Use server prices for text billing estimates

src/utils/modelPricing.test.ts

@@ -0,0 +1,60 @@
+import { describe, expect, it } from "../test/testHarness";
+
+import {
+  millsPerThousandTokensToCreditsPerMillion,
+  modelPriceToTextTokenCreditRate,
+  resolveTextTokenCreditRate,
+} from "./modelPricing";
+
+describe("modelPricing", () => {
+  it("converts backend mills per thousand tokens to credits per million tokens", () => {
+    expect(millsPerThousandTokensToCreditsPerMillion(27)).toBe(2_700);
+    expect(millsPerThousandTokensToCreditsPerMillion(108)).toBe(10_800);
+  });
+
+  it("converts a token model price row to a text token credit rate", () => {
+    expect(
+      modelPriceToTextTokenCreditRate({
+        modelKey: "gpt-4o",
+        inputPriceMills: 27,
+        outputPriceMills: 108,
+        flatPriceMills: null,
+        currency: "CNY",
+        enabled: true,
+      }),
+    ).toEqual({
+      inputCreditsPerMillion: 2_700,
+      outputCreditsPerMillion: 10_800,
+      source: "server",
+      modelKey: "gpt-4o",
+    });
+  });
+
+  it("resolves token pricing by exact or fuzzy model key without accepting flat prices", () => {
+    const prices = [
+      {
+        modelKey: "gemini-3-pro-image",
+        inputPriceMills: null,
+        outputPriceMills: null,
+        flatPriceMills: 200,
+        currency: "CNY",
+        enabled: true,
+      },
+      {
+        modelKey: "gemini-3.1-pro",
+        inputPriceMills: 12,
+        outputPriceMills: 48,
+        flatPriceMills: null,
+        currency: "CNY",
+        enabled: true,
+      },
+    ];
+
+    expect(resolveTextTokenCreditRate(prices, "gemini")).toEqual({
+      inputCreditsPerMillion: 1_200,
+      outputCreditsPerMillion: 4_800,
+      source: "server",
+      modelKey: "gemini-3.1-pro",
+    });
+  });
+});