#-------------------------------------------------------------------------------
# _AcquireMutex
#	Acquires a given quasi-mutex (a simple attempt to make scripts mutually
#		exclusive
# Params:
#	name - the name of the mutex
#	id - the id of the current script
#-------------------------------------------------------------------------------
Sub _AcquireMutex(IN String $name)
{
	string $id = %_sgEnv{'script_command_id'};
	return _AcquireMutex($name, <int>$id);
}
Sub _AcquireMutex(IN String $name, IN int $id)
{
	return _AcquireMutex($name, $id, 10000);
}
Sub _AcquireMutex(IN string $name, IN int $id, IN int $maxTries)
{
	@echo off;
	string $mutexName = __GenerateName($name);
	bool $first = true;

	while (true) {
		if ($first) {
			$first = false;
		} else {
			Sleep(1000);
		}
		int $owner = __GetMutexOwner($mutexName);
		
		if ($owner == $id) {
			# we own the mutex
			return true;
		} else if ($owner == 0) {
			# no-one owns the mutex
			`lpsetenv -name $mutexName -value $id -default`;
		} else if ($owner == -1) {
			# error occurred
		}
		
		$maxTries--;
		if ($maxTries == 0) {
			return false;
		}
	}
	
	return false;
}

#-------------------------------------------------------------------------------
# _ReleaseMutex
#	Releases a given mutex.  It does not matter if you do not yet own it, so
#		be careful of your use of it.
# Params:
#	name - the name of the mutex
#	id - the id of the current script
#-------------------------------------------------------------------------------
Sub _ReleaseMutex(IN String $name)
{
	return _ReleaseMutex($name, <int>%_sgEnv{'script_command_id'});
}

Sub _ReleaseMutex(IN String $name, IN int $id)
{
	string $mutexName = __GenerateName($name);
	# In theory, check to see if the mutex is held
	@echo off;
	int $owner = __GetMutexOwner($mutexName);
	if ($owner == $id) {
		return `lpsetenv -name $mutexName -delete -default`;
	}
	return false;
}

#-------------------------------------------------------------------------------
Sub(string) __GenerateName(IN string $name) {
	return "_MUTEX_$name";
}

#-------------------------------------------------------------------------------
Sub(int) __GetMutexOwner(IN string $mutexName) {
	@record on;
	bool $ret = `lpgetenv -name $mutexName -any`;
	@record off;
	if (!$ret) {
		return 0;
	}
	# false == mutex doesn't exist
	# if it does, we need to check to see what command owns it
	string $value;
	# if we can't get it, we have to assume no one owns it?
	if (!(GetCmdData("envitem::value", $value) && defined($value))) {
		return -1;
	}
	
	if (__IsCommandRunning(<int>$value)) {
		return <int>$value;
	}
	return 0;
}

#---------------------------------------------------------------------#
sub __IsCommandRunning(IN int $id) {
	bool $running;
	if (!(GetCmdData("CommandMetaData::IsRunning", $running, $id) && defined($running))) {
		# assume dead
		return false;
	}
	return $running;
}