//SPDX-License-Identifier: LGPL-3.0-only
//SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®

// A window can update on its own clock (Window::updateInterval) instead of
// the compositor's frame callbacks, which stop while the window is hidden or
// minimized, so an app whose output goes somewhere other than the screen
// keeps rendering. The event loop also wakes for file descriptors the app
// registers (Window::AddPollFd), such as an eventfd another thread signals,
// and SetPresentMode picks MAILBOX so presenting never waits on the display.
//
// The test presents with MAILBOX, updates every 20 ms, and has a thread
// signal an eventfd every 50 ms. Half a second in, it minimizes its own
// window, and then counts the updates and wakes for a second. Before, the
// Wayland loop only updated from frame callbacks, which KWin stops for a
// minimized window, and blocked in wl_display_dispatch, so it never saw
// another descriptor.
//
// Needs a live Wayland compositor that honours set_minimized, and a Vulkan
// device. The validation check only means something with
// CRAFTER_GRAPHICS_VALIDATION set.

#include <cstdio>
#include <cstdlib>
#include <sys/eventfd.h>
#include <unistd.h>
#include "vulkan/vulkan.h"
#include "../../lib/xdg-shell-client-protocol.h"

import Crafter.Graphics;
import Crafter.Event;
import std;

using namespace Crafter;
using namespace std::chrono_literals;

namespace {

int failures = 0;

void Check(bool ok, std::string_view what) {
    std::println("{}  {}", ok ? "PASS" : "FAIL", what);
    if (!ok) ++failures;
}

} // namespace

int main() {
    Device::Initialize();
    Device::validationErrorCount = 0;

    Window window(320, 240, "WindowUpdateClock test");
    window.SetPresentMode(PresentMode::Mailbox);
    std::uint32_t modeCount = 0;
    Device::CheckVkResult(vkGetPhysicalDeviceSurfacePresentModesKHR(Device::physDevice, window.vulkanSurface, &modeCount, nullptr));
    std::vector<VkPresentModeKHR> modes(modeCount);
    Device::CheckVkResult(vkGetPhysicalDeviceSurfacePresentModesKHR(Device::physDevice, window.vulkanSurface, &modeCount, modes.data()));
    const bool mailboxOffered = std::ranges::find(modes, VK_PRESENT_MODE_MAILBOX_KHR) != modes.end();
    Check(window.swapchainPresentMode == (mailboxOffered ? VK_PRESENT_MODE_MAILBOX_KHR : VK_PRESENT_MODE_FIFO_KHR),
          std::format("SetPresentMode(Mailbox) gives MAILBOX where the surface offers it, else FIFO ({})", mailboxOffered ? "offered" : "not offered"));
    window.StartInit();
    window.FinishInit();

    // A thread signals an eventfd every 50 ms; the loop must wake for it.
    const int wake = eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK);
    std::atomic<bool> stopSignalling = false;
    std::thread signaller([&] {
        while (!stopSignalling) {
            const std::uint64_t one = 1;
            (void)write(wake, &one, sizeof(one));
            std::this_thread::sleep_for(50ms);
        }
    });
    std::uint32_t wakes = 0;
    window.AddPollFd(wake, [&] {
        std::uint64_t count = 0;
        (void)read(wake, &count, sizeof(count));
        ++wakes;
    });

    // If an update ever blocks (a present waiting on a hidden surface), fail
    // instead of hanging until the runner's timeout.
    std::atomic<bool> finished = false;
    std::thread watchdog([&] {
        const auto deadline = std::chrono::steady_clock::now() + 15s;
        while (!finished) {
            if (std::chrono::steady_clock::now() > deadline) {
                std::println("FAIL  the event loop stopped making progress");
                // _Exit skips the flush that would print the line.
                std::fflush(stdout);
                std::_Exit(EXIT_FAILURE);
            }
            std::this_thread::sleep_for(50ms);
        }
    });

    const auto start = std::chrono::steady_clock::now();
    bool minimized = false;
    std::uint32_t updatesVisible = 0;
    std::uint32_t updatesMinimized = 0;
    std::uint32_t wakesAtMinimize = 0;
    EventListener<FrameTime> onUpdate(&window.onUpdate, [&](FrameTime) {
        const auto elapsed = std::chrono::steady_clock::now() - start;
        if (!minimized && elapsed >= 500ms) {
            xdg_toplevel_set_minimized(window.xdgToplevel);
            minimized = true;
            wakesAtMinimize = wakes;
        } else if (minimized && elapsed >= 1500ms) {
            window.open = false;
        }
        (minimized ? updatesMinimized : updatesVisible)++;
    });

    window.updateInterval = 20ms;
    window.StartUpdate();
    window.StartSync();
    finished = true;
    watchdog.join();
    stopSignalling = true;
    signaller.join();
    window.RemovePollFd(wake);
    close(wake);
    Device::CheckVkResult(vkQueueWaitIdle(Device::queue));

    // 20 ms apart: 25 updates in the visible half second, 50 in the minimized
    // second. Leave room for a loaded machine, not for a stopped clock.
    std::println("      {} updates visible, {} minimized, {} wakes ({} while minimized)", updatesVisible, updatesMinimized, wakes, wakes - wakesAtMinimize);
    Check(updatesVisible >= 18 && updatesVisible <= 27, "the clock updates every 20 ms while the window is visible");
    Check(updatesMinimized >= 40 && updatesMinimized <= 52, "and keeps updating every 20 ms while it is minimized");
    Check(wakes - wakesAtMinimize >= 14, "the eventfd wakes the loop every 50 ms, minimized too");
    if (std::getenv("CRAFTER_GRAPHICS_VALIDATION") != nullptr) {
        Check(Device::validationErrorCount == 0,
              std::format("no Vulkan validation errors ({} seen)", Device::validationErrorCount));
    }

    std::println("{}", failures == 0 ? "all checks passed" : "check(s) failed");
    return failures == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
}