# Django imports
from django.db.models import (
    Q,
    OuterRef,
    Func,
    F,
    Case,
    Value,
    CharField,
    When,
    Exists,
    Max,
)
from django.utils.decorators import method_decorator
from django.views.decorators.gzip import gzip_page
from django.contrib.postgres.aggregates import ArrayAgg
from django.contrib.postgres.fields import ArrayField
from django.db.models import UUIDField
from django.db.models.functions import Coalesce

# Third party imports
from rest_framework.response import Response
from rest_framework import status

# Module imports
from .. import BaseViewSet
from plane.app.serializers import (
    IssueViewSerializer,
    IssueSerializer,
)
from plane.app.permissions import (
    WorkspaceEntityPermission,
    ProjectEntityPermission,
)
from plane.db.models import (
    Workspace,
    IssueView,
    Issue,
    UserFavorite,
    IssueLink,
    IssueAttachment,
)
from plane.utils.issue_filters import issue_filters
from plane.utils.user_timezone_converter import user_timezone_converter

class GlobalViewViewSet(BaseViewSet):
    serializer_class = IssueViewSerializer
    model = IssueView
    permission_classes = [
        WorkspaceEntityPermission,
    ]

    def perform_create(self, serializer):
        workspace = Workspace.objects.get(slug=self.kwargs.get("slug"))
        serializer.save(workspace_id=workspace.id)

    def get_queryset(self):
        return self.filter_queryset(
            super()
            .get_queryset()
            .filter(workspace__slug=self.kwargs.get("slug"))
            .filter(project__isnull=True)
            .select_related("workspace")
            .order_by(self.request.GET.get("order_by", "-created_at"))
            .distinct()
        )


class GlobalViewIssuesViewSet(BaseViewSet):
    permission_classes = [
        WorkspaceEntityPermission,
    ]

    def get_queryset(self):
        return (
            Issue.issue_objects.annotate(
                sub_issues_count=Issue.issue_objects.filter(
                    parent=OuterRef("id")
                )
                .order_by()
                .annotate(count=Func(F("id"), function="Count"))
                .values("count")
            )
            .filter(workspace__slug=self.kwargs.get("slug"))
            .filter(
                project__project_projectmember__member=self.request.user,
                project__project_projectmember__is_active=True,
            )
            .select_related("workspace", "project", "state", "parent")
            .prefetch_related("assignees", "labels", "issue_module__module")
            .annotate(cycle_id=F("issue_cycle__cycle_id"))
            .annotate(
                link_count=IssueLink.objects.filter(issue=OuterRef("id"))
                .order_by()
                .annotate(count=Func(F("id"), function="Count"))
                .values("count")
            )
            .annotate(
                attachment_count=IssueAttachment.objects.filter(
                    issue=OuterRef("id")
                )
                .order_by()
                .annotate(count=Func(F("id"), function="Count"))
                .values("count")
            )
            .annotate(
                sub_issues_count=Issue.issue_objects.filter(
                    parent=OuterRef("id")
                )
                .order_by()
                .annotate(count=Func(F("id"), function="Count"))
                .values("count")
            )
            .annotate(
                label_ids=Coalesce(
                    ArrayAgg(
                        "labels__id",
                        distinct=True,
                        filter=~Q(labels__id__isnull=True),
                    ),
                    Value([], output_field=ArrayField(UUIDField())),
                ),
                assignee_ids=Coalesce(
                    ArrayAgg(
                        "assignees__id",
                        distinct=True,
                        filter=~Q(assignees__id__isnull=True)
                        & Q(assignees__member_project__is_active=True),
                    ),
                    Value([], output_field=ArrayField(UUIDField())),
                ),
                module_ids=Coalesce(
                    ArrayAgg(
                        "issue_module__module_id",
                        distinct=True,
                        filter=~Q(issue_module__module_id__isnull=True),
                    ),
                    Value([], output_field=ArrayField(UUIDField())),
                ),
            )
        )

    @method_decorator(gzip_page)
    def list(self, request, slug):
        filters = issue_filters(request.query_params, "GET")

        # Custom ordering for priority and state
        priority_order = ["urgent", "high", "medium", "low", "none"]
        state_order = [
            "backlog",
            "unstarted",
            "started",
            "completed",
            "cancelled",
        ]

        order_by_param = request.GET.get("order_by", "-created_at")

        issue_queryset = (
            self.get_queryset()
            .filter(**filters)
            .annotate(cycle_id=F("issue_cycle__cycle_id"))
        )

