/*
 * \brief  Unix emulation environment for Genode
 * \author Norman Feske
 * \date   2011-02-14
 */

/*
 * Copyright (C) 2011-2012 Genode Labs GmbH
 *
 * This file is part of the Genode OS framework, which is distributed
 * under the terms of the GNU General Public License version 2.
 */

/* Genode includes */
#include <cap_session/connection.h>
#include <os/config.h>
#include <os/alarm.h>
#include <timer_session/connection.h>

/* Noux includes */
#include <child.h>
#include <child_env.h>
#include <vfs_io_channel.h>
#include <terminal_io_channel.h>
#include <dummy_input_io_channel.h>
#include <pipe_io_channel.h>
#include <dir_file_system.h>
#include <user_info.h>


static bool trace_syscalls = false;


namespace Noux {

	static Noux::Child *init_child;

	bool is_init_process(Child *child) { return child == init_child; }
	void init_process_exited() { init_child = 0; }
};

extern void (*close_socket)(int);

extern void init_network();


/**
 * Timeout thread for SYSCALL_SELECT
 */

namespace Noux {
	using namespace Genode;

	class Timeout_scheduler : Thread<4096>, public Alarm_scheduler
	{
		private:
			Timer::Connection _timer;
			Alarm::Time       _curr_time;

			enum { TIMER_GRANULARITY_MSEC = 10 };

			void entry()
			{
				for (;;) {
					_timer.msleep(TIMER_GRANULARITY_MSEC);
					Alarm_scheduler::handle(_curr_time);
					_curr_time += TIMER_GRANULARITY_MSEC;
				}
			}

		public:
			Timeout_scheduler() : _curr_time(0) { start(); }

			Alarm::Time curr_time() const { return _curr_time; }
	};

	struct Timeout_state
	{
		bool timed_out;

		Timeout_state() : timed_out(false)  { }
	};

	class Timeout_alarm : public Alarm
	{
		private:
			Timeout_state     *_state;
			Semaphore         *_blocker;
			Timeout_scheduler *_scheduler;

		public:
			Timeout_alarm(Timeout_state *st, Semaphore *blocker, Timeout_scheduler *scheduler, Time timeout)
				:
					_state(st),
					_blocker(blocker),
					_scheduler(scheduler)
		{
			_scheduler->schedule_absolute(this, _scheduler->curr_time() + timeout);
			_state->timed_out = false;
		}

			void discard() { _scheduler->discard(this); }

		protected:
			bool on_alarm()
			{
				_state->timed_out = true;
				_blocker->up();

				return false;
			}
	};
};


/*****************************
 ** Noux syscall dispatcher **
 *****************************/

bool Noux::Child::syscall(Noux::Session::Syscall sc)
{
	if (trace_syscalls)
		Genode::printf("PID %d -> SYSCALL %s\n",
		               pid(), Noux::Session::syscall_name(sc));

	try {
		switch (sc) {

		case SYSCALL_GETCWD:

			Genode::strncpy(_sysio->getcwd_out.path, _env.pwd(),
			                sizeof(_sysio->getcwd_out.path));
			return true;

		case SYSCALL_WRITE:
			{
				size_t const count_in = _sysio->write_in.count;

				for (size_t count = 0; count != count_in; ) {

					Shared_pointer<Io_channel> io = _lookup_channel(_sysio->write_in.fd);

					if (!io->check_unblock(false, true, false))
						_block_for_io_channel(io);

					/*
					 * 'io->write' is expected to update 'write_out.count'
					 */
					if (io->write(_sysio, count) == false)
						return false;
				}
				return true;
			}

		case SYSCALL_READ:
			{
				Shared_pointer<Io_channel> io = _lookup_channel(_sysio->read_in.fd);

				while (!io->check_unblock(true, false, false))
					_block_for_io_channel(io);

				io->read(_sysio);
				return true;
			}

		case SYSCALL_FTRUNCATE:
			{
				Shared_pointer<Io_channel> io = _lookup_channel(_sysio->ftruncate_in.fd);

				while (!io->check_unblock(true, false, false))
					_block_for_io_channel(io);

