// Copyright 2016 The Bazel Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif

#include <wchar.h>
#include <windows.h>

#include <atomic>
#include <memory>
#include <sstream>
#include <string>
#include <type_traits>  // static_assert

#include "src/main/native/jni.h"
#include "src/main/native/windows/file.h"
#include "src/main/native/windows/jni-util.h"
#include "src/main/native/windows/util.h"

// These are the possible return values from the NativeProcess::WaitFor()
// method.
static const int kWaitSuccess = 0;
static const int kWaitTimeout = 1;
static const int kWaitError = 2;

template <typename T>
static std::wstring ToString(const T& e) {
  std::wstringstream s;
  s << e;
  return s.str();
}

extern "C" JNIEXPORT jint JNICALL
Java_com_google_devtools_build_lib_windows_jni_WindowsProcesses_nativeGetpid(
    JNIEnv* env, jclass clazz) {
  return GetCurrentProcessId();
}

class JavaByteArray {
 public:
  JavaByteArray(JNIEnv* env, jbyteArray java_array)
      : env_(env),
        array_(java_array),
        size_(java_array != nullptr ? env->GetArrayLength(java_array) : 0),
        ptr_(java_array != nullptr ? env->GetByteArrayElements(java_array, NULL)
                                   : nullptr) {}

  ~JavaByteArray() {
    if (array_ != nullptr) {
      env_->ReleaseByteArrayElements(array_, ptr_, 0);
      array_ = nullptr;
      size_ = 0;
      ptr_ = nullptr;
    }
  }

  jsize size() { return size_; }
  jbyte* ptr() { return ptr_; }

 private:
  JNIEnv* env_;
  jbyteArray array_;
  jsize size_;
  jbyte* ptr_;
};

class NativeOutputStream {
 public:
  NativeOutputStream()
      : handle_(INVALID_HANDLE_VALUE), error_(L""), closed_(false) {}

  void Close() {
    closed_.store(true);
    if (handle_ == INVALID_HANDLE_VALUE) {
      return;
    }

    // CancelIoEx only cancels I/O operations in the current process.
    // https://msdn.microsoft.com/en-us/library/windows/desktop/aa363792(v=vs.85).aspx
    //
    // Therefore if this process bequested `handle_` to a child process, we
    // cannot cancel I/O in the child process.
    CancelIoEx(handle_, NULL);
    CloseHandle(handle_);
    handle_ = INVALID_HANDLE_VALUE;
  }

  void SetHandle(HANDLE handle) { handle_ = handle; }

  jint ReadStream(JNIEnv* env, jbyteArray java_bytes, jint offset,
                  jint length) {
    JavaByteArray bytes(env, java_bytes);
    if (offset < 0 || length <= 0 || offset > bytes.size() - length) {
      error_ = bazel::windows::MakeErrorMessage(WSTR(__FILE__), __LINE__,
                                                L"nativeReadStream", L"",
                                                L"Array index out of bounds");
      return -1;
    }

    if (handle_ == INVALID_HANDLE_VALUE || closed_.load()) {
      error_ = L"";
      return 0;
    }

    DWORD bytes_read;
    if (!::ReadFile(handle_, bytes.ptr() + offset, length, &bytes_read, NULL)) {
      // Check if either the other end closed the pipe or we did it with
      // NativeOutputStream.Close() . In the latter case, we'll get a "system
      // call interrupted" error.
      if (GetLastError() == ERROR_BROKEN_PIPE || closed_.load()) {
        // End of file.
        error_ = L"";
        bytes_read = 0;
      } else {
        DWORD err_code = GetLastError();
        error_ = bazel::windows::MakeErrorMessage(
            WSTR(__FILE__), __LINE__, L"nativeReadStream", L"", err_code);
        bytes_read = -1;
      }
    } else {
      error_ = L"";
    }

    return bytes_read;
  }

  // Return the last error as a human-readable string and clear it.
  jstring GetLastErrorAsString(JNIEnv* env) {
    jstring result = env->NewString(
        reinterpret_cast<const jchar*>(error_.c_str()), error_.size());
    error_ = L"";
    return result;
  }

