// Copyright (c) 2014-2017, b3log.org & hacpai.com
//
// 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 session

import (
	"crypto/md5"
	"encoding/hex"
	"encoding/json"
	"math/rand"
	"net/http"
	"os"
	"path/filepath"
	"runtime"
	"strconv"
	"strings"
	"sync"
	"text/template"
	"time"

	"github.com/b3log/wide/conf"
	"github.com/b3log/wide/i18n"
	"github.com/b3log/wide/util"
)

const (
	// TODO: i18n

	userExists       = "user exists"
	emailExists      = "email exists"
	userCreated      = "user created"
	userCreateError  = "user create error"
	notAllowRegister = "not allow register"
)

// Exclusive lock for adding user.
var addUserMutex sync.Mutex

// PreferenceHandler handles request of preference page.
func PreferenceHandler(w http.ResponseWriter, r *http.Request) {
	httpSession, _ := HTTPSession.Get(r, "wide-session")

	if httpSession.IsNew {
		http.Redirect(w, r, conf.Wide.Context+"/login", http.StatusFound)

		return
	}

	httpSession.Options.MaxAge = conf.Wide.HTTPSessionMaxAge
	if "" != conf.Wide.Context {
		httpSession.Options.Path = conf.Wide.Context
	}
	httpSession.Save(r, w)

	username := httpSession.Values["username"].(string)
	user := conf.GetUser(username)

	if "GET" == r.Method {
		model := map[string]interface{}{"conf": conf.Wide, "i18n": i18n.GetAll(user.Locale), "user": user,
			"ver": conf.WideVersion, "goos": runtime.GOOS, "goarch": runtime.GOARCH, "gover": runtime.Version(),
			"locales": i18n.GetLocalesNames(), "gofmts": util.Go.GetGoFormats(),
			"themes": conf.GetThemes(), "editorThemes": conf.GetEditorThemes()}

		t, err := template.ParseFiles("views/preference.html")

		if nil != err {
			logger.Error(err)
			http.Error(w, err.Error(), 500)

			return
		}

		t.Execute(w, model)

		return
	}

	// non-GET request as save request

	result := util.NewResult()
	defer util.RetResult(w, r, result)

	args := struct {
		FontFamily       string
		FontSize         string
		GoFmt            string
		Keymap           string
		Workspace        string
		Username         string
		Password         string
		Email            string
		Locale           string
		Theme            string
		EditorFontFamily string
		EditorFontSize   string
		EditorLineHeight string
		EditorTheme      string
		EditorTabSize    string
	}{}

	if err := json.NewDecoder(r.Body).Decode(&args); err != nil {
		logger.Error(err)
		result.Succ = false

		return
	}

	user.FontFamily = args.FontFamily
	user.FontSize = args.FontSize
	user.GoFormat = args.GoFmt
	user.Keymap = args.Keymap
	// XXX: disallow change workspace at present
	// user.Workspace = args.Workspace
	if user.Password != args.Password {
		user.Password = conf.Salt(args.Password, user.Salt)
	}
	user.Email = args.Email

	hash := md5.New()
	hash.Write([]byte(user.Email))
	user.Gravatar = hex.EncodeToString(hash.Sum(nil))

	user.Locale = args.Locale
	user.Theme = args.Theme
	user.Editor.FontFamily = args.EditorFontFamily
	user.Editor.FontSize = args.EditorFontSize
	user.Editor.LineHeight = args.EditorLineHeight
	user.Editor.Theme = args.EditorTheme
	user.Editor.TabSize = args.EditorTabSize

	conf.UpdateCustomizedConf(username)

	now := time.Now().UnixNano()
	user.Lived = now
	user.Updated = now

	result.Succ = user.Save()
}

// LoginHandler handles request of user login.
func LoginHandler(w http.ResponseWriter, r *http.Request) {
	if "GET" == r.Method {
		// show the login page

