/*
 *  fmrxd - a daemon to enable and multiplex access to the N950/N9 radio tuner
 *  Copyright (C) 2011 Javier S. Pedro <maemo@javispedro.com>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.

 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.

 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/

#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <dbus/dbus.h>
#include <dbus/dbus-glib-lowlevel.h>

#include "fmrxd.h"

typedef struct Client {
	int fd;
	GIOChannel *channel;
	guint out_watch;
	guint err_watch;
	unsigned int read_p;
} Client;

static DBusConnection *bus;
static GList *clients;
static guint num_clients;

#if SERVER_ON_DEMAND
static guint server_stop_source;
#endif

struct {
	char data[RING_BUFFER_SIZE];
	unsigned int write_p;
} rbuffer;

static const char * introspect_data = {
	"<!DOCTYPE node PUBLIC \"-//freedesktop//DTD D-BUS Object Introspection 1.0//EN\"\n"
	"\"http://www.freedesktop.org/standards/dbus/1.0/introspect.dtd\">\n"
	"<node>\n"
	"  <interface name=\"org.freedesktop.DBus.Introspectable\">\n"
	"   <method name=\"Introspect\">\n"
	"    <arg type=\"s\" name=\"data\" direction=\"out\" />\n"
	"   </method>\n"
	"  </interface>\n"
	"  <interface name=\"" BUS_INTERFACE "\">\n"
	"   <method name=\"Connect\">\n"
	"     <arg type=\"h\" name=\"pipe\" direction=\"out\" />\n"
	"   </method>\n"
	"   <method name=\"Tune\">\n"
	"     <arg type=\"d\" name=\"frequency\" direction=\"in\" />\n"
	"   </method>\n"
	"   <method name=\"SearchForward\">\n"
	"   </method>\n"
	"   <method name=\"SearchBackward\">\n"
	"   </method>\n"
	"   <signal name=\"Tuned\">\n"
	"     <arg type=\"d\" name=\"frequency\" />\n"
	"   </signal>\n"
	"   <signal name=\"Stopped\">\n"
	"   </signal>\n"
	"   <signal name=\"SignalLevelChanged\">\n"
	"     <arg type=\"q\" name=\"level\" />\n"
	"   </signal>\n"
	"   <signal name=\"PiReceived\">\n"
	"     <arg type=\"q\" name=\"pi\" />\n"
	"   </signal>\n"
	"   <signal name=\"PsReceived\">\n"
	"     <arg type=\"s\" name=\"ps\" />\n"
	"   </signal>\n"
	"   <signal name=\"RtReceived\">\n"
	"     <arg type=\"s\" name=\"rt\" />\n"
	"   </signal>\n"
	"  </interface>\n"
	"</node>\n"
};

static void server_kill_client(Client *c);

static gboolean client_out_callback(GIOChannel *source, GIOCondition condition,
	gpointer data);
static gboolean client_err_callback(GIOChannel *source, GIOCondition condition,
	gpointer data);

static DBusHandlerResult handle_introspect(DBusConnection *conn, DBusMessage *m)
{
	DBusMessage *reply = dbus_message_new_method_return(m);
	dbus_message_append_args(reply, DBUS_TYPE_STRING, &introspect_data, DBUS_TYPE_INVALID);
	dbus_connection_send(conn, reply, NULL);
	dbus_message_unref(reply);

	return DBUS_HANDLER_RESULT_HANDLED;
}

static DBusHandlerResult handle_connect(DBusConnection *conn, DBusMessage *m)
{
	int fd = server_new_client();

	if (fd == -1) {
		g_warning("Error while spawning a new pipe");
		return DBUS_HANDLER_RESULT_NEED_MEMORY;
	}

	DBusMessage *reply = dbus_message_new_method_return(m);
	dbus_message_append_args(reply, DBUS_TYPE_UNIX_FD, &fd, DBUS_TYPE_INVALID);
	dbus_connection_send(conn, reply, NULL);
	dbus_message_unref(reply);

	close(fd);

	return DBUS_HANDLER_RESULT_HANDLED;
}

static DBusHandlerResult handle_tune(DBusConnection *conn, DBusMessage *m)
{
	double freq;
	DBusError err;
	DBusMessage *reply;
	dbus_bool_t ret;

