/* MiniDLNA media server
 * Copyright (C) 2008-2010  Justin Maggard
 *
 * This file is part of MiniDLNA.
 *
 * MiniDLNA is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * MiniDLNA 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 MiniDLNA. If not, see <http://www.gnu.org/licenses/>.
 */
#include "config.h"

#include <stdio.h>
#include <string.h>
#include <stdbool.h>
#include <stdlib.h>
#include <errno.h>
#include <pthread.h>
#include <unistd.h>
#include <dirent.h>
#include <libgen.h>
#include <signal.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>
#ifdef HAVE_INOTIFY
#include <sys/resource.h>
#include <poll.h>
#ifdef HAVE_SYS_INOTIFY_H
#include <sys/inotify.h>
#else
#include "linux/inotify.h"
#include "linux/inotify-syscalls.h"
#endif
#endif
#include "libav.h"

#include "upnpglobalvars.h"
#include "monitor.h"
#include "utils.h"
#include "sql.h"
#include "scanner.h"
#include "metadata.h"
#include "albumart.h"
#include "playlist.h"
#include "log.h"

extern time_t next_pl_fill;

#define EVENT_SIZE  ( sizeof (struct inotify_event) )
#define BUF_LEN     ( 1024 * ( EVENT_SIZE + 16 ) )
#define DESIRED_WATCH_LIMIT 65536

#define PATH_BUF_SIZE PATH_MAX

struct watch
{
	int wd;		/* watch descriptor */
	char *path;	/* watched path */
	struct watch *next;
};

static struct watch *watches;
static struct watch *lastwatch = NULL;
static pthread_t thread_id;

static char *
get_path_from_wd(int wd)
{
	struct watch *w = watches;

	while( w != NULL )
	{
		if( w->wd == wd )
			return w->path;
		w = w->next;
	}

	return NULL;
}

static unsigned int
next_highest(unsigned int num)
{
	num |= num >> 1;
	num |= num >> 2;
	num |= num >> 4;
	num |= num >> 8;
	num |= num >> 16;
	return ++num;
}

static void
raise_watch_limit(unsigned int limit)
{
	FILE *max_watches = fopen("/proc/sys/fs/inotify/max_user_watches", "r+");
	if (!max_watches)
		return;
	if (!limit)
	{
		if (fscanf(max_watches, "%u", &limit) < 1)
			limit = 8192;
		rewind(max_watches);
	}
	fprintf(max_watches, "%u", next_highest(limit));
	fclose(max_watches);
}

int
monitor_add_watch(int fd, const char * path)
{
	struct watch *nw;
	int wd;

	wd = inotify_add_watch(fd, path, IN_CREATE|IN_CLOSE_WRITE|IN_DELETE|IN_MOVE);
	if( wd < 0 && errno == ENOSPC)
	{
		raise_watch_limit(0);
		wd = inotify_add_watch(fd, path, IN_CREATE|IN_CLOSE_WRITE|IN_DELETE|IN_MOVE);
	}
	if( wd < 0 )
	{
		DPRINTF(E_ERROR, L_INOTIFY, "inotify_add_watch(%s) [%s]\n", path, strerror(errno));
		return (errno);
	}

	nw = malloc(sizeof(struct watch));
	if( nw == NULL )
	{
		DPRINTF(E_ERROR, L_INOTIFY, "malloc() error\n");
		return (ENOMEM);
	}
	nw->wd = wd;
	nw->next = NULL;
	nw->path = strdup(path);

	if( watches == NULL )
	{
		watches = nw;
	}

	if( lastwatch != NULL )
	{
		lastwatch->next = nw;
	}
	lastwatch = nw;

