# The contents of this file are subject to the Common Public Attribution
# License Version 1.0. (the "License"); you may not use this file except in
# compliance with the License. You may obtain a copy of the License at
# http://code.reddit.com/LICENSE. The License is based on the Mozilla Public
# License Version 1.1, but Sections 14 and 15 have been added to cover use of
# software over a computer network and provide for limited attribution for the
# Original Developer. In addition, Exhibit A has been modified to be consistent
# with Exhibit B.
#
# Software distributed under the License is distributed on an "AS IS" basis,
# WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for
# the specific language governing rights and limitations under the License.
#
# The Original Code is reddit.
#
# The Original Developer is the Initial Developer.  The Initial Developer of
# the Original Code is reddit Inc.
#
# All portions of the code written by reddit are Copyright (c) 2006-2015 reddit
# Inc. All Rights Reserved.
###############################################################################

from urllib import urlencode
import base64
import simplejson

from pylons import c, g, request, response
from pylons.i18n import _
from r2.config.extensions import set_extension
from r2.lib.base import abort
from reddit_base import RedditController, MinimalController, require_https
from r2.lib.db import tdb_cassandra
from r2.lib.db.thing import NotFound
from r2.models import Account
from r2.models.token import (
    OAuth2Client, OAuth2AuthorizationCode, OAuth2AccessToken,
    OAuth2RefreshToken, OAuth2Scope)
from r2.lib.errors import ForbiddenError, errors
from r2.lib.pages import OAuth2AuthorizationPage
from r2.lib.require import RequirementException, require, require_split
from r2.lib.utils import constant_time_compare, parse_http_basic, UrlParser
from r2.lib.validator import (
    nop,
    validate,
    VRequired,
    VThrottledLogin,
    VOneOf,
    VUser,
    VModhash,
    VOAuth2ClientID,
    VOAuth2Scope,
    VOAuth2RefreshToken,
    VRatelimit,
    VLength,
)


def _update_redirect_uri(base_redirect_uri, params, as_fragment=False):
    parsed = UrlParser(base_redirect_uri)
    if as_fragment:
        parsed.fragment = urlencode(params)
    else:
        parsed.update_query(**params)
    return parsed.unparse()


class OAuth2FrontendController(RedditController):
    def check_for_bearer_token(self):
        pass

    def pre(self):
        RedditController.pre(self)
        require_https()

    def _check_redirect_uri(self, client, redirect_uri):
        if not redirect_uri or not client or redirect_uri != client.redirect_uri:
            abort(ForbiddenError(errors.OAUTH2_INVALID_REDIRECT_URI))

    def _error_response(self, state, redirect_uri, as_fragment=False):
        """Return an error redirect, but only if client_id and redirect_uri are valid."""

        resp = {"state": state}

        if (errors.OAUTH2_INVALID_CLIENT, "client_id") in c.errors:
            resp["error"] = "unauthorized_client"
        elif (errors.OAUTH2_ACCESS_DENIED, "authorize") in c.errors:
            resp["error"] = "access_denied"
        elif (errors.BAD_HASH, None) in c.errors:
            resp["error"] = "access_denied"
        elif (errors.INVALID_OPTION, "response_type") in c.errors:
            resp["error"] = "unsupported_response_type"
        elif (errors.OAUTH2_INVALID_SCOPE, "scope") in c.errors:
            resp["error"] = "invalid_scope"
        else:
            resp["error"] = "invalid_request"

        final_redirect = _update_redirect_uri(redirect_uri, resp, as_fragment)
        return self.redirect(final_redirect, code=302)

    @validate(VUser(),
              response_type = VOneOf("response_type", ("code", "token")),
              client = VOAuth2ClientID(),
              redirect_uri = VRequired("redirect_uri", errors.OAUTH2_INVALID_REDIRECT_URI),
              scope = VOAuth2Scope(),
              state = VRequired("state", errors.NO_TEXT),
              duration = VOneOf("duration", ("temporary", "permanent"),
                                default="temporary"))
    def GET_authorize(self, response_type, client, redirect_uri, scope, state,
                      duration):
        """
        First step in [OAuth 2.0](http://oauth.net/2/) authentication.
        End users will be prompted for their credentials (username/password)
        and asked if they wish to authorize the application identified by
        the **client_id** parameter with the permissions specified by the
        **scope** parameter.  They are then redirected to the endpoint on
        the client application's side specified by **redirect_uri**.

