import stat, os, shutil, urllib, subprocess
from itertools import dropwhile

def create_directory(path, ignore_failure=True, uid=-1, gid=-1, modes=""):
	try:
		os.makedirs(path)
	except OSError, e:
		if ignore_failure:
			pass
		else:
			raise

	if uid != -1 or gid != -1:
		os.chown(path, uid, gid)
	
	if modes != "":
		set_modes(path, modes)

def copy_file(source, destination, ignore_failure=True, uid=-1, gid=-1, modes=""):
	if ignore_failure == False:
		if os.path_exists(destination):
			raise Exception("Destination path already exists.")
	
	try:
		shutil.copy(source, destination)
	except IOError, e:
		if ignore_failure:
			pass
		else:
			raise
	
	if uid != -1 or gid != -1:
		os.chown(destination, uid, gid)
	
	if modes != "":
		set_modes(destination, modes)

def create_file(path, contents="", uid=-1, gid=-1, modes=""):
	f = open(path, "w")
	
	if contents != "":
		f.write(contents)
		
	f.close()
	
	if uid != -1 or gid != -1:
		os.chown(path, uid, gid)
	
	if modes != "":
		set_modes(path, modes)

def set_modes(path, modes):
	mode_map = {
		"u": {
			"r": stat.S_IRUSR,
			"w": stat.S_IWUSR,
			"x": stat.S_IXUSR
		},
		"g": {
			"r": stat.S_IRGRP,
			"w": stat.S_IWGRP,
			"x": stat.S_IXGRP
		},
		"o": {
			"r": stat.S_IROTH,
			"w": stat.S_IWOTH,
			"x": stat.S_IXOTH
		}
		
	}
	
	chunks = modes.split(" ")
	mode = 0
	
	for chunk in chunks:
		usertype, changes = chunk.split("+")
		
		if usertype in mode_map:
			for change in list(changes):
				if change in mode_map[usertype]:
					mode = mode | mode_map[usertype][change]
				else:
					raise Exception("Unknown permission in modes specification.")
		elif usertype == "a":
			for change in list(changes):
				for i in mode_map:
					if change in mode_map[i]:
						mode = mode | mode_map[i][change]
		else:
			raise Exception("Unknown user type in modes specification.")
		
	os.chmod(path, mode)

def download_file(name, mirrors):
	try:
		file_mirrors = mirrors[name]
	except KeyError, e:
		raise Exception("No such file exists in the mirror list.")
	
	for url in file_mirrors:
		try:
			urllib.urlretrieve(url, name)
		except:
			continue
		else:
			return name
	
	raise Exception("No functional mirrors found for this file.")

def install_rpm(path):
	stfu = open("/dev/null", "wb")
	
	result = subprocess.call(["yum", "--nogpgcheck", "install", "-y", path], stdout=stfu, stderr=stfu)
	
	stfu.close()
	
	if result != 0:
		raise Exception("Failed to install package.")

def install_remote_rpm(name, mirrors):
	download_file(name, mirrors)
	install_rpm(name)

def rindex(lst, item):
	# http://stackoverflow.com/a/6892096/1332715
	try:
		return dropwhile(lambda x: lst[x].strip() != item, reversed(xrange(len(lst)))).next()
	except StopIteration:
		raise ValueError, "rindex(lst, item): item not in list"