order: add new TestValidateOrderAccountIsolation test case

In this commit, we add a new test that fails with the current logic in
`validateOrder`. The function as isn't doesn't isolate the orders for
each account, so the orders from account A can prevent a user from
making an order to account B.

order/manager_test.go

@@ -0,0 +1,90 @@
+package order
+
+import (
+	"testing"
+
+	"github.com/btcsuite/btcutil"
+	"github.com/lightninglabs/llm/account"
+	"github.com/lightningnetwork/lnd/keychain"
+)
+
+// TestValidateOrderAccountIsolation tests that when we go to validate that an
+// account has sufficient order for a balance, we only factor in the oust
+// sanding orders for that account, and not all total orders that are open.
+func TestValidateOrderAccountIsolation(t *testing.T) {
+	t.Parallel()
+
+	orderStore := newMockStore()
+	orderManager := NewManager(&ManagerConfig{
+		Store: orderStore,
+	})
+
+	// We'll now create two accounts, one that's 1 BTC in size, while the
+	// other is 2 BTC.
+	accountA := account.Account{
+		Value: btcutil.SatoshiPerBitcoin,
+		TraderKey: &keychain.KeyDescriptor{
+			PubKey: acctKeySmall,
+		},
+	}
+	accountB := account.Account{
+		Value: btcutil.SatoshiPerBitcoin * 2,
+		TraderKey: &keychain.KeyDescriptor{
+			PubKey: acctKeyBig,
+		},
+	}
+
+	// We'll now create an order that will consume at least half (1100
+	// units is 1.1 BTC) of account B (it's an ask order).
+	var acctKeyB [33]byte
+	copy(acctKeyB[:], acctKeyBig.SerializeCompressed())
+	orderB := &Ask{
+		Kit: newKitFromTemplate(Nonce{0x01}, &Kit{
+			State:            StateSubmitted,
+			UnitsUnfulfilled: 1100,
+			FixedRate:        2_000,
+			MaxBatchFeeRate:  1000,
+			AcctKey:          acctKeyB,
+		}),
+		MaxDuration: 144,
+	}
+
+	simpleFeeSchedule := NewLinearFeeSchedule(1, 100)
+
+	// Submitting this order for account B should pass validation.
+	err := orderManager.validateOrder(
+		orderB, &accountB, simpleFeeSchedule,
+	)
+	if err != nil {
+		t.Fatalf("order B validation failed: %v", err)
+	}
+
+	// Simulating order acceptance, we'll now add this order to the order
+	// store.
+	if err := orderStore.SubmitOrder(orderB); err != nil {
+		t.Fatalf("unable to submit order: %v", err)
+	}
+
+	// Next, we'll create a ask that'll consume _most_ (but not all) of account
+	// A's balance. This should pass validation as although account B can't
+	// handle the order account A can.
+	var acctKeyA [33]byte
+	copy(acctKeyA[:], acctKeySmall.SerializeCompressed())
+	orderA := &Ask{
+		Kit: newKitFromTemplate(Nonce{0x01}, &Kit{
+			State:            StateSubmitted,
+			UnitsUnfulfilled: 800,
+			FixedRate:        2_000,
+			MaxBatchFeeRate:  1000,
+			AcctKey:          acctKeyA,
+		}),
+		MaxDuration: 144,
+	}
+
+	err = orderManager.validateOrder(
+		orderA, &accountA, simpleFeeSchedule,
+	)
+	if err != nil {
+		t.Fatalf("order A failed validation: %v", err)
+	}
+}