        If the user granted permission to the application, the response will
        contain a **code** parameter with a temporary authorization code
        which can be exchanged for an access token at
        [/api/v1/access_token](#api_method_access_token).

        **redirect_uri** must match the URI configured for the client in the
        [app preferences](/prefs/apps).  If **client_id** or **redirect_uri**
        is not valid, or if the call does not take place over SSL, a 403
        error will be returned.  For all other errors, a redirect to
        **redirect_uri** will be returned, with a **error** parameter
        indicating why the request failed.
        """

        # Check redirect URI first; it will ensure client exists
        self._check_redirect_uri(client, redirect_uri)

        if response_type == "token" and client.is_confidential():
            # Prevent "confidential" clients from distributing tokens
            # in a non-confidential manner
            c.errors.add((errors.OAUTH2_INVALID_CLIENT, "client_id"))
        if response_type == "token" and duration != "temporary":
            # implicit grant -> No refresh tokens allowed
            c.errors.add((errors.INVALID_OPTION, "duration"))

        if not c.errors:
            return OAuth2AuthorizationPage(client, redirect_uri, scope, state,
                                           duration, response_type).render()
        else:
            return self._error_response(state, redirect_uri,
                                        as_fragment=(response_type == "token"))

    @validate(VUser(),
              VModhash(fatal=False),
              client = VOAuth2ClientID(),
              redirect_uri = VRequired("redirect_uri", errors.OAUTH2_INVALID_REDIRECT_URI),
              scope = VOAuth2Scope(),
              state = VRequired("state", errors.NO_TEXT),
              duration = VOneOf("duration", ("temporary", "permanent"),
                                default="temporary"),
              authorize = VRequired("authorize", errors.OAUTH2_ACCESS_DENIED),
              response_type = VOneOf("response_type", ("code", "token"),
                                     default="code"))
    def POST_authorize(self, authorize, client, redirect_uri, scope, state,
                       duration, response_type):
        """Endpoint for OAuth2 authorization."""

        if response_type == "token" and client.is_confidential():
            # Prevent "confidential" clients from distributing tokens
            # in a non-confidential manner
            c.errors.add((errors.OAUTH2_INVALID_CLIENT, "client_id"))
        if response_type == "token" and duration != "temporary":
            # implicit grant -> No refresh tokens allowed
            c.errors.add((errors.INVALID_OPTION, "duration"))
        self._check_redirect_uri(client, redirect_uri)

        if c.errors:
            return self._error_response(state, redirect_uri,
                                        as_fragment=(response_type == "token"))

        if response_type == "code":
            code = OAuth2AuthorizationCode._new(client._id, redirect_uri,
                                            c.user._id36, scope,
                                            duration == "permanent")
            resp = {"code": code._id, "state": state}
            final_redirect = _update_redirect_uri(redirect_uri, resp)
        elif response_type == "token":
            token = OAuth2AccessToken._new(client._id, c.user._id36, scope)
            token_data = OAuth2AccessController._make_token_dict(token)
            token_data["state"] = state
            final_redirect = _update_redirect_uri(redirect_uri, token_data, as_fragment=True)

        return self.redirect(final_redirect, code=302)

class OAuth2AccessController(MinimalController):
    handles_csrf = True

    def pre(self):
        set_extension(request.environ, "json")
        MinimalController.pre(self)
        require_https()
        c.oauth2_client = self._get_client_auth()

    def _get_client_auth(self):
        auth = request.headers.get("Authorization")
        try:
            client_id, client_secret = parse_http_basic(auth)
            require(client_id)
            client = OAuth2Client.get_token(client_id)
            require(client)
            if client.is_confidential():
                require(client_secret)
                require(constant_time_compare(client.secret, client_secret))
            return client
        except RequirementException:
            abort(401, headers=[("WWW-Authenticate", 'Basic realm="reddit"')])

    @validate(
        grant_type=VOneOf("grant_type",
            (
                 "authorization_code",
                 "refresh_token",
                 "password",
                 "client_credentials",
                 "https://oauth.reddit.com/grants/installed_client",
            )
        ),
    )
    def POST_access_token(self, grant_type):
        """
        Exchange an [OAuth 2.0](http://oauth.net/2/) authorization code
        or refresh token (from [/api/v1/authorize](#api_method_authorize)) for
        an access token.

