Crafter.Build/implementations/Crafter.Build-Platform.cpp

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

module;
#if defined(CRAFTER_BUILD_CONFIGURATION_TARGET_x86_64_pc_windows_msvc) || defined(CRAFTER_BUILD_CONFIGURATION_TARGET_x86_64_w64_mingw32)
#include <windows.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#ifdef CRAFTER_BUILD_CONFIGURATION_TARGET_x86_64_pc_linux_gnu
#include <unistd.h>
#include <dlfcn.h>
#include <sys/wait.h>
#include <sys/file.h>
#include <fcntl.h>
#include <errno.h>
#endif
module Crafter.Build:Platform_impl;
import std;
import :Platform;
import :Clang;
import :Progress;
namespace fs = std::filesystem;
using namespace Crafter;

namespace {
    // Exclusive advisory lock over one PCM cache dir (`<cache>/<target>-<march>/`),
    // held for the duration of a (re)build. Concurrent crafter-build invocations —
    // and the worker threads inside a single invocation — that share a cache
    // serialize their builds through it: the first builder to acquire the lock
    // precompiles std.pcm / the Crafter.Build-*.pcm modules while everyone else
    // blocks, then re-checks freshness and reuses the finished file instead of
    // re-running clang and racing to overwrite the same path. Each builder must
    // pass through the lock before it reaches the compile steps that *read* those
    // PCMs, so a reader never observes a half-written file.
    //
    // The lock lives in the OS, keyed on a `.lock` file in the cache dir, and is
    // released automatically when the descriptor/handle closes — including on
    // process death — so an interrupted build can never leave a stale lock. The
    // descriptor is close-on-exec / non-inheritable so spawned clang processes
    // don't keep the lock alive past our own release.
    class CacheLock {
#ifdef CRAFTER_BUILD_CONFIGURATION_TARGET_x86_64_pc_linux_gnu
        std::int32_t fd_ = -1;
    public:
        explicit CacheLock(const fs::path& cacheDir) {
            fd_ = ::open((cacheDir / ".lock").c_str(), O_RDWR | O_CREAT | O_CLOEXEC, 0644);
            if (fd_ >= 0) {
                while (::flock(fd_, LOCK_EX) != 0 && errno == EINTR) {}
            }
        }
        ~CacheLock() {
            if (fd_ >= 0) {
                ::close(fd_);  // closing the descriptor drops the flock
            }
        }
#else
        HANDLE handle_ = INVALID_HANDLE_VALUE;
    public:
        explicit CacheLock(const fs::path& cacheDir) {
            handle_ = CreateFileW((cacheDir / ".lock").wstring().c_str(), GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, nullptr, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, nullptr);
            if (handle_ != INVALID_HANDLE_VALUE) {
                OVERLAPPED ov{};
                LockFileEx(handle_, LOCKFILE_EXCLUSIVE_LOCK, 0, MAXDWORD, MAXDWORD, &ov);
            }
        }
        ~CacheLock() {
            if (handle_ != INVALID_HANDLE_VALUE) {
                CloseHandle(handle_);  // closing the handle drops the lock
            }
        }
#endif
        CacheLock(const CacheLock&) = delete;
        CacheLock& operator=(const CacheLock&) = delete;
    };

    // The cached Crafter.Build PCMs are keyed by `<target>-<march>` alone, so
    // every crafter-build on the machine writes to the same files regardless of
    // which share/crafter-build its module sources came from. Freshness used to
    // be a per-file mtime comparison, which cannot distinguish "this PCM is
    // newer than my source" from "this PCM was built from *different* sources
    // that happen to be newer" — so a second install or checkout silently
    // compiled its project against the other's declarations. Same failure shape
    // as issue #27: no error, a binary built against a layout nobody linked.
    //
    // A stamp over the bytes of every module source answers what the mtime
    // can't. It covers the whole set rather than one file at a time because the
    // PCMs import each other: a change to :Interface invalidates :Clang's PCM
    // even though Crafter.Build-Clang.cppm is untouched.
    std::string CrafterBuildSourceStamp(const fs::path& sourceDir, std::span<const std::string_view> moduleNames) {
        std::string all;
        auto append = [&all, &sourceDir](const fs::path& relative) {
            std::ifstream in(sourceDir / relative, std::ios::binary);
            std::ostringstream buffer;
            buffer << in.rdbuf();
            all += relative.string();
            all += '\0';
            all += buffer.str();
            all += '\0';
        };
        for (std::string_view name : moduleNames) {
            append(fs::path(std::format("{}.cppm", name)));
        }
        // Exported through `module;` preambles, so its contents land in the PCMs
        // too.
        append("Crafter.Build-Api.h");
        return std::format("{:016x}", std::hash<std::string>{}(all));
    }

    fs::path CacheStampPath(const fs::path& cacheDir) {
        return cacheDir / "crafter-build-sources.stamp";
    }

    std::string ReadCacheStamp(const fs::path& cacheDir) {
        std::ifstream in(CacheStampPath(cacheDir), std::ios::binary);
        std::string stamp;
        std::getline(in, stamp);
        return stamp;
    }

    void WriteCacheStamp(const fs::path& cacheDir, const std::string& stamp) {
        std::ofstream(CacheStampPath(cacheDir), std::ios::binary | std::ios::trunc) << stamp << '\n';
    }
}

fs::path Crafter::GetCrafterBuildHome() {
    if (const char* envHome = std::getenv("CRAFTER_BUILD_HOME")) {
        return fs::path(envHome);
    }
#if defined(CRAFTER_BUILD_CONFIGURATION_TARGET_x86_64_pc_windows_msvc) || defined(CRAFTER_BUILD_CONFIGURATION_TARGET_x86_64_w64_mingw32)
    char buf[MAX_PATH];
    DWORD len = GetModuleFileNameA(nullptr, buf, MAX_PATH);
    if (len == 0 || len == MAX_PATH) {
        throw std::runtime_error("GetModuleFileName failed");
    }
    fs::path hostExe(std::string(buf, len));
#else
    fs::path hostExe = fs::read_symlink("/proc/self/exe");
#endif

