/**
 * Cookie-based session store
 */

#ifndef SESSION_STORE_H
#define SESSION_STORE_H

#include "esp_http_server.h"

#define SESSION_EXPIRY_TIME_S 60*30
#define SESSION_COOKIE_NAME "SESSID"

/** function that frees a session data object */
typedef void (*sess_data_free_fn_t)(void *);

enum session_find_action {
    SESS_DROP, SESS_GET_DATA
};

/**
 * Find session and either get data, or drop it.
 *
 * @param cookie
 * @param action
 * @return
 */
void *session_find_and(const char *cookie, enum session_find_action action);

/**
 * Initialize the session store.
 * Safely empty it if initialized
 */
void session_store_init(void);

// placeholder for when no data is stored
#define SESSION_DUMMY ((void *) 1)

/**
 * Create a new session. Data must not be NULL, because it wouldn't be possible
 * to distinguish between NULL value and session not found in return values.
 * It can be e.g. 1 if no data storage is needed.
 *
 * @param data - data object to attach to the session
 * @param free_fn - function that disposes of the data when the session expires
 * @return NULL on error, or the new session ID. This is a live pointer into the session structure,
 *         must be copied if stored, as it can become invalid at any time
 */
const char *session_new(void *data, sess_data_free_fn_t free_fn);

/**
 * Find a session by it's ID (from a cookie)
 *
 * @param cookie - session ID string
 * @return session data (void*), or NULL
 */
void *session_find(const char *cookie);

/**
 * Loop through all sessions and drop these that expired.
 */
void session_drop_expired(void);

/**
 * Drop a session by its ID. Does nothing if not found.
 *
 * @param cookie - session ID string
 */
void session_drop(const char *cookie);

/**
 * Parse the Cookie header from a request, and do something with the corresponding session.
 *
 * To also delete the cookie, use req_delete_session_cookie(r)
 *
 * @param r - request
 * @param action - what to do with the session
 * @return session data, NULL if removed or not found
 */
void *httpd_req_find_session_and(httpd_req_t *r, enum session_find_action action);

/**
 * Add a header that deletes the session cookie
 *
 * @param r - request
 */
void httpd_resp_delete_session_cookie(httpd_req_t *r);

/**
 * Add a header that sets the session cookie.
 *
 * This must be called after creating a session (e.g. user logged in) to make it persistent.
 *
 * @attention NOT RE-ENTRANT, CAN'T BE USED AGAIN UNTIL THE REQUEST IT WAS CALLED FOR IS DISPATCHED.
 *
 * @param r - request
 * @param cookie - cookie ID
 */
void httpd_resp_set_session_cookie(httpd_req_t *r, const char *cookie);

#endif //SESSION_STORE_H