import { assert, assertEquals } from "@std/assert";
import { withDom } from "@berry/util/dom.ts";
import { rendering } from "./render.tsx";
import type { FileDiff } from "./types.ts";

const file = (lines: string[], path = "file.txt"): FileDiff => ({
  path,
  from: null,
  status: "modified",
  modes: { old: "100644", new: "100644" },
  binary: false,
  hunks: [{ old: 1, new: 1, lines }],
});

async function page(
  test: (env: {
    root: HTMLElement;
    render: ReturnType<typeof rendering>;
    intersect(element: Element, near: boolean, visible?: boolean): void;
    settle(): Promise<void>;
  }) => Promise<void>,
  globals: Record<string, unknown> = {},
) {
  const observers: Visibility[] = [];
  class Visibility {
    targets = new Set<Element>();
    constructor(
      readonly callback: IntersectionObserverCallback,
      readonly options?: IntersectionObserverInit,
    ) {
      observers.push(this);
    }
    observe(target: Element) {
      this.targets.add(target);
    }
    unobserve(target: Element) {
      this.targets.delete(target);
    }
    disconnect() {
      this.targets.clear();
    }
  }
  await withDom(async (window) => {
    const root = document.createElement("div");
    document.body.append(root);
    const render = rendering(root);
    try {
      await test({
        root,
        render,
        intersect(element, near, visible = near) {
          for (const observer of observers) {
            if (!observer.targets.has(element)) continue;
            observer.callback(
              [{
                target: element,
                isIntersecting: observer.options?.rootMargin ? near : visible,
              } as IntersectionObserverEntry],
              observer as unknown as IntersectionObserver,
            );
          }
        },
        settle: () => window.happyDOM.waitUntilComplete(),
      });
    } finally {
      render.dispose();
    }
    for (const observer of observers) assertEquals(observer.targets.size, 0);
  }, { globals: { IntersectionObserver: Visibility, ...globals } });
}

Deno.test("large diffs keep all text searchable but only nearby chunks have rich rows", () =>
  page(async ({ root, render, intersect, settle }) => {
    const lines = Array.from({ length: 10_000 }, (_, i) => `+unique line ${i}`);
    const content = render.file(file(lines), "unified", new Set(), () => {});
    root.append(content.element);
    const chunks = [...root.querySelectorAll(".diff-chunk")];
    assert(chunks.length > 10);
    assertEquals(root.querySelectorAll("table").length, 0);
    assert(root.textContent!.includes("unique line 9999"));
    assert(root.querySelectorAll("*").length < 1000);

    let previous: Element | undefined;
    for (const chunk of [chunks[0], chunks[1], chunks.at(-1)!]) {
      if (previous) intersect(previous, false);
      intersect(chunk, true);
      await settle();
      assertEquals(root.querySelectorAll("table").length, 1);
      assert(root.querySelectorAll("tr").length < 200);
      assert(root.textContent!.includes("unique line 9999"));
      if (previous) assert(previous.querySelector("pre"));
      previous = chunk;
    }
    intersect(chunks[0], true);
    content.dispose();
    await settle();
    assertEquals(chunks[0].querySelector("table"), null);
  }));

Deno.test("hydrating and evicting chunks leave native find matches and selections intact", () =>
  page(async ({ root, render, intersect, settle }) => {
    const content = render.file(file(["+a searchable needle"]), "unified", new Set(), () => {});
    root.append(content.element);
    const chunk = root.querySelector(".diff-chunk")!;
    const pre = chunk.querySelector("pre")!;
    const selection = document.getSelection()!;
    const range = document.createRange();
    range.setStart(pre.firstChild!, 2);
    range.setEnd(pre.firstChild!, 12);
    selection.addRange(range);
    intersect(chunk, true);
    await settle();
    assertEquals(chunk.querySelector("pre"), pre);
    assertEquals(selection.toString(), "searchable");

    selection.removeAllRanges();
    document.dispatchEvent(new Event("selectionchange"));
    await settle();
    const table = chunk.querySelector("table")!;
    assert(table);
    range.selectNodeContents(table.querySelector("td.text")!);
    selection.addRange(range);
    intersect(chunk, false);
    await settle();
    assertEquals(chunk.querySelector("table"), table);
    assertEquals(selection.toString(), "a searchable needle");
    selection.removeAllRanges();
    document.dispatchEvent(new Event("selectionchange"));
    await settle();
    assertEquals(chunk.querySelector("table"), null);
    assertEquals(chunk.querySelector("pre")!.textContent, "a searchable needle\n");
    content.dispose();
  }));

