TreeShare is a file sharing program inspired by Dropbox. It allows
its users to set up a server keeping central file repository which
they can connect to via clients. Each client can 'mount' the top
directory of the tracked directory tree or any other sub directory
in the hierarchy. Any updates to the files (such as creation,
modification and deletion) will then be distributed through the
server to all other clients, which mirror the changes.

Individual clients can be assigned to groups, which can have set
access rights to different files, allowing the prevention of unwanted
modification from individuals (i.e. one man groups) or entire groups.

Directory Layout:
The server contains a directory called 'dir' within the same directory
as the executable, this directory (and his sub directories) get shared
with the clients. A second directory, called 'backup' gets created by
the server and stores a backup of any file that gets changed or
deleted (mimicking the hierarchy in 'dir').

Startup:
The server can be run from the command line using the following
command 'TreeShareServer.exe <addr> <port> <port-lb> <port-ub>'
with arguments:
	<addr> Address the server listens on.
	<port> Port the server listens on.
	<port-lb> Lower bound of the port pool.
	<port-ub> Upper bound of the port pool.

Port pool:
The port pool is a closed interval [port-lb, port-ub], values of which
will get used to redirect clients to (allowing 1 client/port
communication). This interval should have high enough numbers to not
interfere with the 'well-known ports' range of 0-1023 and any other
commonly used port numbers outside this range. (The port pool
should be above ten thousand.)

Groups:
Every group can have multiple users that share access rights to files.
When a file is created, for every group the group's default access
right is assigned to it. When a new user is created, they are
assigned to the group 'default', that has a default right of NONE
and cannot create files. The user can then be reassigned to a
different group from the console by the admin.

Access rights:
The possible rights a group can have to any given file are NONE, WRITE,
READ and READ_WRITE (which behave like flags, so adding WRITE to a
group that only has READ will result in a READ_WRITE access righ).
When adding/removing a right through the console, these have to be
spelled correctly for the server to recognise them.

Console I/O:
After launch, the console window can be used to pass commands directly
to the server and with their help manipulate files, users or groups.
The administrator can use following commands (sans the | ):
(Note: <path> is relative to the executable, so it starts
       with 'dir\'.)

| exit
Saves the database and shuts down the server.

| hide <time>
Hides the console for <time> seconds. (<seconds> <= 0 will cause
the console to disappear for the rest of the session.)

| group-create <name> <right> <create>
Creates a new group with the name <name>, default access right to
files <right> and if <create> is 'true', the ability to create
new files.

| group-add <user> <group>
Adds (or moves) a user with the name <user> to a group with the name
<group>.

| user-add <name>
Creates a new user with the name <name> in the 'default' group.

| file-add <path>
Adds a new (already existing, but untracked) file to the databse and
informs all users about its creation.

| add-right <path> <group> <right>
Adds a new right <right> to the group <group> for the file located
at <path>.

| remove-right <path> <group> <right>
Remoes a right <right> from the group <group> for the file located at
<path>.

| file-inform <path>
Informs all clients about a change in the file located at <path>.

| file-delete <path>
Deletes the file located at <path> and removes it form the database,
then informs all clients about its deletion.

| save-db
Saves the current state of the database.

| load-db
Loads a saved state of the database.

Configuration:
The client loads its configuration on startup from the file
'client.conf', this file can contain entries in the form of
<key>=<value> which can have keys (in no particular order):
(sans the | )

| TrackedDirectory
The value for this option is the name of the directory that is being
synchronized (this can be the root 'dir' directory or any of its
sub directories, but to mount a sub directory, the option
SubTreePrefix has to be specified, see below).
(Note: This value is without quotes as used for 'dir' above.)

| SubTreePrefix
This prefix gets prepended to files when communicating with the
and has to be used if we only mount a sub directory (if
TrackedDirectory is 'dir' without the quotes).
Example: If we mount dir\subdir1\subdir2 then TrackedDirectory
         is 'subdir2' and SubTreePrefix is 'dir\subdir1\' without
	 the quotes.

| CheckPeriod
The value for this option is the number of miliseconds between
the periodic checks that are performed to find changes in the
synchronized files.

| ListenPort
The value for this option determines which port does this client
listen on for server announcements (sent to the server automatically,
this allows multiple clients on one machine).

| ForceManualAuthentization
If the value for this option is equal to '1' (sans the quotes),
the client will require the user to enter his login credentials
through the console regardless of the fact if it finds these
credentials in the user configuration file (generated after
registration).

| Daemonize
If the value for this option is 1, the client will hide the console
window upon startup and will run as a daemon.
Note: This option does not work with manual authentization, so should
      not be used on first run of the client application (which
      in most cases requires registration through the console) or
      when the ForceManualAuthentization option is set.

Directory layout:
In the directory where the TreeShareClient.exe file is located,
a directory with the name equal to the value of the TrackedDirectory
option will be created once the client is run. This directory
will contain all the synchronized files.

Ignored file endings:
In the file 'ignored.conf', the user can specify which file name endings
will be ignored by the client (one ending per line). To ignore an
entire file name, simply write it as an ending, since the files
are checked if they end with the strings contained in this file during
checks.

