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

#include <stdlib.h>
import std;
import Crafter.Build;
namespace fs = std::filesystem;
using namespace Crafter;

// The host PCM cache is keyed by `<target>-<march>` alone, so every
// crafter-build on a machine — a package install and a working checkout, two
// checkouts of different versions — writes the same `Crafter.Build-*.pcm`
// files. Freshness was a per-file mtime comparison, which says "the PCM is
// newer than my source, reuse it" whether or not it was built from *my*
// source. The loser then compiled its project.cpp against the other install's
// declarations: no error, and a project.so built against a layout that doesn't
// match the library it's loaded into — the same silent shape as issue #27.
//
// So the invalidation has to key on the source bytes, and this test asserts it
// notices a change the mtime rule provably cannot see: different content with a
// deliberately *older* timestamp.
namespace {
    std::int32_t Failures = 0;

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

    // The cache subdirectory is named for the host target and march; glob for
    // it rather than reconstructing the naming rule here.
    fs::path FindModuleCacheDir(const fs::path& cacheRoot) {
        for (const fs::directory_entry& entry : fs::directory_iterator(cacheRoot / "crafter.build")) {
            if (entry.is_directory()) return entry.path();
        }
        return {};
    }

    std::string ReadStamp(const fs::path& moduleCacheDir) {
        std::ifstream in(moduleCacheDir / "crafter-build-sources.stamp");
        std::string stamp;
        std::getline(in, stamp);
        return stamp;
    }
}

int main() {
    fs::path installedHome = GetCrafterBuildHome();
    if (!fs::exists(installedHome / "Crafter.Build.cppm")) {
        std::println(std::cerr, "SKIP: no module sources at {}", installedHome.string());
        return 77;
    }

    fs::path scratch = fs::temp_directory_path() / "crafter-build-host-cache-source-stamp";
    std::error_code ec;
    fs::remove_all(scratch, ec);
    fs::create_directories(scratch);

    // A private copy of the module sources, so the mutation below can't touch
    // the real install, and a cold private cache so the first LoadProject has
    // to populate it.
    fs::path home = scratch / "share" / "crafter-build";
    fs::create_directories(home.parent_path());
    fs::copy(installedHome, home, fs::copy_options::recursive);
    setenv("CRAFTER_BUILD_HOME", home.string().c_str(), 1);

    fs::path cacheRoot = scratch / "cache";
    fs::create_directories(cacheRoot);
    setenv("XDG_CACHE_HOME", cacheRoot.string().c_str(), 1);

    fs::path projectDir = scratch / "project";
    fs::create_directories(projectDir);
    fs::path projectFile = projectDir / "project.cpp";
    std::ofstream(projectFile) <<
        "import std;\n"
        "import Crafter.Build;\n"
        "using namespace Crafter;\n"
        "extern \"C\" Configuration CrafterBuildProject(std::span<const std::string_view>) {\n"
        "    Configuration cfg;\n"
        "    cfg.path = \"./\";\n"
        "    cfg.name = \"stamped\";\n"
        "    cfg.outputName = \"stamped\";\n"
        "    cfg.target = HostTarget();\n"
        "    cfg.type = ConfigurationType::Executable;\n"
        "    return cfg;\n"
        "}\n";

    std::array<std::string_view, 0> noArgs = {};

    try {
        (void)LoadProject(projectFile, noArgs);
    } catch (const std::exception& e) {
        std::println(std::cerr, "FAIL: first LoadProject threw: {}", e.what());
        return 1;
    }

    fs::path moduleCacheDir = FindModuleCacheDir(cacheRoot);
    Check(!moduleCacheDir.empty(), "a module cache directory was created");
    if (moduleCacheDir.empty()) return 1;

    fs::path probePcm = moduleCacheDir / "Crafter.Build-Clang.pcm";
    Check(fs::exists(probePcm), "the cold run populated the cache");
    if (!fs::exists(probePcm)) return 1;

    std::string firstStamp = ReadStamp(moduleCacheDir);
    Check(!firstStamp.empty(), "the cold run recorded a source stamp");
    fs::file_time_type afterCold = fs::last_write_time(probePcm);

    // Unchanged sources must be a no-op — the stamp is an invalidation key, not
    // an excuse to precompile eleven modules on every invocation.
    try {
        (void)LoadProject(projectFile, noArgs);
    } catch (const std::exception& e) {
        std::println(std::cerr, "FAIL: warm LoadProject threw: {}", e.what());
        return 1;
    }
    Check(fs::last_write_time(probePcm) == afterCold, "unchanged sources do not rebuild the cache");
    Check(ReadStamp(moduleCacheDir) == firstStamp, "unchanged sources keep the same stamp");

    // Now the case the mtime rule cannot see. The edit lands in a module the
    // probe does not name, because the cached PCMs import each other: a change
    // anywhere in the set invalidates all of them.
    fs::path edited = home / "Crafter.Build-Progress.cppm";
    {
        std::ofstream append(edited, std::ios::app);
        append << "\n// Content change with a backdated timestamp.\n";
    }
    fs::last_write_time(edited, afterCold - std::chrono::hours(24));
    Check(fs::last_write_time(edited) < fs::last_write_time(probePcm), "the edited source really is older than the cached PCM");

    try {
        (void)LoadProject(projectFile, noArgs);
    } catch (const std::exception& e) {
        std::println(std::cerr, "FAIL: LoadProject after the edit threw: {}", e.what());
        return 1;
    }

    Check(fs::last_write_time(probePcm) > afterCold, "a content change rebuilds the cache even when the source's mtime is older");
    Check(ReadStamp(moduleCacheDir) != firstStamp, "the recorded stamp follows the sources");

    fs::remove_all(scratch, ec);

    if (Failures > 0) {
        std::println(std::cerr, "{} assertions failed", Failures);
        return 1;
    }
    return 0;
}