 private:
  HANDLE handle_;
  std::wstring error_;
  std::atomic<bool> closed_;
};

class NativeProcess {
 public:
  NativeProcess()
      : stdin_(INVALID_HANDLE_VALUE),
        stdout_(),
        stderr_(),
        process_(INVALID_HANDLE_VALUE),
        job_(INVALID_HANDLE_VALUE),
        ioport_(INVALID_HANDLE_VALUE),
        exit_code_(STILL_ACTIVE),
        error_(L"") {}

  ~NativeProcess() {
    if (stdin_ != INVALID_HANDLE_VALUE) {
      CloseHandle(stdin_);
    }

    stdout_.Close();
    stderr_.Close();

    if (process_ != INVALID_HANDLE_VALUE) {
      CloseHandle(process_);
    }

    if (job_ != INVALID_HANDLE_VALUE) {
      CloseHandle(job_);
    }

    if (ioport_ != INVALID_HANDLE_VALUE) {
      CloseHandle(ioport_);
    }
  }

  jboolean Create(JNIEnv* env, jstring java_argv0, jstring java_argv_rest,
                  jbyteArray java_env, jstring java_cwd,
                  jstring java_stdout_redirect, jstring java_stderr_redirect,
                  jboolean redirectErrorStream) {
    std::wstring argv0;
    std::wstring wpath(bazel::windows::GetJavaWpath(env, java_argv0));
    std::wstring error_msg(
        bazel::windows::AsExecutablePathForCreateProcess(wpath, &argv0));
    if (!error_msg.empty()) {
      error_ = bazel::windows::MakeErrorMessage(
          WSTR(__FILE__), __LINE__, L"nativeCreateProcess", wpath, error_msg);
      return false;
    }

    std::wstring commandline =
        argv0 + L" " + bazel::windows::GetJavaWstring(env, java_argv_rest);
    std::wstring stdout_redirect = bazel::windows::AddUncPrefixMaybe(
        bazel::windows::GetJavaWpath(env, java_stdout_redirect));
    std::wstring stderr_redirect = bazel::windows::AddUncPrefixMaybe(
        bazel::windows::GetJavaWpath(env, java_stderr_redirect));
    std::wstring cwd;
    std::wstring wcwd(bazel::windows::GetJavaWpath(env, java_cwd));
    error_msg = bazel::windows::AsShortPath(wcwd, &cwd);
    if (!error_msg.empty()) {
      error_ = bazel::windows::MakeErrorMessage(
          WSTR(__FILE__), __LINE__, L"nativeCreateProcess", wpath, error_msg);
      return false;
    }

    const bool stdout_is_stream = stdout_redirect.empty();
    const bool stderr_is_stream =
        redirectErrorStream ? stdout_is_stream : stderr_redirect.empty();
    const bool stderr_same_handle_as_stdout =
        redirectErrorStream ||
        (!stderr_redirect.empty() &&
         stderr_redirect.size() == stdout_redirect.size() &&
         _wcsnicmp(stderr_redirect.c_str(), stdout_redirect.c_str(),
                   stderr_redirect.size()) == 0);

    std::unique_ptr<WCHAR[]> mutable_commandline(
        new WCHAR[commandline.size() + 1]);
    wcsncpy(mutable_commandline.get(), commandline.c_str(),
            commandline.size() + 1);

    SECURITY_ATTRIBUTES sa = {0};
    sa.nLength = sizeof(SECURITY_ATTRIBUTES);
    sa.bInheritHandle = TRUE;

    // Standard file handles are closed even if the process was successfully
    // created. If this was not so, operations on these file handles would not
    // return immediately if the process is terminated.
    // Therefore we make these handles auto-closing (by using AutoHandle).
    bazel::windows::AutoHandle stdin_process;
    bazel::windows::AutoHandle stdout_process;
    bazel::windows::AutoHandle stderr_process;
    bazel::windows::AutoHandle thread;
    PROCESS_INFORMATION process_info = {0};
    JOBOBJECT_EXTENDED_LIMIT_INFORMATION job_info = {0};

