fix: do not auto-resolve refunds with zero, negative, or non-finite amounts

lib/policy.test.ts

@@ -0,0 +1,73 @@
+import { describe, it, expect } from "vitest";
+import { decide } from "./policy";
+import type { InboundPayload, Triage } from "./types";
+
+const baseTriage: Triage = {
+  category: "refund",
+  urgency: "normal",
+  sentiment: "neutral",
+  draftReply: "Thanks for reaching out.",
+  summary: "Customer requesting a refund.",
+};
+
+const basePayload: InboundPayload = {
+  sender: "customer@example.com",
+  body: "I'd like a refund please.",
+};
+
+describe("decide() refund policy", () => {
+  it("auto-resolves a valid refund within the auto-limit", () => {
+    const result = decide(
+      { ...baseTriage, refundAmount: 25 },
+      basePayload,
+    );
+
+    expect(result.status).toBe("resolved");
+    expect(result.actionTaken).not.toBeNull();
+  });
+
+  it("escalates a refund above the auto-limit", () => {
+    const result = decide(
+      { ...baseTriage, refundAmount: 500 },
+      basePayload,
+    );
+
+    expect(result.status).toBe("escalated");
+    expect(result.actionTaken).toBeNull();
+  });
+
+  it("escalates a zero refund amount instead of auto-resolving it", () => {
+    const result = decide({ ...baseTriage, refundAmount: 0 }, basePayload);
+
+    expect(result.status).toBe("escalated");
+    expect(result.actionTaken).toBeNull();
+    expect(result.reason).toMatch(/zero or negative/);
+  });
+
+  it("escalates a negative refund amount instead of auto-resolving it", () => {
+    const result = decide({ ...baseTriage, refundAmount: -10 }, basePayload);
+
+    expect(result.status).toBe("escalated");
+    expect(result.actionTaken).toBeNull();
+    expect(result.reason).toMatch(/zero or negative/);
+  });
+
+  it("escalates a non-finite refund amount instead of auto-resolving it", () => {
+    const result = decide(
+      { ...baseTriage, refundAmount: NaN },
+      basePayload,
+    );
+
+    expect(result.status).toBe("escalated");
+    expect(result.actionTaken).toBeNull();
+    expect(result.reason).toMatch(/not a valid number/);
+  });
+
+  it("escalates when no refund amount was stated", () => {
+    const result = decide({ ...baseTriage, refundAmount: undefined }, basePayload);
+
+    expect(result.status).toBe("escalated");
+    expect(result.actionTaken).toBeNull();
+    expect(result.reason).toBe("refund amount not stated");
+  });
+});

lib/policy.ts

@@ -50,7 +50,13 @@ export function decide(triage: Triage, payload: InboundPayload): Decision {
 
     case "refund": {
       const amount = triage.refundAmount ?? null;
-      if (amount != null && amount <= refundAutoLimit) {
+      const isAutoResolvable =
+        amount != null &&
+        Number.isFinite(amount) &&
+        amount > 0 &&
+        amount <= refundAutoLimit;
+
+      if (isAutoResolvable) {
         return {
           status: "resolved",
           proposedAction: `Issue refund of $${amount}`,
@@ -59,17 +65,28 @@ export function decide(triage: Triage, payload: InboundPayload): Decision {
           draftReply: `Hi, we've issued your refund of $${amount}. ${triage.draftReply}`,
         };
       }
+
+      let reason: string;
+      let proposedAction: string;
+      if (amount == null) {
+        reason = "refund amount not stated";
+        proposedAction = "Confirm refund amount, then approve";
+      } else if (!Number.isFinite(amount)) {
+        reason = `refund amount $${amount} is not a valid number`;
+        proposedAction = "Confirm refund amount, then approve";
+      } else if (amount <= 0) {
+        reason = `refund amount $${amount} is zero or negative`;
+        proposedAction = "Confirm refund amount, then approve";
+      } else {
+        reason = `refund $${amount} exceeds auto-limit $${refundAutoLimit}`;
+        proposedAction = `Approve refund of $${amount}`;
+      }
+
       return {
         status: "escalated",
-        proposedAction:
-          amount != null
-            ? `Approve refund of $${amount}`
-            : "Confirm refund amount, then approve",
+        proposedAction,
         actionTaken: null,
-        reason:
-          amount != null
-            ? `refund $${amount} exceeds auto-limit $${refundAutoLimit}`
-            : "refund amount not stated",
+        reason,
         draftReply: triage.draftReply,
       };
     }