    // Walk up from the exe's directory looking for share/crafter-build with
    // a known module source present as a sentinel. Handles:
    //   <prefix>/bin/crafter-build      -> <prefix>/share/crafter-build  (FHS install)
    //   <repo>/bin/crafter-build        -> <repo>/share/crafter-build    (build.sh)
    //   <repo>/bin/<arch>/crafter-build -> <repo>/share/crafter-build    (self-host)
    fs::path dir = hostExe.parent_path();
    std::vector<fs::path> tried;
    for (;;) {
        fs::path candidate = dir / "share" / "crafter-build";
        tried.push_back(candidate);
        std::error_code ec;
        if (fs::exists(candidate / "Crafter.Build.cppm", ec)) {
            return candidate;
        }
        fs::path parent = dir.parent_path();
        if (parent == dir) break;
        dir = parent;
    }
    std::string msg = std::format("could not locate crafter-build runtime assets relative to {} (set CRAFTER_BUILD_HOME). Tried:", hostExe.string());
    for (const auto& p : tried) {
        msg += std::format("\n  {}", p.string());
    }
    throw std::runtime_error(msg);
}

fs::file_time_type Crafter::NewestPrerequisite(const fs::path& depFile) {
    std::ifstream in(depFile, std::ios::binary);
    if (!in) return fs::file_time_type::max();
    std::ostringstream buffer;
    buffer << in.rdbuf();
    const std::string text = std::move(buffer).str();

    // Make-rule tokenizing, as clang writes it: `target: prereq prereq`, with a
    // trailing '\' continuing the rule onto the next line (clang wraps at ~80
    // columns, so any real depfile has several), '\ ' and '\#' escaping a
    // character into a filename, and '$$' standing for a literal '$'. A
    // backslash that is none of those is a Windows path separator and stays.
    std::vector<std::string> tokens;
    std::string token;
    auto flush = [&tokens, &token]() {
        if (!token.empty()) {
            tokens.push_back(token);
            token.clear();
        }
    };
    for (std::size_t i = 0; i < text.size(); ++i) {
        const char c = text[i];
        const char next = i + 1 < text.size() ? text[i + 1] : '\0';
        if (c == '\\' && (next == '\n' || next == '\r')) {
            flush();
            ++i;
        } else if (c == '\\' && (next == ' ' || next == '\t' || next == '#')) {
            token += next;
            ++i;
        } else if (c == '$' && next == '$') {
            token += '$';
            ++i;
        } else if (c == ' ' || c == '\t' || c == '\n' || c == '\r') {
            flush();
        } else {
            token += c;
        }
    }
    flush();

    // A token ending in ':' names a rule target, not an input. The first one
    // closes the target list (and a Windows `C:\build\x.o:` still ends in ':',
    // where splitting on the first colon would not); a later one opens another
    // rule, as `-MP` phony targets do, whose name is not a file to stat.
    bool sawTarget = false;
    fs::file_time_type newest = fs::file_time_type::min();
    for (const std::string& prerequisite : tokens) {
        if (prerequisite.ends_with(':')) {
            sawTarget = true;
            continue;
        }
        if (!sawTarget) continue;
        std::error_code ec;
        const fs::file_time_type stamp = fs::last_write_time(prerequisite, ec);
        // A prerequisite that has since been deleted makes the recorded set
        // unusable as evidence — the source that included it must have changed
        // too, and rebuilding is what writes a depfile that no longer names it.
        if (ec) return fs::file_time_type::max();
        if (stamp > newest) newest = stamp;
    }
    // No rule at all: a truncated or empty depfile proves nothing.
    if (!sawTarget) return fs::file_time_type::max();
    return newest;
}

bool Crafter::MatchGlob(std::string_view glob, std::string_view name) {
    std::size_t gi = 0;
    std::size_t ni = 0;
    std::size_t star = std::string_view::npos;
    std::size_t mark = 0;
    while (ni < name.size()) {
        if (gi < glob.size() && (glob[gi] == '?' || glob[gi] == name[ni])) {
            ++gi; ++ni;
        } else if (gi < glob.size() && glob[gi] == '*') {
            star = gi++;
            mark = ni;
        } else if (star != std::string_view::npos) {
            gi = star + 1;
            ni = ++mark;
        } else {
            return false;
        }
    }
    while (gi < glob.size() && glob[gi] == '*') ++gi;
    return gi == glob.size();
}

bool Crafter::MatchAny(std::span<const std::string> globs, std::string_view name) {
    if (globs.empty()) return true;
    for (const auto& g : globs) {
        if (MatchGlob(g, name)) return true;
    }
    return false;
}

#if defined(CRAFTER_BUILD_CONFIGURATION_TARGET_x86_64_pc_windows_msvc) || defined(CRAFTER_BUILD_CONFIGURATION_TARGET_x86_64_w64_mingw32)
std::string Crafter::RunCommand(const std::string_view cmd) {
    Progress::EchoCommand(cmd);
    std::array<char, 128> buffer;
    std::string result;

    // Use cmd.exe to interpret redirection
    std::string with = std::format("cmd /C \"{} 2>&1\"", std::string(cmd));

    FILE* pipe = _popen(with.c_str(), "r");
    if (!pipe) {
        throw std::runtime_error("_popen() failed!");
    }

    while (fgets(buffer.data(), static_cast<std::int32_t>(buffer.size()), pipe) != nullptr) {
        result += buffer.data();
    }

    _pclose(pipe);
    return result;
}

CommandResult Crafter::RunCommandChecked(std::string_view cmd) {
    std::array<char, 128> buffer;
    CommandResult result{};

    std::string with = std::format("cmd /C \"{} 2>&1\"", std::string(cmd));

    FILE* pipe = _popen(with.c_str(), "r");
    if (!pipe) {
        throw std::runtime_error("_popen() failed!");
    }

    while (fgets(buffer.data(), static_cast<std::int32_t>(buffer.size()), pipe) != nullptr) {
        result.output += buffer.data();
    }

    result.exitCode = _pclose(pipe);
    return result;
}

CommandResult Crafter::RunCommandWithTimeout(std::string_view cmd, std::chrono::seconds timeout) {
    CommandResult result{};