    JavaByteArray env_map(env, java_env);
    if (env_map.ptr() != nullptr) {
      if (env_map.size() < 4) {
        error_ = bazel::windows::MakeErrorMessage(
            WSTR(__FILE__), __LINE__, L"nativeCreateProcess", wpath,
            std::wstring(
                L"the environment must be at least 4 bytes long, was ") +
                ToString(env_map.size()) + L" bytes");
        return false;
      } else if (env_map.ptr()[env_map.size() - 1] != 0 ||
                 env_map.ptr()[env_map.size() - 2] != 0 ||
                 env_map.ptr()[env_map.size() - 3] != 0 ||
                 env_map.ptr()[env_map.size() - 4] != 0) {
        error_ = bazel::windows::MakeErrorMessage(
            WSTR(__FILE__), __LINE__, L"nativeCreateProcess", wpath,
            L"environment array must end with 4 null bytes");
        return false;
      }
    }

    {
      HANDLE pipe_read_h, pipe_write_h;
      if (!CreatePipe(&pipe_read_h, &pipe_write_h, &sa, 0)) {
        DWORD err_code = GetLastError();
        error_ = bazel::windows::MakeErrorMessage(
            WSTR(__FILE__), __LINE__, L"nativeCreateProcess", wpath, err_code);
        return false;
      }
      stdin_process = pipe_read_h;
      stdin_ = pipe_write_h;
    }

    if (!stdout_is_stream) {
      stdout_.Close();

      stdout_process = CreateFileW(
          /* lpFileName */ stdout_redirect.c_str(),
          /* dwDesiredAccess */ GENERIC_WRITE,
          /* dwShareMode */ 0,
          /* lpSecurityAttributes */ &sa,
          /* dwCreationDisposition */ OPEN_ALWAYS,
          /* dwFlagsAndAttributes */ FILE_ATTRIBUTE_NORMAL,
          /* hTemplateFile */ NULL);

      if (!stdout_process.IsValid()) {
        DWORD err_code = GetLastError();
        error_ = bazel::windows::MakeErrorMessage(WSTR(__FILE__), __LINE__,
                                                  L"nativeCreateProcess",
                                                  stdout_redirect, err_code);
        return false;
      }
      if (!SetFilePointerEx(stdout_process, {0}, NULL, FILE_END)) {
        DWORD err_code = GetLastError();
        error_ = bazel::windows::MakeErrorMessage(WSTR(__FILE__), __LINE__,
                                                  L"nativeCreateProcess",
                                                  stdout_redirect, err_code);
        return false;
      }
    } else {
      HANDLE pipe_read_h, pipe_write_h;
      if (!CreatePipe(&pipe_read_h, &pipe_write_h, &sa, 0)) {
        DWORD err_code = GetLastError();
        error_ = bazel::windows::MakeErrorMessage(
            WSTR(__FILE__), __LINE__, L"nativeCreateProcess", wpath, err_code);
        return false;
      }
      stdout_.SetHandle(pipe_read_h);
      stdout_process = pipe_write_h;
    }

    if (stderr_same_handle_as_stdout) {
      HANDLE stdout_process_dup_h;
      if (!DuplicateHandle(GetCurrentProcess(), stdout_process,
                           GetCurrentProcess(), &stdout_process_dup_h, 0, TRUE,
                           DUPLICATE_SAME_ACCESS)) {
        DWORD err_code = GetLastError();
        error_ = bazel::windows::MakeErrorMessage(
            WSTR(__FILE__), __LINE__, L"nativeCreateProcess", wpath, err_code);
        return false;
      }
      if (!stderr_is_stream) {
        stderr_.Close();
      }

