# Simple sub-process
class Process
	# The pid of the process
	fun id: Int do return data.id

	# Is the process finished?
	fun is_finished: Bool do return data.is_finished

	# Wait the termination of the process
	fun wait
	do
		data.wait
		assert is_finished
	end

	# The status once finished
	#
	# Require: `is_finished`
	fun status: Int
	do
		assert is_finished
		return data.status
	end

	# The target executable
	# Either a file path or the name of an executable available in PATH.
	var command: Text

	# The arguments of the command
	# Starts with the first real arguments---ie. does not include the progname (`argv[0]`, in C)
	var arguments: nullable Array[Text]

	# Launch a command with some arguments
	init(command: Text, arguments: Text...) is old_style_init do
		self.command = command
		self.arguments = arguments
		execute
	end

	# Launch a simple command with arguments passed as an array
	init from_a(command: Text, arguments: nullable Array[Text])
	do
		self.command = command
		self.arguments = arguments
		execute
	end

	# Flags used internally to know which pipe to open
	private fun pipeflags: Int do return 0

	# Internal code to handle execution
	protected fun execute
	do
		var arguments = self.arguments

		var args = new FlatBuffer
		var argc = 1

		if not is_windows then
			# Pass the arguments as a big C string where elements are separated with '\0'
			args.append command
			if arguments != null then
				for a in arguments do
					args.add '\0'
					args.append a
				end
				argc += arguments.length
			end
		else
			# Combine the program and args in a single string
			assert not command.chars.has('"')
			args = new FlatBuffer

			args.add '"'
			args.append command
			args.add '"'

			if arguments != null then
				for a in arguments do
					args.append " \""
					args.append a.replace('"', "\\\"")
					args.add '"'
				end
			end
		end

		data = basic_exec_execute(command.to_cstring, args.to_s.to_cstring, argc, pipeflags)
		assert not data.address_is_null else print_error "Internal error executing: {command}"
	end

	private var data: NativeProcess

	private fun basic_exec_execute(prog, args: CString, argc: Int, pipeflag: Int): NativeProcess `{
#ifdef _WIN32
		SECURITY_ATTRIBUTES sec_attr;
		sec_attr.nLength = sizeof(SECURITY_ATTRIBUTES);
		sec_attr.bInheritHandle = TRUE;
		sec_attr.lpSecurityDescriptor = NULL;

		STARTUPINFO start_info;
		ZeroMemory(&start_info, sizeof(STARTUPINFO));
		start_info.cb = sizeof(STARTUPINFO);
		start_info.dwFlags = STARTF_USESTDHANDLES;

		HANDLE in_fd[2];
		HANDLE out_fd[2];
		HANDLE err_fd[2];

		se_exec_data_t *result = (se_exec_data_t*)malloc(sizeof(se_exec_data_t));

		// Redirect stdin?
		if (pipeflag & 1) {
			if (!CreatePipe(&in_fd[0], &in_fd[1], &sec_attr, 0)) {
				return NULL;
			}
			start_info.hStdInput = in_fd[0];
			result->in_fd = _open_osfhandle((intptr_t)in_fd[1], _O_WRONLY);
			if ( !SetHandleInformation(in_fd[1], HANDLE_FLAG_INHERIT, 0) )
				return NULL;
		} else {
			start_info.hStdInput = GetStdHandle(STD_INPUT_HANDLE);
			result->in_fd = -1;
		}

		// Redirect stdout?
		if (pipeflag & 2) {
			if (!CreatePipe(&out_fd[0], &out_fd[1], &sec_attr, 0)) {
				return NULL;
			}
			start_info.hStdOutput = out_fd[1];
			result->out_fd = _open_osfhandle((intptr_t)out_fd[0], _O_RDONLY);
			if ( !SetHandleInformation(out_fd[0], HANDLE_FLAG_INHERIT, 0) )
				return NULL;
		} else {
			start_info.hStdOutput = GetStdHandle(STD_OUTPUT_HANDLE);
			result->out_fd = -1;
		}