    SECURITY_ATTRIBUTES sa{ sizeof(sa), nullptr, TRUE };
    HANDLE readEnd = nullptr;
    HANDLE writeEnd = nullptr;
    if (!CreatePipe(&readEnd, &writeEnd, &sa, 0)) {
        throw std::runtime_error("CreatePipe failed");
    }
    SetHandleInformation(readEnd, HANDLE_FLAG_INHERIT, 0);

    // KILL_ON_JOB_CLOSE so the cmd.exe wrapper plus whatever it spawned
    // (the test binary, ssh, etc.) all die when the job handle goes away —
    // that's how we enforce the timeout reliably across the whole tree.
    HANDLE job = CreateJobObjectA(nullptr, nullptr);
    if (!job) {
        CloseHandle(readEnd);
        CloseHandle(writeEnd);
        throw std::runtime_error("CreateJobObject failed");
    }
    JOBOBJECT_EXTENDED_LIMIT_INFORMATION jeli{};
    jeli.BasicLimitInformation.LimitFlags = JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE;
    SetInformationJobObject(job, JobObjectExtendedLimitInformation, &jeli, sizeof(jeli));

    STARTUPINFOA si{};
    si.cb = sizeof(si);
    si.dwFlags = STARTF_USESTDHANDLES;
    si.hStdOutput = writeEnd;
    si.hStdError = writeEnd;
    si.hStdInput = GetStdHandle(STD_INPUT_HANDLE);

    PROCESS_INFORMATION pi{};
    // cmd /C "...": gives users the same shell-syntax surface (redirects,
    // &&, ||) as popen("/bin/sh -c …") does on Linux. cmd's special-case
    // /C parsing strips the outer quote pair when the inner text contains
    // additional quotes, which is the common case here.
    std::string wrapped = std::format("cmd /C \"{}\"", std::string(cmd));
    std::vector<char> cmdBuf(wrapped.begin(), wrapped.end());
    cmdBuf.push_back('\0');

    BOOL ok = CreateProcessA(nullptr, cmdBuf.data(), nullptr, nullptr, TRUE, CREATE_NO_WINDOW | CREATE_SUSPENDED, nullptr, nullptr, &si, &pi);
    if (!ok) {
        CloseHandle(readEnd);
        CloseHandle(writeEnd);
        CloseHandle(job);
        throw std::runtime_error("CreateProcess failed");
    }

    AssignProcessToJobObject(job, pi.hProcess);
    ResumeThread(pi.hThread);
    // Drop our writer ref so the read end sees EOF once the child (its
    // own dup of writeEnd) exits.
    CloseHandle(writeEnd);

    std::string output;
    std::jthread reader([&output, readEnd]() {
        char buf[4096];
        DWORD n = 0;
        while (ReadFile(readEnd, buf, sizeof(buf), &n, nullptr) && n > 0) {
            output.append(buf, n);
        }
    });

    DWORD waitMs = static_cast<DWORD>(std::min<std::int64_t>(static_cast<std::int64_t>(timeout.count()) * 1000LL, static_cast<std::int64_t>(INFINITE) - 1));
    DWORD waitResult = WaitForSingleObject(pi.hProcess, waitMs);

    if (waitResult == WAIT_TIMEOUT) {
        TerminateJobObject(job, 1);
        WaitForSingleObject(pi.hProcess, INFINITE);
        result.timedOut = true;
        result.exitCode = 124;
    } else {
        DWORD exit = 0;
        GetExitCodeProcess(pi.hProcess, &exit);
        // NTSTATUS error severity (top two bits set) means the process
        // terminated by exception — STATUS_ACCESS_VIOLATION 0xC0000005,
        // STATUS_STACK_OVERFLOW 0xC00000FD, etc. Surface those as crashes
        // so the runner shows 💥 instead of a numeric exit code.
        if ((exit & 0xC0000000) == 0xC0000000) {
            result.crashed = true;
            result.signal = static_cast<std::int32_t>(exit);
        }
        result.exitCode = static_cast<std::int32_t>(exit);
    }

    reader.join();
    CloseHandle(readEnd);
    CloseHandle(pi.hThread);
    CloseHandle(pi.hProcess);
    CloseHandle(job);

    result.output = std::move(output);
    return result;
}

fs::path Crafter::GetCacheDir() {
    if (const char* local = std::getenv("LOCALAPPDATA")) {
        return fs::path(local) / "crafter.build";
    }

    throw std::runtime_error("LOCALAPPDATA not set");
}

namespace {
    constexpr std::array<std::string_view, 11> CrafterBuildModules = {
        "Crafter.Build-Shader",
        "Crafter.Build-Platform",
        "Crafter.Build-Interface",
        "Crafter.Build-Implementation",
        "Crafter.Build-External",
        "Crafter.Build-Clang",
        "Crafter.Build-Test",
        "Crafter.Build-Lint",
        "Crafter.Build-Progress",
        "Crafter.Build-Asset",
        "Crafter.Build",
    };
}
#endif

#ifdef CRAFTER_BUILD_CONFIGURATION_TARGET_x86_64_pc_windows_msvc
// Native Windows build via build.cmd: MSVC ABI + libc++ from %LIBCXX_DIR%.

std::string Crafter::BuildStdPcm(const Configuration& config, fs::path stdPcm) {
    std::string libcxx = std::getenv("LIBCXX_DIR");
    std::string stdcppm = std::format("{}\\modules\\c++\\v1\\std.cppm", libcxx);

