import { assertEquals } from "@std/assert";
import { withDom } from "@berry/util/dom.ts";
import { code } from "./code.tsx";
import type { HighlightRequest } from "./highlight-worker.ts";

Deno.test("code highlights once on entering view and releases unmounted blocks", async (t) => {
  const observed = new Set<Element>();
  const requests: HighlightRequest[] = [];
  let workers = 0;
  let intersect: (target: Element, isIntersecting: boolean) => void;
  class Visibility {
    constructor(callback: IntersectionObserverCallback) {
      intersect = (target, isIntersecting) => {
        callback(
          [{ target, isIntersecting } as IntersectionObserverEntry],
          this as unknown as IntersectionObserver,
        );
      };
    }
    observe(target: Element) {
      observed.add(target);
    }
    unobserve(target: Element) {
      observed.delete(target);
    }
  }
  class Highlighter {
    onmessage?: (event: { data: { id: number; html: string } }) => void;
    constructor() {
      workers++;
    }
    postMessage(request: HighlightRequest) {
      requests.push(request);
      queueMicrotask(() =>
        this.onmessage?.({
          data: { id: request.id, html: reply(request) },
        })
      );
    }
  }
  let reply = (_: HighlightRequest) => "<a-k>const</a-k> x = 1;";
  const globals = { IntersectionObserver: Visibility, Worker: Highlighter };
  await withDom(async (window) => {
    const block = code("const x = 1;\n", { language: "ts" });
    const container = document.createElement("div");
    container.append(block);
    await t.step("detached and offscreen blocks stay plain without starting a worker", async () => {
      assertEquals(observed.size, 0);
      assertEquals(workers, 0);
      document.body.append(container);
      await window.happyDOM.waitUntilComplete();
      assertEquals(observed.has(block), true);
      intersect(block, false);
      assertEquals(workers, 0);
      assertEquals(block.querySelector(".code-text")?.textContent, "const x = 1;");
    });
    await t.step("entering view highlights once, preserving the source and gutter", async () => {
      intersect(block, true);
      await window.happyDOM.waitUntilComplete();
      assertEquals(workers, 1);
      assertEquals(requests.map(({ language, source }) => ({ language, source })), [
        { language: "typescript", source: "const x = 1;" },
      ]);
      assertEquals(block.querySelector("a-k")?.textContent, "const");
      assertEquals(block.querySelector(".code-text")?.textContent, "const x = 1;");
      assertEquals(observed.has(block), false);
      intersect(block, true);
      container.remove();
      document.body.append(container);
      await window.happyDOM.waitUntilComplete();
      assertEquals(requests.length, 1);
      assertEquals(observed.has(block), false);
    });
    await t.step("blocks without a grammar do not request highlighting", async () => {
      container.replaceChildren(code("plain text"));
      await window.happyDOM.waitUntilComplete();
      assertEquals(observed.size, 0);
      assertEquals(requests.length, 1);
    });
    await t.step("highlighted lines keep the newlines that copying reads", async () => {
      reply = (request) => request.source;
      const multiline = code("const x = 1;\nconst y = 2;", { language: "ts" });
      container.replaceChildren(multiline);
      await window.happyDOM.waitUntilComplete();
      intersect(multiline, true);
      await window.happyDOM.waitUntilComplete();
      const copied = [...multiline.querySelectorAll(".code-text")].map((line) => line.textContent);
      assertEquals(copied.join(""), "const x = 1;\nconst y = 2;");
    });
  }, { globals });
});