Workflow Model Helper for Django

models.py

from django.db import models

from .workflow import Workflow, StateField


class SaleOrder(Workflow, models.Model):

    DRAFT = 'draft'
    QUOTATION = 'quotation'
    CONFIRMED = 'confirmed'
    PROCESSING = 'processing'
    CANCEL = 'cancel'
    DONE = 'done'

    ORDER_STATES = (
        (DRAFT, 'Draft'),
        (QUOTATION, 'Quotation'),
        (CONFIRMED, 'Confirmed'),
        (PROCESSING, 'Processing'),
        (CANCEL, 'Cancel'),
        (DONE, 'Done')
    )

    state = StateField(choices=ORDER_STATES, default=DRAFT)

    _transitions = (
        ((DRAFT, QUOTATION), 'Send Quotation'),
        ((QUOTATION, CONFIRMED), 'Confirm Sale'),
        ((CONFIRMED, PROCESSING), 'Process'),
        ((PROCESSING, PROCESSING), 'Process'),  # To Force an update
        ((PROCESSING, DONE), 'Sale'),
        ((DONE, PROCESSING), 'Update'),
        ((DRAFT, CANCEL), 'Cancel'),
        ((QUOTATION, CANCEL), 'Canel'),
        ((QUOTATION, DRAFT), 'Revert as Draft'),
        ((CANCEL, DRAFT), 'Cancel')
    )

    @Workflow.transition(CANCEL)
    def cancel(self, context):
        pass

    @Workflow.transition(DRAFT)
    def draft(self, context):
        pass

    @Workflow.transition(QUOTATION)
    def quote(self, context):
        pass

    @Workflow.transition(CONFIRMED)
    def confirm(self, context):
        pass

    @Workflow.transition(PROCESSING)
    def proceed(self, context):
        pass

    @Workflow.transition(DONE)
    def do(self, context):
        pass

workflow.py

from django.db.models import CharField
from functools import wraps


class Workflow:
    _state_field_name = 'state'
    _transitions = None

    @staticmethod
    def transition(state):
        """Decorador para transicion"""

        def check_transition(func):
            @wraps(func)
            def wrapper(self, context=None, *args, **kwargs):
                current_state = self.get_current_state()

                # actionable transition
                transition = (current_state, state)

                if self._transitions:

                    # If the transition is declared we will apply
                    for transition, label in self._transitions:
                        if transition in self._transitions:
                            return func(self, context)

            return wrapper

        return check_transition

    def get_current_state(self):
        return getattr(self, self._state_field_name)

    def get_available_transitions(self):
        current_state = self.get_current_state()

        state_field = self._meta.get_field(self._state_field_name)
        current_state_label = dict(state_field.flatchoices).get(current_state, current_state)

        available_transitions = [(current_state, current_state_label)]

        for transition, label in self._transitions:
            step, next_state = transition
            if next_state not in available_transitions and step == current_state:
                available_transitions.append((next_state, label))

        return available_transitions


class StateField(CharField):
    def __init__(self, *args, **kwargs):
        kwargs['max_length'] = 20
        kwargs['db_index'] = True
        kwargs['null'] = False
        kwargs['blank'] = False
        super(CharField, self).__init__(*args, **kwargs)