feat(PORT-001A): add collateral entry basis settings

tests/test_portfolio.py

@@ -2,6 +2,8 @@ from __future__ import annotations
 
 import pytest
 
+from app.models.portfolio import PortfolioConfig
+
 
 def test_ltv_calculation(sample_portfolio) -> None:
     assert sample_portfolio.current_ltv == pytest.approx(0.60, rel=1e-12)
@@ -20,3 +22,57 @@ def test_net_equity_calculation(sample_portfolio) -> None:
 def test_margin_call_threshold(sample_portfolio) -> None:
     assert sample_portfolio.margin_call_price() == pytest.approx(368.0, rel=1e-12)
     assert sample_portfolio.ltv_at_price(sample_portfolio.margin_call_price()) == pytest.approx(0.75, rel=1e-12)
+
+
+def test_portfolio_config_derives_gold_weight_from_start_value_and_entry_price() -> None:
+    config = PortfolioConfig(
+        gold_value=215_000.0,
+        entry_price=215.0,
+        entry_basis_mode="value_price",
+    )
+
+    assert config.gold_ounces == pytest.approx(1_000.0, rel=1e-12)
+    assert config.gold_value == pytest.approx(215_000.0, rel=1e-12)
+    assert config.entry_basis_mode == "value_price"
+
+
+def test_portfolio_config_derives_start_value_from_gold_weight_and_entry_price() -> None:
+    config = PortfolioConfig(
+        gold_ounces=1_000.0,
+        entry_price=215.0,
+        entry_basis_mode="weight",
+    )
+
+    assert config.gold_value == pytest.approx(215_000.0, rel=1e-12)
+    assert config.gold_ounces == pytest.approx(1_000.0, rel=1e-12)
+    assert config.entry_basis_mode == "weight"
+
+
+def test_portfolio_config_serializes_canonical_entry_basis_fields() -> None:
+    config = PortfolioConfig(gold_value=215_000.0, entry_price=215.0)
+
+    data = config.to_dict()
+
+    assert data["gold_value"] == pytest.approx(215_000.0, rel=1e-12)
+    assert data["gold_ounces"] == pytest.approx(1_000.0, rel=1e-12)
+    assert data["entry_price"] == pytest.approx(215.0, rel=1e-12)
+    assert PortfolioConfig.from_dict(data).gold_ounces == pytest.approx(1_000.0, rel=1e-12)
+
+
+def test_portfolio_config_keeps_legacy_gold_value_payloads_compatible() -> None:
+    config = PortfolioConfig.from_dict({"gold_value": 215_000.0, "loan_amount": 145_000.0})
+
+    assert config.gold_value == pytest.approx(215_000.0, rel=1e-12)
+    assert config.entry_price == pytest.approx(215.0, rel=1e-12)
+    assert config.gold_ounces == pytest.approx(1_000.0, rel=1e-12)
+
+
+def test_portfolio_config_rejects_invalid_entry_basis_values() -> None:
+    with pytest.raises(ValueError, match="Entry price must be positive"):
+        PortfolioConfig(entry_price=0.0)
+
+    with pytest.raises(ValueError, match="Gold weight must be positive"):
+        PortfolioConfig(gold_ounces=-1.0, entry_price=215.0, entry_basis_mode="weight")
+
+    with pytest.raises(ValueError, match="Gold value and weight contradict each other"):
+        PortfolioConfig(gold_value=215_000.0, gold_ounces=900.0, entry_price=215.0)