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"""

tileset.py contains the TileSet class, and in general, routines that manage a
set of output tiles corresponding to a requested rendermode for a world. In
general, there will be one TileSet object per world per rendermode requested by
the user.

The TileSet class implements the Worker interface. This interface has the
following methods:

do_preprocessing()
    This method is called before iterate_work_items(). It should do any work
    that needs to be done prior to iterate_work_items(). It is not called for
    instances that will not have iterate_work_items() called.

get_num_phases()
    This method returns an integer indicating how many phases of work this
    worker has to perform. Each phase of work is completed serially with the
    other phases... all work done by one phase is done before the next phase is
    started.

iterate_work_items(phase)
    Takes a phase number (a non-negative integer). This method should return an
    iterator over work items. The work items can be any pickelable object; they
    are treated as opaque by the Dispatcher. The work item objects are passed
    back in to the do_work() method (perhaps in a different, identically
    configured instance)

do_work(workobj)
    Does the work for a given work object. This method is not expected to
    return anything, so the results of its work should be reflected on the
    filesystem or by sending signals.


"""

class TileSet(object):
    """The TileSet object manages the work required to produce a set of tiles
    on disk. It calculates the work that needs to be done and tells the
    dipatcher (through the Worker interface) this information. The Dispatcher
    then tells this object when and where to do the work of rendering the tiles.

    """

    def __init__(self, regionsetobj, assetmanagerobj, options, outputdir):
        """Construct a new TileSet object with the given configuration options
        dictionary.

        options is a dictionary of configuration parameters (strings mapping to
        values) that are interpreted by the rendering engine.

        regionsetobj is the RegionSet object that is used to render the tiles.

        assetmanagerobj is the AssetManager object that represents the
        destination directory where we'll put our tiles.

        outputdir is the absolute path to the tile output directory where the
        tiles are saved.
        TODO: This should probably be relative to the asset manager's output
        directory to avoid redundancy.

        """
        pass

    def do_preprocessing(self):
        """For the preprocessing step of the Worker interface, this does the
        chunk scan and stores the resulting tree as a private instance
        attribute for later use in iterate_work_items()

        """
        pass

    def get_num_phases(self):
        """Returns the number of levels in the quadtree, which is equal to the
        number of phases of work that need to be done.

        """
        pass

    def iterate_work_items(self, phase):
        """Iterates over the dirty tiles in the tree at level depth-phase. So
        the first phase iterates over the deepest tiles in the tree, and works
        its way to the root node of the tree.

        """
        pass

    def do_work(self, tileobj):
        """Renders the given tile.

        """

    def get_persistent_data(self):
        """Returns a dictionary representing the persistent data of this
        TileSet. Typically this is called by AssetManager

        """
        pass