#!/usr/bin/env python

import re, sys, os
from stat import *
import getpass, grp


def usage():
    usage_str = "Usage: " + sys.argv[0] + """[--no-grades]
    You must be in <base directory> to execute this.
  looks up each file and subdirectory under
    <base directory>/spool
 owned by the user, and changes its group to the grades group name.  It
also makes the file group readable, writeable, and if a directory,
executable and with the setgid bit and sticky bit.
If the option --no-grades is there, files with name
beginning with GRADE- will not be changed: maybe you do not want to make
the grades visible yet.
"""
    sys.stderr.write(usage_str)
    sys.exit(1)


def ch_grpown_dir(path, uid, gid, grades, prefix):
    """Change the group ownership in the directory tree under path.

    ARGS:
    prefix helps in displaying the tree during the recursive calls."""

    if re.match("^GRADE-", os.path.basename(path)) and not grades: return
    
    print prefix, os.path.basename(path)
    
    try:
        stat_return = os.lstat(path) 
    except OSError, detail:
        sys.stderr.write("lstat " + path + " failed: " +
                         detail.strerror + "\n")
        return

    if uid == stat_return[ST_UID]:
        if gid != stat_return[ST_GID]: 
            try:
                os.chown(path, uid, gid)
            except OSError, detail:
                sys.stderr.write("chown " + path + " failed: " +
                                 detail.strerror + "\n")
                return
        mode = stat_return[ST_MODE]
        newmode = mode & 0777
        if os.path.isdir(path):     # or # if ST_ISDIR(mode):
            try:
                os.chmod(path, newmode | 03070)
            except OSError, detail:
                sys.stderr.write("chmod " + path + " failed: " +
                                 detail.strerror + "\n")
                return
        else:
            if "HEADER" != os.path.basename(path):
                try:
                    os.chmod(path, newmode | 0060)
                except OSError, detail:
                    sys.stderr.write("chmod " + path + " failed: " +
                                     detail.strerror + "\n")
                    return
                
    if os.path.isdir(path):
        try:
            dirlist = os.listdir(path)
        except OSError, detail:
            sys.stderr.write("os.listdir(" + path + ") failed: " +
                                     detail.strerror + "\n")
            return
        for file in dirlist:
            ch_grpown_dir(os.path.join(path, file), uid, gid, grades,
                          prefix + "  ")

"main"

argc = len(sys.argv)
if 2 < argc : usage()
grades = 1
if 2 == argc:
    if "--no-grades" != sys.argv[1]: usage()
    else: grades = 0

logname = getpass.getuser() # Not really used.
print "Login name: ", logname
uid = os.getuid()

# cwd = /cs/course/cs410/homework
spool = os.path.join(os.getcwd(), "spool");
sys.stderr.write("Spool directory: " + spool + "\n")

try:
    stat_return = os.lstat(spool) 
except OSError, detail:
    sys.stderr.write("lstat " + spool + " failed: " +
                     detail.strerror + "\n")
    exit(1)
gid = stat_return[ST_GID]
try:
    gname = grp.getgrgid(gid)[0] # Not really used.
except OSError, detail:
    sys.stderr.write("getgrgid" + gid + " failed: " +
                     detail.strerror + "\n")
    exit(1)
print "Group name: ", gname

ch_grpown_dir(spool, uid, gid, grades, "")