package controllers

import (
	"context"
	"encoding/json"
	"errors"
	"github.com/go-oauth2/oauth2/v4"
	"github.com/go-oauth2/oauth2/v4/manage"
	"github.com/go-oauth2/oauth2/v4/models"
	"github.com/go-oauth2/oauth2/v4/server"
	"github.com/go-oauth2/oauth2/v4/store"
	"github.com/go-session/session"
	"log"
	"net/http"
	"nucleus/internal"
	"time"
)

type UserInfo struct {
	Username string `json:"username"`
	Gender   string `json:"gender"`
}

var manager *manage.Manager
var srv *server.Server
var userInfoMap = make(map[string]UserInfo)

type Oauth2Controller struct {
	internal.Controller
}

func (c *Oauth2Controller) Init() {
	clientStore := store.NewClientStore()
	clientStore.Set("juejin", &models.Client{ID: "juejin", Secret: "xxxxx", Domain: "http://juejin.com"})

	// 设置 manager, manager 参与校验 code/access token 请求
	manager = manage.NewDefaultManager()

	// 校验 redirect_uri 和 client 的 Domain, 简单起见, 不做校验
	manager.SetValidateURIHandler(func(baseURI, redirectURI string) error {
		return nil
	})

	manager.MustTokenStorage(store.NewMemoryTokenStore())

	// manger 包含 client 信息
	manager.MapClientStorage(clientStore)

	// 也包含 manger, client 信息
	srv = server.NewServer(server.NewConfig(), manager)

	// 根据 client id 从 manager 中获取 client info, 在获取 access token 校验过程中会被用到
	srv.SetClientInfoHandler(func(r *http.Request) (clientID, clientSecret string, err error) {
		clientInfo, err := srv.Manager.GetClient(r.Context(), r.URL.Query().Get("client_id"))
		if err != nil {
			log.Println(err)
			return "", "", err
		}
		return clientInfo.GetID(), clientInfo.GetSecret(), nil
	})

	// 设置为 authorization code 模式
	srv.SetAllowedGrantType(oauth2.AuthorizationCode)

	// authorization code 模式,  第一步获取code,然后再用code换取 access token, 而不是直接获取 access token
	srv.SetAllowedResponseType(oauth2.Code)

	// 校验授权请求用户的handler, 会重定向到 登陆页面, 返回"", nil
	srv.SetUserAuthorizationHandler(handleUserAuthorization)

	// 校验授权请求的用户的账号密码, 给 LoginHandler 使用, 简单起见, 只允许一个用户授权
	srv.SetPasswordAuthorizationHandler(func(ctx context.Context, clientID, username, password string) (userID string, err error) {
		if username == "Tom" && password == "123456" {
			return "0001", nil
		}
		return "", errors.New("username or password error")
	})

	// 允许使用 get 方法请求授权
	srv.SetAllowGetAccessRequest(true)

	// 储存用户信息的一个 map
	userInfoMap["0001"] = UserInfo{
		"Tom", "Male",
	}
}

// HandleAuthorizeRequest 授权入口
func (c *Oauth2Controller) HandleAuthorizeRequest(w http.ResponseWriter, r *http.Request) {
	err := srv.HandleAuthorizeRequest(w, r)
	if err != nil {
		log.Println(err)
		http.Error(w, err.Error(), http.StatusBadRequest)
	}
}

// HandleLoginRequest 登陆入口
func (c *Oauth2Controller) HandleLoginRequest(w http.ResponseWriter, r *http.Request) {
	sessionStore, err := session.Start(r.Context(), w, r)
	if err != nil {
		log.Println(err)
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	if r.Method == http.MethodPost {
		userId, err := srv.PasswordAuthorizationHandler(
			r.Context(),
			r.FormValue("client_id"),
			r.FormValue("username"),
			r.FormValue("password"),
		)
		if err != nil {
			log.Println(err)
			http.Error(w, err.Error(), http.StatusUnauthorized)
			return
		}

		// 保存登录状态
		sessionStore.Set("LoggedInUserId", userId)
		sessionStore.Save()

		// 跳转到 同意授权页面
		w.Header().Set("Location", "/oauth2/agree-auth")
		w.WriteHeader(http.StatusFound)
		return
	}

	// 若请求方法错误, 提供login.html页面
	c.Render(w, r, "static/login.html")
}

// HandleAgreeAuthRequest 同意授权的页面
func (c *Oauth2Controller) HandleAgreeAuthRequest(w http.ResponseWriter, r *http.Request) {
	store, err := session.Start(r.Context(), w, r)
	if err != nil {
		log.Println(err)
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	// 如果没有查询到登陆状态, 则跳转到 登陆页面
	if _, ok := store.Get("LoggedInUserId"); !ok {
		w.Header().Set("Location", "/oauth2/login")
		w.WriteHeader(http.StatusFound)
		return
	}

	// 如果有登陆状态, 会跳转到 确认授权页面
	c.Render(w, r, "static/agree-auth.html")
}

// HandleAccessTokenRequest 使用 code 换取 access token
func (c *Oauth2Controller) HandleAccessTokenRequest(w http.ResponseWriter, r *http.Request) {
	err := srv.HandleTokenRequest(w, r)
	if err != nil {
		log.Println(err)
		http.Error(w, err.Error(), http.StatusBadRequest)
	}
}

// HandleUserInfoRequest 使用 access_token 换取用户信息
func (c *Oauth2Controller) HandleUserInfoRequest(w http.ResponseWriter, r *http.Request) {
	// 获取 access token
	accessToken, ok := srv.BearerAuth(r)
	if !ok {
		log.Println("Failed to get access token from request")
		return
	}

	rootCtx := context.Background()
	ctx, cancelFunc := context.WithTimeout(rootCtx, time.Second)
	defer cancelFunc()

	// 从 access token 中获取 信息
	tokenInfo, err := srv.Manager.LoadAccessToken(ctx, accessToken)
	if err != nil {
		log.Println(err)
		return
	}

	// 获取 user id
	userId := tokenInfo.GetUserID()
	grantScope := tokenInfo.GetScope()

	userInfo := UserInfo{}

	// 根据 grant scope 决定获取哪些用户信息
	if grantScope != "read_user_info" {
		log.Println("invalid grant scope")
		w.Write([]byte("invalid grant scope"))
		return
	}

	userInfo = userInfoMap[userId]
	resp, err := json.Marshal(userInfo)
	w.Write(resp)
	return
}

// AuthorizeHandler 内部使用, 用于查看是否有登陆状态
func handleUserAuthorization(w http.ResponseWriter, r *http.Request) (userId string, err error) {
	store, err := session.Start(r.Context(), w, r)
	if err != nil {
		log.Println(err)
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	uid, ok := store.Get("LoggedInUserId")
	// 如果没有查询到登陆状态, 则跳转到登陆页面
	if !ok {
		if r.Form == nil {
			r.ParseForm()
		}

		w.Header().Set("Location", "/oauth2/login")
		w.WriteHeader(http.StatusFound)
		return "", nil
	}
	// 若有登录状态, 返回 user id
	userId = uid.(string)
	return userId, nil
}