/*]  Copyright (c) 2009-2010, Charles McGarvey  [**************************
**]  All rights reserved.
*
* vi:ts=4 sw=4 tw=75
*
* Distributable under the terms and conditions of the 2-clause BSD license;
* see the file COPYING for a complete text of the license.
*
**************************************************************************/

#include "config.h"

#include <queue>

#if ENABLE_HOTLOADING
#include <sys/inotify.h>
#include <sys/ioctl.h>
#endif

#include <boost/algorithm/string.hpp>
#include <boost/weak_ptr.hpp>
#include <stlplus/portability/file_system.hpp>

#include "hash.hh"
#include "resource.hh"


#ifndef BUF_SIZE
#define BUF_SIZE 4096
#endif


namespace moof {
	

/*] Filesystem searching
 *************************************************************************/

static std::vector<std::string> search_paths_;

void resource::set_search_paths(const std::string& paths)
{
	boost::split(search_paths_, paths, boost::is_any_of(":"));
}


std::string resource::find_file(const std::string& name)
{
	std::string ext = stlplus::extension_part(name);
	std::string prefix;
	std::string path;

	loader_ptr loader;
	call_registry(ext, loader, lookup);
	if (loader) prefix = loader->prefix();

	std::vector<std::string>::iterator it;
	for (it = search_paths_.begin(); it != search_paths_.end(); ++it)
	{
		if (!prefix.empty())
		{
			// try it with the prefix first
			path = stlplus::filespec_to_path(*it, prefix);
			path = stlplus::filespec_to_path(path, name);
			log_debug("looking for", name, "at", path);
			if (stlplus::file_exists(path)) return path;
		}

		path = stlplus::filespec_to_path(*it, name);
		log_debug("looking for", name, "at", path);
		if (stlplus::file_exists(path)) return path;
	}

	log_error("cannot find resource file:", name);
	return std::string();
}

std::string resource::find_file(const std::string& name,
								const std::string& ext)
{
	std::string actual_ext = stlplus::extension_part(name);
	if (actual_ext != ext)
	{
		// try the explicit extension first
		return find_file(stlplus::create_filename(name, ext));
	}
	return find_file(name);
}


/*] Resource loading
 *************************************************************************/

typedef boost::weak_ptr<resource> resource_weakptr;
static struct rsrc_list
{
	// this table holds weak references to any and all loaded resources
	hash<std::string,resource_weakptr,hash_function> table;

#ifdef DEBUG
	// this destructor will let us know if the program exits while
	// resources are still being held
	~rsrc_list()
	{
		hash<std::string,resource_weakptr,hash_function>::iterator it;
		for (it = table.begin(); it != table.end(); ++it)
		{
			log_warning("leaked resource:", (*it).first);
		}
	}
#endif
} rsrc_list;

#if ENABLE_HOTLOADING
static struct watch_list
{
	// this table associates a watch descriptor with a loaded resource
	hash<int,resource_weakptr,hash_function> table;

	int fd;				// the inotify file descriptor

	watch_list() :
		fd(inotify_init1(IN_NONBLOCK)) {}

	~watch_list()
	{
		close(fd);
	}

	int add(resource_ptr rsrc)
	{
		int wd = inotify_add_watch(fd, rsrc->path().c_str(),
								   IN_DELETE_SELF | IN_MODIFY);
		table[wd] = rsrc;
		return wd;
	}
	void remove(int wd)
	{
		if (wd != -1) inotify_rm_watch(fd, wd);
	}
} watch_list;
#endif


resource_ptr resource::load(const std::string& name)
{
	std::string ext = stlplus::extension_part(name);
	return load_with_path(find_file(name, ext), ext);
}

resource_ptr resource::load(const std::string& name,
							const std::string& ext)
{
	return load_with_path(find_file(name, ext), ext);
}


resource_ptr resource::load_with_path(const std::string& path,
									  const std::string& ext)
{
	if (path.empty()) return resource_ptr();

	// first try to lookup the resource
	hash<std::string,resource_weakptr,hash_function>::iterator it;
	it = rsrc_list.table.find(path);
	if (it != rsrc_list.table.end())
	{
		resource_ptr rsrc = (*it).second.lock();
		if (rsrc) return rsrc;
	}

	// then proceed to use the registered loader to get the resource
	loader_ptr loader;
	call_registry(ext, loader, lookup);
	if (loader)
	{
		resource_ptr rsrc(loader->load(path));
		rsrc_list.table[path] = rsrc;
		rsrc->path_ = path;
		rsrc->type_ = ext;
#if ENABLE_HOTLOADING
		rsrc->wd_ = watch_list.add(rsrc);
#endif
		return rsrc;
	}

	log_warning("cannot load resource of unregistered type:", path);
	return resource_ptr();
}


/*] Hotloading
 *************************************************************************/

int resource::reload_as_needed()
{
	int count = 0;

#if ENABLE_HOTLOADING
	char bytes[BUF_SIZE];
	int num_bytes;
	// an inotify file descriptor lets your read inotify_event structures
	if (0 < (num_bytes = read(watch_list.fd, bytes, sizeof(bytes))))
	{
		char* end = bytes + num_bytes;
		char* byte = bytes;

		while (byte < end)
		{
			struct inotify_event* event = (struct inotify_event*)byte;
			byte += sizeof(*event) + event->len;

			hash<int,resource_weakptr,hash_function>::iterator it;
			it = watch_list.table.find(event->wd);
			if (it != watch_list.table.end())
			{
				resource_ptr rsrc = (*it).second.lock();
				if (rsrc)
				{
					rsrc->reload();
					++count;

					if (event->mask & IN_IGNORED)
					{
						watch_list.table.erase(event->wd);
						rsrc->wd_ = watch_list.add(rsrc);
					}
				}
				else
				{
					// if we can't lock the resource, it was unloaded so we
					// don't need to watch it anymore
					watch_list.table.erase(event->wd);
				}
			}
		}
	}
#endif

	return count;
}

void resource::reload()
{
	loader_ptr loader;
	call_registry(type_, loader, lookup);

	resource_ptr resource(loader->load(path_));
	resource_ = resource->resource_;
	typeinfo_ = resource->typeinfo_;
	unloader_ = resource->unloader_;
}

resource::~resource()
{
	rsrc_list.table.erase(path_);
#if ENABLE_HOTLOADING
	watch_list.remove(wd_);
#endif
}


/*] Resource registration
 *************************************************************************/

bool resource::call_registry(const std::string& ext,
							 loader_ptr& loader,
							 registry_action action)
{
	static std::map<std::string,loader_ptr> table;

	switch (action)
	{
		case set:
		{
			if (loader) table[ext] = loader;
			else        table.erase(ext);
			break;
		}

		case lookup:
		{
			std::map<std::string,loader_ptr>::iterator it;
			it = table.find(ext);
			if (it != table.end()) loader = (*it).second;
			break;
		}
	}

	return loader;
}


} // namespace moof