	dbus_error_init(&err);
	ret = dbus_message_get_args(m, &err, DBUS_TYPE_DOUBLE, &freq, DBUS_TYPE_INVALID);
	if (!ret) {
		reply = dbus_message_new_error(m, err.name, err.message);
		dbus_connection_send(conn, reply, NULL);
		dbus_message_unref(reply);
		return DBUS_HANDLER_RESULT_HANDLED;
	}

	if (!tuner_set_frequency(freq)) {
		reply = dbus_message_new_error(m, BUS_INTERFACE ".TunerError",
			"Failed to tune to the specified frequency");
	} else {
		reply = dbus_message_new_method_return(m);
	}

	dbus_connection_send(conn, reply, NULL);
	dbus_message_unref(reply);
	return DBUS_HANDLER_RESULT_HANDLED;
}

static DBusHandlerResult handle_search(DBusConnection *conn, DBusMessage *m, bool forward)
{
	DBusMessage *reply;

	if (!tuner_search(forward)) {
		reply = dbus_message_new_error(m, BUS_INTERFACE ".TunerError",
			"Failed to start a search");
	} else {
		reply = dbus_message_new_method_return(m);
	}

	dbus_connection_send(conn, reply, NULL);
	dbus_message_unref(reply);
	return DBUS_HANDLER_RESULT_HANDLED;
}

static DBusHandlerResult on_message(DBusConnection *connection, DBusMessage *message, void *user_data)
{
	if (dbus_message_is_method_call(message, DBUS_INTERFACE_INTROSPECTABLE, "Introspect")) {
		return handle_introspect(connection, message);
	} else if (dbus_message_is_method_call(message, BUS_INTERFACE, "Connect")) {
		return handle_connect(connection, message);
	} else if (dbus_message_is_method_call(message, BUS_INTERFACE, "Tune")) {
		return handle_tune(connection, message);
	} else if (dbus_message_is_method_call(message, BUS_INTERFACE, "SearchForward")) {
		return handle_search(connection, message, true);
	} else if (dbus_message_is_method_call(message, BUS_INTERFACE, "SearchBackward")) {
		return handle_search(connection, message, false);
	}

	return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
}

static DBusObjectPathVTable bus_vtable = {
	.message_function = on_message
};

static inline char * client_data_p(Client *c)
{
	return &rbuffer.data[c->read_p];
}

// This does not return all available data, but only
// max contiguous segment. This is by design.
static inline size_t client_data_avail(Client *c)
{
	if (rbuffer.write_p >= c->read_p) {
		return rbuffer.write_p - c->read_p;
	} else {
		return RING_BUFFER_SIZE - c->read_p;
	}
}

static inline void client_data_forget(Client *c, size_t bytes)
{
	c->read_p = (c->read_p + bytes) % RING_BUFFER_SIZE;
}

static inline void client_watch(Client *c)
{
	g_return_if_fail(c->out_watch == 0);
	c->out_watch = g_io_add_watch(c->channel, G_IO_OUT, client_out_callback, c);
}

static inline void client_unwatch(Client *c)
{
	g_return_if_fail(c->out_watch != 0);
	g_source_remove(c->out_watch);
	c->out_watch = 0;
}

static inline bool client_watched(const Client *c)
{
	return c->out_watch != 0;
}

static bool client_try_send(Client *c)
{
	size_t avail = client_data_avail(c);
	char *p = client_data_p(c);
	ssize_t written;

	written = write(c->fd, p, avail);

	if (written == -1) {
		switch (errno) {
		case EAGAIN:
			// Client turned out to be busy
			//  just assume nothing was written.
			written = 0;
			break;
		case EPIPE:
			// Broken pipe; kill client.
			g_message("Client pipe broken, closing client");
			server_kill_client(c);
			return FALSE;
		default:
			g_warning("Failed to send buffer to client in %d: %s",
				c->fd, strerror(errno));
			server_kill_client(c);
			return FALSE;
		}
	} else if (written > 0) {
		client_data_forget(c, written);
	}

