feat: add relationships from person to org

Resolves #77
See #78

people/models/relationship.py

@@ -2,11 +2,10 @@
 Models describing relationships between people.
 """
 
-from django.core.exceptions import ObjectDoesNotExist
 from django.db import models
 from django.urls import reverse
 
-from .person import Person
+from .person import Organisation, Person
 from .question import AnswerSet, Question, QuestionChoice
 
 __all__ = [
@@ -14,6 +13,10 @@ __all__ = [
     'RelationshipQuestionChoice',
     'RelationshipAnswerSet',
     'Relationship',
+    'OrganisationRelationshipQuestion',
+    'OrganisationRelationshipQuestionChoice',
+    'OrganisationRelationshipAnswerSet',
+    'OrganisationRelationship',
 ]
 
 
@@ -32,24 +35,10 @@ class RelationshipQuestionChoice(QuestionChoice):
                                  null=False)
 
 
-# class ExternalPerson(models.Model):
-#     """Model representing a person external to the project.
-
-#     These will never need to be linked to a :class:`User` as they
-#     will never log in to the system.
-#     """
-#     name = models.CharField(max_length=255,
-#                             blank=False, null=False)
-
-#     def __str__(self) -> str:
-#         return self.name
-
-
 class Relationship(models.Model):
     """
     A directional relationship between two people allowing linked questions.
     """
-
     class Meta:
         constraints = [
             models.UniqueConstraint(fields=['source', 'target'],
@@ -57,9 +46,11 @@ class Relationship(models.Model):
         ]
 
     #: Person reporting the relationship
-    source = models.ForeignKey(Person, related_name='relationships_as_source',
+    source = models.ForeignKey(Person,
+                               related_name='relationships_as_source',
                                on_delete=models.CASCADE,
-                               blank=False, null=False)
+                               blank=False,
+                               null=False)
 
     #: Person with whom the relationship is reported
     target = models.ForeignKey(Person,
@@ -67,15 +58,6 @@ class Relationship(models.Model):
                                on_delete=models.CASCADE,
                                blank=False,
                                null=False)
-    #   blank=True,
-    #   null=True)
-
-    # target_external_person = models.ForeignKey(
-    #     ExternalPerson,
-    #     related_name='relationships_as_target',
-    #     on_delete=models.CASCADE,
-    #     blank=True,
-    #     null=True)
 
     #: When was this relationship defined?
     created = models.DateTimeField(auto_now_add=True)
@@ -100,8 +82,7 @@ class Relationship(models.Model):
 
         @raise Relationship.DoesNotExist: When the reverse relationship is not known
         """
-        return type(self).objects.get(source=self.target,
-                                      target=self.source)
+        return type(self).objects.get(source=self.target, target=self.source)
 
 
 class RelationshipAnswerSet(AnswerSet):
@@ -119,3 +100,78 @@ class RelationshipAnswerSet(AnswerSet):
 
     def get_absolute_url(self):
         return self.relationship.get_absolute_url()
+
+
+class OrganisationRelationshipQuestion(Question):
+    """Question which may be asked about an :class:`OrganisationRelationship`."""
+
+
+class OrganisationRelationshipQuestionChoice(QuestionChoice):
+    """Allowed answer to a :class:`OrganisationRelationshipQuestion`."""
+
+    #: Question to which this answer belongs
+    question = models.ForeignKey(OrganisationRelationshipQuestion,
+                                 related_name='answers',
+                                 on_delete=models.CASCADE,
+                                 blank=False,
+                                 null=False)
+
+
+class OrganisationRelationship(models.Model):
+    """A directional relationship between a person and an organisation with linked questions."""
+    class Meta:
+        constraints = [
+            models.UniqueConstraint(fields=['source', 'target'],
+                                    name='unique_relationship'),
+        ]
+
+    #: Person reporting the relationship
+    source = models.ForeignKey(
+        Person,
+        related_name='organisation_relationships_as_source',
+        on_delete=models.CASCADE,
+        blank=False,
+        null=False)
+
+    #: Organisation with which the relationship is reported
+    target = models.ForeignKey(
+        Organisation,
+        related_name='organisation_relationships_as_target',
+        on_delete=models.CASCADE,
+        blank=False,
+        null=False)
+
+    #: When was this relationship defined?
+    created = models.DateTimeField(auto_now_add=True)
+
+    #: When was this marked as expired?  Default None means it has not expired
+    expired = models.DateTimeField(blank=True, null=True)
+
+    @property
+    def current_answers(self) -> 'OrganisationRelationshipAnswerSet':
+        return self.answer_sets.last()
+
+    def get_absolute_url(self):
+        return reverse('people:organisation.relationship.detail',
+                       kwargs={'pk': self.pk})
+
+    def __str__(self) -> str:
+        return f'{self.source} -> {self.target}'
+
+
+class OrganisationRelationshipAnswerSet(AnswerSet):
+    """The answers to the organisation relationship questions at a particular point in time."""
+
+    #: OrganisationRelationship to which this answer set belongs
+    relationship = models.ForeignKey(OrganisationRelationship,
+                                     on_delete=models.CASCADE,
+                                     related_name='answer_sets',
+                                     blank=False,
+                                     null=False)
+
+    #: Answers to :class:`OrganisationRelationshipQuestion`s
+    question_answers = models.ManyToManyField(
+        OrganisationRelationshipQuestionChoice)
+
+    def get_absolute_url(self):
+        return self.relationship.get_absolute_url()