    CacheLock lock(stdPcm.parent_path());
    if(!fs::exists(stdPcm) || fs::last_write_time(stdPcm) < fs::last_write_time(stdcppm)) {
        return RunCommand(std::format("clang++ --target={} -march={} -mtune={} -isystem %LIBCXX_DIR%\\include\\c++\\v1 -nostdinc++ -nostdlib++ -std=c++26 -Wno-reserved-identifier -Wno-reserved-module-identifier --precompile %LIBCXX_DIR%\\modules\\c++\\v1\\std.cppm -o {}", config.target, config.march, config.mtune, stdPcm.string()));
    }
    return "";
}

std::string Crafter::GetBaseCommand(const Configuration& config) {
    return std::format("clang++ -nostdinc++ -nostdlib++ -isystem %LIBCXX_DIR%\\include\\c++\\v1");
}

namespace {
    void EnsureCrafterBuildPcms(const fs::path& sourceDir, const fs::path& cacheDir) {
        CacheLock lock(cacheDir);
        // Re-derived under the lock: another builder may have refreshed the
        // cache from its own sources while we waited.
        std::string stamp = CrafterBuildSourceStamp(sourceDir, CrafterBuildModules);
        bool upToDate = ReadCacheStamp(cacheDir) == stamp;
        for (std::string_view name : CrafterBuildModules) {
            fs::path cppmPath = sourceDir / std::format("{}.cppm", name);
            fs::path pcmPath = cacheDir / std::format("{}.pcm", name);
            if (!fs::exists(cppmPath)) {
                throw std::runtime_error(std::format("module source {} not found in {} (set CRAFTER_BUILD_HOME)", name, sourceDir.string()));
            }
            if (upToDate && fs::exists(pcmPath)) {
                continue;
            }
            std::string cmd = std::format(
                "clang++ --target=x86_64-pc-windows-msvc -march=native -mtune=native "
                "-std=c++26 -O3 -D CRAFTER_BUILD_DLL_IMPORT "
                "-nostdinc++ -nostdlib++ -isystem %LIBCXX_DIR%\\include\\c++\\v1 "
                "-Wno-reserved-identifier -Wno-reserved-module-identifier "
                "-fprebuilt-module-path={} "
                "--precompile {} -o {}",
                cacheDir.string(), cppmPath.string(), pcmPath.string());
            CommandResult r = Crafter::RunCommandChecked(cmd);
            if (r.exitCode != 0) {
                throw std::runtime_error(std::format("Failed to precompile {} (exit {}): {}", name, r.exitCode, r.output));
            }
        }
        // Last, so an interrupted rebuild leaves the stamp disagreeing with the
        // sources and the next run starts over rather than trusting a half-built
        // set of PCMs.
        if (!upToDate) WriteCacheStamp(cacheDir, stamp);
    }
}

Configuration Crafter::LoadProject(const fs::path& projectFile, std::span<const std::string_view> args) {
    fs::path absProject = fs::canonical(projectFile);
    fs::path buildDir = absProject.parent_path() / "build";
    if (!fs::exists(buildDir)) {
        fs::create_directories(buildDir);
    }
    fs::path dllPath = buildDir / std::format("{}.dll", absProject.stem().string());

    char hostExeBuf[MAX_PATH];
    DWORD hostExeLen = GetModuleFileNameA(nullptr, hostExeBuf, MAX_PATH);
    if (hostExeLen == 0 || hostExeLen == MAX_PATH) {
        throw std::runtime_error("GetModuleFileName failed");
    }
    fs::path hostExe(std::string(hostExeBuf, hostExeLen));

    fs::path sourceDir = Crafter::GetCrafterBuildHome();

    Configuration hostConfig;
    hostConfig.target = "x86_64-pc-windows-msvc";
    hostConfig.march = "native";
    hostConfig.mtune = "native";
    fs::path cacheDir = GetCacheDir() / std::format("{}-{}", hostConfig.target, hostConfig.march);
    if (!fs::exists(cacheDir)) fs::create_directories(cacheDir);

    std::string stdResult = BuildStdPcm(hostConfig, cacheDir / "std.pcm");
    if (!stdResult.empty()) {
        throw std::runtime_error(std::format("Failed to build std.pcm: {}", stdResult));
    }

    EnsureCrafterBuildPcms(sourceDir, cacheDir);

    bool stale = !fs::exists(dllPath) || fs::last_write_time(dllPath) < fs::last_write_time(absProject) || fs::last_write_time(dllPath) < fs::last_write_time(hostExe);

    if (stale) {
        fs::path crafterBuildLib = hostExe.parent_path() / "crafter-build.lib";

        std::string compileCmd = std::format(
            "clang++ --target=x86_64-pc-windows-msvc -march=native -mtune=native "
            "-std=c++26 -shared -O3 -Wno-return-type-c-linkage -fuse-ld=lld "
            "-D CRAFTER_BUILD_DLL_IMPORT "
            "-nostdinc++ -nostdlib++ -isystem %LIBCXX_DIR%\\include\\c++\\v1 "
            "-fprebuilt-module-path={} "
            "-Wl,/EXPORT:CrafterBuildProject "
            "{} {} -o {} -L %LIBCXX_DIR%\\lib -lc++",
            cacheDir.string(),
            absProject.string(), crafterBuildLib.string(), dllPath.string());

        std::string result = RunCommand(compileCmd);
        if (!result.empty()) {
            throw std::runtime_error(std::format("Failed to compile project {}: {}", absProject.string(), result));
        }
    }

    // project.dll links libc++ dynamically (-lc++) and the dll typically lives
    // under %LIBCXX_DIR%\lib. Add it to the loader's search path so the user
    // doesn't have to put it on PATH manually.
    if (const char* libcxx = std::getenv("LIBCXX_DIR"); libcxx && *libcxx) {
        fs::path libcxxLib = fs::path(libcxx) / "lib";
        SetDllDirectoryA(libcxxLib.string().c_str());
    }

