# -*- encoding: UTF-8 -*-
#
# Form based authentication for CherryPy. Requires the
# Session tool to be loaded.
#

import cherrypy

SESSION_KEY = '_cp_username'

def check_credentials(username, password):
    """Verifies credentials for username and password.
    Returns None on success or a string describing the error on failure"""
    from spwd import getspnam
    from crypt import crypt

    try:
        enc_pwd = getspnam(username)[1]
    except KeyError:
        raise OSError("user '%s' not found" % username)
    else:
        if enc_pwd in ['NP', '!', '', None]:
            raise OSError("user '%s' has no password set" % username)
        elif enc_pwd in ['LK', '*']:
            raise OSError('account is locked')
        elif enc_pwd == "!!":
            raise OSError('password is expired')

        if crypt(password, enc_pwd) == enc_pwd:
            return True
        else:
            raise OSError('incorrect password')

def unix_authenticate(username, password):
    """Fallback authentication for BSD"""
    from crypt import crypt
    from pwd import getpwnam
    
    cryptedpasswd = getpwnam(username)[1]
    if cryptedpasswd:
        if cryptedpasswd == 'x' or cryptedpasswd == '*':
            raise NotImplementedError("Shadow passwords not supported")
        return crypt(password, cryptedpasswd) == cryptedpasswd
    else:
        return False

def check_auth(*args, **kwargs):
    """A tool that looks in config for 'auth.require'. If found and it
    is not None, a login is required and the entry is evaluated as a list of
    conditions that the user must fulfill"""
    conditions = cherrypy.request.config.get('auth.require', None)
    if conditions is not None:
        username = cherrypy.session.get(SESSION_KEY)
        if username:
            cherrypy.request.login = username
            for condition in conditions:
                # A condition is just a callable that returns true or false
                if not condition():
                    raise cherrypy.HTTPRedirect("/auth/login")
        else:
            raise cherrypy.HTTPRedirect("/auth/login")
    
cherrypy.tools.auth = cherrypy.Tool('before_handler', check_auth)

def require(*conditions):
    """A decorator that appends conditions to the auth.require config
    variable."""
    def decorate(f):
        if not hasattr(f, '_cp_config'):
            f._cp_config = dict()
        if 'auth.require' not in f._cp_config:
            f._cp_config['auth.require'] = []
        f._cp_config['auth.require'].extend(conditions)
        return f
    return decorate

# Controller to provide login and logout actions

class AuthController(object):
    def __init__(self):
        self.html_directory = cherrypy.config['misc.html_directory']

    def on_login(self, username):
        """Called on successful login"""
    
    def on_logout(self, username):
        """Called on logout"""
    
    def get_loginform(self):
        import os
        from cherrypy.lib.static import serve_file

        try:
            return serve_file(os.path.join(self.html_directory,
                                           'login_%s.html' % cherrypy.config['misc.localization']))
        except cherrypy.NotFound:
            return serve_file(os.path.join(self.html_directory,
                                           'login_en.html'))
    
    @cherrypy.expose
    def login(self, username=None, password=None, hide=None, from_page='/'):
        if not username or not password:
            return self.get_loginform()

        validated = False
        try:      
            validated = check_credentials(username, password)
        except OSError:
            import pam
            validated = pam.authenticate(username, password)
        except ImportError:
            validated = unix_authenticate(username, password)
        finally:
            if validated:
                cherrypy.session.regenerate()
                cherrypy.session[SESSION_KEY] = cherrypy.request.login = username
                self.on_login(username)
                raise cherrypy.HTTPRedirect("/")
            else:
                return self.get_loginform()
    
    @cherrypy.expose
    def logout(self):
        sess = cherrypy.session
        username = sess.get(SESSION_KEY, None)
        sess[SESSION_KEY] = None
        if username:
            cherrypy.request.login = None
            self.on_logout(username)
        raise cherrypy.HTTPRedirect("/index")