				return io->ftruncate(_sysio);
			}

		case SYSCALL_STAT:
		case SYSCALL_LSTAT: /* XXX implement difference between 'lstat' and 'stat' */

			return _root_dir->stat(_sysio, Absolute_path(_sysio->stat_in.path,
			                                             _env.pwd()).base());

		case SYSCALL_FSTAT:

			return _lookup_channel(_sysio->fstat_in.fd)->fstat(_sysio);

		case SYSCALL_FCNTL:

			if (_sysio->fcntl_in.cmd == Sysio::FCNTL_CMD_SET_FD_FLAGS) {

				/* we assume that there is only the close-on-execve flag */
				_lookup_channel(_sysio->fcntl_in.fd)->close_on_execve =
					!!_sysio->fcntl_in.long_arg;
				return true;
			}

			return _lookup_channel(_sysio->fcntl_in.fd)->fcntl(_sysio);

		case SYSCALL_OPEN:
			{
				Absolute_path absolute_path(_sysio->open_in.path, _env.pwd());

				Vfs_handle *vfs_handle = _root_dir->open(_sysio, absolute_path.base());
				if (!vfs_handle)
					return false;

				char const *leaf_path = _root_dir->leaf_path(absolute_path.base());

				/*
				 * File descriptors of opened directories are handled by
				 * '_root_dir'. In this case, we use the absolute path as leaf
				 * path because path operations always refer to the global
				 * root.
				 */
				if (vfs_handle->ds() == _root_dir)
					leaf_path = absolute_path.base();

				Shared_pointer<Io_channel>
					channel(new Vfs_io_channel(absolute_path.base(),
					                           leaf_path, _root_dir, vfs_handle),
					        Genode::env()->heap());

				_sysio->open_out.fd = add_io_channel(channel);
				return true;
			}

		case SYSCALL_CLOSE:
			{
				/**
				 * We have to explicitly close Socket_io_channel fd's because
				 * these are currently handled separately.
				 */
				if (close_socket)
					close_socket(_sysio->close_in.fd);

				remove_io_channel(_sysio->close_in.fd);
				return true;
			}

		case SYSCALL_IOCTL:

			return _lookup_channel(_sysio->ioctl_in.fd)->ioctl(_sysio);

		case SYSCALL_LSEEK:

			return _lookup_channel(_sysio->lseek_in.fd)->lseek(_sysio);

		case SYSCALL_DIRENT:

			return _lookup_channel(_sysio->dirent_in.fd)->dirent(_sysio);

		case SYSCALL_FCHDIR:

			return _lookup_channel(_sysio->fchdir_in.fd)->fchdir(_sysio, &_env);

		case SYSCALL_EXECVE:
			{
				Absolute_path absolute_path(_sysio->execve_in.filename, _env.pwd());

				Dataspace_capability binary_ds = _root_dir->dataspace(absolute_path.base());

				if (!binary_ds.valid())
					throw Child::Binary_does_not_exist();

				Child_env<sizeof(_sysio->execve_in.args)> child_env(
				    absolute_path.base(), binary_ds, _sysio->execve_in.args,
				    _sysio->execve_in.env);

				try {
					Child *child = new Child(child_env.binary_name(),
					                         parent(),
					                         pid(),
					                         _sig_rec,
					                         _root_dir,
					                         child_env.args(),
					                         child_env.env(),
					                         _env.pwd(),
					                         _cap_session,
					                         _parent_services,
					                         _resources.ep,
					                         false);

					/* replace ourself by the new child at the parent */
					parent()->remove(this);
					parent()->insert(child);

					_assign_io_channels_to(child);

					/* signal main thread to remove ourself */
					Genode::Signal_transmitter(_execve_cleanup_context_cap).submit();

					/* start executing the new process */
					child->start();

