"""Check the Mesh sort policy without rebuilding a complete FreeCAD runtime."""
from pathlib import Path
import shutil
import subprocess
import tempfile
import unittest


ROOT = Path(__file__).resolve().parents[1]
SOURCE = r'''
#include <cerrno>
#include <functional>
#include <numeric>
#include <pthread.h>
#include <random>
#include <vector>
#include "src/Mod/Mesh/App/Core/Functional.h"

static int threadAttempts = 0;
extern "C" int __wrap_pthread_create(pthread_t*, const pthread_attr_t*, void* (*)(void*), void*)
{
    ++threadAttempts;
    return EAGAIN;
}

int main()
{
    std::mt19937 random(42);
    for (const int size : {0, 1, 2, 36, 65536}) {
        std::vector<int> original(size);
        for (auto& value : original) value = static_cast<int>(random() % 1000);
        for (const int threads : {0, 1, 2, 64}) {
            auto expected = original;
            auto actual = original;
            std::sort(expected.begin(), expected.end(), std::greater<int>());
            MeshCore::parallel_sort(actual.begin(), actual.end(), std::greater<int>(), threads);
            if (actual != expected) return 1;
        }
    }
    return threadAttempts ? 2 : 0;
}
'''


class MeshWasmSortTests(unittest.TestCase):
    @unittest.skipUnless(shutil.which("c++"), "C++ compiler is required")
    def test_wasm_sort_preserves_results_without_attempting_pthreads(self):
        with tempfile.TemporaryDirectory(prefix="freecad-mesh-sort-") as directory:
            source = Path(directory) / "sort.cpp"
            binary = Path(directory) / "sort"
            source.write_text(SOURCE)
            subprocess.run(["c++", "-std=c++17", "-O2", "-D__EMSCRIPTEN__", "-pthread",
                            "-Wl,--wrap=pthread_create", "-I", str(ROOT / "freecad-source"),
                            str(source), "-o", str(binary)], check=True, capture_output=True, text=True, timeout=30)
            subprocess.run([str(binary)], check=True, capture_output=True, text=True, timeout=5)


if __name__ == "__main__":
    unittest.main()