import { test, expect } from "@playwright/test";
import {
  createMockSessions,
  handleSessionsRoute,
  sessionsRoutePattern,
} from "./helpers/mock-sessions";
import {
  ITEM_HEIGHT,
} from "../src/lib/components/sidebar/session-list-utils";
import {
  getScrollTop,
  scrollListTo,
  waitForScrollHeight,
} from "./helpers/virtual-list-helpers";
import { SessionsPage } from "./pages/sessions-page";

const TOTAL_SESSIONS = 500;
const DEEP_SESSIONS = 2000;
const MIDDLE_INDEX = Math.floor(DEEP_SESSIONS / 2);
const LAST_INDEX = DEEP_SESSIONS - 1;
const DEEP_SCROLL_HEIGHT = DEEP_SESSIONS * ITEM_HEIGHT;

/** Expected header text after all deep sessions load (en-US). */
const DEEP_COUNT_TEXT = `${DEEP_SESSIONS.toLocaleString("en-US")} sessions`;

const sessions = createMockSessions(
  TOTAL_SESSIONS,
  "session",
  (i) => (i % 2 === 0 ? "project-alpha" : "project-beta"),
);

const deepSessions = createMockSessions(
  DEEP_SESSIONS,
  "deep-session",
  () => "deep",
);

const tinySessions = [sessions[0]];

test.describe("Virtual list behavior", () => {
  let sp: SessionsPage;

  test.beforeEach(async ({ page }) => {
    await page.route(
      sessionsRoutePattern,
      handleSessionsRoute([
        { sessions, project: null },
        { sessions: deepSessions, project: "deep" },
        { sessions: tinySessions, project: "tiny" },
      ]),
    );

    await page.route("**/api/v1/projects*", async (route) => {
      await route.fulfill({
        json: {
          projects: [
            { name: "project-alpha", session_count: 250 },
            { name: "project-beta", session_count: 250 },
            { name: "tiny", session_count: 1 },
            { name: "deep", session_count: DEEP_SESSIONS },
          ],
        },
      });
    });

    sp = new SessionsPage(page);
    await page.goto("/");
    await expect(sp.sessionItems.first()).toBeVisible();
  });

  test("renders end of list when scrolling down", async () => {
    await scrollListTo(sp.sessionListScroll, "bottom");

    await expect(
      sp.page.getByText(
        `Hello from session ${TOTAL_SESSIONS - 1}`,
      ),
    ).toBeVisible();
  });

  test("clamps scroll position when filtering", async () => {
    await scrollListTo(sp.sessionListScroll, 2000);

    await expect
      .poll(() => getScrollTop(sp.sessionListScroll))
      .toBeGreaterThan(0);

    await sp.filterByProject("tiny");

    // Wait for filtered results to render before checking
    // scroll position — on CI the re-render can be slow.
    await expect(sp.sessionCount).toHaveText("1 session", {
      timeout: 5_000,
    });

    await expect
      .poll(() => getScrollTop(sp.sessionListScroll), {
        timeout: 5_000,
      })
      .toBe(0);
  });

  test("scrolls to an unloaded middle range", async () => {
    await sp.filterByProject("deep");

    // Wait for all pages to load so scrollHeight reflects the
    // full dataset. The virtual list sizes itself from
    // sessions.length, so scrolling before loading completes
    // would land at the wrong position.
    await expect(sp.sessionListHeader).toContainText(
      DEEP_COUNT_TEXT,
      { timeout: 15_000 },
    );
    await waitForScrollHeight(
      sp.sessionListScroll,
      DEEP_SCROLL_HEIGHT,
    );

    await scrollListTo(sp.sessionListScroll, "middle");

    await expect(
      sp.page.getByRole("button", {
        name: new RegExp(
          `Hello from deep-session ${MIDDLE_INDEX}`,
          "i",
        ),
      }),
    ).toBeVisible({ timeout: 10_000 });
  });

  test("scrolls to the end of a large list", async () => {
    await sp.filterByProject("deep");

    await expect(sp.sessionListHeader).toContainText(
      DEEP_COUNT_TEXT,
      { timeout: 15_000 },
    );
    await waitForScrollHeight(
      sp.sessionListScroll,
      DEEP_SCROLL_HEIGHT,
    );

    await scrollListTo(sp.sessionListScroll, "bottom");

    await expect(
      sp.page.getByRole("button", {
        name: new RegExp(
          `Hello from deep-session ${LAST_INDEX}`,
          "i",
        ),
      }),
    ).toBeVisible({ timeout: 10_000 });
  });
});