one/dist/esm/link/prefetchIntent.test.js

One is a new React Framework that makes Vite serve both native and web.

import { describe, expect, it, beforeEach } from "vitest";
import { createPrefetchIntent } from "./prefetchIntent";
const rect = (x, y, w = 100, h = 40) => ({
  left: x,
  top: y,
  right: x + w,
  bottom: y + h,
  width: w,
  height: h,
  x,
  y,
  toJSON: () => ({})
});
describe("prefetchIntent", () => {
  let prefetched, intent;
  beforeEach(() => {
    prefetched = [], intent = createPrefetchIntent({
      onPrefetch: (href) => prefetched.push(href)
    });
  }), describe("basic targeting", () => {
    it("prefetches when moving directly toward a link", () => {
      intent.setRects([{ r: rect(500, 300), h: "/about" }]), intent.move(100, 300, 0, 0), intent.move(140, 300, 40, 0), intent.move(200, 300, 60, 0), expect(prefetched).toEqual(["/about"]);
    }), it("does not prefetch when moving away from a link", () => {
      intent.setRects([{ r: rect(500, 300), h: "/about" }]), intent.move(400, 300, 0, 0), intent.move(380, 300, -20, 0), intent.move(350, 300, -30, 0), expect(prefetched).toEqual([]);
    }), it("does not prefetch when moving perpendicular to a link", () => {
      intent.setRects([{ r: rect(500, 300), h: "/about" }]), intent.move(200, 300, 0, 0), intent.move(200, 330, 0, 30), intent.move(200, 370, 0, 40), expect(prefetched).toEqual([]);
    }), it("prefetches link at long distance with good aim", () => {
      intent.setRects([{ r: rect(500, 280), h: "/far" }]), intent.move(100, 300, 0, 0), intent.move(140, 300, 40, 0), intent.move(200, 300, 60, 0), expect(prefetched).toEqual(["/far"]);
    }), it("does not prefetch when aim is slightly off at long distance", () => {
      intent.setRects([{ r: rect(600, 300), h: "/far" }]), intent.move(100, 300, 0, 0), intent.move(140, 320, 40, 20), intent.move(200, 360, 60, 40), expect(prefetched).toEqual([]);
    });
  }), describe("prevents over-fetching", () => {
    it("only prefetches each href once", () => {
      intent.setRects([{ r: rect(500, 300), h: "/about" }]), intent.move(100, 300, 0, 0), intent.move(140, 300, 40, 0), intent.move(200, 300, 60, 0), expect(prefetched).toEqual(["/about"]), intent.move(100, 300, -100, 0), intent.move(140, 300, 40, 0), intent.move(200, 300, 60, 0), expect(prefetched).toEqual(["/about"]);
    }), it("removes prefetched links from future consideration", () => {
      intent.setRects([
        { r: rect(400, 300), h: "/first" },
        { r: rect(600, 300), h: "/second" }
      ]), intent.move(100, 300, 0, 0), intent.move(150, 300, 50, 0), expect(prefetched).toEqual(["/first"]), intent.move(250, 300, 100, 0), intent.move(350, 300, 100, 0), expect(prefetched).toEqual(["/first", "/second"]);
    });
  }), describe("winner-takes-all with clustered links", () => {
    it("only prefetches the best target when multiple links are in path", () => {
      intent.setRects([
        { r: rect(500, 280), h: "/top" },
        { r: rect(500, 320), h: "/middle" },
        { r: rect(500, 360), h: "/bottom" }
      ]), intent.move(100, 340, 0, 0), intent.move(150, 340, 50, 0), expect(prefetched.length).toBe(1), expect(prefetched[0]).toBe("/middle");
    }), it("handles dense nav with 20 links", () => {
      const links = Array.from({ length: 20 }, (_, i) => ({
        r: rect(100 + i * 60, 50, 50, 30),
        h: `/nav-${i}`
      }));
      intent.setRects(links), intent.move(700, 200, 0, 0), intent.move(700, 150, 0, -50), intent.move(700, 100, 0, -50), expect(prefetched.length).toBe(1), expect(prefetched[0]).toBe("/nav-10");
    }), it("picks closer link when two are roughly aligned", () => {
      intent.setRects([
        { r: rect(300, 300), h: "/near" },
        { r: rect(600, 300), h: "/far" }
      ]), intent.move(100, 320, 0, 0), intent.move(150, 320, 50, 0), expect(prefetched).toEqual(["/near"]);
    }), it("picks better-aimed link over closer link", () => {
      intent.setRects([
        { r: rect(200, 400), h: "/close-but-off" },
        // closer but significantly off-axis
        { r: rect(400, 300), h: "/far-but-aimed" }
        // farther but dead-on
      ]), intent.move(100, 300, 0, 0), intent.move(150, 300, 50, 0), expect(prefetched).toEqual(["/far-but-aimed"]);
    });
  }), describe("velocity and smoothing", () => {
    it("does not prefetch when mouse is stationary", () => {
      intent.setRects([{ r: rect(500, 300), h: "/about" }]), intent.move(400, 300, 0, 0), intent.move(400, 300, 0, 0), intent.move(400, 300, 0, 0), expect(prefetched).toEqual([]);
    }), it("does not prefetch when mouse is moving slowly", () => {
      intent.setRects([{ r: rect(500, 300), h: "/about" }]), intent.move(400, 300, 0, 0), intent.move(401, 300, 1, 0), intent.move(402, 300, 1, 0), expect(prefetched).toEqual([]);
