#------------------------------------------------------------------------------
# Copyright (c) 2005, Enthought, Inc.
# All rights reserved.
# 
# This software is provided without warranty under the terms of the BSD
# license included in enthought/LICENSE.txt and may be redistributed only
# under the conditions described in the aforementioned license.  The license
# is also available online at http://www.enthought.com/licenses/BSD.txt
# Thanks for using Enthought open source!
# 
# Author: Enthought, Inc.
# Description: <Enthought logger package component>
#------------------------------------------------------------------------------

# Standard library imports.
from logging import Handler

# Enthought library imports.
from enthought.util.ring_buffer import RingBuffer


class LogQueueHandler(Handler):
    
    """ Buffers up the log messages so that we can display them later. 
        This is important on startup when log messages are generated before
        the ui has started.  By putting them in this queue we can display 
        them once the ui is ready.   
    """
    
    # The view where updates will go
    _view = None
    

    def __init__(self, size=1000):
        Handler.__init__(self)
        # only buffer 1000 log records
        self.size = size
        self.ring = RingBuffer(self.size)
        self.dirty = False
        return


    def emit(self, record):
        """ Actually this is more like an enqueue than an emit()."""
        self.ring.append(record)
        if self._view is not None:
            try:
                self._view.update()
            except Exception, e:
                pass
        self.dirty = True
        return


    def get(self):
        self.dirty = False
        
        try:
            result = self.ring.get()
        except Exception, msg:
            # we did our best and it won't cause too much damage 
            # to just return a bogus message 
            result = []
             
        return result


    def has_new_records(self):
        return self.dirty


    def reset(self):
        # start over with a new empty buffer 
        self.ring = RingBuffer(self.size)
        if self._view is not None:
            try:
                self._view.update()
            except Exception, e:
                pass
        self.dirty = True
        return

            
## EOF ##################################################################