		// Redirect stderr?
		if (pipeflag & 4) {
			if (!CreatePipe(&err_fd[0], &err_fd[1], &sec_attr, 0)) {
				return NULL;
			}
			start_info.hStdError = err_fd[1];
			result->err_fd = _open_osfhandle((intptr_t)err_fd[0], _O_RDONLY);
			if ( !SetHandleInformation(err_fd[0], HANDLE_FLAG_INHERIT, 0) )
				return NULL;
		} else {
			start_info.hStdError = GetStdHandle(STD_ERROR_HANDLE);
			result->err_fd = -1;
		}

		PROCESS_INFORMATION proc_info;
		ZeroMemory(&proc_info, sizeof(PROCESS_INFORMATION));

		BOOL created = CreateProcess(NULL,
			args,       // command line
			NULL,       // process security attributes
			NULL,       // primary thread security attributes
			TRUE,       // inherit handles
			0,          // creation flags
			NULL,       // use parent's environment
			NULL,       // use parent's current directory
			&start_info,
			&proc_info);

		if (pipeflag & 1) CloseHandle(in_fd[0]);
		if (pipeflag & 2) CloseHandle(out_fd[1]);
		if (pipeflag & 3) CloseHandle(err_fd[1]);

		// Error?
		if (!created) {
			result->running = 0;
			result->status = 127;

			// Close subprocess pipes
			if (pipeflag & 1) CloseHandle(in_fd[1]);
			if (pipeflag & 2) CloseHandle(out_fd[0]);
			if (pipeflag & 3) CloseHandle(err_fd[0]);
		} else {
			result->h_process = proc_info.hProcess;
			result->h_thread = proc_info.hThread;
			result->id = GetProcessId(proc_info.hProcess);
			result->running = 1;
		}

		return result;
#else
		se_exec_data_t* result = NULL;
		int id;
		int in_fd[2];
		int out_fd[2];
		int err_fd[2];
		if (pipeflag & 1) {
			int res = pipe(in_fd);
			if ( res == -1 ) {
				return NULL;
			}
		}
		if (pipeflag & 2) {
			int res = pipe(out_fd);
			if ( res == -1 ) {
				return NULL;
			}
		}
		if (pipeflag & 4) {
			int res = pipe(err_fd);
			if ( res == -1 ) {
				return NULL;
			}
		}

		id = fork();
		if (id == 0)
			{ /* child */
			char **arg = malloc(sizeof(char*) * (argc+1));
			char *c = args;
			int i;

			/* Prepare args */
			for(i=0; i<argc; i++)
			{
				arg[i] = c;
				c += strlen(c) + 1;
			}
			arg[argc] = NULL;

			/* Connect pipe */
			if (pipeflag & 1)
			{
				close(0);
				dup2(in_fd[0], 0);
				close(in_fd[0]);
				close(in_fd[1]);
			}
			if (pipeflag & 2)
			{
				close(1);
				dup2(out_fd[1], 1);
				close(out_fd[0]);
				close(out_fd[1]);
			}
			if (pipeflag & 4)
			{
				close(2);
				dup2(err_fd[1], 2);
				close(err_fd[0]);
				close(err_fd[1]);
			}

			/* calls */
			execvp(prog, arg);
			_exit(127);
		}
		else if (id > 0)
			{ /* father */
			result = (se_exec_data_t*)malloc(sizeof(se_exec_data_t));
			result->id = id;
			result->running = 1;
			if (pipeflag & 1)
			{
				result->in_fd = in_fd[1];
				close(in_fd[0]);
			} else
				result->in_fd = -1;

			if (pipeflag & 2)
			{
				result->out_fd = out_fd[0];
				close(out_fd[1]);
			} else
				result->out_fd = -1;

			if (pipeflag & 4)
			{
				result->err_fd = err_fd[0];
				close(err_fd[1]);
			} else
				result->err_fd = -1;
		} else {
			perror("Process:");
			return NULL;
		}

		return result;
#endif
	`}
end