        # Priority Ordering
        if order_by_param == "priority" or order_by_param == "-priority":
            priority_order = (
                priority_order
                if order_by_param == "priority"
                else priority_order[::-1]
            )
            issue_queryset = issue_queryset.annotate(
                priority_order=Case(
                    *[
                        When(priority=p, then=Value(i))
                        for i, p in enumerate(priority_order)
                    ],
                    output_field=CharField(),
                )
            ).order_by("priority_order")

        # State Ordering
        elif order_by_param in [
            "state__name",
            "state__group",
            "-state__name",
            "-state__group",
        ]:
            state_order = (
                state_order
                if order_by_param in ["state__name", "state__group"]
                else state_order[::-1]
            )
            issue_queryset = issue_queryset.annotate(
                state_order=Case(
                    *[
                        When(state__group=state_group, then=Value(i))
                        for i, state_group in enumerate(state_order)
                    ],
                    default=Value(len(state_order)),
                    output_field=CharField(),
                )
            ).order_by("state_order")
        # assignee and label ordering
        elif order_by_param in [
            "labels__name",
            "-labels__name",
            "assignees__first_name",
            "-assignees__first_name",
        ]:
            issue_queryset = issue_queryset.annotate(
                max_values=Max(
                    order_by_param[1::]
                    if order_by_param.startswith("-")
                    else order_by_param
                )
            ).order_by(
                "-max_values"
                if order_by_param.startswith("-")
                else "max_values"
            )
        else:
            issue_queryset = issue_queryset.order_by(order_by_param)

        if self.fields:
            issues = IssueSerializer(
                issue_queryset, many=True, fields=self.fields
            ).data
        else:
            issues = issue_queryset.values(
                "id",
                "name",
                "state_id",
                "sort_order",
                "completed_at",
                "estimate_point",
                "priority",
                "start_date",
                "target_date",
                "sequence_id",
                "project_id",
                "parent_id",
                "cycle_id",
                "module_ids",
                "label_ids",
                "assignee_ids",
                "sub_issues_count",
                "created_at",
                "updated_at",
                "created_by",
                "updated_by",
                "attachment_count",
                "link_count",
                "is_draft",
                "archived_at",
            )
            datetime_fields = ["created_at", "updated_at"]
            issues = user_timezone_converter(
                issues, datetime_fields, request.user.user_timezone
            )
        return Response(issues, status=status.HTTP_200_OK)


class IssueViewViewSet(BaseViewSet):
    serializer_class = IssueViewSerializer
    model = IssueView
    permission_classes = [
        ProjectEntityPermission,
    ]

    def perform_create(self, serializer):
        serializer.save(project_id=self.kwargs.get("project_id"))

    def get_queryset(self):
        subquery = UserFavorite.objects.filter(
            user=self.request.user,
            entity_identifier=OuterRef("pk"),
            entity_type="view",
            project_id=self.kwargs.get("project_id"),
            workspace__slug=self.kwargs.get("slug"),
        )
        return self.filter_queryset(
            super()
            .get_queryset()
            .filter(workspace__slug=self.kwargs.get("slug"))
            .filter(project_id=self.kwargs.get("project_id"))
            .filter(
                project__project_projectmember__member=self.request.user,
                project__project_projectmember__is_active=True,
                project__archived_at__isnull=True,
            )
            .select_related("project")
            .select_related("workspace")
            .annotate(is_favorite=Exists(subquery))
            .order_by("-is_favorite", "name")
            .distinct()
        )

    def list(self, request, slug, project_id):
        queryset = self.get_queryset()
        fields = [
            field
            for field in request.GET.get("fields", "").split(",")
            if field
        ]
        views = IssueViewSerializer(
            queryset, many=True, fields=fields if fields else None
        ).data
        return Response(views, status=status.HTTP_200_OK)


class IssueViewFavoriteViewSet(BaseViewSet):
    model = UserFavorite

    def get_queryset(self):
        return self.filter_queryset(
            super()
            .get_queryset()
            .filter(workspace__slug=self.kwargs.get("slug"))
            .filter(user=self.request.user)
            .select_related("view")
        )

    def create(self, request, slug, project_id):
        _ = UserFavorite.objects.create(
            user=request.user,
            entity_identifier=request.data.get("view"),
            entity_type="view",
            project_id=project_id,
        )
        return Response(status=status.HTTP_204_NO_CONTENT)

    def destroy(self, request, slug, project_id, view_id):
        view_favorite = UserFavorite.objects.get(
            project=project_id,
            user=request.user,
            workspace__slug=slug,
            entity_type="view",
            entity_identifier=view_id,
        )
        view_favorite.delete()
        return Response(status=status.HTTP_204_NO_CONTENT)