:rackconcept_list'),
        })

    def post(self, request):
        form = forms.MergeConceptsForm(request.POST)

        if form.is_valid():
            try:
                merged, warnings = deploy.merge_concepts(
                    concept_bottom=form.cleaned_data['concept_bottom'],
                    concept_top=form.cleaned_data['concept_top'],
                    name=form.cleaned_data['name'],
                    status=form.cleaned_data['status'],
                    tenant=form.cleaned_data['tenant'],
                    tenant_group=form.cleaned_data['tenant_group'],
                    width=form.cleaned_data['width'],
                    u_height=form.cleaned_data['u_height'],
                    starting_unit=form.cleaned_data['starting_unit'],
                    description=form.cleaned_data['description'],
                )
            except ValidationError as exc:
                form.add_error(None, exc)
            else:
                for warning in warnings:
                    messages.warning(request, warning)
                messages.success(request, _('Created %(merged)s by merging %(bottom)s and %(top)s.') % {
                    'merged': merged,
                    'bottom': form.cleaned_data['concept_bottom'],
                    'top': form.cleaned_data['concept_top'],
                })
                return redirect(merged.get_absolute_url())

        return render(request, 'netbox_rack_concept/concept_merge.html', {
            'form': form,
            'return_url': reverse('plugins:netbox_rack_concept:rackconcept_list'),
        })


class MergeRacksToConceptView(ObjectPermissionRequiredMixin, View):
    """Combine two real racks directly into one new, stacked blueprint."""
    queryset = RackConcept.objects.all()

    def get_required_permission(self):
        return 'netbox_rack_concept.add_rackconcept'

    def get(self, request):
        form = forms.MergeRacksForm(initial={
            'rack_bottom': request.GET.get('rack_bottom'),
            'rack_top': request.GET.get('rack_top'),
        })
        return render(request, 'netbox_rack_concept/racks_merge.html', {
            'form': form,
            'return_url': reverse('dcim:rack_list'),
        })

    def post(self, request):
        form = forms.MergeRacksForm(request.POST)

        if form.is_valid():
            try:
                concept, warnings = deploy.merge_racks_to_concept(
                    rack_bottom=form.cleaned_data['rack_bottom'],
                    rack_top=form.cleaned_data['rack_top'],
                    name=form.cleaned_data['name'],
                    status=form.cleaned_data['status'],
                    tenant=form.cleaned_data['tenant'],
                    tenant_group=form.cleaned_data['tenant_group'],
                    include_devices=form.cleaned_data['include_devices'],
                    include_device_names=form.cleaned_data['include_device_names'],
                    width=form.cleaned_data['width'],
                    u_height=form.cleaned_data['u_height'],
                    starting_unit=form.cleaned_data['starting_unit'],
                    description=form.cleaned_data['description'],
                )
            except ValidationError as exc:
                form.add_error(None, exc)
            else:
                for warning in warnings:
                    messages.warning(request, warning)
                messages.success(request, _('Created concept %(concept)s from %(bottom)s and %(top)s.') % {
                    'concept': concept,
                    'bottom': form.cleaned_data['rack_bottom'],
                    'top': form.cleaned_data['rack_top'],
                })
                return redirect(concept.get_absolute_url())

        return render(request, 'netbox_rack_concept/racks_merge.html', {
            'form': form,
            'return_url': reverse('dcim:rack_list'),
        })


@register_model_view(RackConcept, 'clone_concept', path='clone')
class RackConceptCloneView(ObjectPermissionRequiredMixin, View):
    """Duplicate a concept to build a variant."""
    queryset = RackConcept.objects.all()

    def get_required_permission(self):
        return 'netbox_rack_concept.add_rackconcept'

    def get(self, request, pk):
        concept = get_object_or_404(self.queryset.restrict(request.user, 'view'), pk=pk)
        form = forms.RackConceptCloneForm(initial={
            'name': _('%(name)s (copy)') % {'name': concept.name},
            'tenant': concept.tenant_id,
        })
        return render(request, 'netbox_rack_concept/concept_clone.html', {
            'object': concept,
            'form': form,
            'return_url': concept.get_absolute_url(),
        })

    def post(self, request, pk):
        concept = get_object_or_404(self.queryset.restrict(request.user, 'view'), pk=pk)
        form = forms.RackConceptCloneForm(request.POST)

        if form.is_valid():
            try:
                clone = deploy.clone_concept(
                    concept=concept,
                    name=form.cleaned_data['name'],
                    status=form.cleaned_data['status'],
                    tenant=form.cleaned_data['tenant'],
                    include_devices=form.cleaned_data['include_devices'],
                )
            except ValidationError as exc:
                form.add_error(None, exc)
            else:
                messages.success(request, _('Cloned %(source)s into %(clone)s.') % {
                    'source': concept, 'clone': clone
                })
                return redirect(clone.get_absolute_url())

        return render(request, 'netbox_rack_concept/concept_clone.html', {
            'object': concept,
            'form': form,
            'return_url': concept.get_absolute_url(),
        })