	DPRINTF(E_INFO, L_INOTIFY, "Added watch to %s [%d]\n", path, wd);
	return (0);
}

int
monitor_remove_watch(int fd, const char * path)
{
	struct watch *w;

	for( w = watches; w; w = w->next )
	{
		if( strcmp(path, w->path) == 0 )
			return(inotify_rm_watch(fd, w->wd));
	}

	return 1;
}

static int
inotify_create_watches(int fd)
{
	FILE * max_watches;
	unsigned int num_watches = 0, watch_limit;
	char **result;
	int i, rows = 0;
	struct media_dir_s * media_path;

	for( media_path = media_dirs; media_path != NULL; media_path = media_path->next )
	{
		DPRINTF(E_DEBUG, L_INOTIFY, "Add watch to %s\n", media_path->path);
		monitor_add_watch(fd, media_path->path);
		num_watches++;
	}
	sql_get_table(db, "SELECT PATH from DETAILS where MIME is NULL and PATH is not NULL", &result, &rows, NULL);
	for( i=1; i <= rows; i++ )
	{
		DPRINTF(E_DEBUG, L_INOTIFY, "Add watch to %s\n", result[i]);
		monitor_add_watch(fd, result[i]);
		num_watches++;
	}
	sqlite3_free_table(result);

	max_watches = fopen("/proc/sys/fs/inotify/max_user_watches", "r");
	if( max_watches )
	{
		if( fscanf(max_watches, "%10u", &watch_limit) < 1 )
			watch_limit = 8192;
		fclose(max_watches);
		if( (watch_limit < DESIRED_WATCH_LIMIT) || (watch_limit < (num_watches*4/3)) )
		{
			if (access("/proc/sys/fs/inotify/max_user_watches", W_OK) == 0)
			{
				if( DESIRED_WATCH_LIMIT >= (num_watches*3/4) )
				{
					raise_watch_limit(8191U);
				}
				else if( next_highest(num_watches) >= (num_watches*3/4) )
				{
					raise_watch_limit(num_watches);
				}
				else
				{
					raise_watch_limit(next_highest(num_watches));
				}
			}
			else
			{
				DPRINTF(E_WARN, L_INOTIFY, "WARNING: Inotify max_user_watches [%u] is low or close to the number of used watches [%u] "
				                        "and I do not have permission to increase this limit.  Please do so manually by "
				                        "writing a higher value into /proc/sys/fs/inotify/max_user_watches.\n", watch_limit, num_watches);
			}
		}
	}
	else
	{
		DPRINTF(E_WARN, L_INOTIFY, "WARNING: Could not read inotify max_user_watches!  "
		                        "Hopefully it is enough to cover %u current directories plus any new ones added.\n", num_watches);
	}

	return rows;
}

static int
inotify_remove_watches(int fd)
{
	struct watch *w = watches;
	struct watch *last_w;
	int rm_watches = 0;

	while( w )
	{
		last_w = w;
		inotify_rm_watch(fd, w->wd);
		free(w->path);
		rm_watches++;
		w = w->next;
		free(last_w);
	}

	return rm_watches;
}

static void *
inotify_thread(void *arg)
{
	struct pollfd pollfds[1];
	char buffer[BUF_LEN];
	char path_buf[PATH_MAX];
	int length, i = 0;
	char * esc_name = NULL;
	struct stat st;
	sigset_t set;

	sigfillset(&set);
	sigdelset(&set, SIGCHLD);
	pthread_sigmask(SIG_BLOCK, &set, NULL);

	pollfds[0].fd = inotify_init();
	pollfds[0].events = POLLIN;

	if ( pollfds[0].fd < 0 )
		DPRINTF(E_ERROR, L_INOTIFY, "inotify_init() failed!\n");

	inotify_create_watches(pollfds[0].fd);
	if (setpriority(PRIO_PROCESS, 0, 19) == -1)
		DPRINTF(E_WARN, L_INOTIFY,  "Failed to reduce inotify thread priority\n");
	sqlite3_release_memory(1<<31);

	while( !quitting )
	{
		int timeout = -1;
		if (next_pl_fill)
		{
			time_t diff = next_pl_fill - time(NULL);
			if (diff < 0)
				timeout = 0;
			else
				timeout = diff * 1000;
		}
		length = poll(pollfds, 1, timeout);
		if( !length )
		{
			if( next_pl_fill && (time(NULL) >= next_pl_fill) )
			{
				fill_playlists();
				next_pl_fill = 0;
			}
			continue;
		}
		else if( length < 0 )
		{
			if( (errno == EINTR) || (errno == EAGAIN) )
				continue;
			else
				DPRINTF(E_ERROR, L_INOTIFY, "read failed!\n");
		}
		else
		{
			length = read(pollfds[0].fd, buffer, BUF_LEN);
			buffer[BUF_LEN-1] = '\0';
		}

