SnapOtter/tests/unit/api/output-format.test.ts

import { describe, expect, it } from "vitest";
import { resolveOutputFormat } from "../../../apps/api/src/lib/output-format.js";
import { fixtures, readFixture } from "../../fixtures/index.js";

const JPG = readFixture(fixtures.image.base.jpg100);
const PNG = readFixture(fixtures.image.base.png200);
const WEBP = readFixture(fixtures.image.base.webp50);

describe("resolveOutputFormat", () => {
  it("detects JPEG input and returns jpeg config", async () => {
    const result = await resolveOutputFormat(JPG, "photo.jpg");
    expect(result.format).toBe("jpeg");
    expect(result.extension).toBe("jpg");
    expect(result.contentType).toBe("image/jpeg");
    expect(result.quality).toBe(95);
  });

  it("detects PNG input and returns png config with no quality", async () => {
    const result = await resolveOutputFormat(PNG, "image.png");
    expect(result.format).toBe("png");
    expect(result.extension).toBe("png");
    expect(result.contentType).toBe("image/png");
    // Sharp reads `quality` on PNG as "quantise to a palette", so a default
    // quality silently dithered every PNG that passed through (issue #710).
    // Only an explicit override may request that.
    expect(result.quality).toBeUndefined();
  });

  it("detects WebP input and returns webp config", async () => {
    const result = await resolveOutputFormat(WEBP, "image.webp");
    expect(result.format).toBe("webp");
    expect(result.extension).toBe("webp");
    expect(result.contentType).toBe("image/webp");
    expect(result.quality).toBe(95);
  });

  it("falls back to PNG for unknown format", async () => {
    const garbage = Buffer.from("not an image at all");
    const result = await resolveOutputFormat(garbage, "mystery.bin");
    expect(result.format).toBe("png");
    expect(result.extension).toBe("png");
    expect(result.contentType).toBe("image/png");
    // The fallback produces PNG too, so it gets the same lossless treatment.
    expect(result.quality).toBeUndefined();
  });

  it("respects quality override for lossy formats", async () => {
    const result = await resolveOutputFormat(JPG, "photo.jpg", 50);
    expect(result.quality).toBe(50);
  });

  it("accepts quality override for PNG without error", async () => {
    const result = await resolveOutputFormat(PNG, "image.png", 50);
    expect(result.format).toBe("png");
    expect(result.quality).toBe(50);
  });
});