add "debit_card" as a new AccountType (#16)

backend/app/models/enums.py

@@ -4,6 +4,7 @@ import enum
 
 class AccountType(str, enum.Enum):
     CHECKING = "checking"
+    DEBIT_CARD = "debit_card"
     SAVINGS = "savings"
     CREDIT_CARD = "credit_card"
     CASH = "cash"

backend/app/services/insights_service.py

@@ -33,7 +33,7 @@ MAX_LOOKBACK_MONTHS = 24
 # Accounts where a big, untouched balance means money isn't working — a
 # credit card balance isn't "your cash", an investment account is already
 # invested, and OTHER is too ambiguous to guess at.
-_IDLE_CASH_ACCOUNT_TYPES = (AccountType.CHECKING, AccountType.SAVINGS, AccountType.CASH)
+_IDLE_CASH_ACCOUNT_TYPES = (AccountType.CHECKING, AccountType.DEBIT_CARD, AccountType.SAVINGS, AccountType.CASH)
 
 
 def _previous_month(year: int, month: int) -> tuple[int, int]:

backend/app/services/net_worth_service.py

@@ -2,7 +2,7 @@
 asset class.
 
 Design note: "Cash" is not stored anywhere — it's derived live from
-Account/Transaction data (checking/savings/cash/investment accounts) so the
+Account/Transaction data (checking/debit-card/savings/cash/investment accounts) so the
 Transactions feature stays the single source of truth for liquid money.
 Investment accounts count here too: their balance is uninvested/unallocated
 money sitting on the account, not the market value of what's actually
@@ -36,7 +36,13 @@ from app.schemas.net_worth import (
     RiskLevelSummary,
 )
 
-CASH_ACCOUNT_TYPES = {AccountType.CHECKING, AccountType.SAVINGS, AccountType.CASH, AccountType.INVESTMENT}
+CASH_ACCOUNT_TYPES = {
+    AccountType.CHECKING,
+    AccountType.DEBIT_CARD,
+    AccountType.SAVINGS,
+    AccountType.CASH,
+    AccountType.INVESTMENT,
+}
 
 RANGE_DAYS = {"30d": 30, "90d": 90, "1y": 365, "5y": 365 * 5}
 

backend/tests/test_accounts.py

@@ -0,0 +1,34 @@
+"""Account-type behavior shared by the accounts API and financial summaries."""
+from datetime import date
+
+from httpx import AsyncClient
+
+from tests.helpers import money, txn_payload
+
+
+async def test_debit_card_is_a_liquid_account_type(client: AsyncClient, categories):
+    response = await client.post(
+        "/accounts",
+        json={"name": "Debit card", "type": "debit_card", "currency": "RUB"},
+    )
+
+    assert response.status_code == 201
+    debit_card = response.json()
+    assert debit_card["type"] == "debit_card"
+
+    transaction = await client.post(
+        "/transactions",
+        json=txn_payload(
+            debit_card["id"],
+            type="income",
+            amount="1000.00",
+            category_id=categories["Salary"]["id"],
+            date=date.today().isoformat(),
+        ),
+    )
+    assert transaction.status_code == 201
+
+    summary = await client.get("/net-worth/summary", params={"range": "all"})
+
+    assert summary.status_code == 200
+    assert money(summary.json()["current"]) == money("1000.00")

backend/tests/test_insights.py

@@ -51,6 +51,25 @@ async def test_idle_cash_ignores_investment_accounts(client: AsyncClient, catego
     assert "idle_cash" not in await _alert_keys(client)
 
 
+async def test_idle_cash_includes_debit_cards(client: AsyncClient, categories):
+    debit_card = await client.post(
+        "/accounts", json={"name": "Debit card", "type": "debit_card", "currency": "USD"}
+    )
+    debit_card_id = debit_card.json()["id"]
+    await client.post(
+        "/transactions",
+        json=_txn(
+            debit_card_id,
+            type="income",
+            amount="5000.00",
+            category_id=categories["Salary"]["id"],
+            date=STALE_DATE,
+        ),
+    )
+
+    assert "idle_cash" in await _alert_keys(client)
+
+
 async def test_idle_cash_respects_custom_threshold(client: AsyncClient, account_id, categories):
     await client.post(
         "/transactions",