					/* this child will be removed by the execve_finalization_dispatcher */
					return true;
				}
				catch (Child::Binary_does_not_exist) {
					_sysio->error.execve = Sysio::EXECVE_NONEXISTENT; }

				return false;
			}

		case SYSCALL_SELECT:
			{
				Sysio::Select_fds &in_fds = _sysio->select_in.fds;
				size_t in_fds_total = in_fds.total_fds();

				int _rd_array[in_fds_total];
				int _wr_array[in_fds_total];

				long timeout_sec     = _sysio->select_in.timeout.sec;
				long timeout_usec    = _sysio->select_in.timeout.usec;
				bool timeout_reached = false;

				/*
				 * Block for one action of the watched file descriptors
				 */
				for (;;) {

					/*
					 * Check I/O channels of specified file descriptors for
					 * unblock condition. Return if one I/O channel satisfies
					 * the condition.
					 */
					size_t unblock_rd = 0;
					size_t unblock_wr = 0;
					size_t unblock_ex = 0;
					
					/* process read fds */
					for (Genode::size_t i = 0; i < in_fds_total; i++) {

						int fd = in_fds.array[i];
						if (!fd_in_use(fd)) continue;

						Shared_pointer<Io_channel> io = io_channel_by_fd(fd);

						if (io->check_unblock(in_fds.watch_for_rd(i),
								      in_fds.watch_for_wr(i),
								      in_fds.watch_for_ex(i))) {

							if (io->check_unblock(true, false, false)) {
								_rd_array[unblock_rd++] = fd;
							//	io->clear_unblock(true, false, false);
							}
							if (io->check_unblock(false, true, false)) {
								_wr_array[unblock_wr++] = fd;
							//	io->clear_unblock(false, true, false);
							}

							if (io->check_unblock(false, false, true)) {
								unblock_ex++;
							//	io->clear_unblock(false, false, true);
							}

						}
					}

					if (unblock_rd || unblock_wr || unblock_ex) {
						for (size_t i = 0; i < unblock_rd; i++) {
							_sysio->select_out.fds.array[i] = _rd_array[i];
							_sysio->select_out.fds.num_rd = unblock_rd;
						}
						for (size_t i = 0; i < unblock_wr; i++) {
							_sysio->select_out.fds.array[i] = _wr_array[i];
							_sysio->select_out.fds.num_wr = unblock_wr;
						}

						_sysio->select_out.fds.num_ex = unblock_ex;

						return true;
					}

					/*
					 * Return if I/O channel triggered, but timeout exceeded
					 */
					
					if (_sysio->select_in.timeout.zero() || timeout_reached) {
						/*
						if (timeout_reached) PINF("timeout_reached");
						else                 PINF("timeout.zero()");
						*/
						_sysio->select_out.fds.num_rd = 0;
						_sysio->select_out.fds.num_wr = 0;
						_sysio->select_out.fds.num_ex = 0;

						return true;
					}

					/*
					 * Register ourself at all watched I/O channels
					 *
					 * We instantiate as many notifiers as we have file
					 * descriptors to observe. Each notifier is associated
					 * with the child's blocking semaphore. When any of the
					 * notifiers get woken up, the semaphore gets unblocked.
					 *
					 * XXX However, the semaphore may get unblocked for other
					 *     conditions such as the destruction of the child.
					 *     ...to be done.
					 */

					Wake_up_notifier notifiers[in_fds_total];

					for (Genode::size_t i = 0; i < in_fds_total; i++) {
						int fd = in_fds.array[i];
						if (!fd_in_use(fd)) continue;

						Shared_pointer<Io_channel> io = io_channel_by_fd(fd);
						notifiers[i].semaphore = &_blocker;
						io->register_wake_up_notifier(&notifiers[i]);
					}

					/*
					 * Block at barrier except when reaching the timeout
					 */

					if (!_sysio->select_in.timeout.infinite()) {
						unsigned long to_msec = (timeout_sec * 1000) + (timeout_usec / 1000);
						Timeout_state ts;
						Timeout_alarm ta(&ts, &_blocker, Noux::timeout_scheduler(), to_msec);

						/* block until timeout is reached or we were unblocked */
						_blocker.down();

						if (ts.timed_out) {
							timeout_reached = 1;
						}
						else {
							/*
							 * We woke up before reaching the timeout,
							 * so we discard the alarm
							 */
							ta.discard();
						}
					}
					else {
						/* let's block infinitely */
						_blocker.down();
					}

