Add control code preview generation

Signed-off-by: Roberto Rosario <roberto.rosario@mayan-edms.com>

mayan/apps/control_codes/models.py

@@ -0,0 +1,154 @@
+from __future__ import unicode_literals
+
+import hashlib
+import json
+import logging
+
+from furl import furl
+
+from django.apps import apps
+from django.conf import settings
+from django.contrib.contenttypes.fields import GenericForeignKey
+from django.contrib.contenttypes.models import ContentType
+from django.core import serializers
+from django.db import models
+from django.db.models import Max
+from django.urls import reverse
+from django.utils.encoding import (
+    force_bytes, force_text, python_2_unicode_compatible
+)
+from django.utils.functional import cached_property
+from django.utils.translation import ugettext_lazy as _
+
+from mayan.apps.common.serialization import yaml_load
+from mayan.apps.common.validators import YAMLValidator
+
+from .classes import ControlCode
+from .literals import CONTROL_SHEET_CODE_IMAGE_CACHE_NAME
+
+logger = logging.getLogger(__name__)
+
+
+@python_2_unicode_compatible
+class ControlSheet(models.Model):
+    label = models.CharField(
+        max_length=196, unique=True, verbose_name=_('Label')
+    )
+
+    def __str__(self):
+        return self.label
+
+    def get_absolute_url(self):
+        return reverse(
+            viewname='control_codes:control_sheet_detail', kwargs={
+                'control_sheet_id': self.pk
+            }
+        )
+
+    class Meta:
+        ordering = ('label',)
+        verbose_name = _('Control sheet')
+        verbose_name_plural = _('Control sheets')
+
+
+class ControlSheetCode(models.Model):
+    control_sheet = models.ForeignKey(
+        on_delete=models.CASCADE, related_name='codes', to=ControlSheet,
+        verbose_name=_('Control sheet')
+    )
+    order = models.PositiveIntegerField(
+        blank=True, db_index=True, default=0, help_text=_(
+            'Order in which the transformations will be executed. If left '
+            'unchanged, an automatic order value will be assigned.'
+        ), verbose_name=_('Order')
+    )
+    name = models.CharField(
+        choices=ControlCode.get_choices(),
+        max_length=128, verbose_name=_('Name')
+    )
+    arguments = models.TextField(
+        blank=True, help_text=_(
+            'Enter the arguments for the control code as a YAML '
+            'dictionary.'
+        ), validators=[YAMLValidator()], verbose_name=_('Arguments')
+    )
+    enabled = models.BooleanField(default=True, verbose_name=_('Enabled'))
+
+    class Meta:
+        verbose_name = _('Control sheet code')
+        verbose_name_plural = _('Control sheet codes')
+
+    @cached_property
+    def cache(self):
+        Cache = apps.get_model(app_label='file_caching', model_name='Cache')
+        return Cache.objects.get(name=CONTROL_SHEET_CODE_IMAGE_CACHE_NAME)
+
+    @cached_property
+    def cache_partition(self):
+        partition, created = self.cache.partitions.get_or_create(
+            name='{}'.format(self.pk)
+        )
+        return partition
+
+    def delete(self, *args, **kwargs):
+        self.cache_partition.delete()
+        return super(Workflow, self).delete(*args, **kwargs)
+
+    def generate_image(self):
+        cache_filename = '{}'.format(self.get_hash())
+
+        if self.cache_partition.get_file(filename=cache_filename):
+            logger.debug(
+                'workflow cache file "%s" found', cache_filename
+            )
+        else:
+            logger.debug(
+                'workflow cache file "%s" not found', cache_filename
+            )
+
+            image = self.render()
+            with self.cache_partition.create_file(filename=cache_filename) as file_object:
+                #file_object.write(image)
+                image.save(file_object)
+
+        return cache_filename
+
+    def get_api_image_url(self, *args, **kwargs):
+        final_url = furl()
+        final_url.args = kwargs
+        final_url.path = reverse(
+            viewname='rest_api:workflow-image',
+            kwargs={'pk': self.pk}
+        )
+        final_url.args['_hash'] = self.get_hash()
+
+        return final_url.tostr()
+
+    def get_arguments(self):
+        return yaml_load(self.arguments or '{}')
+
+    def get_control_code_class(self):
+        return ControlCode.get(name=self.name)
+
+    def get_hash(self):
+        objects_lists = list(
+            ControlSheetCode.objects.filter(pk=self.pk)
+        )
+
+        return hashlib.sha256(
+            force_bytes(
+                serializers.serialize('json', objects_lists)
+            )
+        ).hexdigest()
+
+    def render(self):
+        return self.get_control_code_class()(**self.get_arguments()).image
+
+    def save(self, *args, **kwargs):
+        if not self.order:
+            last_order = ControlSheetCode.objects.filter(
+                control_sheet=self.control_sheet
+            ).aggregate(Max('order'))['order__max']
+            if last_order is not None:
+                self.order = last_order + 1
+        super(ControlSheetCode, self).save(*args, **kwargs)