      stderr_process = stdout_process_dup_h;
    } else if (!stderr_redirect.empty()) {
      stderr_.Close();
      stderr_process = CreateFileW(
          /* lpFileName */ stderr_redirect.c_str(),
          /* dwDesiredAccess */ GENERIC_WRITE,
          /* dwShareMode */ 0,
          /* lpSecurityAttributes */ &sa,
          /* dwCreationDisposition */ OPEN_ALWAYS,
          /* dwFlagsAndAttributes */ FILE_ATTRIBUTE_NORMAL,
          /* hTemplateFile */ NULL);

      if (!stderr_process.IsValid()) {
        DWORD err_code = GetLastError();
        error_ = bazel::windows::MakeErrorMessage(WSTR(__FILE__), __LINE__,
                                                  L"nativeCreateProcess",
                                                  stderr_redirect, err_code);
        return false;
      }
      if (!SetFilePointerEx(stderr_process, {0}, NULL, FILE_END)) {
        DWORD err_code = GetLastError();
        error_ = bazel::windows::MakeErrorMessage(WSTR(__FILE__), __LINE__,
                                                  L"nativeCreateProcess",
                                                  stderr_redirect, err_code);
        return false;
      }
    } else {
      HANDLE pipe_read_h, pipe_write_h;
      if (!CreatePipe(&pipe_read_h, &pipe_write_h, &sa, 0)) {
        DWORD err_code = GetLastError();
        error_ = bazel::windows::MakeErrorMessage(
            WSTR(__FILE__), __LINE__, L"nativeCreateProcess", wpath, err_code);
        return false;
      }
      stderr_.SetHandle(pipe_read_h);
      stderr_process = pipe_write_h;
    }

    // MDSN says that the default for job objects is that breakaway is not
    // allowed. Thus, we don't need to do any more setup here.
    HANDLE job = CreateJobObject(NULL, NULL);
    if (job == NULL) {
      DWORD err_code = GetLastError();
      error_ = bazel::windows::MakeErrorMessage(
          WSTR(__FILE__), __LINE__, L"nativeCreateProcess", wpath, err_code);
      return false;
    }

    job_ = job;

    job_info.BasicLimitInformation.LimitFlags =
        JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE;
    if (!SetInformationJobObject(job, JobObjectExtendedLimitInformation,
                                 &job_info, sizeof(job_info))) {
      DWORD err_code = GetLastError();
      error_ = bazel::windows::MakeErrorMessage(
          WSTR(__FILE__), __LINE__, L"nativeCreateProcess", wpath, err_code);
      return false;
    }

    HANDLE ioport = CreateIoCompletionPort(INVALID_HANDLE_VALUE, nullptr, 0, 1);
    if (ioport == nullptr) {
      DWORD err_code = GetLastError();
      error_ = bazel::windows::MakeErrorMessage(
          WSTR(__FILE__), __LINE__, L"nativeCreateProcess", wpath, err_code);
      return false;
    }
    ioport_ = ioport;
    JOBOBJECT_ASSOCIATE_COMPLETION_PORT port;
    port.CompletionKey = job;
    port.CompletionPort = ioport;
    if (!SetInformationJobObject(job,
                                 JobObjectAssociateCompletionPortInformation,
                                 &port, sizeof(port))) {
      DWORD err_code = GetLastError();
      error_ = bazel::windows::MakeErrorMessage(
          WSTR(__FILE__), __LINE__, L"nativeCreateProcess", wpath, err_code);
      return false;
    }

    std::unique_ptr<bazel::windows::AutoAttributeList> attr_list;
    if (!bazel::windows::AutoAttributeList::Create(
            stdin_process, stdout_process, stderr_process, &attr_list,
            &error_msg)) {
      error_ = bazel::windows::MakeErrorMessage(
          WSTR(__FILE__), __LINE__, L"nativeCreateProcess", L"", error_msg);
      return false;
    }

