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

// SetTitle on the Wayland backend sends xdg_toplevel.set_title with exactly
// the view's bytes. It handed title.data() on, which set_title reads up to
// a NUL: a view into a longer string sent the whole string, and an empty
// view, whose data() is null, sent a null string, which libwayland refuses
// with a fatal error on the display.
//
// The toplevel is a proxy on a wl_display connected to one end of a
// socketpair, and the test reads the requests off the other end, so no
// compositor is needed. Needs the Wayland backend, hence Linux only.

#include <wayland-client.h>
#include <sys/socket.h>
#include <unistd.h>
#include <cerrno>
#include <cstdlib>
#include <cstring>
#include "../../lib/xdg-shell-client-protocol.h"

import Crafter.Graphics;
import std;
using namespace Crafter;

namespace {

int failures = 0;

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

// What the display has written so far.
std::vector<std::uint8_t> Sent(wl_display* display, int peer) {
    wl_display_flush(display);
    std::vector<std::uint8_t> wire;
    std::uint8_t chunk[4096];
    for (ssize_t n; (n = recv(peer, chunk, sizeof(chunk), MSG_DONTWAIT)) > 0;) {
        wire.insert(wire.end(), chunk, chunk + n);
    }
    return wire;
}

// The titles of the set_title requests on `object` in `wire`. A request is
// its object id, then its size and opcode in one word, then its arguments;
// set_title's one argument is a string, its length with the NUL, then its
// bytes padded to a word.
std::vector<std::string> Titles(const std::vector<std::uint8_t>& wire, std::uint32_t object) {
    std::vector<std::string> titles;
    for (std::size_t at = 0; at + 8 <= wire.size();) {
        std::uint32_t header[2];
        std::memcpy(header, wire.data() + at, sizeof(header));
        const std::uint32_t size = header[1] >> 16;
        if (size < 8 || at + size > wire.size()) break;
        if (header[0] == object && (header[1] & 0xFFFF) == XDG_TOPLEVEL_SET_TITLE && size >= 12) {
            std::uint32_t length;
            std::memcpy(&length, wire.data() + at + 8, sizeof(length));
            if (length > 0 && 12 + length <= size) {
                titles.emplace_back(reinterpret_cast<const char*>(wire.data() + at + 12), length - 1);
            }
        }
        at += size;
    }
    return titles;
}

} // namespace

int main() {
    int fds[2];
    if (socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, fds) != 0) {
        std::println("FAIL  socketpair: {}", std::strerror(errno));
        return EXIT_FAILURE;
    }
    // The display owns fds[0] from here.
    wl_display* display = wl_display_connect_to_fd(fds[0]);
    if (display == nullptr) {
        std::println("FAIL  wl_display_connect_to_fd: {}", std::strerror(errno));
        return EXIT_FAILURE;
    }
    // libwayland makes whatever proxy it is asked to bind; nothing answers.
    wl_registry* registry = wl_display_get_registry(display);
    auto* toplevel = static_cast<xdg_toplevel*>(wl_registry_bind(registry, 1, &xdg_toplevel_interface, 1));
    const std::uint32_t id = wl_proxy_get_id(reinterpret_cast<wl_proxy*>(toplevel));
    Sent(display, fds[1]);

    {
        // A default-constructed window, which ~Window can tear down without
        // a display, holding the proxy as its toplevel.
        Window window;
        window.xdgToplevel = toplevel;

        const std::string longer = "Crafter.Graphics";
        window.SetTitle(std::string_view(longer).substr(0, 7));
        const std::vector<std::string> sliced = Titles(Sent(display, fds[1]), id);
        Check(sliced == std::vector<std::string>{ "Crafter" }, "a view into a longer string: the view's bytes only");
        if (sliced != std::vector<std::string>{ "Crafter" }) {
            for (const std::string& title : sliced) std::println("      set_title \"{}\"", title);
        }

        window.SetTitle(std::string_view{});
        const std::vector<std::string> empty = Titles(Sent(display, fds[1]), id);
        const int error = wl_display_get_error(display);
        Check(error == 0 && empty == std::vector<std::string>{ "" }, "an empty view: an empty title, not a null string");
        if (error != 0) std::println("      the display failed: {}", std::strerror(error));
        // ~Window destroys the toplevel.
    }
    wl_registry_destroy(registry);
    wl_display_disconnect(display);
    close(fds[1]);

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