JobTargetStatus as a means of tracking job progress

photoapp/types.py

@@ -241,6 +241,7 @@ class Job(Base):
     status = Column(Enum(JobStatus), nullable=False, default=JobStatus.paused)
 
     targets = relationship("JobTarget", back_populates="job")
+    target_statuses = relationship("JobTargetStatus", back_populates="job")
 
     def to_json(self):
         return {attr: getattr(self, attr) for attr in
@@ -260,8 +261,41 @@ class JobTarget(Base):
     job_id = Column(Integer, ForeignKey("jobs.id"), nullable=False)
     job = relationship("Job", back_populates="targets", foreign_keys=[job_id])
     target_type = Column(Enum(JobTargetType), nullable=False)
-    target = Column(Integer, nullable=False)
+    target = Column(Integer, nullable=False)  #TODO should we refactor this to multiple columns with null and proper constraints?
+
+    statuses = relationship("JobTargetStatus", back_populates="job_target")
 
     def to_json(self):
         return {attr: getattr(self, attr) for attr in
                 {"target_type", "target"}}
+
+
+class JobTargetState(enum.Enum):
+    new = 0
+    running = 1
+    complete = 2
+    error = 3
+    cancelled = 4
+
+
+class JobTargetStatus(Base):
+    __tablename__ = 'job_target_status'
+
+    id = Column(Integer, primary_key=True)
+    job_id = Column(Integer, ForeignKey("jobs.id"), nullable=False)
+    job = relationship("Job", back_populates="target_statuses", foreign_keys=[job_id])
+
+    job_target_id = Column(Integer, ForeignKey("job_targets.id"), nullable=False)
+    job_target = relationship("JobTarget", back_populates="statuses", foreign_keys=[job_target_id])
+
+    """
+    all jobs are progressed by photo_id. PhotoSets can have many Photos so this is the best logical unit. How this works
+    for the different `JobTargetType`s is broken down as follows:
+        - photo: (obvious)
+        - photoset: the job planner is given the opportunity to create JobTargetStatus for zero-all Photos under
+            a PhotoSet
+        - tag: same as photoset but iterated across all photosets with the tag
+    """
+    target_photo_id = Column(Integer, ForeignKey("photos.id"), nullable=False)
+
+    status = Column(Enum(JobTargetState), nullable=False)