import { describe, it, expect } from "vitest";
import { previewPriority } from "./preview";

/**
 * A preview job is created when its render finishes, so it is always newer than
 * the renders queued beside it. With the queue ordered by priority then age,
 * equal priority means every pending render goes first — a batch of ten shots
 * runs as ten renders and then ten previews, and nothing is reviewable until
 * the end.
 */
describe("previewPriority", () => {
  const URGENT = 20;

  it("outranks other work of the same priority so a shot finishes end to end", () => {
    expect(previewPriority(50, 1, URGENT)).toBe(49);
  });

  it("keeps an urgent export's preview urgent", () => {
    // Urgent renders may claim outside the render window; their previews have
    // to be able to follow, or the shot stalls one step from being reviewable.
    expect(previewPriority(20, 1, URGENT)).toBe(19);
    expect(previewPriority(19, 1, URGENT)).toBeLessThanOrEqual(URGENT);
  });

  it("never promotes a normal job across the urgent line", () => {
    // 21 - 1 would be 20, quietly granting the preview permission to run
    // outside the render window that its render never had.
    expect(previewPriority(21, 1, URGENT)).toBe(21);
    expect(previewPriority(25, 10, URGENT)).toBe(21);
  });

  it("a boost of zero restores the old phase behaviour", () => {
    expect(previewPriority(50, 0, URGENT)).toBe(50);
  });

  it("ignores a negative boost and never goes below zero", () => {
    expect(previewPriority(50, -5, URGENT)).toBe(50);
    expect(previewPriority(0, 5, URGENT)).toBe(0);
  });
});