	// Determine if we need to start/stop watching the client
	if (client_watched(c) && client_data_avail(c) == 0) {
		// No more data to be sent.
		client_unwatch(c);
	} else if (!client_watched(c) && client_data_avail(c) > 0) {
		// Client is not watched but there is still data to be sent
		client_watch(c);
	}

	return TRUE;
}

static gboolean client_out_callback(GIOChannel *source, GIOCondition condition,
	gpointer data)
{
	Client *c = (Client*) data;

	if (condition & G_IO_OUT) {
		return client_try_send(c);
	}

	return TRUE;
}

static gboolean client_err_callback(GIOChannel *source, GIOCondition condition,
	gpointer data)
{
	Client *c = (Client*) data;

	if (condition & G_IO_HUP) {
		g_message("Client pipe closed, closing client");
		server_kill_client(c);
		return FALSE;
	}
	if (condition & G_IO_ERR) {
		g_message("Client pipe broken, closing client");
		server_kill_client(c);
		return FALSE;
	}

	return TRUE;
}

int server_start()
{
	DBusError err;
	int ret;
	dbus_error_init(&err);

	clients = NULL;
	num_clients = 0;

	rbuffer.write_p = 0;

	bus = dbus_bus_get(DBUS_BUS_SYSTEM, &err);
	if (dbus_error_is_set(&err)) {
		g_critical("Cannot connect to the system message bus: %s", err.message);
		return -1;
	}
	g_assert(bus != NULL);

	ret = dbus_bus_request_name(bus, BUS_NAME, DBUS_NAME_FLAG_REPLACE_EXISTING, &err);
	if (dbus_error_is_set(&err)) {
		g_critical("Cannot claim ownership of my bus name: %s", err.message);
		return -1;
	}
	g_assert(ret == DBUS_REQUEST_NAME_REPLY_PRIMARY_OWNER);

	ret = dbus_connection_register_object_path(bus, BUS_PATH, &bus_vtable, NULL);
	if (!ret) {
		g_critical("Cannot register fmrxd object in bus");
		return -1;
	}

	dbus_connection_setup_with_g_main(bus, g_main_loop_get_context(main_loop));

#if SERVER_ON_DEMAND
	// Set up the timer for inactivity, in case we do not get any clients.
	server_queue_stop();
#endif

	return 0;
}

void server_stop()
{
	g_warn_if_fail(num_clients == 0);
	dbus_connection_unregister_object_path(bus, BUS_PATH);
	dbus_bus_release_name(bus, BUS_NAME, NULL);
}

#if SERVER_ON_DEMAND
static gboolean server_stop_func(gpointer data)
{
	g_message("Stopping service because of inactivity");
	server_stop();
	g_main_loop_quit(main_loop);
	return FALSE;
}

void server_queue_stop()
{
	if (!server_stop_source) {
		server_stop_source = g_timeout_add_seconds(SERVER_LINGER_TIME,
			server_stop_func, NULL);
	}
}
#endif

int server_new_client()
{
	int fds[2];
	int ret = pipe(fds);
	if (ret < 0) {
		g_warning("Could not create a pipe");
		return -1;
	}

	Client* c = g_slice_new(Client);
	c->fd = fds[1];
	c->channel = g_io_channel_unix_new(c->fd);
	c->out_watch = 0;
	c->err_watch = g_io_add_watch(c->channel, G_IO_ERR | G_IO_HUP,
								  client_err_callback, c);
	c->read_p = rbuffer.write_p;

	// Configure some flags of the pipe using GLib
	GIOFlags flags = g_io_channel_get_flags(c->channel);
	if (g_io_channel_set_flags(c->channel, flags | G_IO_FLAG_NONBLOCK, NULL)
			!= G_IO_STATUS_NORMAL) {
		g_warning("Failed to set non-blocking flag for pipe fd");
	}
	g_io_channel_set_encoding(c->channel, NULL, NULL);
	g_io_channel_set_buffered(c->channel, FALSE);

	g_debug("New pipe, write fd = %d", fds[1]);

	// Add client to list
	clients = g_list_append(clients, c);

	if (num_clients == 0) {
		// First client, start tuner.
		radio_queue_start();
#if SERVER_ON_DEMAND
		if (server_stop_source) {
			g_source_remove(server_stop_source);
			server_stop_source = 0;
		}
#endif
	}
	num_clients++;

	// Return the other end of the pipe
	return fds[0];
}

static void server_kill_client(Client *c)
{
	g_source_remove(c->err_watch);
	if (c->out_watch) g_source_remove(c->out_watch);

	clients = g_list_remove(clients, c);

	g_io_channel_shutdown(c->channel, TRUE, NULL);
	g_io_channel_unref(c->channel);

	g_slice_free(Client, c);

	if (num_clients == 1) {
		// Last client leaving, stop tuner.
		radio_queue_stop();
#if SERVER_ON_DEMAND
		server_queue_stop();
#endif
	}
	num_clients--;
}

size_t server_get_buffer(size_t size, void **buffer)
{
	g_return_val_if_fail(buffer != NULL, 0);
	g_return_val_if_fail(size > 0, 0);

