/*
 *
 * 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/identityprovider"
	"kubesphere.io/kubesphere/pkg/apiserver/authentication/oauth"
	authoptions "kubesphere.io/kubesphere/pkg/apiserver/authentication/options"
	"kubesphere.io/kubesphere/pkg/apiserver/authentication/token"
	"kubesphere.io/kubesphere/pkg/apiserver/request"
	"net/http"
)

type oauthHandler struct {
	issuer  token.Issuer
	options *authoptions.AuthenticationOptions
}

func newOAUTHHandler(issuer token.Issuer, options *authoptions.AuthenticationOptions) *oauthHandler {
	return &oauthHandler{issuer: issuer, options: options}
}

// 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")
	redirectURI := req.QueryParameter("redirect_uri")

	conf, err := h.options.OAuthOptions.OAuthClient(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
	}

	expiresIn := h.options.OAuthOptions.AccessTokenMaxAge

	if conf.AccessTokenMaxAge != nil {
		expiresIn = *conf.AccessTokenMaxAge
	}

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

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

	redirectURL, err := conf.ResolveRedirectURL(redirectURI)

	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", redirectURL, accessToken)

	if expiresIn > 0 {
		redirectURL = fmt.Sprintf("%s&expires_in=%v", redirectURL, expiresIn.Seconds())
	}

	resp.Header().Set("Content-Type", "text/plain")
	http.Redirect(resp, req.Request, redirectURL, http.StatusFound)
}

func (h *oauthHandler) OAuthCallBackHandler(req *restful.Request, resp *restful.Response) {

	code := req.QueryParameter("code")
	name := req.PathParameter("callback")

	if code == "" {
		err := apierrors.NewUnauthorized("Unauthorized: missing code")
		resp.WriteError(http.StatusUnauthorized, err)
	}

	idP, err := h.options.OAuthOptions.IdentityProviderOptions(name)

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

	oauthIdentityProvider, err := identityprovider.ResolveOAuthProvider(idP.Type, idP.Provider)

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

	user, err := oauthIdentityProvider.IdentityExchange(code)

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

	expiresIn := h.options.OAuthOptions.AccessTokenMaxAge

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

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

	result := oauth.Token{
		AccessToken: accessToken,
		TokenType:   "Bearer",
		ExpiresIn:   int(expiresIn.Seconds()),
	}

	resp.WriteEntity(result)
	return
}