from django.db import models

from evolus.models import Version


class Process(models.Model):
    process_type = models.CharField(max_length=50)
    document_version = models.ForeignKey(Version)

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        if not self.pk and not self.process_type:
            self.process_type = self.PROCESS_TYPE

    def __str__(self):
        return '{}: {}'.format(self.process_type, self.document_version)

    def create_task(self, assigned_to):
        task, created = Task.objects.get_or_create(status=1, assigned_to=assigned_to, process=self)

        if created:
            task.save()

    def allow_tasks_delegation(self):
        return True

    def save(self):
        raise NotImplemented('is_valid has to be implemented on the subprocess')


TASK_STATUS = (
    (1, 'Created'),
    (3, 'Completed')
)


class Task(models.Model):
    assigned_to = models.EmailField()
    process = models.ForeignKey(Process)
    status = models.IntegerField(choices=TASK_STATUS)

    def __str__(self):
        return '{} - {}'.format(self.process, self.assigned_to)


class PublishedProcessMixin(object):
    def save(self, *args, **kwargs):
        if self.document_version.status == 'Draft':
            raise TypeError('Review flow cant apply to draft documents')
        return super().save(*args, **kwargs)


class DraftProcessMixin(object):
    def save(self, *args, **kwargs):
        if self.document_version.status == 'Published':
            raise TypeError('Review flow cant apply to published documents')
        return super().save(*args, **kwargs)


class Review(Process, PublishedProcessMixin):
    PROCESS_TYPE = 'Review'

    def __str__(self):
        return 'Review: {}'.format(self.document_version)


class Approval(Process, DraftProcessMixin):
    PROCESS_TYPE = 'Approval'


class GatherComments(Process, DraftProcessMixin):
    PROCESS_TYPE = 'GatherComments'


class Knowledge(Process, PublishedProcessMixin):
    PROCESS_TYPE = 'Knowledge'

    def allow_tasks_delegation(self):
        return False