import assert from "node:assert/strict";
import { readdirSync, readFileSync } from "node:fs";
import test from "node:test";

/**
 * The chat panel must never be scrollable, and nothing inside it may ask the
 * browser to scroll an ancestor.
 *
 * Observed on staging: after answering three rectification questions the 46px
 * header was gone. The grid was right (`46px 1297px`, panel at y=0) but the
 * header's own rect was at **y = -88** — the panel had been scrolled 88px.
 * `overflow: hidden` still creates a scroll container: it only removes the
 * scrollbar, so a programmatic scroll sticks and the user cannot undo it.
 *
 * The cause was `BirthTimeChoiceQuestion` focusing the first option after every
 * answered question. Focus scrolls every scrollable ancestor by default, and the
 * transcript's own `useConversationScrollAnchor` was not the box that moved.
 */

const globalStyles = readFileSync(new URL("../src/app/globals.css", import.meta.url), "utf8");

function rule(selector: string): string {
  const match = globalStyles.match(new RegExp(`^\\${selector} \\{([^}]*)\\}`, "m"));
  assert.ok(match, `${selector} must exist in globals.css`);
  return match![1];
}

test("the chat panel and app shell clip rather than hide, so neither is a scroll container", () => {
  // `hidden` would pass a naive "does it overflow" check while still being
  // scrollable; `clip` is the only value that makes the box unscrollable.
  assert.match(rule(".chat-panel"), /overflow: clip/);
  assert.match(rule(".chat-app"), /overflow: clip/);
  assert.doesNotMatch(rule(".chat-panel"), /overflow: hidden/);
  assert.doesNotMatch(rule(".chat-app"), /overflow: hidden/);
});

test("nothing inside the chat panel focuses without preventScroll", () => {
  // Components that render inside `.chat-panel`. A focus() here reaches the
  // panel through the default scroll-into-view; the transcript has its own
  // anchor and does not want the browser's.
  const insidePanel = [
    "src/app/(app)/page.tsx",
    "src/hooks/use-consultation-run.ts",
    "src/components/birth-time-choice-question.tsx",
    "src/components/birth-time-rectification.tsx",
    "src/components/rectification-agentic-chat.tsx",
    "src/components/rectification-board.tsx",
  ];
  /* Dialog focus management is the one legitimate bare focus() in these files:
     an account dialog is an overlay above the panel, not content inside it, and
     moving focus into it must not be suppressed. */
  const dialogFocus = /closeButton|returnTarget|focusTrap/;
  for (const path of insidePanel) {
    const source = readFileSync(new URL(`../${path}`, import.meta.url), "utf8");
    for (const [line] of source.matchAll(/^.*\.focus\((.*)$/gm)) {
      if (/focus-visible|:focus|onFocus/.test(line)) continue;
      if (dialogFocus.test(line)) continue;
      assert.match(
        line,
        /focus\(\{ preventScroll: true \}\)/,
        `${path}: ${line.trim()}\n`
          + "A bare focus() inside the chat panel scrolls it. Pass { preventScroll: true } "
          + "and let useConversationScrollAnchor own the transcript's scroll position.",
      );
    }
  }
});

test("the guard covers every component that renders inside the panel today", () => {
  // If a new rectification/consultation component starts calling focus(), this
  // list has to grow with it — otherwise the contract above silently stops
  // covering the surface it was written for.
  const components = readdirSync(new URL("../src/components/", import.meta.url), { recursive: true, encoding: "utf8" })
    .filter((entry) => entry.endsWith(".tsx") && /rectification|birth-time|chat-/.test(entry));
  const missing: string[] = [];
  for (const entry of components) {
    const source = readFileSync(new URL(`../src/components/${entry}`, import.meta.url), "utf8");
    for (const [line] of source.matchAll(/^.*\.focus\((.*)$/gm)) {
      if (/focus-visible|:focus|onFocus/.test(line)) continue;
      if (!/preventScroll: true/.test(line)) missing.push(`${entry}: ${line.trim()}`);
    }
  }
  assert.deepEqual(missing, [], "these focus() calls inside the chat surface would scroll the panel");
});