		model := map[string]interface{}{"conf": conf.Wide, "i18n": i18n.GetAll(conf.Wide.Locale),
			"locale": conf.Wide.Locale, "ver": conf.WideVersion, "year": time.Now().Year()}

		t, err := template.ParseFiles("views/login.html")

		if nil != err {
			logger.Error(err)
			http.Error(w, err.Error(), 500)

			return
		}

		t.Execute(w, model)

		return
	}

	// non-GET request as login request
	result := util.NewResult()
	defer util.RetResult(w, r, result)

	args := struct {
		Username string
		Password string
	}{}

	args.Username = r.FormValue("username")
	args.Password = r.FormValue("password")

	result.Succ = false
	for _, user := range conf.Users {
		if user.Name == args.Username && user.Password == conf.Salt(args.Password, user.Salt) {
			result.Succ = true

			break
		}
	}

	if !result.Succ {
		return
	}

	// create a HTTP session
	httpSession, _ := HTTPSession.Get(r, "wide-session")
	httpSession.Values["username"] = args.Username
	httpSession.Values["id"] = strconv.Itoa(rand.Int())
	httpSession.Options.MaxAge = conf.Wide.HTTPSessionMaxAge
	if "" != conf.Wide.Context {
		httpSession.Options.Path = conf.Wide.Context
	}
	httpSession.Save(r, w)

	logger.Debugf("Created a HTTP session [%s] for user [%s]", httpSession.Values["id"].(string), args.Username)
}

// LogoutHandler handles request of user logout (exit).
func LogoutHandler(w http.ResponseWriter, r *http.Request) {
	result := util.NewResult()
	defer util.RetResult(w, r, result)

	httpSession, _ := HTTPSession.Get(r, "wide-session")

	httpSession.Options.MaxAge = -1
	httpSession.Save(r, w)
}

// SignUpUserHandler handles request of registering user.
func SignUpUserHandler(w http.ResponseWriter, r *http.Request) {
	if "GET" == r.Method {
		// show the user sign up page

		model := map[string]interface{}{"conf": conf.Wide, "i18n": i18n.GetAll(conf.Wide.Locale),
			"locale": conf.Wide.Locale, "ver": conf.WideVersion, "dir": conf.Wide.UsersWorkspaces,
			"pathSeparator": conf.PathSeparator, "year": time.Now().Year()}

		t, err := template.ParseFiles("views/sign_up.html")

		if nil != err {
			logger.Error(err)
			http.Error(w, err.Error(), 500)

			return
		}

		t.Execute(w, model)

		return
	}

	// non-GET request as add user request

	result := util.NewResult()
	defer util.RetResult(w, r, result)

	var args map[string]interface{}

	if err := json.NewDecoder(r.Body).Decode(&args); err != nil {
		logger.Error(err)
		result.Succ = false

		return
	}

	username := args["username"].(string)
	password := args["password"].(string)
	email := args["email"].(string)

	msg := addUser(username, password, email)
	if userCreated != msg {
		result.Succ = false
		result.Msg = msg

		return
	}

	// create a HTTP session
	httpSession, _ := HTTPSession.Get(r, "wide-session")
	httpSession.Values["username"] = username
	httpSession.Values["id"] = strconv.Itoa(rand.Int())
	httpSession.Options.MaxAge = conf.Wide.HTTPSessionMaxAge
	if "" != conf.Wide.Context {
		httpSession.Options.Path = conf.Wide.Context
	}
	httpSession.Save(r, w)
}

// FixedTimeSave saves online users' configurations periodically (1 minute).
//
// Main goal of this function is to save user session content, for restoring session content while user open Wide next time.
func FixedTimeSave() {
	go func() {
		defer util.Recover()

		for _ = range time.Tick(time.Minute) {
			users := getOnlineUsers()

			for _, u := range users {
				if u.Save() {
					logger.Tracef("Saved online user [%s]'s configurations", u.Name)
				}
			}
		}
	}()
}

