# Copyright 2010, 2011  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 fcntl
import signal
import struct
import sys
import termios
import time


class Messager(object):

    '''Write messages to the terminal.'''
    
    def __init__(self, output=None, period=None, open_tty=None):
        self._enabled = True
        if output:
            self.output = output
        else:
            try:
                self.output = (open_tty or self._open_tty)()
            except IOError:
                self.output = None
        self._period = 1.0 if period is None else period
        self._last_msg = '' # What did we write last?
        self._last_time = 0 # When did we write last?
        self._cached_msg = '' # Last message from user, to write() method.
        self.set_width(self._get_terminal_width()) # Width of terminal
        signal.signal(signal.SIGWINCH, self._sigwinch_handler)
        signal.siginterrupt(signal.SIGWINCH, False)

    def _open_tty(self): # pragma: no cover
        return open('/dev/tty', 'w')
        
    def set_width(self, actual_width):
        self.width = actual_width - 1
        
    def _now(self):
        '''Return current time.'''
        # This is a wrapper around time.time(), for testing.
        return time.time()
        
    def _get_terminal_width(self): # pragma: no cover
        '''Return width of terminal in characters.

        If this fails, assume 80.
        
        Borrowed and adapted from bzrlib.
        
        '''
        
        default_width = 80
        if self.output is None:
            return default_width
        try:
            s = struct.pack('HHHH', 0, 0, 0, 0)
            x = fcntl.ioctl(self.output.fileno(), termios.TIOCGWINSZ, s)
            return struct.unpack('HHHH', x)[1]
        except IOError:
            return default_width
        except AttributeError:
            if not hasattr(self.output, 'fileno'):
                return default_width
            raise

    def _sigwinch_handler(self, signum, frame): # pragma: no cover
        # Clear the terminal from old stuff, using the old width.
        self.clear()
        # Get new width.
        self.set_width(self._get_terminal_width())

    def _raw_write(self, string):
        '''Write raw data if output is terminal.'''
        
        if self._enabled and self.output and self.output.isatty():
            try:
                self.output.write(string)
                self.output.flush()
            except IOError: # pragma: no cover
                self._enabled = False

    def _overwrite(self, string):
        '''Overwrite current message on terminal.'''
        if self._last_msg:
            self._raw_write('\r' + (' ' * len(self._last_msg)) + '\r')
        self._raw_write(string)
        self._last_msg = string

    def time_to_write(self):
        '''Is it time to write now?'''
        return self._now() - self._last_time >= self._period
            
    def write(self, string):
        '''Write raw data, but only once per period.'''
        string = string[:self.width]
        if self.time_to_write():
            self._overwrite(string)
            self._last_time = self._now()
        self._cached_msg = string
            
    def clear(self):
        '''Remove current message from terminal.'''
        self._overwrite('')
        
    def notify(self, string, f):
        '''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.
        
        '''

        if self._enabled:
            old = self._last_msg
            self.clear()
            try:
                f.write('%s\n' % string)
                f.flush()
            except IOError:
                # We ignore these. No point in crashing if terminal is bad.
                pass
            self._overwrite(old)
        
    def finish(self):
        '''Finalize output.'''
        if self._last_msg or self._cached_msg:
            self._overwrite(self._cached_msg)
            self._raw_write('\n')
        
    def disable(self):
        '''Disable all output.'''
        self._enabled = False
        
    def enable(self):
        '''Enable output to happen.'''
        self._enabled = True