feat: add usage cost reporting

src/utils/usage-format.test.ts

@@ -0,0 +1,60 @@
+import { describe, expect, it } from "vitest";
+import type { ClawdbotConfig } from "../config/config.js";
+import {
+  estimateUsageCost,
+  formatTokenCount,
+  formatUsd,
+  resolveModelCostConfig,
+} from "./usage-format.js";
+
+describe("usage-format", () => {
+  it("formats token counts", () => {
+    expect(formatTokenCount(999)).toBe("999");
+    expect(formatTokenCount(1234)).toBe("1.2k");
+    expect(formatTokenCount(12000)).toBe("12k");
+    expect(formatTokenCount(2_500_000)).toBe("2.5m");
+  });
+
+  it("formats USD values", () => {
+    expect(formatUsd(1.234)).toBe("$1.23");
+    expect(formatUsd(0.5)).toBe("$0.50");
+    expect(formatUsd(0.0042)).toBe("$0.0042");
+  });
+
+  it("resolves model cost config and estimates usage cost", () => {
+    const config = {
+      models: {
+        providers: {
+          test: {
+            models: [
+              {
+                id: "m1",
+                cost: { input: 1, output: 2, cacheRead: 0.5, cacheWrite: 0 },
+              },
+            ],
+          },
+        },
+      },
+    } as ClawdbotConfig;
+
+    const cost = resolveModelCostConfig({
+      provider: "test",
+      model: "m1",
+      config,
+    });
+
+    expect(cost).toEqual({
+      input: 1,
+      output: 2,
+      cacheRead: 0.5,
+      cacheWrite: 0,
+    });
+
+    const total = estimateUsageCost({
+      usage: { input: 1000, output: 500, cacheRead: 2000 },
+      cost,
+    });
+
+    expect(total).toBeCloseTo(0.003);
+  });
+});