    HMODULE handle = LoadLibraryA(dllPath.string().c_str());
    if (!handle) {
        throw std::runtime_error(std::format("Failed to load project {}: error {}", dllPath.string(), GetLastError()));
    }

    using ProjectFn = Configuration (*)(std::span<const std::string_view>);
    auto fn = reinterpret_cast<ProjectFn>(GetProcAddress(handle, "CrafterBuildProject"));
    if (!fn) {
        throw std::runtime_error(std::format("CrafterBuildProject not found in {}: error {}", dllPath.string(), GetLastError()));
    }

    return fn(args);
}
#endif

#ifdef CRAFTER_BUILD_CONFIGURATION_TARGET_x86_64_w64_mingw32
// Linux→mingw cross-compile run on Windows: mingw ABI + libstdc++ from msys2.
// Resolves the mingw sysroot at C:\msys64\ucrt64 by default (UCRT runtime,
// matching the Arch cross-compile that produced this binary). User can
// override with CRAFTER_MINGW_DIR if they have mingw-w64 installed elsewhere
// or want the legacy MSVCRT mingw at C:\msys64\mingw64. clang itself is the
// user's existing standalone clang on PATH.

namespace {
    fs::path MingwPrefix() {
        if (const char* env = std::getenv("CRAFTER_MINGW_DIR"); env && *env) {
            return fs::path(env);
        }
        return "C:\\msys64\\ucrt64";
    }

    std::string MingwGccVersion() {
        fs::path includeRoot = MingwPrefix() / "include" / "c++";
        if (!fs::exists(includeRoot)) {
            throw std::runtime_error(std::format("mingw-w64 not found at {} (install msys2 mingw-w64-x86_64-toolchain or set CRAFTER_MINGW_DIR)", MingwPrefix().string()));
        }
        std::vector<std::string> versions;
        for (const auto& entry : fs::directory_iterator(includeRoot)) {
            if (entry.is_directory()) versions.push_back(entry.path().filename().string());
        }
        if (versions.empty()) {
            throw std::runtime_error(std::format("no C++ versions under {}", includeRoot.string()));
        }
        std::sort(versions.begin(), versions.end(), std::greater<>());
        return versions.front();
    }
}

std::string Crafter::BuildStdPcm(const Configuration& config, fs::path stdPcm) {
    CacheLock lock(stdPcm.parent_path());
    if (config.target == "x86_64-pc-windows-msvc") {
        // MSVC target on mingw host: same MSVC libc++ logic as the
        // native-MSVC LoadProject path. User must have LIBCXX_DIR pointing
        // at a Windows libc++ install.
        const char* libcxxEnv = std::getenv("LIBCXX_DIR");
        if (!libcxxEnv || !*libcxxEnv) {
            return "MSVC target requires LIBCXX_DIR pointing at a Windows libc++ install";
        }
        std::string stdcppm = std::format("{}\\modules\\c++\\v1\\std.cppm", libcxxEnv);
        if (fs::exists(stdPcm) && fs::last_write_time(stdPcm) >= fs::last_write_time(stdcppm)) {
            return "";
        }
        return RunCommand(std::format(
            "clang++ --target={} -march={} -mtune={} -isystem %LIBCXX_DIR%\\include\\c++\\v1 "
            "-nostdinc++ -nostdlib++ -std=c++26 -Wno-reserved-identifier -Wno-reserved-module-identifier "
            "--precompile %LIBCXX_DIR%\\modules\\c++\\v1\\std.cppm -o {}",
            config.target, config.march, config.mtune, stdPcm.string()));
    }

    // Default: mingw target. Look up mingw-w64 libstdc++ via the msys2 prefix.
    fs::path prefix = MingwPrefix();
    fs::path stdCc = prefix / "include" / "c++" / MingwGccVersion() / "bits" / "std.cc";
    if (!fs::exists(stdCc)) {
        return std::format("std.cc not found at {}", stdCc.string());
    }
    if (fs::exists(stdPcm) && fs::last_write_time(stdPcm) >= fs::last_write_time(stdCc)) {
        return "";
    }
    // Copy std.cc → std.cppm in C++ rather than via cmd's `copy /Y` because
    // `copy` always prints "1 file(s) copied." to stdout and RunCommand
    // treats any output as an error. Held under the cache lock, so a plain
    // filename is safe — no other builder writes this path concurrently.
    fs::path stdCppm = stdPcm.parent_path() / "std.cppm";
    std::error_code ec;
    fs::copy_file(stdCc, stdCppm, fs::copy_options::overwrite_existing, ec);
    if (ec) {
        return std::format("copy {} -> {}: {}", stdCc.string(), stdCppm.string(), ec.message());
    }
    return RunCommand(std::format(
        "clang++ --target={} -march={} -mtune={} "
        "--sysroot=\"{}\" -femulated-tls "
        "-O3 -std=c++26 -Wno-reserved-identifier -Wno-reserved-module-identifier "
        "--precompile \"{}\" -o {}",
        config.target, config.march, config.mtune,
        prefix.string(),
        stdCppm.string(),
        stdPcm.string()));
}

std::string Crafter::GetBaseCommand(const Configuration& config) {
    if (config.target == "x86_64-pc-windows-msvc") {
        return std::format("clang++ -nostdinc++ -nostdlib++ -isystem %LIBCXX_DIR%\\include\\c++\\v1");
    }
    return std::format("clang++ --sysroot=\"{}\" -femulated-tls", MingwPrefix().string());
}

namespace {
    void EnsureCrafterBuildPcms(const fs::path& sourceDir, const fs::path& cacheDir) {
        CacheLock lock(cacheDir);
        // Re-derived under the lock: another builder may have refreshed the
        // cache from its own sources while we waited.
        std::string stamp = CrafterBuildSourceStamp(sourceDir, CrafterBuildModules);
        bool upToDate = ReadCacheStamp(cacheDir) == stamp;
        fs::path prefix = MingwPrefix();
        for (std::string_view name : CrafterBuildModules) {
            fs::path cppmPath = sourceDir / std::format("{}.cppm", name);
            fs::path pcmPath = cacheDir / std::format("{}.pcm", name);
            if (!fs::exists(cppmPath)) {
                throw std::runtime_error(std::format("module source {} not found in {} (set CRAFTER_BUILD_HOME)", name, sourceDir.string()));
            }
            if (upToDate && fs::exists(pcmPath)) {
                continue;
            }
            std::string cmd = std::format(
                "clang++ --target=x86_64-w64-mingw32 -march=native -mtune=native "
                "--sysroot=\"{}\" -femulated-tls "
                "-std=c++26 -O3 -D CRAFTER_BUILD_DLL_IMPORT "
                "-Wno-reserved-identifier -Wno-reserved-module-identifier "
                "-fprebuilt-module-path={} "
                "--precompile {} -o {}",
                prefix.string(), cacheDir.string(), cppmPath.string(), pcmPath.string());
            CommandResult r = Crafter::RunCommandChecked(cmd);
            if (r.exitCode != 0) {
                throw std::runtime_error(std::format("Failed to precompile {} (exit {}): {}", name, r.exitCode, r.output));
            }
        }
        // Last, so an interrupted rebuild leaves the stamp disagreeing with the
        // sources and the next run starts over rather than trusting a half-built
        // set of PCMs.
        if (!upToDate) WriteCacheStamp(cacheDir, stamp);
    }
}

