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/database/models.py

@@ -50,7 +50,7 @@ class Spool(Base):
     last_used: Mapped[Optional[datetime]] = mapped_column()
     filament_id: Mapped[int] = mapped_column(ForeignKey("filament.id"))
     filament: Mapped["Filament"] = relationship(back_populates="spools")
-    weight: Mapped[float] = mapped_column()
+    used_weight: Mapped[float] = mapped_column()
     location: Mapped[Optional[str]] = mapped_column(String(64))
     lot_nr: Mapped[Optional[str]] = mapped_column(String(64))
     comment: Mapped[Optional[str]] = mapped_column(String(1024))

spoolman/database/spool.py

@@ -16,7 +16,8 @@ async def create(
     *,
     db: AsyncSession,
     filament_id: int,
-    weight: Optional[float] = None,
+    remaining_weight: Optional[float] = None,
+    used_weight: Optional[float] = None,
     first_used: Optional[datetime] = None,
     last_used: Optional[datetime] = None,
     location: Optional[str] = None,
@@ -25,14 +26,17 @@ async def create(
 ) -> models.Spool:
     """Add a new spool to the database. Leave weight empty to assume full spool."""
     filament_item = await filament.get_by_id(db, filament_id)
-    if weight is None:
-        if filament_item.weight is None:
-            raise ItemCreateError("The weight for neither the spool nor its filament type is set.")
-        weight = filament_item.weight
+    if used_weight is None:
+        if remaining_weight is not None:
+            if filament_item.weight is None:
+                raise ItemCreateError("remaining_weight can only be used if the filament type has a weight set.")
+            used_weight = max(filament_item.weight - remaining_weight, 0)
+        else:
+            used_weight = 0
 
     db_item = models.Spool(
         filament=filament_item,
-        weight=weight,
+        used_weight=used_weight,
         first_used=first_used,
         last_used=last_used,
         location=location,
@@ -105,6 +109,10 @@ async def update(
     for k, v in data.items():
         if k == "filament_id":
             spool.filament = await filament.get_by_id(db, v)
+        elif k == "remaining_weight":
+            if spool.filament.weight is None:
+                raise ItemCreateError("remaining_weight can only be used if the filament type has a weight set.")
+            spool.used_weight = max(spool.filament.weight - v, 0)
         else:
             setattr(spool, k, v)
     await db.flush()
@@ -119,33 +127,33 @@ async def delete(db: AsyncSession, spool_id: int) -> None:
 
 # TODO: Make unit tests for race conditions on these
 async def use_weight(db: AsyncSession, spool_id: int, weight: float) -> models.Spool:
-    """Reduce the weight of a spool.
+    """Consume filament from a spool by weight.
 
     Does nothing if the spool is empty.
 
     Args:
         db (AsyncSession): Database session
         spool_id (int): Spool ID
-        weight (float): Weight loss in grams
+        weight (float): Filament weight to consume, in grams
 
     Returns:
         models.Spool: Updated spool object
     """
     spool = await get_by_id(db, spool_id, with_for_update=True)
-    spool.weight -= min(spool.weight, weight)
+    spool.used_weight += weight
     await db.flush()
     return spool
 
 
 async def use_length(db: AsyncSession, spool_id: int, length: float) -> models.Spool:
-    """Reduce the weight of a spool by using a length of filament.
+    """Consume filament from a spool by length.
 
     Does nothing if the spool is empty.
 
     Args:
         db (AsyncSession): Database session
         spool_id (int): Spool ID
-        length (float): Length of filament to reduce by
+        length (float): Length of filament to consume, in mm
 
     Returns:
         models.Spool: Updated spool object
@@ -154,11 +162,10 @@ async def use_length(db: AsyncSession, spool_id: int, length: float) -> models.S
 
     filament = spool.filament
 
-    weight = weight_from_length(
+    spool.used_weight += weight_from_length(
         length=length,
         radius=filament.diameter / 2,
         density=filament.density,
     )
-    spool.weight -= min(spool.weight, weight)
     await db.flush()
     return spool