    // kMaxCmdline value: see lpCommandLine parameter of CreateProcessW.
    static constexpr size_t kMaxCmdline = 32767;

    std::wstring cmd_sample = mutable_commandline.get();
    if (cmd_sample.size() > 200) {
      cmd_sample = cmd_sample.substr(0, 195) + L"(...)";
    }
    if (wcsnlen_s(mutable_commandline.get(), kMaxCmdline) == kMaxCmdline) {
      std::wstringstream error_msg;
      error_msg << L"command is longer than CreateProcessW's limit ("
                << kMaxCmdline << L" characters)";
      error_ = bazel::windows::MakeErrorMessage(
          WSTR(__FILE__), __LINE__, L"CreateProcessWithExplicitHandles",
          cmd_sample, error_msg.str().c_str());
      return false;
    }

    STARTUPINFOEXW info;
    attr_list->InitStartupInfoExW(&info);
    if (!CreateProcessW(
            /* lpApplicationName */ NULL,
            /* lpCommandLine */ mutable_commandline.get(),
            /* lpProcessAttributes */ NULL,
            /* lpThreadAttributes */ NULL,
            /* bInheritHandles */ TRUE,
            /* dwCreationFlags */ CREATE_NO_WINDOW  // Don't create console
                                                    // window
                |
                CREATE_NEW_PROCESS_GROUP  // So that Ctrl-Break isn't propagated
                | CREATE_SUSPENDED  // So that it doesn't start a new job itself
                | EXTENDED_STARTUPINFO_PRESENT | CREATE_UNICODE_ENVIRONMENT,
            /* lpEnvironment */ env_map.ptr(),
            /* lpCurrentDirectory */ cwd.empty() ? NULL : cwd.c_str(),
            /* lpStartupInfo */ &info.StartupInfo,
            /* lpProcessInformation */ &process_info)) {
      DWORD err = GetLastError();
      error_ = bazel::windows::MakeErrorMessage(
          WSTR(__FILE__), __LINE__, L"CreateProcessW", cmd_sample, err);
      return false;
    }

    pid_ = process_info.dwProcessId;
    process_ = process_info.hProcess;
    thread = process_info.hThread;

    if (!AssignProcessToJobObject(job_, process_)) {
      BOOL is_in_job = false;
      if (IsProcessInJob(process_, NULL, &is_in_job) && is_in_job &&
          !NestedJobsSupported()) {
        // We are on a pre-Windows 8 system and the Bazel is already in a job.
        // We can't create nested jobs, so just revert to TerminateProcess() and
        // hope for the best. In batch mode, the launcher puts Bazel in a job so
        // that will take care of cleanup once the command finishes.
        CloseHandle(job_);
        job_ = INVALID_HANDLE_VALUE;
        CloseHandle(ioport_);
        ioport_ = INVALID_HANDLE_VALUE;
      } else {
        DWORD err_code = GetLastError();
        error_ = bazel::windows::MakeErrorMessage(
            WSTR(__FILE__), __LINE__, L"nativeCreateProcess", wpath, err_code);
        return false;
      }
    }

    // Now that we put the process in a new job object, we can start executing
    // it
    if (ResumeThread(thread) == -1) {
      DWORD err_code = GetLastError();
      error_ = bazel::windows::MakeErrorMessage(
          WSTR(__FILE__), __LINE__, L"nativeCreateProcess", wpath, err_code);
      return false;
    }

    error_ = L"";
    return true;
  }

  // Wait for this process to exit (or timeout).
  jint WaitFor(jlong timeout_msec) {
    DWORD win32_timeout = timeout_msec < 0 ? INFINITE : timeout_msec;
    jint result;
    switch (WaitForSingleObject(process_, win32_timeout)) {
      case WAIT_OBJECT_0:
        result = kWaitSuccess;
        break;

      case WAIT_TIMEOUT:
        result = kWaitTimeout;
        break;

      // Any other case is an error and should be reported back to Bazel.
      default:
        DWORD err_code = GetLastError();
        error_ = bazel::windows::MakeErrorMessage(WSTR(__FILE__), __LINE__,
                                                  L"NativeProcess:WaitFor",
                                                  ToString(pid_), err_code);
        return kWaitError;
    }

    if (stdin_ != INVALID_HANDLE_VALUE) {
      CloseHandle(stdin_);
      stdin_ = INVALID_HANDLE_VALUE;
    }

