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

import std;
import Crafter.Build;
namespace fs = std::filesystem;
using namespace Crafter;

// A std module rebuilt in place has to recompile the units that import it.
// The std PCM is rebuilt in its directory whenever its source changes under
// the same compiler and flags: a libc++ update, or mingw-w64's under the
// same prefix. A .cpp unit's depfile listed only its source and headers,
// because the driver records imported BMIs for --precompile alone, so such
// a unit kept its object and the next build only relinked it.
//
// The project is one main.cpp that imports std. Its object is dated before
// std.pcm and after its source, as a std module rebuilt after the object
// leaves them, and the next build has to compile it again. XDG_CACHE_HOME keeps the std PCM out of the real
// cache, whose other users the change of date would rebuild.

extern "C" int setenv(const char* name, const char* value, int overwrite);

namespace {
    std::int32_t failures = 0;

    void Check(bool cond, std::string_view msg) {
        if (!cond) {
            std::println(std::cerr, "FAIL: {}", msg);
            ++failures;
        }
    }

    BuildResult BuildOnce(Configuration& cfg) {
        std::unordered_map<fs::path, std::shared_future<BuildResult>> depResults;
        std::mutex depMutex;
        return Build(cfg, depResults, depMutex);
    }
}

int main() {
    const fs::path scratch = fs::temp_directory_path() / "crafter-build-std-pcm-rebuild";
    std::error_code ec;
    fs::remove_all(scratch, ec);
    fs::create_directories(scratch);
    const fs::path project = scratch / "project";
    fs::copy(fs::current_path() / "tests" / "StdPcmRebuild" / "fixture", project, fs::copy_options::recursive);
    setenv("XDG_CACHE_HOME", (scratch / "cache").c_str(), 1);

    Configuration cfg;
    cfg.path = project;
    cfg.name = "rebuilt";
    cfg.outputName = "rebuilt";
    cfg.type = ConfigurationType::Executable;
    std::array<fs::path, 0> ifaces = {};
    std::array<fs::path, 1> impls = { "main" };
    cfg.GetInterfacesAndImplementations(ifaces, impls);

    BuildResult built = BuildOnce(cfg);
    Check(built.result.empty(), std::format("the project builds: {}", built.result));
    const fs::path object = cfg.BuildDir() / "main_impl.o";
    const fs::path stdPcm = StdPcmDir(cfg) / "std.pcm";
    Check(fs::exists(object) && fs::exists(stdPcm), std::format("{} and {} exist", object.string(), stdPcm.string()));
    if (!fs::exists(object) || !fs::exists(stdPcm)) return 1;

    const fs::file_time_type first = fs::last_write_time(object);
    built = BuildOnce(cfg);
    Check(built.result.empty(), std::format("an idle build succeeds: {}", built.result));
    Check(fs::last_write_time(object) == first, "and compiles nothing again");

    // The source before the object and the object before std.pcm, so that
    // nothing but the std module makes the object stale.
    const fs::file_time_type older = fs::last_write_time(stdPcm) - std::chrono::seconds(10);
    fs::last_write_time(project / "main.cpp", older - std::chrono::seconds(10));
    fs::last_write_time(object, older);
    built = BuildOnce(cfg);
    Check(built.result.empty(), std::format("the build after the std module succeeds: {}", built.result));
    Check(fs::last_write_time(object) > older, "a unit importing a std module newer than its object is compiled again");

    fs::remove_all(scratch, ec);
    if (failures > 0) {
        std::println(std::cerr, "{} assertions failed", failures);
        return 1;
    }
    return 0;
}