	*buffer = &rbuffer.data[rbuffer.write_p];

	size_t avail_size = RING_BUFFER_SIZE - rbuffer.write_p;
	if (size > avail_size) {
		return avail_size;
	} else {
		return size;
	}
}

static void overflow_check_func(gpointer data, gpointer user_data)
{
	Client * c = (Client*) data;
	unsigned int new_write_p = *(unsigned int*)user_data;
	unsigned int old_write_p = rbuffer.write_p;
	unsigned int data_lost = 0;

	if (new_write_p < rbuffer.write_p) {
		// write_p wraparound: Overflow happens if the read_p was
		//  positioned right after old write_p.
		g_warn_if_fail(new_write_p == 0); // Valid simplification here
		if (c->read_p > old_write_p) {
			data_lost = c->read_p - old_write_p;
			g_warn_if_fail(data_lost < RING_BUFFER_SIZE);
		}
	} else {
		if (c->read_p > old_write_p && c->read_p <= new_write_p) {
			data_lost = new_write_p - c->read_p;
			g_warn_if_fail(data_lost < RING_BUFFER_SIZE);
		}
	}

	if (data_lost > 0) {
		g_message("Overflow detected (%u bytes), glitch!", data_lost);
		c->read_p = (new_write_p) % RING_BUFFER_SIZE;
	}
}

static void commit_buffer_func(gpointer data, gpointer user_data)
{
	Client * c = (Client*) data;

	client_try_send(c);
}

void server_commit_buffer(size_t size)
{
	g_return_if_fail(size > 0);
	g_warn_if_fail(size < RING_BUFFER_SIZE);

	unsigned int new_write_p = (rbuffer.write_p + size) % RING_BUFFER_SIZE;

	g_list_foreach(clients, overflow_check_func, &new_write_p);

	rbuffer.write_p = new_write_p;

	g_list_foreach(clients, commit_buffer_func, NULL);
}

void server_notify_tuned(double mhz)
{
	DBusMessage *m = dbus_message_new_signal(BUS_PATH, BUS_INTERFACE, "Tuned");
	g_return_if_fail(m != NULL);
	dbus_message_append_args(m, DBUS_TYPE_DOUBLE, &mhz, DBUS_TYPE_INVALID);
	dbus_connection_send(bus, m, NULL);
	dbus_message_unref(m);
}

void server_notify_stopped()
{
	DBusMessage *m = dbus_message_new_signal(BUS_PATH, BUS_INTERFACE, "Stopped");
	g_return_if_fail(m != NULL);
	dbus_connection_send(bus, m, NULL);
	dbus_message_unref(m);
}

void server_notify_signal(uint16_t signal)
{
	DBusMessage *m = dbus_message_new_signal(BUS_PATH, BUS_INTERFACE, "SignalLevelChanged");
	g_return_if_fail(m != NULL);
	dbus_message_append_args(m, DBUS_TYPE_UINT16, &signal, DBUS_TYPE_INVALID);
	dbus_connection_send(bus, m, NULL);
	dbus_message_unref(m);
}

void server_notify_pi(uint16_t pi)
{
	DBusMessage *m = dbus_message_new_signal(BUS_PATH, BUS_INTERFACE, "PiChanged");
	g_return_if_fail(m != NULL);
	dbus_message_append_args(m, DBUS_TYPE_UINT16, &pi, DBUS_TYPE_INVALID);
	dbus_connection_send(bus, m, NULL);
	dbus_message_unref(m);
}

void server_notify_ps(const char *ps)
{
	DBusMessage *m = dbus_message_new_signal(BUS_PATH, BUS_INTERFACE, "PsChanged");
	g_return_if_fail(m != NULL);
	dbus_message_append_args(m, DBUS_TYPE_STRING, &ps, DBUS_TYPE_INVALID);
	dbus_connection_send(bus, m, NULL);
	dbus_message_unref(m);
}

void server_notify_rt(const char *rt)
{
	DBusMessage *m = dbus_message_new_signal(BUS_PATH, BUS_INTERFACE, "RtChanged");
	g_return_if_fail(m != NULL);
	dbus_message_append_args(m, DBUS_TYPE_STRING, &rt, DBUS_TYPE_INVALID);
	dbus_connection_send(bus, m, NULL);
	dbus_message_unref(m);
}