    }), it("smooths velocity to avoid jitter false positives", () => {
      intent.setRects([{ r: rect(500, 300), h: "/about" }]), intent.move(100, 300, 0, 0), intent.move(130, 305, 30, 5), intent.move(160, 298, 30, -7), intent.move(195, 303, 35, 5), expect(prefetched).toEqual(["/about"]);
    });
  }), describe("diagonal movement", () => {
    it("prefetches with diagonal approach", () => {
      intent.setRects([{ r: rect(500, 500), h: "/corner" }]), intent.move(200, 200, 0, 0), intent.move(240, 240, 40, 40), intent.move(290, 290, 50, 50), expect(prefetched).toEqual(["/corner"]);
    }), it("handles angled approach to horizontal nav", () => {
      intent.setRects([
        { r: rect(400, 50), h: "/link1" },
        { r: rect(500, 50), h: "/link2" },
        { r: rect(600, 50), h: "/link3" }
      ]), intent.move(300, 300, 0, 0), intent.move(340, 260, 40, -40), intent.move(390, 210, 50, -50), expect(prefetched.length).toBe(1);
    });
  }), describe("edge cases", () => {
    it("handles empty rect list", () => {
      intent.setRects([]), intent.move(100, 100, 0, 0), intent.move(150, 100, 50, 0), expect(prefetched).toEqual([]);
    }), it("handles link at cursor position", () => {
      intent.setRects([{ r: rect(100, 100), h: "/here" }]), intent.move(150, 120, 0, 0), intent.move(160, 120, 10, 0), expect(prefetched.length).toBeLessThanOrEqual(1);
    }), it("cleans up when observe returns cleanup function", () => {
      intent.observe(
        { getBoundingClientRect: () => rect(500, 300) },
        "/test"
      )(), intent.move(100, 300, 0, 0), intent.move(150, 300, 50, 0), expect(prefetched).toEqual([]);
    }), it("re-enables prefetch for href after cleanup", () => {
      const el = { getBoundingClientRect: () => rect(500, 300) }, cleanup = intent.observe(el, "/test");
      intent.setRects([{ r: rect(500, 300), h: "/test" }]), intent.move(100, 300, 0, 0), intent.move(140, 300, 40, 0), intent.move(200, 300, 60, 0), expect(prefetched).toEqual(["/test"]), cleanup(), prefetched.length = 0, intent.observe(el, "/test"), intent.setRects([{ r: rect(500, 300), h: "/test" }]), intent.move(100, 300, 0, 0), intent.move(140, 300, 40, 0), intent.move(200, 300, 60, 0), expect(prefetched).toEqual(["/test"]);
    });
  }), describe("reach configuration", () => {
    it("respects maxReach option", () => {
      const shortReach = createPrefetchIntent({
        onPrefetch: (href) => prefetched.push(href),
        maxReach: 200
      });
      shortReach.setRects([{ r: rect(500, 300), h: "/far" }]), shortReach.move(100, 300, 0, 0), shortReach.move(150, 300, 50, 0), expect(prefetched).toEqual([]);
    }), it("respects perpWeight option for aim strictness", () => {
      const strictAim = createPrefetchIntent({
        onPrefetch: (href) => prefetched.push(href),
        perpWeight: 10
        // very strict
      });
      strictAim.setRects([{ r: rect(400, 350), h: "/off" }]), strictAim.move(100, 300, 0, 0), strictAim.move(150, 300, 50, 0), expect(prefetched).toEqual([]);
    });
  }), describe("memory and performance", () => {
    it("does not leak elements after cleanup", () => {
      const cleanups = [];
      for (let i = 0; i < 100; i++) {
        const el = {};
        cleanups.push(intent.observe(el, `/page-${i}`));
      }
      expect(intent.nodes.size).toBe(100), cleanups.forEach((c) => c()), expect(intent.nodes.size).toBe(0), expect(intent.done.size).toBe(0);
    }), it("handles rapid observe/unobserve cycles", () => {
      const el = {};
      for (let i = 0; i < 100; i++)
        intent.observe(el, "/test")();
      expect(intent.nodes.size).toBe(0);
    }), it("processes 100 links efficiently", () => {
      const links = [];
      for (let row = 0; row < 10; row++)
        for (let col = 0; col < 10; col++)
          links.push({
            r: rect(100 + col * 80, 100 + row * 50, 60, 30),
            h: `/link-${row}-${col}`
          });
      intent.setRects(links);
      const start = performance.now();
      for (let i = 0; i < 100; i++)
        intent.move(50 + i * 5, 300, 5, 0);
      const elapsed = performance.now() - start;
      expect(elapsed).toBeLessThan(50);
    }), it("removes prefetched links from rects to speed up future checks", () => {
      const links = Array.from({ length: 10 }, (_, i) => ({
        r: rect(200 + i * 100, 300),
        h: `/link-${i}`
      }));
      intent.setRects(links), intent.move(100, 320, 0, 0), intent.move(150, 320, 50, 0), expect(prefetched.length).toBe(1), intent.move(100, 320, -50, 0), intent.move(150, 320, 50, 0), intent.move(200, 320, 50, 0), expect(prefetched.length).toBe(2), expect(prefetched[0]).not.toBe(prefetched[1]);
    });
  });
});
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