/**
  @file
  @author Stefan Frings
*/

#ifndef HTTPSESSIONSTORE_H
#define HTTPSESSIONSTORE_H

#include <QObject>
#include <QMap>
#include <QTimer>
#include <QMutex>
#include "httpglobal.h"
#include "httpsession.h"
#include "httpresponse.h"
#include "httprequest.h"

namespace stefanfrings {

/**
  Stores HTTP sessions and deletes them when they have expired.
  The following configuration settings are required in the config file:
  <code><pre>
  expirationTime=3600000
  cookieName=sessionid
  </pre></code>
  The following additional configurations settings are optionally:
  <code><pre>
  cookiePath=/
  cookieComment=Session ID
  ;cookieDomain=stefanfrings.de
  </pre></code>
*/

class DECLSPEC HttpSessionStore : public QObject {
    Q_OBJECT
    Q_DISABLE_COPY(HttpSessionStore)
public:

    /**
      Constructor.
      @param settings Configuration settings, usually stored in an INI file. Must not be 0.
      Settings are read from the current group, so the caller must have called settings->beginGroup().
      Because the group must not change during runtime, it is recommended to provide a
      separate QSettings instance that is not used by other parts of the program.
      The HttpSessionStore does not take over ownership of the QSettings instance, so the
      caller should destroy it during shutdown.
      @param parent Parent object
     */
    HttpSessionStore(const QSettings* settings, QObject* parent=nullptr);

    /** Destructor */
    virtual ~HttpSessionStore();

    /**
       Get the ID of the current HTTP session, if it is valid.
       This method is thread safe.
       @warning Sessions may expire at any time, so subsequent calls of
       getSession() might return a new session with a different ID.
       @param request Used to get the session cookie
       @param response Used to get and set the new session cookie
       @return Empty string, if there is no valid session.
    */
    QByteArray getSessionId(HttpRequest& request, HttpResponse& response);

    /**
       Get the session of a HTTP request, eventually create a new one.
       This method is thread safe. New sessions can only be created before
       the first byte has been written to the HTTP response.
       @param request Used to get the session cookie
       @param response Used to get and set the new session cookie
       @param allowCreate can be set to false, to disable the automatic creation of a new session.
       @return If autoCreate is disabled, the function returns a null session if there is no session.
       @see HttpSession::isNull()
    */
    HttpSession getSession(HttpRequest& request, HttpResponse& response, const bool allowCreate=true);

    /**
       Get a HTTP session by it's ID number.
       This method is thread safe.
       @return If there is no such session, the function returns a null session.
       @param id ID number of the session
       @see HttpSession::isNull()
    */
    HttpSession getSession(const QByteArray id);

    /** Delete a session */
    void removeSession(const HttpSession session);

protected:
    /** Storage for the sessions */
    QMap<QByteArray,HttpSession> sessions;

private:

    /** Configuration settings */
    const QSettings* settings;

    /** Timer to remove expired sessions */
    QTimer cleanupTimer;

    /** Name of the session cookie */
    QByteArray cookieName;

    /** Time when sessions expire (in ms)*/
    int expirationTime;

    /** Used to synchronize threads */
    QMutex mutex;

private slots:

    /** Called every minute to cleanup expired sessions. */
    void sessionTimerEvent();

signals:

    /**
      Emitted when the session is deleted.
      @param sessionId The ID number of the session.
    */
    void sessionDeleted(const QByteArray& sessionId);
};

} // end of namespace

#endif // HTTPSESSIONSTORE_H