Configuration Crafter::LoadProject(const fs::path& projectFile, std::span<const std::string_view> args) {
    fs::path absProject = fs::canonical(projectFile);
    fs::path buildDir = absProject.parent_path() / "build";
    if (!fs::exists(buildDir)) fs::create_directories(buildDir);
    fs::path dllPath = buildDir / std::format("{}.dll", absProject.stem().string());

    char hostExeBuf[MAX_PATH];
    DWORD hostExeLen = GetModuleFileNameA(nullptr, hostExeBuf, MAX_PATH);
    if (hostExeLen == 0 || hostExeLen == MAX_PATH) {
        throw std::runtime_error("GetModuleFileName failed");
    }
    fs::path hostExe(std::string(hostExeBuf, hostExeLen));

    fs::path sourceDir = Crafter::GetCrafterBuildHome();

    Configuration hostConfig;
    hostConfig.target = "x86_64-w64-mingw32";
    hostConfig.march = "native";
    hostConfig.mtune = "native";
    fs::path cacheDir = GetCacheDir() / std::format("{}-{}", hostConfig.target, hostConfig.march);
    if (!fs::exists(cacheDir)) fs::create_directories(cacheDir);

    std::string stdResult = BuildStdPcm(hostConfig, cacheDir / "std.pcm");
    if (!stdResult.empty()) {
        throw std::runtime_error(std::format("Failed to build std.pcm: {}", stdResult));
    }

    EnsureCrafterBuildPcms(sourceDir, cacheDir);

    bool stale = !fs::exists(dllPath) || fs::last_write_time(dllPath) < fs::last_write_time(absProject) || fs::last_write_time(dllPath) < fs::last_write_time(hostExe);

    if (stale) {
        // The import lib lives next to the launcher exe (Build()'s mingw
        // copy step puts libcrafter-build.dll.a there) so -L<exe-dir>
        // -lcrafter-build resolves it.
        fs::path prefix = MingwPrefix();
        std::string compileCmd = std::format(
            "clang++ --target=x86_64-w64-mingw32 -march=native -mtune=native "
            "--sysroot=\"{}\" -femulated-tls "
            "-std=c++26 -shared -O3 -Wno-return-type-c-linkage -fuse-ld=lld "
            "-D CRAFTER_BUILD_DLL_IMPORT "
            "-fprebuilt-module-path={} "
            // mingw-lld doesn't accept /EXPORT:NAME — use the catch-all so
            // CrafterBuildProject is reachable via GetProcAddress without
            // forcing project.cpp templates to add __declspec(dllexport).
            "-Wl,--export-all-symbols "
            "{} -o {} -L\"{}\" -lcrafter-build -lstdc++exp -lpthread",
            prefix.string(),
            cacheDir.string(),
            absProject.string(), dllPath.string(),
            hostExe.parent_path().string());

        std::string result = RunCommand(compileCmd);
        if (!result.empty()) {
            throw std::runtime_error(std::format("Failed to compile project {}: {}", absProject.string(), result));
        }
    }

    // project.dll is a mingw DLL linking libstdc++-6.dll / libgcc_s_seh-1.dll /
    // libwinpthread-1.dll dynamically (LoadProject's compile uses -lstdc++exp
    // -lpthread, not -static). We already know where they live from
    // MingwPrefix(), so add bin/ to the loader's search path here instead of
    // requiring the user to prepend it to PATH manually.
    fs::path mingwBin = MingwPrefix() / "bin";
    SetDllDirectoryA(mingwBin.string().c_str());

    HMODULE handle = LoadLibraryA(dllPath.string().c_str());
    if (!handle) {
        throw std::runtime_error(std::format("Failed to load project {}: error {}", dllPath.string(), GetLastError()));
    }

    using ProjectFn = Configuration (*)(std::span<const std::string_view>);
    auto fn = reinterpret_cast<ProjectFn>(GetProcAddress(handle, "CrafterBuildProject"));
    if (!fn) {
        throw std::runtime_error(std::format("CrafterBuildProject not found in {}: error {}", dllPath.string(), GetLastError()));
    }

    return fn(args);
}
#endif

#ifdef CRAFTER_BUILD_CONFIGURATION_TARGET_x86_64_pc_linux_gnu

std::string Crafter::RunCommand(const std::string_view cmd) {
    Progress::EchoCommand(cmd);
    std::array<char, 128> buffer;
    std::string result;

    std::string with = std::format("{} 2>&1", cmd);
    // Open pipe to file
    FILE* pipe = popen(with.c_str(), "r");
    if (!pipe) throw std::runtime_error("popen() failed!");

    // Read till end of process:
    while (fgets(buffer.data(), buffer.size(), pipe) != nullptr) {
        result += buffer.data();
    }

    // Close pipe
    pclose(pipe);
    return result;
}

CommandResult Crafter::RunCommandChecked(std::string_view cmd) {
    std::array<char, 128> buffer;
    CommandResult result{};

    std::string with = std::format("{} 2>&1", cmd);
    FILE* pipe = popen(with.c_str(), "r");
    if (!pipe) throw std::runtime_error("popen() failed!");

    while (fgets(buffer.data(), buffer.size(), pipe) != nullptr) {
        result.output += buffer.data();
    }

    std::int32_t status = pclose(pipe);
    if (WIFEXITED(status)) {
        result.exitCode = WEXITSTATUS(status);
    } else if (WIFSIGNALED(status)) {
        result.signal = WTERMSIG(status);
        result.exitCode = 128 + result.signal;
        result.crashed = true;
    } else {
        result.exitCode = -1;
    }
    return result;
}