@register_model_view(RackConcept, 'deploy')
class RackConceptDeployView(ObjectPermissionRequiredMixin, View):
    """Materialise a concept as one or more real racks."""
    queryset = RackConcept.objects.all()

    def get_required_permission(self):
        # The mixin restricts against this view's queryset, so it has to be a concept
        # permission. The permission to create racks is checked separately below.
        return 'netbox_rack_concept.view_rackconcept'

    def _context(self, request, concept, form):
        # An unchecked checkbox is simply absent from the POST data.
        create_devices = 'create_devices' in form.data if form.is_bound else True
        deployable, warnings = deploy.validate_deployment(concept, create_devices=create_devices)
        return {
            'object': concept,
            'form': form,
            'deployable_count': len(deployable),
            'warnings': warnings,
            'return_url': concept.get_absolute_url(),
        }

    def get(self, request, pk):
        concept = get_object_or_404(self.queryset.restrict(request.user, 'view'), pk=pk)
        form = forms.ConceptDeployForm(concept=concept)
        return render(request, 'netbox_rack_concept/concept_deploy.html', self._context(request, concept, form))

    def post(self, request, pk):
        concept = get_object_or_404(self.queryset.restrict(request.user, 'view'), pk=pk)
        form = forms.ConceptDeployForm(request.POST, concept=concept)

        if not request.user.has_perm('dcim.add_rack'):
            return HttpResponseForbidden(_('You do not have permission to create racks.'))

        if form.is_valid():
            try:
                racks, devices, warnings = deploy.deploy_concept(
                    concept=concept,
                    rack_names=form.cleaned_data['rack_names'],
                    site=form.cleaned_data['site'],
                    location=form.cleaned_data['location'],
                    tenant=form.cleaned_data['tenant'],
                    create_devices=form.cleaned_data['create_devices'],
                    device_name_pattern=form.cleaned_data['device_name_pattern'],
                    skip_unnamed_devices=form.cleaned_data['skip_unnamed_devices'],
                    user=request.user,
                )
            except ValidationError as exc:
                # Nothing was written: deploy_concept runs in a transaction.
                messages.error(request, _('Deployment failed, nothing was created.'))
                form.add_error(None, exc)
            else:
                for warning in warnings:
                    messages.warning(request, warning)
                messages.success(request, _('Created %(racks)s rack(s) and %(devices)s device(s).') % {
                    'racks': len(racks), 'devices': len(devices)
                })
                if len(racks) == 1:
                    return redirect(racks[0].get_absolute_url())
                return redirect(
                    reverse('dcim:rack_list') + f'?site_id={form.cleaned_data["site"].pk}'
                )

        return render(request, 'netbox_rack_concept/concept_deploy.html', self._context(request, concept, form))


@register_model_view(RackConcept, 'reorder')
class RackConceptReorderView(ObjectPermissionRequiredMixin, View):
    """
    Endpoint for the drag & drop elevation. Accepts a JSON body of the shape
    {"devices": [{"id": 1, "position": "12.0", "face": "front", "horizontal_position": 0}]}
    and applies all moves in one transaction so a rejected move leaves nothing half-applied.
    """
    queryset = RackConcept.objects.all()
    http_method_names = ['post']

    def get_required_permission(self):
        return 'netbox_rack_concept.change_conceptdevice'

    def post(self, request, pk):
        concept = get_object_or_404(self.queryset.restrict(request.user, 'view'), pk=pk)

        try:
            payload = json.loads(request.body or '{}')
            moves = payload['devices']
        except (json.JSONDecodeError, KeyError, TypeError):
            return JsonResponse({'error': _('Malformed request body.')}, status=400)

        by_pk = {d.pk: d for d in concept.devices.select_related('device_type')}
        updated = []

        try:
            with transaction.atomic():
                for move in moves:
                    device = by_pk.get(int(move['id']))
                    if device is None:
                        raise ValidationError(_('Device %(id)s does not belong to this concept.') % {'id': move['id']})
                    try:
                        device.position = Decimal(str(move['position'])) if move.get('position') is not None else None
                    except InvalidOperation:
                        raise ValidationError(_('Invalid position %(position)r.') % {'position': move.get('position')})
                    if 'face' in move:
                        device.face = move['face']
                    if 'horizontal_position' in move:
                        device.horizontal_position = int(move['horizontal_position'])
                    if 'width_fraction' in move:
                        device.width_fraction = int(move['width_fraction'])
                    updated.append(device)

                # Validate only after every move is staged, so swapping two devices works.
                for device in updated:
                    device.save()
                for device in updated:
                    device.full_clean()
        except ValidationError as exc:
            return JsonResponse({'error': ' '.join(exc.messages)}, status=400)

        return JsonResponse({'status': 'ok', 'updated': len(updated)})