# -*- coding: utf-8 -*-
"""
    flask.ext.security.decorators
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    Flask-Security decorators module

    :copyright: (c) 2012 by Matt Wright.
    :license: MIT, see LICENSE for more details.
"""

from collections import namedtuple
from functools import wraps

from flask import current_app, Response, request, redirect, _request_ctx_stack
from flask.ext.login import current_user, login_required
from flask.ext.principal import RoleNeed, Permission, Identity, identity_changed
from werkzeug.local import LocalProxy

from . import utils


# Convenient references
_security = LocalProxy(lambda: current_app.extensions['security'])


_default_unauthorized_html = """
    <h1>Unauthorized</h1>
    <p>The server could not verify that you are authorized to access the URL
    requested. You either supplied the wrong credentials (e.g. a bad password),
    or your browser doesn't understand how to supply the credentials required.</p>
    """

BasicAuth = namedtuple('BasicAuth', 'username, password')


def _get_unauthorized_response(text=None, headers=None):
    text = text or _default_unauthorized_html
    headers = headers or {}
    return Response(text, 401, headers)


def _get_unauthorized_view():
    cv = utils.get_url(utils.config_value('UNAUTHORIZED_VIEW'))
    utils.do_flash(*utils.get_message('UNAUTHORIZED'))
    return redirect(cv or request.referrer or '/')


def _check_token():
    header_key = _security.token_authentication_header
    args_key = _security.token_authentication_key
    header_token = request.headers.get(header_key, None)
    token = request.args.get(args_key, header_token)
    if request.get_json(silent=True):
        token = request.json.get(args_key, token)

    user = _security.login_manager.token_callback(token)

    if user and user.is_authenticated():
        app = current_app._get_current_object()
        _request_ctx_stack.top.user = user
        identity_changed.send(app, identity=Identity(user.id))
        return True

    return False


def _check_http_auth():
    auth = request.authorization or BasicAuth(username=None, password=None)
    user = _security.datastore.find_user(email=auth.username)

    if user and utils.verify_and_update_password(auth.password, user):
        _security.datastore.commit()
        app = current_app._get_current_object()
        _request_ctx_stack.top.user = user
        identity_changed.send(app, identity=Identity(user.id))
        return True

    return False


def http_auth_required(realm):
    """Decorator that protects endpoints using Basic HTTP authentication.
    The username should be set to the user's email address.

    :param realm: optional realm name"""

    def decorator(fn):
        @wraps(fn)
        def wrapper(*args, **kwargs):
            if _check_http_auth():
                return fn(*args, **kwargs)
            r = _security.default_http_auth_realm if callable(realm) else realm
            h = {'WWW-Authenticate': 'Basic realm="%s"' % r}
            return _get_unauthorized_response(headers=h)
        return wrapper

    if callable(realm):
        return decorator(realm)
    return decorator


def auth_token_required(fn):
    """Decorator that protects endpoints using token authentication. The token
    should be added to the request by the client by using a query string
    variable with a name equal to the configuration value of
    `SECURITY_TOKEN_AUTHENTICATION_KEY` or in a request header named that of
    the configuration value of `SECURITY_TOKEN_AUTHENTICATION_HEADER`
    """

    @wraps(fn)
    def decorated(*args, **kwargs):
        if _check_token():
            return fn(*args, **kwargs)
        return _get_unauthorized_response()
    return decorated


def auth_required(*auth_methods):
    """
    Decorator that protects enpoints through multiple mechanisms
    Example::

        @app.route('/dashboard')
        @auth_required('token', 'session')
        def dashboard():
            return 'Dashboard'

    :param auth_methods: Specified mechanisms.
    """
    login_mechanisms = {
        'token': lambda: _check_token(),
        'basic': lambda: _check_http_auth(),
        'session': lambda: current_user.is_authenticated()
    }

    def wrapper(fn):
        @wraps(fn)
        def decorated_view(*args, **kwargs):
            mechanisms = [login_mechanisms.get(method) for method in auth_methods]
            for mechanism in mechanisms:
                if mechanism and mechanism():
                    return fn(*args, **kwargs)
            return _get_unauthorized_response()
        return decorated_view
    return wrapper


def roles_required(*roles):
    """Decorator which specifies that a user must have all the specified roles.
    Example::

        @app.route('/dashboard')
        @roles_required('admin', 'editor')
        def dashboard():
            return 'Dashboard'

    The current user must have both the `admin` role and `editor` role in order
    to view the page.

    :param args: The required roles.
    """
    def wrapper(fn):
        @wraps(fn)
        def decorated_view(*args, **kwargs):
            perms = [Permission(RoleNeed(role)) for role in roles]
            for perm in perms:
                if not perm.can():
                    return _get_unauthorized_view()
            return fn(*args, **kwargs)
        return decorated_view
    return wrapper


def roles_accepted(*roles):
    """Decorator which specifies that a user must have at least one of the
    specified roles. Example::

        @app.route('/create_post')
        @roles_accepted('editor', 'author')
        def create_post():
            return 'Create Post'

    The current user must have either the `editor` role or `author` role in
    order to view the page.

    :param args: The possible roles.
    """
    def wrapper(fn):
        @wraps(fn)
        def decorated_view(*args, **kwargs):
            perm = Permission(*[RoleNeed(role) for role in roles])
            if perm.can():
                return fn(*args, **kwargs)
            return _get_unauthorized_view()
        return decorated_view
    return wrapper


def anonymous_user_required(f):
    @wraps(f)
    def wrapper(*args, **kwargs):
        if current_user.is_authenticated():
            return redirect(utils.get_url(_security.post_login_view))
        return f(*args, **kwargs)
    return wrapper
