## helpers.py
## Implement policies required for the sos system support tool

## Copyright (C) 2006 Steve Conklin <sconklin@redhat.com>

### 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 2 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, write to the Free Software
## Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

## Some code adapted from "Python Cookbook, 2nd ed", by Alex
## Martelli, Anna Martelli Ravenscroft, and David Ascher
## (O'Reilly Media, 2005) 0-596-00797-3
##

"""
helper functions used by sosreport and plugins
"""
import os, fcntl, select, itertools, sys, commands
from time import time
from tempfile import mkdtemp
from subprocess import Popen, PIPE, STDOUT

def importPlugin(pluginname, name):
    """ Import a plugin to extend capabilities of sosreport
    """
    try:
        plugin = __import__(pluginname, globals(), locals(), [name])
    except ImportError:
        return None
    return getattr(plugin, name)


def sosFindTmpDir(tmpdir):
    """Find a temp directory to form the root for our gathered information
    and reports.
    """
    try:
	if not os.path.isdir(tmpdir):
	    os.mkdir(tmpdir)
	workingBase = mkdtemp("","sos_", tmpdir)
    except:
	return None
    return workingBase


def makeNonBlocking(afd):
    """ Make the file descriptor non-blocking. This prevents deadlocks.
    """
    fl = fcntl.fcntl(afd, fcntl.F_GETFL)
    try:
        fcntl.fcntl(afd, fcntl.F_SETFL, fl | os.O_NDELAY)
    except AttributeError:
        fcntl.fcntl(afd, fcntl.F_SETFL, fl | os.FNDELAY)


def sosGetCommandOutput(command):
    """ Execute a command and gather stdin, stdout, and return status.
    """
    stime = time()
    cmd_env = os.environ
    cmd_env['LC_ALL'] = 'C'
    p = Popen(command, shell = True,
              stdout = PIPE, stderr = STDOUT,
              bufsize = -1, env = cmd_env)
    stdout, stderr = p.communicate()
    # hack to delete trailing '\n' added by p.communicate()
    if stdout[-1:] == '\n': stdout = stdout[:-1]
    return (p.returncode, stdout, time()-stime)

# FIXME: this needs to be made clean and moved to the plugin tools, so
# that it prints nice color output like sysreport if the progress bar
# is not enabled.
def sosStatus(stat):
    """ Complete a status line that has been output to the console,
    providing pass/fail indication.
    """
    if not stat:
        print "    [   OK   ]"
    else:
        print "    [ FAILED ]"
    sys.stdout.flush()
    return


def allEqual(elements):
    ''' return True if all the elements are equal, otherwise False. '''
    first_element = elements[0]
    for other_element in elements[1:]:
        if other_element != first_element:
            return False
    return True


def commonPrefix(*sequences):
    ''' return a list of common elements at the start of all sequences,
        then a list of lists that are the unique tails of each sequence. '''
    # if there are no sequences at all, we're done
    if not sequences:
        return [], []
    # loop in parallel on the sequences
    common = []
    for elements in itertools.izip(*sequences):
        # unless all elements are equal, bail out of the loop
        if not allEqual(elements):
            break
        # got one more common element, append it and keep looping
        common.append(elements[0])
    # return the common prefix and unique tails
    return common, [ sequence[len(common):] for sequence in sequences ]

def sosRelPath(path1, path2, sep=os.path.sep, pardir=os.path.pardir):
    ''' return a relative path from path1 equivalent to path path2.
        In particular: the empty string, if path1 == path2;
                       path2, if path1 and path2 have no common prefix.
    '''
    try:
        common, (u1, u2) = commonPrefix(path1.split(sep), path2.split(sep))
    except AttributeError:
        return path2

    if not common:
        return path2      # leave path absolute if nothing at all in common
    return sep.join( [pardir]*len(u1) + u2 )