        On success, returns a URL-encoded dictionary containing
        **access_token**, **token_type**, **expires_in**, and **scope**.
        If an authorization code for a permanent grant was given, a
        **refresh_token** will be included. If there is a problem, an **error**
        parameter will be returned instead.

        Must be called using SSL, and must contain a HTTP `Authorization:`
        header which contains the application's client identifier as the
        username and client secret as the password.  (The client id and secret
        are visible on the [app preferences page](/prefs/apps).)

        Per the OAuth specification, **grant_type** must be one of:

        * ``authorization_code`` for the initial access token ("standard" OAuth2 flow)
        * ``refresh_token`` for renewing the access token.
        * ``password`` for script-type apps using password auth
        * ``client_credentials`` for application-only (signed out) access - confidential clients
        * ``https://oauth.reddit.com/grants/installed_client`` extension grant for application-only (signed out)
                access - non-confidential (installed) clients

        **redirect_uri** must exactly match the value that was used in the call
        to [/api/v1/authorize](#api_method_authorize) that created this grant.

        See reddit's [OAuth2 wiki](https://github.com/reddit/reddit/wiki/OAuth2) for
        more information.

        """
        if grant_type == "authorization_code":
            return self._access_token_code()
        elif grant_type == "refresh_token":
            return self._access_token_refresh()
        elif grant_type == "password":
            return self._access_token_password()
        elif grant_type == "client_credentials":
            return self._access_token_client_credentials()
        elif grant_type == "https://oauth.reddit.com/grants/installed_client":
            return self._access_token_extension_client_credentials()
        else:
            resp = {"error": "unsupported_grant_type"}
            return self.api_wrapper(resp)

    def _check_for_errors(self):
        resp = {}
        if (errors.INVALID_OPTION, "scope") in c.errors:
            resp["error"] = "invalid_scope"
        else:
            resp["error"] = "invalid_request"
        return resp

    @classmethod
    def _make_token_dict(cls, access_token, refresh_token=None):
        if not access_token:
            return {"error": "invalid_grant"}
        expires_in = int(access_token._ttl) if access_token._ttl else None
        resp = {
            "access_token": access_token._id,
            "token_type": access_token.token_type,
            "expires_in": expires_in,
            "scope": access_token.scope,
        }
        if refresh_token:
            resp["refresh_token"] = refresh_token._id
        return resp

    @validate(code=nop("code"),
              redirect_uri=VRequired("redirect_uri",
                                     errors.OAUTH2_INVALID_REDIRECT_URI))
    def _access_token_code(self, code, redirect_uri):
        if not code:
            c.errors.add("NO_TEXT", field="code")
        if c.errors:
            return self.api_wrapper(self._check_for_errors())

        access_token = None
        refresh_token = None

        auth_token = OAuth2AuthorizationCode.use_token(
            code, c.oauth2_client._id, redirect_uri)
        if auth_token:
            if auth_token.refreshable:
                refresh_token = OAuth2RefreshToken._new(
                    auth_token.client_id, auth_token.user_id,
                    auth_token.scope)
            access_token = OAuth2AccessToken._new(
                auth_token.client_id, auth_token.user_id,
                auth_token.scope,
                refresh_token._id if refresh_token else "")

        resp = self._make_token_dict(access_token, refresh_token)

        return self.api_wrapper(resp)

    @validate(refresh_token=VOAuth2RefreshToken("refresh_token"))
    def _access_token_refresh(self, refresh_token):
        resp = {}
        access_token = None
        if refresh_token:
            access_token = OAuth2AccessToken._new(
                refresh_token.client_id, refresh_token.user_id,
                refresh_token.scope,
                refresh_token=refresh_token._id)
        else:
            c.errors.add("NO_TEXT", field="refresh_token")

        if c.errors:
            resp = self._check_for_errors()
        else:
            resp = self._make_token_dict(access_token)
        return self.api_wrapper(resp)

