Use list[tuple[datetime, Decimal]] consistently

This type is useful for finance-py in general. It is often required to
handle money in datetime context. Using this type consistently makes the
code easier to read and maintain.

4 files changed, 14 insertions, 19 deletions

diff --git a/demo b/demo
index db48ea7..bb9cb98 100755
--- a/demo
+++ b/demo
@@ -16,11 +16,11 @@ DESCRIPTION = "Demo application plotting financial data with finance-py"
 def main() -> None:
     argparse.ArgumentParser(description=DESCRIPTION).parse_args()
 
-    measured = (
+    measured = [
         (datetime(2024, 1, 1), Decimal(105.0)),
         (datetime(2024, 2, 1), Decimal(207.0)),
         (datetime(2024, 3, 1), Decimal(334.0)),
-    )
+    ]
 
     flows = (
         Flow(amount=Decimal(100.0), since=None, until=None),
diff --git a/finance/flow.py b/finance/flow.py
index 4cf68db..c6b28c0 100644
--- a/finance/flow.py
+++ b/finance/flow.py
@@ -46,7 +46,7 @@ def monthly_candidates(start: datetime) -> Generator[datetime, None, None]:
 
 def simulate(
     start: datetime, end: datetime, flows: tuple[Flow, ...]
-) -> tuple[list[datetime], list[Decimal]]:
+) -> list[tuple[datetime, Decimal]]:
     dates: list[datetime] = []
     values: list[Decimal] = []
 
@@ -63,4 +63,4 @@ def simulate(
             value += flow.integrate(start, date)
         values.append(value)
 
-    return (dates, values)
+    return [(date, values[index]) for index, date in enumerate(dates)]
diff --git a/finance/test_flow.py b/finance/test_flow.py
index db1b695..91d189b 100644
--- a/finance/test_flow.py
+++ b/finance/test_flow.py
@@ -31,22 +31,17 @@ def test_flow_integration() -> None:
 def test_simulate() -> None:
     flows = (Flow(amount=Decimal(100.0), since=None, until=None),)
 
-    dates, values = simulate(
+    simulated = simulate(
         start=datetime(2024, 1, 1),
         end=datetime(2024, 4, 1),
         flows=flows,
     )
 
-    assert dates == [
-        datetime(2024, 1, 1),
-        datetime(2024, 2, 1),
-        datetime(2024, 3, 1),
-        datetime(2024, 4, 1),
+    expected = [
+        (datetime(2024, 1, 1), Decimal(100.0)),
+        (datetime(2024, 2, 1), Decimal(200.0)),
+        (datetime(2024, 3, 1), Decimal(300.0)),
+        (datetime(2024, 4, 1), Decimal(400.0)),
     ]
 
-    assert values == [
-        Decimal(100.0),
-        Decimal(200.0),
-        Decimal(300.0),
-        Decimal(400.0),
-    ]
+    assert simulated == expected
diff --git a/finance/visualize.py b/finance/visualize.py
index c7a7c60..66943c7 100644
--- a/finance/visualize.py
+++ b/finance/visualize.py
@@ -5,12 +5,12 @@ import matplotlib.pyplot
 
 
 def display(
-    simulated: tuple[list[datetime], list[Decimal]],
+    simulated: list[tuple[datetime, Decimal]],
     measured: list[tuple[datetime, Decimal]],
 ) -> None:
     matplotlib.pyplot.plot(
-        list(simulated[0]),  # type: ignore
-        [float(i) for i in simulated[1]],
+        [i[0] for i in simulated],  # type: ignore
+        [float(i[1]) for i in simulated],
         label="Simulated",
     )
     matplotlib.pyplot.plot(