		i = 0;
		while( !quitting && i < length )
		{
			struct inotify_event * event = (struct inotify_event *) &buffer[i];
			if( event->len )
			{
				if( *(event->name) == '.' )
				{
					i += EVENT_SIZE + event->len;
					continue;
				}
				esc_name = modifyString(strdup(event->name), "&", "&amp;amp;", 0);
				snprintf(path_buf, sizeof(path_buf), "%s/%s", get_path_from_wd(event->wd), event->name);
				if ( event->mask & IN_ISDIR && (event->mask & (IN_CREATE|IN_MOVED_TO)) )
				{
					DPRINTF(E_DEBUG, L_INOTIFY,  "The directory %s was %s.\n",
						path_buf, (event->mask & IN_MOVED_TO ? "moved here" : "created"));
					monitor_insert_directory(pollfds[0].fd, esc_name, path_buf);
				}
				else if ( (event->mask & (IN_CLOSE_WRITE|IN_MOVED_TO|IN_CREATE)) &&
				          (lstat(path_buf, &st) == 0) )
				{
					if( (event->mask & (IN_MOVED_TO|IN_CREATE)) && (S_ISLNK(st.st_mode) || st.st_nlink > 1) )
					{
						DPRINTF(E_DEBUG, L_INOTIFY, "The %s link %s was %s.\n",
							(S_ISLNK(st.st_mode) ? "symbolic" : "hard"),
							path_buf, (event->mask & IN_MOVED_TO ? "moved here" : "created"));
						if( stat(path_buf, &st) == 0 && S_ISDIR(st.st_mode) )
							monitor_insert_directory(pollfds[0].fd, esc_name, path_buf);
						else
							monitor_insert_file(esc_name, path_buf);
					}
					else if( event->mask & (IN_CLOSE_WRITE|IN_MOVED_TO) && st.st_size > 0 )
					{
						if( (event->mask & IN_MOVED_TO) ||
						    (sql_get_int_field(db, "SELECT TIMESTAMP from DETAILS where PATH = '%q'", path_buf) != st.st_mtime) )
						{
							DPRINTF(E_DEBUG, L_INOTIFY, "The file %s was %s.\n",
								path_buf, (event->mask & IN_MOVED_TO ? "moved here" : "changed"));
							monitor_insert_file(esc_name, path_buf);
						}
					}
				}
				else if ( event->mask & (IN_DELETE|IN_MOVED_FROM) )
				{
					DPRINTF(E_DEBUG, L_INOTIFY, "The %s %s was %s.\n",
						(event->mask & IN_ISDIR ? "directory" : "file"),
						path_buf, (event->mask & IN_MOVED_FROM ? "moved away" : "deleted"));
					if ( event->mask & IN_ISDIR )
						monitor_remove_directory(pollfds[0].fd, path_buf);
					else
					{
						monitor_remove_file(path_buf);
						/*
						 * When a symlink to a directory is deleted
						 * we cannot tell it from a regular file deletion
						 * to prevent its children from becoming orphans
						 * we delete the whole tree when it exists
						 */
						monitor_remove_tree(path_buf);
					}
				}
				free(esc_name);
			}
			i += EVENT_SIZE + event->len;
		}
	}
	inotify_remove_watches(pollfds[0].fd);
	close(pollfds[0].fd);

	return 0;
}

void
monitor_start(void)
{

	if (!sqlite3_threadsafe() || sqlite3_libversion_number() < 3005001) {
		DPRINTF(E_ERROR, L_GENERAL, "SQLite library is not threadsafe!"
		    "Inotify will be disabled.\n");
		return;
	}
	if (pthread_create(&thread_id, NULL, inotify_thread, NULL) != 0)
		DPRINTF(E_FATAL, L_GENERAL, "pthread_create() failed [%s]\n",
		    strerror(errno));
}

void
monitor_stop(void)
{

	if (thread_id != 0) {
		pthread_kill(thread_id, SIGCHLD);
		pthread_join(thread_id, NULL);
	}
}