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"""Parse & decompose router addresses"""



class Address(str):
    """A router address. Immutable, hashable.
    Subclasses str, so inherits all hash, comparison etc. properties.
    Provides a central place for logic to construct addresses of various types.
    """

    # FIXME aconway 2015-02-06: not finished:
    # - Move to C, make accessible in C code also - provide python wrapper.
    # - Provide access to parts of address using C field iterator, avoid duplicating that logic
    # - (Maybe) separate address logic out of general field iterator logic for clarity.

    AMQP="amqp:"
    TOPO="_topo"

    def __new__(self, addr): # Subclassing immutable type, must use __new__ not __init__
        if addr.startswith(self.AMQP): return str.__new__(addr)
        else: return str.__new__(Address, "%s/%s" % (self.AMQP, addr))

    @classmethod
    def mobile(cls, path):
        """Create a mobile address, can be moved to and referenced from anywhere in the network.
        @param path: The mobile address string.
        """
        return Address(path)

    @classmethod
    def topological(cls, router_id, path=None, area=None):
        """Create a topological address, references a specific router.
        @param router_id: ID of target router.
        @param path: Path part of address.
        @param area: Routing area (placeholder)
        """
        addr = "%s/%s/%s" % (cls.TOPO, area, router_id)
        if path: addr = "%s/%s" % (addr, path)
        return Address(addr)

    def __repr__(self): return "Address(%r)" % str(self)