    @validate(user=VThrottledLogin(["username", "password"]),
              scope=nop("scope"))
    def _access_token_password(self, user, scope):
        # username:password auth via OAuth is only allowed for
        # private use scripts
        client = c.oauth2_client
        if client.app_type != "script":
            return self.api_wrapper({"error": "unauthorized_client",
                "error_description": "Only script apps may use password auth"})
        dev_ids = client._developer_ids
        if not user or user._id not in dev_ids:
            return self.api_wrapper({"error": "invalid_grant"})
        if c.errors:
            return self.api_wrapper(self._check_for_errors())

        if scope:
            scope = OAuth2Scope(scope)
            if not scope.is_valid():
                c.errors.add(errors.INVALID_OPTION, "scope")
                return self.api_wrapper({"error": "invalid_scope"})
        else:
            scope = OAuth2Scope(OAuth2Scope.FULL_ACCESS)

        access_token = OAuth2AccessToken._new(
                client._id,
                user._id36,
                scope
        )
        resp = self._make_token_dict(access_token)
        return self.api_wrapper(resp)

    @validate(
        scope=nop("scope"),
    )
    def _access_token_client_credentials(self, scope):
        client = c.oauth2_client
        if not client.is_confidential():
            return self.api_wrapper({"error": "unauthorized_client",
                "error_description": "Only confidential clients may use client_credentials auth"})
        if scope:
            scope = OAuth2Scope(scope)
            if not scope.is_valid():
                c.errors.add(errors.INVALID_OPTION, "scope")
                return self.api_wrapper({"error": "invalid_scope"})
        else:
            scope = OAuth2Scope(OAuth2Scope.FULL_ACCESS)

        access_token = OAuth2AccessToken._new(
            client._id,
            "",
            scope,
        )
        resp = self._make_token_dict(access_token)
        return self.api_wrapper(resp)

    @validate(
        scope=nop("scope"),
        device_id=VLength("device_id", 50, min_length=20),
    )
    def _access_token_extension_client_credentials(self, scope, device_id):
        if ((errors.NO_TEXT, "device_id") in c.errors or
                (errors.TOO_SHORT, "device_id") in c.errors or
                (errors.TOO_LONG, "device_id") in c.errors):
            return self.api_wrapper({
                "error": "invalid_request",
                "error_description": "bad device_id",
            })

        client = c.oauth2_client
        if scope:
            scope = OAuth2Scope(scope)
            if not scope.is_valid():
                c.errors.add(errors.INVALID_OPTION, "scope")
                return self.api_wrapper({"error": "invalid_scope"})
        else:
            scope = OAuth2Scope(OAuth2Scope.FULL_ACCESS)

        access_token = OAuth2AccessToken._new(
            client._id,
            "",
            scope,
            device_id=device_id,
        )
        resp = self._make_token_dict(access_token)
        return self.api_wrapper(resp)

    @validate(
        VRatelimit(rate_user=False, rate_ip=True, prefix="rate_revoke_token_"),
        token_id=nop("token"),
        token_hint=VOneOf("token_type_hint", ("access_token", "refresh_token")),
    )
    def POST_revoke_token(self, token_id, token_hint):
        '''Revoke an OAuth2 access or refresh token.

        token_type_hint is optional, and hints to the server
        whether the passed token is a refresh or access token.

        A call to this endpoint is considered a success if
        the passed `token_id` is no longer valid. Thus, if an invalid
        `token_id` was passed in, a successful 204 response will be returned.

        See [RFC7009](http://tools.ietf.org/html/rfc7009)

        '''
        # In success cases, this endpoint returns no data.
        response.status = 204

        if not token_id:
            return

        types = (OAuth2AccessToken, OAuth2RefreshToken)
        if token_hint == "refresh_token":
            types = reversed(types)

        for token_type in types:
            try:
                token = token_type._byID(token_id)
            except tdb_cassandra.NotFound:
                continue
            else:
                break
        else:
            # No Token found. The given token ID is already gone
            # or never existed. Either way, from the client's perspective,
            # the passed in token is no longer valid.
            return

        if constant_time_compare(token.client_id, c.oauth2_client._id):
            token.revoke()
        else:
            # RFC 7009 is not clear on how to handle this case.
            # Given that a malicious client could do much worse things
            # with a valid token then revoke it, returning an error
            # here is best as it may help certain clients debug issues
            response.status = 400
            return self.api_wrapper({"error": "unauthorized_client"})


def require_oauth2_scope(*scopes):
    def oauth2_scope_wrap(fn):
        fn.oauth2_perms = {"required_scopes": scopes, "oauth2_allowed": True}
        return fn
    return oauth2_scope_wrap


def allow_oauth2_access(fn):
    fn.oauth2_perms = {"required_scopes": [], "oauth2_allowed": True}
    return fn