					/*
					 * Unregister barrier at watched I/O channels
					 */
					for (Genode::size_t i = 0; i < in_fds_total; i++) {
						int fd = in_fds.array[i];
						if (!fd_in_use(fd)) continue;

						Shared_pointer<Io_channel> io = io_channel_by_fd(fd);
						io->unregister_wake_up_notifier(&notifiers[i]);
					}

				}

				return true;
			}

		case SYSCALL_FORK:
			{
				Genode::addr_t ip              = _sysio->fork_in.ip;
				Genode::addr_t sp              = _sysio->fork_in.sp;
				Genode::addr_t parent_cap_addr = _sysio->fork_in.parent_cap_addr;

				int const new_pid = pid_allocator()->alloc();

				/*
				 * XXX To ease debugging, it would be useful to generate a
				 *     unique name that includes the PID instead of just
				 *     reusing the name of the parent.
				 */
				Child *child = new Child(_child_policy.name(),
				                         this,
				                         new_pid,
				                         _sig_rec,
				                         _root_dir,
				                         _args,
				                         _env.env(),
				                         _env.pwd(),
				                         _cap_session,
				                         _parent_services,
				                         _resources.ep,
				                         true);

				Family_member::insert(child);

				_assign_io_channels_to(child);

				/* copy our address space into the new child */
				_resources.rm.replay(child->ram(), child->rm(),
				                     child->ds_registry(), _resources.ep);

				/* start executing the main thread of the new process */
				child->start_forked_main_thread(ip, sp, parent_cap_addr);

				/* activate child entrypoint, thereby starting the new process */
				child->start();

				_sysio->fork_out.pid = new_pid;

				return true;
			}

		case SYSCALL_GETPID:
			{
				_sysio->getpid_out.pid = pid();
				return true;
			}

		case SYSCALL_WAIT4:
			{
				Family_member *exited = _sysio->wait4_in.nohang ? poll4() : wait4();

				if (exited) {
					_sysio->wait4_out.pid    = exited->pid();
					_sysio->wait4_out.status = exited->exit_status();
					Family_member::remove(exited);

					PINF("submit exit signal for PID %d", exited->pid());
					static_cast<Child *>(exited)->submit_exit_signal();

				} else {
					_sysio->wait4_out.pid    = 0;
					_sysio->wait4_out.status = 0;
				}
				return true;
			}

		case SYSCALL_PIPE:
			{
				Shared_pointer<Pipe> pipe(new Pipe, Genode::env()->heap());

				Shared_pointer<Io_channel> pipe_sink(new Pipe_sink_io_channel(pipe, *_sig_rec),
				                                     Genode::env()->heap());
				Shared_pointer<Io_channel> pipe_source(new Pipe_source_io_channel(pipe, *_sig_rec),
				                                       Genode::env()->heap());

				_sysio->pipe_out.fd[0] = add_io_channel(pipe_source);
				_sysio->pipe_out.fd[1] = add_io_channel(pipe_sink);

				return true;
			}

		case SYSCALL_DUP2:
			{
				add_io_channel(io_channel_by_fd(_sysio->dup2_in.fd),
				               _sysio->dup2_in.to_fd);
				return true;
			}

		case SYSCALL_UNLINK:

			return _root_dir->unlink(_sysio, Absolute_path(_sysio->unlink_in.path,
			                                               _env.pwd()).base());

		case SYSCALL_RENAME:

			return _root_dir->rename(_sysio, Absolute_path(_sysio->rename_in.from_path,
			                                               _env.pwd()).base(),
			                                 Absolute_path(_sysio->rename_in.to_path,
			                                               _env.pwd()).base());

		case SYSCALL_MKDIR:

			return _root_dir->mkdir(_sysio, Absolute_path(_sysio->mkdir_in.path,
			                                              _env.pwd()).base());

		case SYSCALL_USERINFO:
			{
				if (_sysio->userinfo_in.request == Sysio::USERINFO_GET_UID
				    || _sysio->userinfo_in.request == Sysio::USERINFO_GET_GID) {
					_sysio->userinfo_out.uid = Noux::user_info()->uid;
					_sysio->userinfo_out.gid = Noux::user_info()->gid;

					return true;
				}

				/*
				 * Since NOUX supports exactly one user, return false if we
				 * got a unknown uid.
				 */
				if (_sysio->userinfo_in.uid != Noux::user_info()->uid)
					return false;

