import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';

vi.mock('$app/environment', () => ({ browser: true }));

let documentStub: EventTarget & { visibilityState: string };
let stop: (() => void) | undefined;
const changed = () => window.dispatchEvent(new Event('ec:fleet-changed'));
const visibility = (state: string) => {
    documentStub.visibilityState = state;
    documentStub.dispatchEvent(new Event('visibilitychange'));
};
const response = (url: string) => Response.json(url === '/api/servers'
    ? { serverNow: Date.now(), servers: [], integrations: {} } : { operations: [] });

beforeEach(() => {
    vi.resetModules();
    vi.useFakeTimers();
    vi.setSystemTime(new Date('2026-10-05T12:00:00Z'));
    documentStub = Object.assign(new EventTarget(), { visibilityState: 'visible' });
    vi.stubGlobal('document', documentStub);
    vi.stubGlobal('window', new EventTarget());
    vi.stubGlobal('fetch', vi.fn(async (url: string) => response(url)));
});
afterEach(() => {
    stop?.(); stop = undefined;
    vi.useRealTimers(); vi.unstubAllGlobals(); vi.restoreAllMocks();
});
async function setup() {
    const store = await import('../../src/lib/ui/stores/fleet.js');
    store.fleet.set({ servers: [], operations: [], receivedAt: Date.now() });
    stop = store.startFleetMonitor();
    return store;
}

describe('fleet event refreshes', () => {
    it('coalesces bursts and refreshes at most once every two seconds with a trailing refresh', async () => {
        await setup();
        changed(); changed(); changed();
        await vi.advanceTimersByTimeAsync(249);
        expect(fetch).not.toHaveBeenCalled();
        await vi.advanceTimersByTimeAsync(1);
        expect(fetch).toHaveBeenCalledTimes(2);
        for (let i = 0; i < 7; i++) {
            changed();
            await vi.advanceTimersByTimeAsync(250);
            expect(fetch).toHaveBeenCalledTimes(2);
        }
        await vi.advanceTimersByTimeAsync(250);
        expect(fetch).toHaveBeenCalledTimes(4);
        changed();
        await vi.advanceTimersByTimeAsync(2000);
        expect(fetch).toHaveBeenCalledTimes(6);
        await vi.advanceTimersByTimeAsync(5000);
        expect(fetch).toHaveBeenCalledTimes(6);
    });

    it('keeps events during a request without an immediate follow-up when it finishes', async () => {
        await setup();
        let finish!: () => void;
        const gate = new Promise<void>(resolve => { finish = resolve; });
        vi.mocked(fetch).mockImplementation(async url => { await gate; return response(String(url)); });
        changed();
        await vi.advanceTimersByTimeAsync(250);
        expect(fetch).toHaveBeenCalledTimes(2);
        changed(); changed();
        await vi.advanceTimersByTimeAsync(500);
        finish();
        await vi.advanceTimersByTimeAsync(1499);
        expect(fetch).toHaveBeenCalledTimes(2);
        await vi.advanceTimersByTimeAsync(1);
        expect(fetch).toHaveBeenCalledTimes(4);
    });

    it('waits for a slow manual refresh and coalesces events arriving during it', async () => {
        const { refreshFleet } = await setup();
        let finish!: () => void;
        const gate = new Promise<void>(resolve => { finish = resolve; });
        vi.mocked(fetch).mockImplementation(async url => { await gate; return response(String(url)); });
        const manual = refreshFleet();
        changed();
        await vi.advanceTimersByTimeAsync(3000);
        changed(); changed();
        expect(fetch).toHaveBeenCalledTimes(2);
        finish(); await manual;
        await vi.advanceTimersByTimeAsync(0);
        expect(fetch).toHaveBeenCalledTimes(4);
        await vi.advanceTimersByTimeAsync(3000);
        expect(fetch).toHaveBeenCalledTimes(4);
    });

    it('skips queued refreshes while hidden, refreshes on return, and cancels on stop', async () => {
        await setup();
        changed(); visibility('hidden');
        await vi.advanceTimersByTimeAsync(250);
        changed();
        await vi.advanceTimersByTimeAsync(3000);
        expect(fetch).not.toHaveBeenCalled();
        visibility('visible');
        await vi.advanceTimersByTimeAsync(0);
        expect(fetch).toHaveBeenCalledTimes(2);
        changed(); stop!();
        await vi.advanceTimersByTimeAsync(3000);
        expect(fetch).toHaveBeenCalledTimes(2);
    });

    it('cancels a follow-up waiting for an active request when stopped', async () => {
        const { refreshFleet } = await setup();
        let finish!: () => void;
        const gate = new Promise<void>(resolve => { finish = resolve; });
        vi.mocked(fetch).mockImplementation(async url => { await gate; return response(String(url)); });
        const manual = refreshFleet();
        changed();
        await vi.advanceTimersByTimeAsync(250);
        stop!(); finish(); await manual;
        await vi.advanceTimersByTimeAsync(3000);
        expect(fetch).toHaveBeenCalledTimes(2);
    });
});