Deno.test("line pairing and word changes survive chunk boundaries in either layout", async () => {
  for (const layout of ["unified", "split"] as const) {
    await page(async ({ root, render, intersect, settle }) => {
      const lines = [
        ...Array.from({ length: 150 }, (_, i) => `-const before_${i} = value;`),
        ...Array.from({ length: 150 }, (_, i) => `+const after_${i} = value;`),
      ];
      const content = render.file(file(lines), layout, new Set(), () => {});
      root.append(content.element);
      for (const chunk of root.querySelectorAll(".diff-chunk")) intersect(chunk, true);
      await settle();
      assertEquals(root.querySelectorAll("td.text.del").length, 150);
      assertEquals(root.querySelectorAll("td.text.add").length, 150);
      assertEquals(root.querySelector("td.del mark.word")!.textContent, "before_0");
      assertEquals(root.querySelector("td.add mark.word")!.textContent, "after_0");
      if (layout === "split") {
        for (const [i, row] of [...root.querySelectorAll("tr")].entries()) {
          assertEquals(row.querySelector(".del")!.textContent, `const before_${i} = value;`);
          assertEquals(row.querySelector(".add")!.textContent, `const after_${i} = value;`);
        }
      }
      content.dispose();
    });
  }
});

Deno.test("syntax work waits for visible chunks, skips departed files, and releases offscreen results", async () => {
  const requests: { id: number; source: string }[] = [];
  let worker: Highlighter | undefined;
  class Highlighter {
    onmessage?: (event: { data: { id: number; html: string } }) => void;
    constructor() {
      worker = this;
    }
    postMessage(request: typeof requests[number]) {
      requests.push(request);
    }
    reply() {
      for (const { id, source } of requests.splice(0)) {
        this.onmessage?.({ data: { id, html: `<a-k>${source}</a-k>` } });
      }
    }
  }
  await page(async ({ root, render, intersect, settle }) => {
    const first = render.file(file(["-old", "+new"], "first.ts"), "unified", new Set(), () => {});
    const second = render.file(file(["+second"], "second.ts"), "unified", new Set(), () => {});
    root.append(first.element, second.element);
    const a = first.element.querySelector(".diff-chunk")!;
    const b = second.element.querySelector(".diff-chunk")!;
    intersect(a, true, false);
    await settle();
    assertEquals(worker, undefined);
    intersect(a, true);
    intersect(b, true);
    await settle();
    assertEquals(requests.map((request) => request.source), ["old", "new"]);
    intersect(a, false);
    intersect(b, false);
    await settle();
    worker!.reply();
    await settle();
    assertEquals(requests.length, 0);
    assertEquals(root.querySelectorAll("a-k, table").length, 0);

    intersect(a, true);
    await settle();
    assertEquals(requests.map((request) => request.source), ["old", "new"]);
    const table = a.querySelector("table")!;
    const selection = document.getSelection()!;
    const range = document.createRange();
    range.selectNodeContents(a.querySelector("td.text")!);
    selection.addRange(range);
    worker!.reply();
    await settle();
    assertEquals(a.querySelector("table"), table);
    assertEquals(a.querySelector("a-k"), null);
    assertEquals(selection.toString(), "old");
    selection.removeAllRanges();
    document.dispatchEvent(new Event("selectionchange"));
    await settle();
    assertEquals(a.querySelector("a-k")?.textContent, "old");
    intersect(a, true);
    await settle();
    assertEquals(requests.length, 0);

    intersect(b, true);
    await settle();
    assertEquals(requests.map((request) => request.source), ["second"]);
    second.dispose();
    second.element.remove();
    worker!.reply();
    await settle();
    assertEquals(second.element.querySelector("a-k"), null);
    first.dispose();
  }, { Worker: Highlighter });
});