				Genode::memcpy(_sysio->userinfo_out.name,  Noux::user_info()->name,  sizeof(Noux::user_info()->name));
				Genode::memcpy(_sysio->userinfo_out.shell, Noux::user_info()->shell, sizeof(Noux::user_info()->shell));
				Genode::memcpy(_sysio->userinfo_out.home,  Noux::user_info()->home,  sizeof(Noux::user_info()->home));

				_sysio->userinfo_out.uid = user_info()->uid;
				_sysio->userinfo_out.gid = user_info()->gid;

				return true;
			}

		case SYSCALL_SOCKET:
		case SYSCALL_GETSOCKOPT:
		case SYSCALL_SETSOCKOPT:
		case SYSCALL_ACCEPT:
		case SYSCALL_BIND:
		case SYSCALL_LISTEN:
		case SYSCALL_SEND:
		case SYSCALL_SENDTO:
		case SYSCALL_RECV:
		case SYSCALL_RECVFROM:
		case SYSCALL_GETPEERNAME:
		case SYSCALL_SHUTDOWN:
		case SYSCALL_CONNECT:
		case SYSCALL_GETADDRINFO:

			return _syscall_net(sc);

		case SYSCALL_INVALID: break;
		}
	}

	catch (Invalid_fd) {
		_sysio->error.general = Sysio::ERR_FD_INVALID;
		PERR("Invalid file descriptor"); }

	catch (...) { PERR("Unexpected exception"); }

	return false;
}


/**
 * Return name of init process as specified in the config
 */
static char *name_of_init_process()
{
	enum { INIT_NAME_LEN = 128 };
	static char buf[INIT_NAME_LEN];
	Genode::config()->xml_node().sub_node("start").attribute("name").value(buf, sizeof(buf));
	return buf;
}


/**
 * Read command-line arguments of init process from config
 */
static Noux::Args const &args_of_init_process()
{
	static char args_buf[4096];
	static Noux::Args args(args_buf, sizeof(args_buf));

	Genode::Xml_node start_node = Genode::config()->xml_node().sub_node("start");

	try {
		/* the first argument is the program name */
		args.append(name_of_init_process());

		Genode::Xml_node arg_node = start_node.sub_node("arg");
		for (; ; arg_node = arg_node.next("arg")) {
			static char buf[512];
			arg_node.attribute("value").value(buf, sizeof(buf));
			args.append(buf);
		}
	}
	catch (Genode::Xml_node::Nonexistent_sub_node) { }
	catch (Noux::Args::Overrun) { PERR("Argument buffer overrun"); }

	return args;
}


static void quote(char *buf, Genode::size_t buf_len)
{
	/*
	 * Make sure to leave space at the end of buffer for the finishing '"' and
	 * the null-termination.
	 */
	char c = '"';
	unsigned i = 0;
	for (; c && (i + 2 < buf_len); i++)
	{
		/*
		 * So shouldn't this have a special case for '"' characters inside the
		 * string? This is actually not needed because such a string could
		 * never be constructed via the XML config anyway. You can sneak in '"'
		 * characters only by quoting them in the XML file. Then, however, they
		 * are already quoted.
		 */
		char next_c = buf[i];
		buf[i] = c;
		c = next_c;
	}
	buf[i + 0] = '"';
	buf[i + 1] = 0;
}


/**
 * Return string containing the environment variables of init
 *
 * The string is formatted according to the 'Genode::Arg_string' rules.
 */
static char const *env_string_of_init_process()
{
	static char env_buf[4096];

	Genode::Arg_string::set_arg(env_buf, sizeof(env_buf), "PWD", "\"/\"");