    // Ensure that the process is really terminated (if WaitForSingleObject
    // above timed out, we have to explicitly kill it) and that it doesn't
    // leave behind any subprocesses.
    if (!Terminate()) {
      return 2;
    }

    if (job_ != INVALID_HANDLE_VALUE) {
      // Wait for the job object to complete, signalling that all subprocesses
      // have exited.
      DWORD CompletionCode;
      ULONG_PTR CompletionKey;
      LPOVERLAPPED Overlapped;
      while (GetQueuedCompletionStatus(ioport_, &CompletionCode, &CompletionKey,
                                       &Overlapped, INFINITE) &&
             !((HANDLE)CompletionKey == job_ &&
               CompletionCode == JOB_OBJECT_MSG_ACTIVE_PROCESS_ZERO)) {
        // Still waiting...
      }

      CloseHandle(job_);
      job_ = INVALID_HANDLE_VALUE;

      CloseHandle(ioport_);
      ioport_ = INVALID_HANDLE_VALUE;
    }

    // Fetch and store the exit code in case Bazel asks us for it later,
    // because we cannot do this anymore after we closed the handle.
    GetExitCode();

    if (process_ != INVALID_HANDLE_VALUE) {
      CloseHandle(process_);
      process_ = INVALID_HANDLE_VALUE;
    }

    return result;
  }

  // Returns the exit code of the process if it has already exited. If the
  // process is still running, returns STILL_ACTIVE (= 259).
  jint GetExitCode() {
    if (exit_code_ == STILL_ACTIVE) {
      if (!GetExitCodeProcess(process_, &exit_code_)) {
        DWORD err_code = GetLastError();
        error_ = bazel::windows::MakeErrorMessage(WSTR(__FILE__), __LINE__,
                                                  L"NativeProcess::GetExitCode",
                                                  ToString(pid_), err_code);
        return -1;
      }
    }

    return exit_code_;
  }

  jint GetPid() { return pid_; }

  jint WriteStdin(JNIEnv* env, jbyteArray java_bytes, jint offset,
                  jint length) {
    JavaByteArray bytes(env, java_bytes);
    if (offset < 0 || length <= 0 || offset > bytes.size() - length) {
      error_ = bazel::windows::MakeErrorMessage(
          WSTR(__FILE__), __LINE__, L"NativeProcess:WriteStdin", ToString(pid_),
          L"Array index out of bounds");
      return -1;
    }

    DWORD bytes_written;

    if (!::WriteFile(stdin_, bytes.ptr() + offset, length, &bytes_written,
                     NULL)) {
      DWORD err_code = GetLastError();
      error_ = bazel::windows::MakeErrorMessage(WSTR(__FILE__), __LINE__,
                                                L"NativeProcess:WriteStdin",
                                                ToString(pid_), err_code);
      return -1;
    }

    error_ = L"";
    return bytes_written;
  }

  NativeOutputStream* GetStdoutStream() { return &stdout_; }

  NativeOutputStream* GetStderrStream() { return &stderr_; }

  // Terminates this process (and subprocesses, if job objects are available).
  jboolean Terminate() {
    static const UINT exit_code = 130;  // 128 + SIGINT, like on Linux

    if (job_ != INVALID_HANDLE_VALUE) {
      if (!TerminateJobObject(job_, exit_code)) {
        DWORD err_code = GetLastError();
        error_ = bazel::windows::MakeErrorMessage(WSTR(__FILE__), __LINE__,
                                                  L"NativeProcess::Terminate",
                                                  ToString(pid_), err_code);
        return JNI_FALSE;
      }
    } else if (process_ != INVALID_HANDLE_VALUE) {
      if (!TerminateProcess(process_, exit_code)) {
        DWORD err_code = GetLastError();
        std::wstring our_error = bazel::windows::MakeErrorMessage(
            WSTR(__FILE__), __LINE__, L"NativeProcess::Terminate",
            ToString(pid_), err_code);

