/*
 *
 * Copyright 2020 The KubeSphere Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * /
 */

package oauth

import (
	"fmt"
	"github.com/emicklei/go-restful"
	apierrors "k8s.io/apimachinery/pkg/api/errors"
	"k8s.io/klog"
	"kubesphere.io/kubesphere/pkg/api"
	"kubesphere.io/kubesphere/pkg/api/auth"
	"kubesphere.io/kubesphere/pkg/apiserver/authentication/oauth"
	"kubesphere.io/kubesphere/pkg/apiserver/authentication/token"
	"kubesphere.io/kubesphere/pkg/apiserver/request"
	"net/http"
)

type oauthHandler struct {
	issuer token.Issuer
	config oauth.Configuration
}

func newOAUTHHandler(issuer token.Issuer, config oauth.Configuration) *oauthHandler {
	return &oauthHandler{issuer: issuer, config: config}
}

// Implement webhook authentication interface
// https://kubernetes.io/docs/reference/access-authn-authz/authentication/#webhook-token-authentication
func (h *oauthHandler) TokenReviewHandler(req *restful.Request, resp *restful.Response) {
	var tokenReview auth.TokenReview

	err := req.ReadEntity(&tokenReview)

	if err != nil {
		klog.Error(err)
		api.HandleBadRequest(resp, req, err)
		return
	}

	if err = tokenReview.Validate(); err != nil {
		klog.Error(err)
		api.HandleBadRequest(resp, req, err)
		return
	}

	user, _, err := h.issuer.Verify(tokenReview.Spec.Token)

	if err != nil {
		klog.Errorln(err)
		api.HandleInternalError(resp, req, err)
		return
	}

	success := auth.TokenReview{APIVersion: tokenReview.APIVersion,
		Kind: auth.KindTokenReview,
		Status: &auth.Status{
			Authenticated: true,
			User:          map[string]interface{}{"username": user.GetName(), "uid": user.GetUID()},
		},
	}

	resp.WriteEntity(success)
}

func (h *oauthHandler) AuthorizeHandler(req *restful.Request, resp *restful.Response) {
	user, ok := request.UserFrom(req.Request.Context())
	clientId := req.QueryParameter("client_id")
	responseType := req.QueryParameter("response_type")

	conf, err := h.config.Load(clientId)

	if err != nil {
		err := apierrors.NewUnauthorized(fmt.Sprintf("Unauthorized: %s", err))
		resp.WriteError(http.StatusUnauthorized, err)
		return
	}

	if responseType != "token" {
		err := apierrors.NewUnauthorized(fmt.Sprintf("Unauthorized: response type %s is not supported", responseType))
		resp.WriteError(http.StatusUnauthorized, err)
		return
	}

	if !ok {
		err := apierrors.NewUnauthorized("Unauthorized")
		resp.WriteError(http.StatusUnauthorized, err)
		return
	}

	accessToken, clm, err := h.issuer.IssueTo(user)

	if err != nil {
		err := apierrors.NewUnauthorized(fmt.Sprintf("Unauthorized: %s", err))
		resp.WriteError(http.StatusUnauthorized, err)
		return
	}

	redirectURL := fmt.Sprintf("%s?access_token=%s&token_type=Bearer", conf.RedirectURL, accessToken)
	expiresIn := clm.ExpiresAt - clm.IssuedAt
	if expiresIn > 0 {
		redirectURL = fmt.Sprintf("%s&expires_in=%v", redirectURL, expiresIn)
	}

	http.Redirect(resp, req.Request, redirectURL, http.StatusFound)
}