workflow.py

from django.db import models
from django.db.transaction import atomic
from django.urls import reverse

from tasks.models.queue import Queue
from tasks.models.queue import QueueItem
from tasks.models.task import Task
from tasks.models.task import TaskBase

# ----------------------
# - Workflows and tasks.
# ----------------------


class TaskWorkflow(Queue):
    """Workflow of ordered Tasks."""

    summary_task = models.OneToOneField(
        Task,
        on_delete=models.PROTECT,
    )
    """Provides task-like filtering and display capabilities for this
    workflow."""
    creator_template = models.ForeignKey(
        "tasks.TaskWorkflowTemplate",
        null=True,
        on_delete=models.SET_NULL,
    )
    """The template from which this workflow was created, if any."""

    def get_tasks(self) -> models.QuerySet:
        """Get a QuerySet of the Tasks associated through their TaskItem
        instances to this TaskWorkflow, ordered by the position of the
        TaskItem."""
        return Task.objects.filter(taskitem__queue=self).order_by("taskitem__position")

    def __str__(self):
        return self.title


class TaskItem(QueueItem):
    """Task item queue management for Task instances (these should always be
    subtasks)."""

    queue = models.ForeignKey(
        TaskWorkflow,
        related_name="queue_items",
        on_delete=models.CASCADE,
    )
    task = models.OneToOneField(
        "tasks.Task",
        on_delete=models.CASCADE,
    )
    """The Task instance managed by this TaskItem."""


# ----------------------------------------
# - Template workflows and template tasks.
# ----------------------------------------


class TaskWorkflowTemplate(Queue):
    """Template used to create TaskWorkflow instance."""

    title = models.CharField(
        max_length=255,
    )
    """
    A title name for the instance.

    This isn't the same as the title assigned to a TaskWorkflow instance
    generated from a template.
    """
    description = models.TextField(
        blank=True,
        help_text="Description of what this workflow template is used for. ",
    )
    """
    Description of what the instance is used for.

    This isn't the same as the description that may be applied to a TaskWorkflow
    instance generated from a template.
    """

    def get_task_templates(self) -> models.QuerySet:
        """Get a QuerySet of the TaskTemplates associated through their
        TaskItemTemplate instances to this TaskWorkflowTemplate, ordered by the
        position of the TaskItemTemplate."""
        return TaskTemplate.objects.filter(taskitemtemplate__queue=self).order_by(
            "taskitemtemplate__position",
        )

    @atomic
    def create_task_workflow(self, title: str, description: str) -> "TaskWorkflow":
        """Create a workflow and it subtasks, using values from this template
        workflow and its task templates."""

        summary_task = Task.objects.create(title=title, description=description)
        task_workflow = TaskWorkflow.objects.create(
            summary_task=summary_task,
            creator_template=self,
        )

        task_item_templates = TaskItemTemplate.objects.select_related(
            "task_template",
        ).filter(queue=self)
        for task_item_template in task_item_templates:
            task_template = task_item_template.task_template
            task = Task.objects.create(
                title=task_template.title,
                description=task_template.description,
                category=task_template.category,
            )
            TaskItem.objects.create(
                position=task_item_template.position,
                queue=task_workflow,
                task=task,
            )

        return task_workflow

    def get_url(self, action: str = "detail"):
        if action == "detail":
            return reverse(
                "workflow:task-workflow-template-ui-detail",
                kwargs={"pk": self.pk},
            )
        elif action == "edit":
            return reverse(
                "workflow:task-workflow-template-ui-update",
                kwargs={"pk": self.pk},
            )
        elif action == "delete":
            return reverse(
                "workflow:task-workflow-template-ui-delete",
                kwargs={"pk": self.pk},
            )

        return "#NOT-IMPLEMENTED"


class TaskItemTemplate(QueueItem):
    """Queue item management for TaskTemplate instances."""

    queue = models.ForeignKey(
        TaskWorkflowTemplate,
        related_name="queue_items",
        on_delete=models.CASCADE,
    )
    task_template = models.OneToOneField(
        "tasks.TaskTemplate",
        on_delete=models.CASCADE,
    )


class TaskTemplate(TaskBase):
    """Template used to create Task instances from within a template
    workflow."""

    def get_url(self, action: str = "detail"):
        if action == "detail":
            return reverse("workflow:task-template-ui-detail", kwargs={"pk": self.pk})
        elif action == "edit":
            return reverse("workflow:task-template-ui-update", kwargs={"pk": self.pk})

        return "#NOT-IMPLEMENTED"

    def __str__(self):
        return self.title