        // If the process exited, despite TerminateProcess having failed, we're
        // still happy and just ignore the error. It might have been a race
        // where the process exited by itself just before we tried to kill it.
        // However, if the process is *still* running at this point (evidenced
        // by its exit code still being STILL_ACTIVE) then something went
        // really unexpectedly wrong and we should report that error.
        if (GetExitCode() == STILL_ACTIVE) {
          // Restore the error message from TerminateProcess - it will be much
          // more helpful for debugging in case something goes wrong here.
          error_ = our_error;
          return JNI_FALSE;
        }
      }

      if (WaitForSingleObject(process_, INFINITE) != WAIT_OBJECT_0) {
        DWORD err_code = GetLastError();
        error_ = bazel::windows::MakeErrorMessage(WSTR(__FILE__), __LINE__,
                                                  L"NativeProcess::Terminate",
                                                  ToString(pid_), err_code);
        return JNI_FALSE;
      }
    }

    error_ = L"";
    return JNI_TRUE;
  }

  // Return the last error as a human-readable string and clear it.
  jstring GetLastErrorAsString(JNIEnv* env) {
    jstring result = env->NewString(
        reinterpret_cast<const jchar*>(error_.c_str()), error_.size());
    error_ = L"";
    return result;
  }

 private:
  bool NestedJobsSupported() {
    OSVERSIONINFOEX version_info;
    version_info.dwOSVersionInfoSize = sizeof(version_info);
    if (!GetVersionEx(reinterpret_cast<OSVERSIONINFO*>(&version_info))) {
      return false;
    }

    return version_info.dwMajorVersion > 6 ||
           (version_info.dwMajorVersion == 6 &&
            version_info.dwMinorVersion >= 2);
  }

  HANDLE stdin_;
  NativeOutputStream stdout_;
  NativeOutputStream stderr_;
  HANDLE process_;
  HANDLE job_;
  HANDLE ioport_;
  DWORD pid_;
  DWORD exit_code_;
  std::wstring error_;
};

// Ensure we can safely cast jlong to void*.
static_assert(sizeof(jlong) == sizeof(void*),
              "jlong and void* should be the same size");

static_assert(sizeof(jchar) == sizeof(WCHAR),
              "jchar and WCHAR should be the same size");

static jlong PtrAsJlong(void* p) { return reinterpret_cast<jlong>(p); }

extern "C" JNIEXPORT jlong JNICALL
Java_com_google_devtools_build_lib_windows_jni_WindowsProcesses_nativeCreateProcess(
    JNIEnv* env, jclass clazz, jstring java_argv0, jstring java_argv_rest,
    jbyteArray java_env, jstring java_cwd, jstring java_stdout_redirect,
    jstring java_stderr_redirect, jboolean redirectErrorStream) {
  NativeProcess* result = new NativeProcess();
  // TODO(philwo) The `Create` method returns false in case of an error. But
  // there seems to be no good way to signal an error at this point to Bazel.
  // The way the code currently works is that the Java code explicitly calls
  // nativeProcessGetLastError(), so it's OK, but it would be nice if we
  // could just throw an exception here.
  result->Create(env, java_argv0, java_argv_rest, java_env, java_cwd,
                 java_stdout_redirect, java_stderr_redirect,
                 redirectErrorStream);
  return PtrAsJlong(result);
}

extern "C" JNIEXPORT jint JNICALL
Java_com_google_devtools_build_lib_windows_jni_WindowsProcesses_nativeWriteStdin(
    JNIEnv* env, jclass clazz, jlong process_long, jbyteArray java_bytes,
    jint offset, jint length) {
  NativeProcess* process = reinterpret_cast<NativeProcess*>(process_long);
  return process->WriteStdin(env, java_bytes, offset, length);
}