// CanAccess determines whether the user specified by the given username can access the specified path.
func CanAccess(username, path string) bool {
	path = filepath.FromSlash(path)

	userWorkspace := conf.GetUserWorkspace(username)
	workspaces := filepath.SplitList(userWorkspace)

	for _, workspace := range workspaces {
		if strings.HasPrefix(path, workspace) {
			return true
		}
	}

	return false
}

func getOnlineUsers() []*conf.User {
	ret := []*conf.User{}

	usernames := map[string]string{} // distinct username
	for _, s := range WideSessions {
		usernames[s.Username] = s.Username
	}

	for _, username := range usernames {
		u := conf.GetUser(username)

		if "playground" == username { // user [playground] is a reserved mock user
			continue
		}

		if nil == u {
			logger.Warnf("Not found user [%s]", username)

			continue
		}

		ret = append(ret, u)
	}

	return ret
}

// addUser add a user with the specified username, password and email.
//
//  1. create the user's workspace
//  2. generate 'Hello, 世界' demo code in the workspace (a console version and a HTTP version)
//  3. update the user customized configurations, such as style.css
//  4. serve files of the user's workspace via HTTP
//
// Note: user [playground] is a reserved mock user
func addUser(username, password, email string) string {
	if !conf.Wide.AllowRegister {
		return notAllowRegister
	}

	if "playground" == username {
		return userExists
	}

	addUserMutex.Lock()
	defer addUserMutex.Unlock()

	for _, user := range conf.Users {
		if strings.ToLower(user.Name) == strings.ToLower(username) {
			return userExists
		}

		if strings.ToLower(user.Email) == strings.ToLower(email) {
			return emailExists
		}
	}

	workspace := filepath.Join(conf.Wide.UsersWorkspaces, username)

	newUser := conf.NewUser(username, password, email, workspace)
	conf.Users = append(conf.Users, newUser)

	if !newUser.Save() {
		return userCreateError
	}

	conf.CreateWorkspaceDir(workspace)
	helloWorld(workspace)
	conf.UpdateCustomizedConf(username)

	http.Handle("/workspace/"+username+"/",
		http.StripPrefix("/workspace/"+username+"/", http.FileServer(http.Dir(newUser.GetWorkspace()))))

	logger.Infof("Created a user [%s]", username)

	return userCreated
}

// helloWorld generates the 'Hello, 世界' source code.
//  1. src/hello/main.go
//  2. src/web/main.go
func helloWorld(workspace string) {
	consoleHello(workspace)
	webHello(workspace)
}

func consoleHello(workspace string) {
	dir := workspace + conf.PathSeparator + "src" + conf.PathSeparator + "hello"
	if err := os.MkdirAll(dir, 0755); nil != err {
		logger.Error(err)

		return
	}

	fout, err := os.Create(dir + conf.PathSeparator + "main.go")
	if nil != err {
		logger.Error(err)

		return
	}

	fout.WriteString(conf.HelloWorld)

	fout.Close()
}

func webHello(workspace string) {
	dir := workspace + conf.PathSeparator + "src" + conf.PathSeparator + "web"
	if err := os.MkdirAll(dir, 0755); nil != err {
		logger.Error(err)

		return
	}

	fout, err := os.Create(dir + conf.PathSeparator + "main.go")
	if nil != err {
		logger.Error(err)

		return
	}

	code := `package main

import (
	"fmt"
	"math/rand"
	"net/http"
	"strconv"
	"time"
)

func main() {
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		w.Write([]byte("Hello, 世界"))
	})

	port := getPort()

	// you may need to change the address
	fmt.Println("Open http://wide.b3log.org:" + port + " in your browser to see the result") 

	if err := http.ListenAndServe(":"+port, nil); nil != err {
		fmt.Println(err)
	}
}

func getPort() string {
	rand.Seed(time.Now().UnixNano())

	return strconv.Itoa(7000 + rand.Intn(8000-7000))
}

`

	fout.WriteString(code)

	fout.Close()
}