Spool weight now counts upwards instead

The used filament weight is now kept track of instead of remaining weight. This adds robustness to measurement errors which could accumulate and then the filament usage wouldn't get tracked anymore once the weight hit 0. Now it will just keep going.

spoolman/api/v1/models.py

@@ -91,7 +91,15 @@ class Spool(BaseModel):
     first_used: Optional[datetime] = Field(description="First logged occurence of spool usage.")
     last_used: Optional[datetime] = Field(description="Last logged occurence of spool usage.")
     filament: Filament = Field(description="The filament type of this spool.")
-    weight: float = Field(ge=0, description="Remaining weight of filament on the spool.", example=500)
+    remaining_weight: Optional[float] = Field(
+        default=None,
+        ge=0,
+        description=(
+            "Estimated remaining weight of filament on the spool. Only set if the filament type has a weight set."
+        ),
+        example=500,
+    )
+    used_weight: float = Field(ge=0, description="Consumed weight of filament from the spool.", example=500)
     location: Optional[str] = Field(max_length=64, description="Where this spool can be found.", example="Shelf A")
     lot_nr: Optional[str] = Field(
         max_length=64,
@@ -107,13 +115,19 @@ class Spool(BaseModel):
     @staticmethod
     def from_db(item: models.Spool) -> "Spool":
         """Create a new Pydantic spool object from a database spool object."""
+        filament = Filament.from_db(item.filament)
+        remaining_weight: Optional[float] = None
+        if filament.weight is not None:
+            remaining_weight = max(filament.weight - item.used_weight, 0)
+
         return Spool(
             id=item.id,
             registered=item.registered,
             first_used=item.first_used,
             last_used=item.last_used,
-            filament=Filament.from_db(item.filament),
-            weight=item.weight,
+            filament=filament,
+            used_weight=item.used_weight,
+            remaining_weight=remaining_weight,
             location=item.location,
             lot_nr=item.lot_nr,
             comment=item.comment,

spoolman/api/v1/spool.py

@@ -27,14 +27,14 @@ class SpoolParameters(BaseModel):
     first_used: Optional[datetime] = Field(description="First logged occurence of spool usage.")
     last_used: Optional[datetime] = Field(description="Last logged occurence of spool usage.")
     filament_id: int = Field(description="The ID of the filament type of this spool.")
-    weight: Optional[float] = Field(
+    remaining_weight: Optional[float] = Field(
         ge=0,
         description=(
-            "Remaining weight of filament on the spool. "
-            "Leave empty to assume a full spool based on the weight parameters of the filament type."
+            "Remaining weight of filament on the spool. Can only be used if the filament type has a weight set."
         ),
-        example=500,
+        example=800,
     )
+    used_weight: Optional[float] = Field(ge=0, description="Used weight of filament on the spool.", example=200)
     location: Optional[str] = Field(max_length=64, description="Where this spool can be found.", example="Shelf A")
     lot_nr: Optional[str] = Field(
         max_length=64,
@@ -132,7 +132,11 @@ async def get(
 @router.post(
     "/",
     name="Add spool",
-    description="Add a new spool to the database.",
+    description=(
+        "Add a new spool to the database. "
+        "Only specify either remaining_weight or used_weight. "
+        "If no weight is set, the spool will be assumed to be full."
+    ),
     response_model_exclude_none=True,
     response_model=Spool,
     responses={
@@ -143,11 +147,18 @@ async def create(  # noqa: ANN201
     db: Annotated[AsyncSession, Depends(get_db_session)],
     body: SpoolParameters,
 ):
+    if body.remaining_weight is not None and body.used_weight is not None:
+        return JSONResponse(
+            status_code=400,
+            content={"message": "Only specify either remaining_weight or used_weight."},
+        )
+
     try:
         db_item = await spool.create(
             db=db,
             filament_id=body.filament_id,
-            weight=body.weight,
+            remaining_weight=body.remaining_weight,
+            used_weight=body.used_weight,
             first_used=body.first_used,
             last_used=body.last_used,
             location=body.location,
@@ -165,26 +176,46 @@ async def create(  # noqa: ANN201
 @router.patch(
     "/{spool_id}",
     name="Update spool",
-    description="Update any attribute of a spool. Only fields specified in the request will be affected.",
+    description=(
+        "Update any attribute of a spool. "
+        "Only fields specified in the request will be affected. "
+        "remaining_weight and used_weight can't be set at the same time."
+    ),
     response_model_exclude_none=True,
+    response_model=Spool,
+    responses={
+        400: {"model": Message},
+    },
 )
-async def update(
+async def update(  # noqa: ANN201
     db: Annotated[AsyncSession, Depends(get_db_session)],
     spool_id: int,
     body: SpoolUpdateParameters,
-) -> Spool:
+):
     patch_data = body.dict(exclude_unset=True)
 
+    if body.remaining_weight is not None and body.used_weight is not None:
+        return JSONResponse(
+            status_code=400,
+            content={"message": "Only specify either remaining_weight or used_weight."},
+        )
+
     if "filament_id" in patch_data and body.filament_id is None:
         raise RequestValidationError(
             [ErrorWrapper(ValueError("filament_id cannot be unset"), ("query", "filament_id"))],
         )
 
-    db_item = await spool.update(
-        db=db,
-        spool_id=spool_id,
-        data=patch_data,
-    )
+    try:
+        db_item = await spool.update(
+            db=db,
+            spool_id=spool_id,
+            data=patch_data,
+        )
+    except ItemCreateError as exc:
+        return JSONResponse(
+            status_code=400,
+            content={"message": str(exc)},
+        )
 
     return Spool.from_db(db_item)