/*
* @Author: Bartuccio Antoine
* @Date:   2018-07-16 14:07:07
* @Last Modified by:   klmp200
* @Last Modified time: 2018-07-18 00:03:26
 */

package gowebframework

import (
	"fmt"
	"github.com/google/uuid"
	"log"
	"net/http"
	"net/url"
	"sync"
	"time"
)

var SESSION *SessionManager
var providers = make(map[string]Provider)

type SessionManager struct {
	cookieName  string // Name of the cookie on the client side
	lock        sync.Mutex
	provider    Provider
	maxLifetime time.Duration
}

type Session interface {
	Set(key string, value interface{}) error // set a session value
	Get(key string) interface{}              // get session value
	Delete(key string) error                 // delete session value
	SessionUUID() string                     // get the current session UUID
}

type Provider interface {
	SessionInit(uuid string) (Session, error)
	SessionRead(uuid string) (Session, error)
	SessionDestroy(uuid string) error
	SessionClearExpired(maxLifetime time.Duration)
}

func (manager *SessionManager) generateUUID() string {
	return uuid.New().String()
}

// Launch a Clear Expired Sessions task at fixed rate
func clearExpiredSessionsCron() {
	SESSION.lock.Lock()
	lifetime := SESSION.maxLifetime
	SESSION.lock.Unlock()
	for {
		SESSION.lock.Lock()
		SESSION.provider.SessionClearExpired(lifetime)
		SESSION.lock.Unlock()
		time.Sleep(lifetime)
	}
}

func SessionProviderRegister(provider Provider, providerName string) error {
	if provider == nil {
		return fmt.Errorf("No provider found for provider name %s", providerName)
	}
	if _, exists := providers[providerName]; exists {
		return fmt.Errorf("Provider with name %s already exists", providerName)
	}
	providers[providerName] = provider
	return nil
}

func (manager *SessionManager) GetSession(w http.ResponseWriter, r *http.Request) Session {
	var session Session
	manager.lock.Lock()
	defer manager.lock.Unlock()
	cookie, err := r.Cookie(manager.cookieName)
	if err != nil || cookie.Value == "" {
		// Create a new session
		session_id := manager.generateUUID()
		s, err := manager.provider.SessionInit(session_id)
		if err != nil {
			log.Fatal(err)
		}
		session = s
		AddCookie(w, manager.cookieName, url.QueryEscape(session_id), manager.maxLifetime)
	} else {
		// Get the session
		session_id, _ := url.QueryUnescape(cookie.Value)
		s, err := manager.provider.SessionRead(session_id)
		if err != nil {
			log.Fatal(err)
		}
		session = s
	}
	return session
}

func newSessionManager(providerName string, cookieName string, maxLifetime time.Duration) (*SessionManager, error) {
	provider, ok := providers[providerName]
	if !ok {
		return nil, fmt.Errorf("Session error: unknown provider %s", providerName)
	}
	return &SessionManager{provider: provider, cookieName: cookieName, maxLifetime: maxLifetime}, nil
}