CommandResult Crafter::RunCommandWithTimeout(std::string_view cmd, std::chrono::seconds timeout) {
    std::array<char, 128> buffer;
    CommandResult result{};

    std::string wrapped = std::format("timeout --kill-after=2 {} {} 2>&1", timeout.count(), cmd);

    FILE* pipe = popen(wrapped.c_str(), "r");
    if (!pipe) throw std::runtime_error("popen() failed!");

    while (fgets(buffer.data(), buffer.size(), pipe) != nullptr) {
        result.output += buffer.data();
    }

    std::int32_t status = pclose(pipe);
    if (WIFEXITED(status)) {
        std::int32_t code = WEXITSTATUS(status);
        if (code == 124) {
            result.timedOut = true;
            result.exitCode = 124;
        } else if (code >= 128) {
            result.signal = code - 128;
            result.exitCode = code;
            result.crashed = true;
        } else {
            result.exitCode = code;
        }
    } else if (WIFSIGNALED(status)) {
        result.signal = WTERMSIG(status);
        result.exitCode = 128 + result.signal;
        result.crashed = true;
    } else {
        result.exitCode = -1;
    }
    return result;
}

std::string Crafter::BuildStdPcm(const Configuration& config, fs::path stdPcm) {
    CacheLock lock(stdPcm.parent_path());
    if(config.target == "x86_64-w64-mingw32") {
        std::vector<std::string> folders;

        // Iterate through the directory and collect all subdirectories
        for (const auto& entry : fs::directory_iterator("/usr/x86_64-w64-mingw32/include/c++")) {
            if (entry.is_directory()) {
                folders.push_back(entry.path().filename().string());
            }
        }

        // Sort the folders by version in descending order
        std::sort(folders.begin(), folders.end(), [](const std::string& a, const std::string& b) {
            return std::lexicographical_compare(b.begin(), b.end(), a.begin(), a.end());
        });

        std::string mingWversion = folders.front();

        fs::path stdCc = fs::path(std::format("/usr/x86_64-w64-mingw32/include/c++/{}/bits/std.cc", mingWversion));

        if(!fs::exists(stdPcm) || fs::last_write_time(stdPcm) < fs::last_write_time(stdCc)) {
            // -femulated-tls keeps PCM TLS access matching libstdc++'s emutls
            // definitions; mismatch surfaces as undefined std::__once_callable.
            // The std.cc → std.cppm copy uses a plain filename: held under the
            // cache lock, no other builder writes this path concurrently.
            fs::path stdCppm = stdPcm.parent_path() / "std.cppm";
            std::error_code copyEc;
            fs::copy_file(stdCc, stdCppm, fs::copy_options::overwrite_existing, copyEc);
            if (copyEc) {
                return std::format("copy {} -> {}: {}", stdCc.string(), stdCppm.string(), copyEc.message());
            }
            return RunCommand(std::format("clang++ --target={} -march={} -mtune={} -femulated-tls -O3 -std=c++26 -Wno-reserved-identifier -Wno-reserved-module-identifier --precompile {} -o {}", config.target, config.march, config.mtune, stdCppm.string(), stdPcm.string()));
        } else {
            return "";
        }
    } else {
        const bool isWasm = config.target.starts_with("wasm32");
        // wasi-sdk drops std.cppm at <sysroot>/share/libc++/v1/, the rest of
        // the libc++ ecosystem (e.g. /opt/aarch64-rootfs) follows FHS at
        // <sysroot>/usr/share/libc++/v1/.
        std::string stdCppm;
        if (isWasm) {
            stdCppm = std::format("{}/share/libc++/v1/std.cppm", config.sysroot);
        } else if (config.sysroot.empty()) {
            stdCppm = "/usr/share/libc++/v1/std.cppm";
        } else {
            stdCppm = std::format("{}/usr/share/libc++/v1/std.cppm", config.sysroot);
            // not every distro ships the std module sources (Alpine's
            // libc++-dev doesn't); the host copy is interchangeable as long
            // as the libc++ versions line up, which the compile of the PCM
            // against the sysroot's headers verifies anyway
            if (!fs::exists(stdCppm) && fs::exists("/usr/share/libc++/v1/std.cppm")) {
                stdCppm = "/usr/share/libc++/v1/std.cppm";
            }
        }
        std::string sysrootFlag = config.sysroot.empty()
            ? std::string()
            : std::format(" --sysroot={}", config.sysroot);
        // wasm32 rejects -march. wasi-libc++ headers require these baselines
        // to compile: setjmp.h needs -mllvm -wasm-enable-sjlj (lowered to wasm
        // EH); signal.h requires the emulation define; and EH itself isn't
        // wired up so -fno-exceptions stays.
        std::string archFlags = isWasm
            ? std::string(" -fno-exceptions -msimd128 -fno-c++-static-destructors -mllvm -wasm-enable-sjlj -D_WASI_EMULATED_SIGNAL")
            : std::format(" -march={} -mtune={}", config.march, config.mtune);
        // Match the variant codegen flags the consuming TUs are built with
        // (e.g. -mrelaxed-simd) so the std BMI is feature-compatible. wasm only;
        // wasmVariantFlags is empty on every other path.
        if (isWasm) {
            for (const std::string& f : config.wasmVariantFlags) archFlags += std::format(" {}", f);
        }
        // non-wasm cross builds: the driver ranks the host toolchain's own
        // libc++ headers (<install>/../include/c++/v1) above --sysroot, so
        // the PCM would mix host libc++ with the foreign libc — force the
        // sysroot's copy (same trick as the Windows LIBCXX_DIR path)
        if (!isWasm && !config.sysroot.empty()) {
            archFlags += std::format(" -nostdinc++ -isystem {}/usr/include/c++/v1", config.sysroot);
        }
        if(!fs::exists(stdPcm) || fs::last_write_time(stdPcm) < fs::last_write_time(stdCppm)) {
            return RunCommand(std::format("clang++ --target={} -std=c++26 -stdlib=libc++{}{} -O3 -Wno-reserved-identifier -Wno-reserved-module-identifier --precompile {} -o {}", config.target, sysrootFlag, archFlags, stdCppm, stdPcm.string()));
        } else {
            return "";
        }
    }
}