	/* read environment variables for init process from config */
	Genode::Xml_node start_node = Genode::config()->xml_node().sub_node("start");
	try {
		Genode::Xml_node arg_node = start_node.sub_node("env");
		for (; ; arg_node = arg_node.next("env")) {
			static char name_buf[256], value_buf[256];

			arg_node.attribute("name").value(name_buf, sizeof(name_buf));
			arg_node.attribute("value").value(value_buf, sizeof(value_buf));
			quote(value_buf, sizeof(value_buf));

			Genode::Arg_string::set_arg(env_buf, sizeof(env_buf),
			                            name_buf, value_buf);
		}
	}
	catch (Genode::Xml_node::Nonexistent_sub_node) { }

	return env_buf;
}


Noux::Pid_allocator *Noux::pid_allocator()
{
	static Noux::Pid_allocator inst;
	return &inst;
}


Noux::Timeout_scheduler *Noux::timeout_scheduler()
{
	static Noux::Timeout_scheduler inst;
	return &inst;
}


Noux::User_info* Noux::user_info()
{
	static Noux::User_info inst;
	return &inst;
}


void *operator new (Genode::size_t size) {
	return Genode::env()->heap()->alloc(size); }


int main(int argc, char **argv)
{
	using namespace Noux;
	PINF("--- noux started ---");

	/* look for dynamic linker */
	try {
		static Genode::Rom_connection rom("ld.lib.so");
		Genode::Process::dynamic_linker(rom.dataspace());
	} catch (...) { }

	/* whitelist of service requests to be routed to the parent */
	static Genode::Service_registry parent_services;
	char const *service_names[] = { "LOG", "ROM", "Timer", 0 };
	for (unsigned i = 0; service_names[i]; i++)
		parent_services.insert(new Genode::Parent_service(service_names[i]));

	static Genode::Cap_connection cap;

	/* obtain global configuration */
	try {
		trace_syscalls = config()->xml_node().attribute("trace_syscalls").has_value("yes");
	} catch (Xml_node::Nonexistent_attribute) { }

	/* initialize virtual file system */
	static Dir_file_system
		root_dir(config()->xml_node().sub_node("fstab"));

	/* set user information */
	try {
		user_info()->set_info(config()->xml_node().sub_node("user"));
	}
	catch (...) { }

	/* initialize network */
	init_network();

	/*
	 * Entrypoint used to virtualize child resources such as RAM, RM
	 */
	enum { STACK_SIZE = 1024*sizeof(long) };
	static Genode::Rpc_entrypoint resources_ep(&cap, STACK_SIZE, "noux_rsc_ep");

	/* create init process */
	static Genode::Signal_receiver sig_rec;

	init_child = new Noux::Child(name_of_init_process(),
	                             0,
	                             pid_allocator()->alloc(),
	                             &sig_rec,
	                             &root_dir,
	                             args_of_init_process(),
	                             env_string_of_init_process(),
	                             "/",
	                             &cap,
	                             parent_services,
	                             resources_ep,
	                             false);

	static Terminal::Connection terminal;

	/*
	 * I/O channels must be dynamically allocated to handle cases where the
	 * init program closes one of these.
	 */
	typedef Terminal_io_channel Tio; /* just a local abbreviation */
	Shared_pointer<Io_channel>
		channel_0(new Tio(terminal, Tio::STDIN,  sig_rec), Genode::env()->heap()),
		channel_1(new Tio(terminal, Tio::STDOUT, sig_rec), Genode::env()->heap()),
		channel_2(new Tio(terminal, Tio::STDERR, sig_rec), Genode::env()->heap());

	init_child->add_io_channel(channel_0, 0);
	init_child->add_io_channel(channel_1, 1);
	init_child->add_io_channel(channel_2, 2);

	init_child->start();

	/* handle asynchronous events */
	while (init_child) {

		Genode::Signal signal = sig_rec.wait_for_signal();

		Signal_dispatcher *dispatcher =
			static_cast<Signal_dispatcher *>(signal.context());

		for (int i = 0; i < signal.num(); i++)
			dispatcher->dispatch();
	}

	PINF("-- exiting noux ---");
	return 0;
}