Added used_length and remaining_length API fields

They're calculated from the weights

Resolves #37

spoolman/api/v1/models.py

@@ -6,6 +6,7 @@ from typing import Optional
 from pydantic import BaseModel, Field
 
 from spoolman.database import models
+from spoolman.math import length_from_weight
 
 
 class Message(BaseModel):
@@ -118,11 +119,26 @@ class Spool(BaseModel):
         default=None,
         ge=0,
         description=(
-            "Estimated remaining weight of filament on the spool. Only set if the filament type has a weight set."
+            "Estimated remaining weight of filament on the spool in grams. "
+            "Only set if the filament type has a weight set."
         ),
-        example=500,
+        example=500.6,
+    )
+    used_weight: float = Field(ge=0, description="Consumed weight of filament from the spool in grams.", example=500.3)
+    remaining_length: Optional[float] = Field(
+        default=None,
+        ge=0,
+        description=(
+            "Estimated remaining length of filament on the spool in millimeters."
+            " Only set if the filament type has a weight set."
+        ),
+        example=5612.4,
+    )
+    used_length: float = Field(
+        ge=0,
+        description="Consumed length of filament from the spool in millimeters.",
+        example=50.7,
     )
-    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,
@@ -139,9 +155,22 @@ class Spool(BaseModel):
     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  # noqa: FA100
+        remaining_length: Optional[float] = None  # noqa: FA100
         if filament.weight is not None:
             remaining_weight = max(filament.weight - item.used_weight, 0)
+            remaining_length = length_from_weight(
+                weight=remaining_weight,
+                density=filament.density,
+                diameter=filament.diameter,
+            )
+
+        used_length = length_from_weight(
+            weight=item.used_weight,
+            density=filament.density,
+            diameter=filament.diameter,
+        )
 
         return Spool(
             id=item.id,
@@ -150,7 +179,9 @@ class Spool(BaseModel):
             last_used=item.last_used,
             filament=filament,
             used_weight=item.used_weight,
+            used_length=used_length,
             remaining_weight=remaining_weight,
+            remaining_length=remaining_length,
             location=item.location,
             lot_nr=item.lot_nr,
             comment=item.comment,

tests_integration/tests/conftest.py

@@ -1,5 +1,6 @@
 """Test fixtures for integration tests."""
 
+import math
 import os
 import time
 from enum import Enum
@@ -92,3 +93,19 @@ def random_filament(random_vendor: dict[str, Any]):
 
     # Delete filament
     httpx.delete(f"{URL}/api/v1/filament/{filament['id']}").raise_for_status()
+
+
+def length_from_weight(*, weight: float, diameter: float, density: float) -> float:
+    """Calculate the length of a piece of filament.
+
+    Args:
+        weight (float): Filament weight in g
+        diameter (float): Filament diameter in mm
+        density (float): Density of filament material in g/cm3
+
+    Returns:
+        float: Length in mm
+    """
+    volume_cm3 = weight / density
+    volume_mm3 = volume_cm3 * 1000
+    return volume_mm3 / (math.pi * (diameter / 2) ** 2)

tests_integration/tests/test_spool.py

@@ -7,6 +7,8 @@ from typing import Any
 import httpx
 import pytest
 
+from .conftest import length_from_weight
+
 URL = "http://spoolman:8000"
 
 
@@ -32,6 +34,18 @@ def test_add_spool_remaining_weight(random_filament: dict[str, Any]):
     result.raise_for_status()
 
