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# Copyright 2010 Lars Wirzenius
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
import sys
import time
class Messager(object):
'''Write messages to the terminal.'''
def __init__(self, output=None):
self.output = output or sys.stderr
self._last_msg = '' # What did we write last?
self._last_time = 0 # When did we write last?
self._period = 1 # How long between updates?
def _now(self):
'''Return current time.'''
# This is a wrapper around time.time(), for testing.
return time.time()
def _raw_write(self, string):
'''Write raw data if output is terminal.'''
if self.output.isatty():
if self._last_msg:
self.output.write('\r' + (' ' * len(self._last_msg)) + '\r')
self.output.write(string)
self._last_msg = string
def write(self, string):
'''Write raw data, but only once per period.'''
now = self._now()
if now - self._last_time >= self._period:
self._raw_write(string)
self._last_time = now
def clear(self):
'''Remove current message from terminal.'''
self._raw_write('')
def notify(self, string):
'''Show a notification message string to the user.
Notifications are meant for error messages and other things
that do not belong in, say, progress bars. Whatever is currently
on the terminal is wiped, then the notification message is shown,
a new line is started, and the old message is restored.
Notifications are written even when the output is not going
to a terminal.
'''
old = self._last_msg
self.clear()
self.output.write('%s\n' % string)
self._raw_write(old)
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