extern "C" JNIEXPORT jlong JNICALL
Java_com_google_devtools_build_lib_windows_jni_WindowsProcesses_nativeGetStdout(
    JNIEnv* env, jclass clazz, jlong process_long) {
  NativeProcess* process = reinterpret_cast<NativeProcess*>(process_long);
  return PtrAsJlong(process->GetStdoutStream());
}

extern "C" JNIEXPORT jlong JNICALL
Java_com_google_devtools_build_lib_windows_jni_WindowsProcesses_nativeGetStderr(
    JNIEnv* env, jclass clazz, jlong process_long) {
  NativeProcess* process = reinterpret_cast<NativeProcess*>(process_long);
  return PtrAsJlong(process->GetStderrStream());
}

extern "C" JNIEXPORT jint JNICALL
Java_com_google_devtools_build_lib_windows_jni_WindowsProcesses_nativeReadStream(
    JNIEnv* env, jclass clazz, jlong stream_long, jbyteArray java_bytes,
    jint offset, jint length) {
  NativeOutputStream* stream =
      reinterpret_cast<NativeOutputStream*>(stream_long);
  return stream->ReadStream(env, java_bytes, offset, length);
}

extern "C" JNIEXPORT jint JNICALL
Java_com_google_devtools_build_lib_windows_jni_WindowsProcesses_nativeGetExitCode(
    JNIEnv* env, jclass clazz, jlong process_long) {
  NativeProcess* process = reinterpret_cast<NativeProcess*>(process_long);
  return process->GetExitCode();
}

// return values:
// 0: Wait completed successfully
// 1: Timeout
// 2: Wait returned with an error
extern "C" JNIEXPORT jint JNICALL
Java_com_google_devtools_build_lib_windows_jni_WindowsProcesses_nativeWaitFor(
    JNIEnv* env, jclass clazz, jlong process_long, jlong java_timeout) {
  NativeProcess* process = reinterpret_cast<NativeProcess*>(process_long);
  return process->WaitFor(java_timeout);
}

extern "C" JNIEXPORT jint JNICALL
Java_com_google_devtools_build_lib_windows_jni_WindowsProcesses_nativeGetProcessPid(
    JNIEnv* env, jclass clazz, jlong process_long) {
  NativeProcess* process = reinterpret_cast<NativeProcess*>(process_long);
  return process->GetPid();
}

extern "C" JNIEXPORT jboolean JNICALL
Java_com_google_devtools_build_lib_windows_jni_WindowsProcesses_nativeTerminate(
    JNIEnv* env, jclass clazz, jlong process_long) {
  NativeProcess* process = reinterpret_cast<NativeProcess*>(process_long);
  return process->Terminate();
}

extern "C" JNIEXPORT void JNICALL
Java_com_google_devtools_build_lib_windows_jni_WindowsProcesses_nativeDeleteProcess(
    JNIEnv* env, jclass clazz, jlong process_long) {
  delete reinterpret_cast<NativeProcess*>(process_long);
}

extern "C" JNIEXPORT void JNICALL
Java_com_google_devtools_build_lib_windows_jni_WindowsProcesses_nativeCloseStream(
    JNIEnv* env, jclass clazz, jlong stream_long) {
  NativeOutputStream* stream =
      reinterpret_cast<NativeOutputStream*>(stream_long);
  stream->Close();
}

extern "C" JNIEXPORT jstring JNICALL
Java_com_google_devtools_build_lib_windows_jni_WindowsProcesses_nativeProcessGetLastError(
    JNIEnv* env, jclass clazz, jlong process_long) {
  NativeProcess* process = reinterpret_cast<NativeProcess*>(process_long);
  return process->GetLastErrorAsString(env);
}

extern "C" JNIEXPORT jstring JNICALL
Java_com_google_devtools_build_lib_windows_jni_WindowsProcesses_nativeStreamGetLastError(
    JNIEnv* env, jclass clazz, jlong stream_long) {
  NativeOutputStream* stream =
      reinterpret_cast<NativeOutputStream*>(stream_long);
  return stream->GetLastErrorAsString(env);
}