# Python imports.

from operator import attrgetter

class Rule(object):

    """

    Class representing a single iptables rule. The representation does not

    include the chain to which it is applied, or how it is applied (append vs

    insert).

    The instances of this class can be used for easily outputting a single rule.

    """

    def __init__(self, source, destination, protocol, port, description=""):

        """

        Initialises a rule instance. Sets-up the necessary information passed

        with arguments.

        Arguments:

        source - Source of communication, in format IP/NETMASK.

        destination - Destination of communication, in format IP/NETMASK.

        protocol - Protocol used by the rule. Currently supported values are

        UDP, TCP, and ICMP.

        port - Destination port in a rule if protocol specified is UDP or

        TCP. In case of ICMP this should be the ICMP packet type.

        description - Rule description. This can be used by other classes to

        produce comments in the output.

        """

        if protocol not in ("TCP", "UDP", "ICMP"):

            raise ValueError("Unsupported protocol specified: %s" % protocol)

        self.source = source

        self.destination = destination

        self.protocol = protocol

        self.port = port

        self.description = description

    def __unicode__(self):

        """

        Creates string representation of the rule. The format is:

        -s SOURCE -d DESTINATION -p PROTOCOL -m PROTOCOL (--dport|--icmp-type) PORT -j ACCEPT

        Returns:

        String representation of the rule.

        """

        if self.protocol.upper() in ("TCP", "UDP"):

            return "-s %s -d %s -p %s -m %s --dport %s -j ACCEPT" % (self.source, self.destination, self.protocol, self.protocol, self.port)

        elif self.protocol.upper() in ("ICMP"):

            return "-s %s -d %s -p %s -m %s --icmp-type %s -j ACCEPT" % (self.source, self.destination, self.protocol, self.protocol, self.port)

    def __str__(self):

        """

        Creates string representation of the rule. Calls the __unicode__

        function.

        Returns:

        String representation of the rule.        

        """

        return self.__unicode__()

class Chain(object):

    """

    Class representing a full iptables chain. Every chain has a name, default

    target, and contains a number of rules.

    The instances of this class can be used for easily outputting iptables rules

    for a single chain.

    """

    def __init__(self, name, default):

        """

        Initialises a chain instance. Sets-up the necessary information passed

        through the arguments.

        Arguments:

        name - The chain name (for example, INPUT, OUTPUT, FORWARD).

        default - Default target. Currently supported values are ACCEPT, DROP,

        and REJECT.

        """

        if default not in ("ACCEPT", "DROP", "REJECT"):

            raise ValueError("Unsupported default target specified: %s" % default)

        self.name = name

        self.default = default

        self.rules = []

    def add_rule(self, rule):

        """

        Adds a new rule to the chain.

        Arguments:

        rule - Instance of Rule that should be added to the chain.

        """

        self.rules.append(rule)

    def __unicode__(self):

        """

        Creates string representing of the chain. The format will be:

        :NAME DEFAULT [0:0]

        # DESC_RULE_1

        -A NAME RULE_1

        # DESC_RULE_2

        -A NAME RULE_2

        ...

        # DESC_RULE_N

        -A NAME RULE_N

        It should be noted that the rules will be grouped by their

        description. Description line is not output if description is empty.

        """

        # Set-up the "header".

        rendering = ":%s %s [0:0]\n" % (self.name, self.default)

        # Group the rules by description.

        previous_description=""

        rules = list(self.rules)

        rules.sort(key=attrgetter("description"))

        # Process each rule.

        for rule in rules:

            if rule.description != previous_description:

                rendering += "\n"

                if rule.description:

                    rendering += "# %s\n" % rule.description

                previous_description = rule.description

            rendering += "%s\n" % rule

        return rendering

    def __str__(self):

        """

        Creates string representation of the chain. Calls the __unicode__

        function.

        Returns:

        String representation of the chain.

        """

        return self.__unicode__()

class Table(object):

    """

    Class representing a single iptables table (i.e. nat, or filter). Each table

    has a name, and a number of associated chains.

    The instances of this class can be used for easily outputting iptables rules

    for a single table.

    """

    def __init__(self, name):

        """

        Initialises a table instance. Sets-up the necessary information passed

        through the arguments.

        Arguments:

        name - Table name (for example, nat or filter).

        """

        self.name = name

        self.chains = []

    def add_chain(self, chain):

        """

        Adds a new chain to the table.

        Arguments:

        chain - Instance of Chain that should be added to the chain.

        """

        self.chains.append(chain)

    def __unicode__(self):

        """

        Creates string representing of the table. The format will be:

        *NAME

        CHAIN_1

        CHAIN_2

        COMMIT

        """

        rendering = "*%s\n" % self.name

        for chain in self.chains:

            rendering += "%s" % chain

        rendering += "COMMIT\n"

        return rendering

    def __str__(self):

        """

        Creates string representation of the table. Calls the __unicode__

        function.

        Returns:

        String representation of the table.

        """

        return self.__unicode__()