     # Verify
+    used_weight = random_filament["weight"] - remaining_weight
+    used_length = length_from_weight(
+        weight=used_weight,
+        density=random_filament["density"],
+        diameter=random_filament["diameter"],
+    )
+    remaining_length = length_from_weight(
+        weight=remaining_weight,
+        density=random_filament["density"],
+        diameter=random_filament["diameter"],
+    )
+
     spool = result.json()
     assert spool == {
         "id": spool["id"],
@@ -40,7 +54,9 @@ def test_add_spool_remaining_weight(random_filament: dict[str, Any]):
         "last_used": "2023-01-02T11:00:00",
         "filament": random_filament,
         "remaining_weight": pytest.approx(remaining_weight),
-        "used_weight": pytest.approx(random_filament["weight"] - remaining_weight),
+        "used_weight": pytest.approx(used_weight),
+        "remaining_length": pytest.approx(remaining_length),
+        "used_length": pytest.approx(used_length),
         "location": location,
         "lot_nr": lot_nr,
         "comment": comment,
@@ -74,6 +90,18 @@ def test_add_spool_used_weight(random_filament: dict[str, Any]):
     result.raise_for_status()
 
     # Verify
+    remaining_weight = random_filament["weight"] - used_weight
+    used_length = length_from_weight(
+        weight=used_weight,
+        density=random_filament["density"],
+        diameter=random_filament["diameter"],
+    )
+    remaining_length = length_from_weight(
+        weight=remaining_weight,
+        density=random_filament["density"],
+        diameter=random_filament["diameter"],
+    )
+
     spool = result.json()
     assert spool == {
         "id": spool["id"],
@@ -81,8 +109,10 @@ def test_add_spool_used_weight(random_filament: dict[str, Any]):
         "first_used": first_used,
         "last_used": last_used,
         "filament": random_filament,
-        "remaining_weight": pytest.approx(random_filament["weight"] - used_weight),
+        "remaining_weight": pytest.approx(remaining_weight),
         "used_weight": pytest.approx(used_weight),
+        "remaining_length": pytest.approx(remaining_length),
+        "used_length": pytest.approx(used_length),
         "location": location,
         "lot_nr": lot_nr,
         "comment": comment,
@@ -106,13 +136,27 @@ def test_add_spool_required(random_filament: dict[str, Any]):
     result.raise_for_status()
 
     # Verify
+    remaining_weight = random_filament["weight"] - used_weight
+    used_length = length_from_weight(
+        weight=used_weight,
+        density=random_filament["density"],
+        diameter=random_filament["diameter"],
+    )
+    remaining_length = length_from_weight(
+        weight=remaining_weight,
+        density=random_filament["density"],
+        diameter=random_filament["diameter"],
+    )
+
     spool = result.json()
     assert spool == {
         "id": spool["id"],
         "registered": spool["registered"],
         "filament": random_filament,
         "used_weight": pytest.approx(used_weight),
-        "remaining_weight": pytest.approx(random_filament["weight"] - used_weight),
+        "remaining_weight": pytest.approx(remaining_weight),
+        "used_length": pytest.approx(used_length),
+        "remaining_length": pytest.approx(remaining_length),
     }
 
     # Clean up
@@ -389,11 +433,25 @@ def test_update_spool(random_filament: dict[str, Any]):
     result.raise_for_status()
 
     # Verify
+    used_weight = random_filament["weight"] - remaining_weight
+    used_length = length_from_weight(
+        weight=used_weight,
+        density=random_filament["density"],
+        diameter=random_filament["diameter"],
+    )
+    remaining_length = length_from_weight(
+        weight=remaining_weight,
+        density=random_filament["density"],
+        diameter=random_filament["diameter"],
+    )
+
     spool = result.json()
     assert spool["first_used"] == "2023-01-01T10:00:00"
     assert spool["last_used"] == "2023-01-02T10:00:00"
     assert spool["remaining_weight"] == pytest.approx(remaining_weight)
-    assert spool["used_weight"] == pytest.approx(random_filament["weight"] - remaining_weight)
+    assert spool["used_weight"] == pytest.approx(used_weight)
+    assert spool["remaining_length"] == pytest.approx(remaining_length)
+    assert spool["used_length"] == pytest.approx(used_length)
     assert spool["location"] == location
     assert spool["lot_nr"] == lot_nr
     assert spool["comment"] == comment