const assert = require("node:assert/strict");
const fs = require("node:fs");
const path = require("node:path");
const test = require("node:test");
const vm = require("node:vm");

const source = fs.readFileSync(
  path.join(__dirname, "../docs/javascripts/mathjax.js"),
  "utf8"
);
const settle = () => new Promise(resolve => setImmediate(resolve));

function setup(base = "https://notes.example/javascripts/mathjax.js") {
  const scripts = [];
  const errors = [];
  const calls = [];
  let subscriber;
  let content;
  const window = {};
  const renderer = {
    startup: {
      promise: Promise.resolve(),
      output: { clearCache: () => calls.push("cache") }
    },
    typesetClear: () => calls.push("clear"),
    texReset: () => calls.push("reset"),
    typesetPromise: async elements => calls.push(elements[0])
  };

  vm.runInNewContext(source, {
    URL,
    window,
    console: { error: (...args) => errors.push(args) },
    document: {
      currentScript: { src: base },
      querySelector: () => content,
      createElement: () => ({ remove() { this.removed = true; } }),
      head: { append: script => scripts.push(script) }
    },
    document$: { subscribe: callback => { subscriber = callback; } }
  });

  return {
    scripts, errors, calls, renderer, window,
    navigate(math) {
      content = { querySelector: () => math ? {} : null };
      subscriber();
      return content;
    },
    load() {
      window.MathJax = renderer;
      scripts.at(-1).onload();
    }
  };
}

test("non-maths pages do not load or initialize MathJax", async () => {
  const site = setup();
  site.navigate(false);
  await settle();
  assert.equal(site.scripts.length, 0);
  assert.equal(site.window.MathJax, undefined);
});

test("maths pages wait for startup and use local assets under a subpath", async () => {
  const site = setup("https://notes.example/jupiter/javascripts/mathjax.js");
  const content = site.navigate(true);
  await settle();
  assert.equal(site.scripts.length, 1);
  assert.equal(site.scripts[0].src, "https://notes.example/jupiter/assets/vendor/mathjax/tex-mml-chtml.js");
  const config = site.window.MathJax;
  assert.equal(config.startup.typeset, false);
  assert.equal(config.loader.paths.sre, "https://notes.example/jupiter/assets/vendor/mathjax/sre/mathmaps");
  assert.equal(config.chtml.fontURL, "https://notes.example/jupiter/assets/vendor/mathjax/output/chtml/fonts/woff-v2");
  let ready;
  site.renderer.startup.promise = new Promise(resolve => { ready = resolve; });
  site.load();
  await settle();
  assert.equal(site.calls.length, 0);
  ready();
  await settle();
  assert.deepEqual(site.calls, ["cache", "clear", "reset", content]);
});

test("navigation during loading renders only the latest page and reuses the renderer", async () => {
  const site = setup();
  const first = site.navigate(true);
  await settle();
  const second = site.navigate(true);
  site.load();
  await settle();
  assert.equal(site.scripts.length, 1);
  assert.ok(!site.calls.includes(first));
  assert.equal(site.calls.at(-1), second);
  const third = site.navigate(true);
  await settle();
  assert.equal(site.scripts.length, 1);
  assert.equal(site.calls.at(-1), third);
});

test("leaving a maths page during loading does not typeset detached content", async () => {
  const site = setup();
  site.navigate(true);
  await settle();
  site.navigate(false);
  site.load();
  await settle();
  assert.deepEqual(site.calls, ["clear"]);
});

test("returning to a non-maths page clears old maths without another download", async () => {
  const site = setup();
  site.navigate(true);
  await settle();
  site.load();
  await settle();
  site.navigate(false);
  await settle();
  assert.equal(site.calls.at(-1), "clear");
  assert.equal(site.scripts.length, 1);
});

test("typesetting is serialized across navigation", async () => {
  const site = setup();
  let finish;
  site.renderer.typesetPromise = elements => {
    site.calls.push(elements[0]);
    return new Promise(resolve => { finish = resolve; });
  };
  const first = site.navigate(true);
  await settle();
  site.load();
  await settle();
  const second = site.navigate(true);
  await settle();
  assert.equal(site.calls.at(-1), first);
  finish();
  await settle();
  assert.equal(site.calls.at(-1), second);
  finish();
  await settle();
});

test("load errors are reported and a later maths page can retry", async () => {
  const site = setup();
  site.navigate(true);
  await settle();
  site.scripts[0].onerror();
  await settle();
  assert.equal(site.errors.length, 1);
  assert.match(site.errors[0][1].message, /Failed to load MathJax/);
  assert.equal(site.scripts[0].removed, true);
  const content = site.navigate(true);
  await settle();
  assert.equal(site.scripts.length, 2);
  site.load();
  await settle();
  assert.equal(site.calls.at(-1), content);
});