Startup:
The client can be run from the command line using the command
'TreeShareClient.exe <addr> <port>' with arguments:
	<addr> Address of the server.
	<port> Port the server listens on.
Upon the start of the application, it will check for a 'user.conf'
file (which contains user name and a hashed password). If this file
is not found, the user will be prompted to either register or
login and for their credentials (which then get saved into the
'user.conf' file). This prompt will also appear whenever the
ForceManualAuthentization option is set in the client config
file.

Note: Due to the nature of this application only a brief description
      is given here about the individual server and client classes,
      while rest of their documentation can be found in the auto
      generated documentation.
      This is because the main part of the program that needs
      to be documented is the communication protocol, which has
      been moved to a separate part (3.4).

The database holds information about files, users and groups
(ServerDatabase) or about files (ClientDatabase) and provides
auxiliary functions for data management.
Both of these database classes inherit from the abstract class
SerializableDatabase, which provides a function to serialize
a DatabaseTable instance and two abstract functions for saving
and loading, which the derived database classes override and fill
with serializing steps (for their different tables).
More information about the functions of these and other classes
as well as about their public and private fields can be found
in the auto generated documentation.

The server has two primary threads (+ the main thread, which sleeps
until a shutdown has been initiated from the console). One of these
threads serves for console I/O, through which the user can issue
commands such as user/group/file management and shutdown
(for all available commands see user's documentation).
The second thread waits for incoming client connections and spawns
a task for each and reassigns the client to a new port from its
port pool.
More information about the function of this class as well as about
its public and private fields can be found in the auto generated
documentation.

The client has a single primary thread that loops indefinetly
accepting incoming server connections, which then handles. Alongside
this main thread a timer is created that asynchronously starts
periodic checks, during which it scans the tracked directory for
file updates and then informs the server if necessary.
More information about the function of this class as well as about
its public and private fields can be found in the auto generated
documentation.

This is an overview of the program's communication protocol, showing
possible messages sent between the server and its clients and their
expected responses.
Note that whenever a file path is being sent, it is always relative
to the location of the server executable and thus starting with
the 'dir' directory. The clients must make sure to prepend the
file paths with their <SubTreePrefix> when sending them to the
server and with <SubTreePrefix + TrackedDirectory + '\'> when
checking if the file belongs to their subtree.
The messages that can be sent are as follows:

| AUTHENTICATE & REGISTER
These messages are the only possible openings of a communication
between the server and a client , as they
cause the server to retrieve the client's user entry in the
database, which is then used for file access authorization.
The only difference between AUTHENTICATE and REGISTER is that
when REGISTER is sent, new user account gets created and the
communication will result in a FAIL if the user's name is taken
already.
[CLIENT]			[SERVER]
AUTHENTICATE/REGISTER
<name>
<pass-hash>
				SUCCESS/FAIL

| NEW_CONNECTION
This is the message a client sends to the server after startup once
it has been initially authenticated. It will tell the server the
client is now ready to accept its announcements and also which
port they will listen on for them. (Note: No response.)
[CLIENT]			[SERVER]
NEW_CONNECTION
<port>

| REQUEST_INITIAL_INFO
This is the message a client sends to the server after startup once
they have been authenticated and sent their listening port numbers.
It requests all files the client has READ access to and their times
of last modification, which the clients uses to choose files they
need updated. In case the response to this message is FAIL or
the server finnishes sending file info to the client, the
connection remains open and needs to be closed by the message
TRANSMISSION_END (from client, see below) or the client can send another
message (like REQUEST_FILE_CONTENTS for the files he needs).
[CLIENT]			[SERVER]
REQUEST_INITIAL_INFO
				SUCCESS/FAIL
				<file_1>
				<time_1>
				<file_2>
				<time_2>
				  ...
				<file_n>
				<time_n>
				TRANSMISSION_END

| REQUEST_FILE_CONTENTS
This message can be sent by a client to request the contents of
a file it has READ access to.
[CLIENT]			[SERVER]
REQUEST_FILE_CONTENTS
<file>
				SUCCESS/FAIL
				<file>
SUCCESS/FAIL
				<file contents>
				TRANSMISSION_END

| FILE_CHANGED, FILE_CREATED, FILE_DELETE
These messages are used to notify about the change in the contents
of a file (newer version, new file, deleted file) and can be sent
both client->server and	server->client. Note that in the case of
FILE_DELETED, the communication ends once <file> is sent and
acknowledged by SUCCESS or FAIL.
> Client->Server:
[CLIENT]			[SERVER]
FILE_CHANGED/DELETE/CREATED
<file>
				SUCCESS/FAIL
<file contents>
TRANSMISSION_END

> Server->Client: (Differs for FILE_DELETED.)
[CLIENT]			[SERVER]
				FILE_CHANGED/CREATED
				<file>
SUCCESS/FAIL+T_E
				<file contents>
				TRANSMISSION_END

> Server->Client: (FILE_DELETED variant.)
[CLIENT]			[SERVER]
				FILE_DELETED
				<file>
				TRANSMISSION_END

| TRANSMISSION_END
Serves to signal an end of a connection or a connection segment
(e.g. sending file contents).
This message should end all connections to the server.