The cynagora protocol
=====================

Introduction
------------

### Notations:

 - c->s:    from client to cynagora server
 - s->c:    from cynagora server to client
 - EXPIRE:  if missing, means forever
            if positive, a number of second since EPOCH, invalid after it
 - CACHEID: a 32 bits positive integer
 - ID:      a string

Messages
--------

### hello

synopsis:

	c->s cynagora 1
	s->c done 1 CACHEID

The client present itself with the version of the protocol it expects to
speak (today version 1 only). The server answer yes with the acknoledged
version it will use and the CACHEID that identify the cache (see note on
CACHEID)

If hello is used, it must be the first message. If it is not used, the
protocol implicitely switch to the default version.


### invalidate cache

synopsis:

	s->c clear CACHEID

The server ask the client to clear its cache and to start the cache whose
identifier is CACHEID
  

### test a permission

synopsis:

	c->s test ID CLIENT SESSION USER PERMISSION
	s->c (ack|yes|no) ID [EXPIRE]



### check a permission

synopsis:

	c->s check ID CLIENT SESSION USER PERMISSION
	s->c (yes|no) ID [EXPIRE]



### enter critical (admin)

synopsis:

	c->s enter
	s->c done

### leave critical (admin)

synopsis:

	c->s leave [commit|rollback]
	s->c done|error ...

### erase (admin)

synopsis:

	c->s drop CLIENT SESSION USER PERMISSION
	s->c done|error ...

### set (admin)

synopsis:

	c->s set CLIENT SESSION USER PERMISSION VALUE [EXPIRE]
	s->c done|error ...

### list permissions (admin):

synopsis:

	c->s get CLIENT SESSION USER PERMISSION
	s->c item CLIENT SESSION USER PERMISSION VALUE [EXPIRE]
	s->c ...
	s->c done

### logging set/get (admin)

synopsis:

	c->s log [on|off]
	s->c done (on|off)

### register agent (agent)

synopsis:

	c->s agent NAME
	s->c done|error ...

### ask agent (agent):

synopsis:

	s->c ask ASKID NAME VALUE CLIENT SESSION USER PERMISSION
	c->s reply ASKID ([yes|no] [always|session|one-time|EXPIRE])

### sub check (agent):

synopsis:

	c->s sub ASKID ID CLIENT SESSION USER PERMISSION
	s->c (yes|no) ID [EXPIRE]

Notes
-----

### CACHEID

The cacheid identify the current cache. It changes each time the database
changes. After a disconnection, clients can use HELLO to check whether their
version of cache is still valid. This is implemented by the default C library.