fs::path Crafter::GetCacheDir() {
    if (const char* xdg = std::getenv("XDG_CACHE_HOME"); xdg && *xdg) {
        return fs::path(xdg) / "crafter.build";
    }

    if (const char* home = std::getenv("HOME")) {
        return fs::path(home) / ".cache" / "crafter.build";
    }

    throw std::runtime_error("Neither XDG_CACHE_HOME nor HOME set");
}

std::string Crafter::GetBaseCommand(const Configuration& config) {
    std::string stdlib;
    if(config.target == "x86_64-w64-mingw32") {
        stdlib = "";
    } else {
        stdlib = "-stdlib=libc++";
    }
    return std::format("clang++ {}", stdlib);
}

namespace {
    constexpr std::array<std::string_view, 11> CrafterBuildModules = {
        "Crafter.Build-Shader",
        "Crafter.Build-Platform",
        "Crafter.Build-Interface",
        "Crafter.Build-Implementation",
        "Crafter.Build-External",
        "Crafter.Build-Clang",
        "Crafter.Build-Test",
        "Crafter.Build-Lint",
        "Crafter.Build-Progress",
        "Crafter.Build-Asset",
        "Crafter.Build",
    };

    void EnsureCrafterBuildPcms(const fs::path& sourceDir, const fs::path& cacheDir) {
        CacheLock lock(cacheDir);
        // Re-derived under the lock: another builder may have refreshed the
        // cache from its own sources while we waited.
        std::string stamp = CrafterBuildSourceStamp(sourceDir, CrafterBuildModules);
        const bool upToDate = ReadCacheStamp(cacheDir) == stamp;
        for (std::string_view name : CrafterBuildModules) {
            fs::path cppmPath = sourceDir / std::format("{}.cppm", name);
            fs::path pcmPath = cacheDir / std::format("{}.pcm", name);
            if (!fs::exists(cppmPath)) {
                throw std::runtime_error(std::format("module source {} not found in {} (set CRAFTER_BUILD_HOME)", name, sourceDir.string()));
            }
            if (upToDate && fs::exists(pcmPath)) {
                continue;
            }
            std::string cmd = std::format(
                "clang++ --target=x86_64-pc-linux-gnu -march=native -mtune=native "
                "-std=c++26 -stdlib=libc++ -O3 "
                "-Wno-reserved-identifier -Wno-reserved-module-identifier "
                "-fprebuilt-module-path={} "
                "--precompile {} -o {}",
                cacheDir.string(), cppmPath.string(), pcmPath.string());
            CommandResult r = Crafter::RunCommandChecked(cmd);
            if (r.exitCode != 0) {
                throw std::runtime_error(std::format("Failed to precompile {} (exit {}): {}", name, r.exitCode, r.output));
            }
        }
        // Last, so an interrupted rebuild leaves the stamp disagreeing with the
        // sources and the next run starts over rather than trusting a half-built
        // set of PCMs.
        if (!upToDate) WriteCacheStamp(cacheDir, stamp);
    }
}

Configuration Crafter::LoadProject(const fs::path& projectFile, std::span<const std::string_view> args) {
    fs::path absProject = fs::canonical(projectFile);
    fs::path buildDir = absProject.parent_path() / "build";
    if (!fs::exists(buildDir)) {
        fs::create_directories(buildDir);
    }
    fs::path soPath = buildDir / std::format("{}.so", absProject.stem().string());

    fs::path hostExe = fs::read_symlink("/proc/self/exe");

    fs::path sourceDir = Crafter::GetCrafterBuildHome();

    Configuration hostConfig;
    hostConfig.target = "x86_64-pc-linux-gnu";
    hostConfig.march = "native";
    hostConfig.mtune = "native";
    fs::path cacheDir = GetCacheDir() / std::format("{}-{}", hostConfig.target, hostConfig.march);
    if (!fs::exists(cacheDir)) fs::create_directories(cacheDir);

    std::string stdResult = BuildStdPcm(hostConfig, cacheDir / "std.pcm");
    if (!stdResult.empty()) {
        throw std::runtime_error(std::format("Failed to build std.pcm: {}", stdResult));
    }

    EnsureCrafterBuildPcms(sourceDir, cacheDir);

    const bool stale = !fs::exists(soPath) || fs::last_write_time(soPath) < fs::last_write_time(absProject) || fs::last_write_time(soPath) < fs::last_write_time(hostExe);

    if (stale) {
        std::string compileCmd = std::format(
            "clang++ --target=x86_64-pc-linux-gnu -march=native -mtune=native "
            "-std=c++26 -stdlib=libc++ -shared -fPIC -O3 "
            "-Wno-return-type-c-linkage "
            "-fprebuilt-module-path={} "
            "{} -o {}",
            cacheDir.string(),
            absProject.string(), soPath.string());

        std::string result = RunCommand(compileCmd);
        if (!result.empty()) {
            throw std::runtime_error(std::format("Failed to compile project {}: {}", absProject.string(), result));
        }
    }

    void* handle = dlopen(soPath.c_str(), RTLD_NOW | RTLD_GLOBAL);
    if (!handle) {
        throw std::runtime_error(std::format("Failed to load project {}: {}", soPath.string(), dlerror()));
    }

    using ProjectFn = Configuration (*)(std::span<const std::string_view>);
    dlerror();
    auto fn = reinterpret_cast<ProjectFn>(dlsym(handle, "CrafterBuildProject"));
    if (const char* err = dlerror()) {
        throw std::runtime_error(std::format("CrafterBuildProject not found in {}: {}", soPath.string(), err));
    }

    return fn(args);
}

#endif