/* file StreamEndpointDescr.hpp
 *
 * author: Roland Conybeare, Sep 2022
 */

#pragma once

#include "web_util/Alist.hpp"
#include "callback/CallbackSet.hpp"
#include "refcnt/Refcounted.hpp"
#include "indentlog/print/tag.hpp"
#include "indentlog/print/tostr.hpp"
#include <functional>

namespace xo {
  namespace reactor { class AbstractSink; }

  namespace web {
    /* a function that creates an event subscription */
    using StreamSubscribeFn = std::function<fn::CallbackId (ref::rp<reactor::AbstractSink> const & ws_sink)>;
    using StreamUnsubscribeFn = std::function<void (fn::CallbackId id)>;

    /* describes a stream endpoint
     * this comprises
     * - a uri pattern (matches stream name)
     * - a function that establishes subscription
     *   (by attaching supplied WebsocketSink to an event source)
     */
    class StreamEndpointDescr {
    public:
      StreamEndpointDescr(std::string uri_pattern,
              StreamSubscribeFn subscribe_fn,
              StreamUnsubscribeFn unsubscribe_fn)
    : uri_pattern_{std::move(uri_pattern)},
      subscribe_fn_{std::move(subscribe_fn)},
      unsubscribe_fn_{std::move(unsubscribe_fn)} {}

      std::string const & uri_pattern() const { return uri_pattern_; }
      StreamSubscribeFn const & subscribe_fn() const { return subscribe_fn_; }
      StreamUnsubscribeFn const & unsubscribe_fn() const { return unsubscribe_fn_; }

      void display(std::ostream & os) const {
    using xo::xtag;

    os << "<StreamEndpointDescr" << xtag("uri_pattern", uri_pattern_) << ">";
      } /*display*/

      std::string display_string() const { return xo::tostr(*this); }

    private:
      /* unique pattern in URI-space for this endpoint
       * for example
       *    .uri_pattern = /stem/${foo}/${bar}
       * means this endpoint generates contents for uri's
       *    /stem/apple/banana
       *    /stem/aphid/green
       * but not for
       *    /stem/apple/banana/carrot
       */
      std::string uri_pattern_;
      /* a function that subscribes to an event stream
       * (by attaching a websocket sink)
       */
      StreamSubscribeFn subscribe_fn_;
      /* reverses effect of a particular call to .subscribe_fn */
      StreamUnsubscribeFn unsubscribe_fn_;
    }; /*StreamEndpointDescr*/

    inline std::ostream &
    operator<<(std::ostream & os, StreamEndpointDescr const & x) {
      x.display(os);
      return os;
    } /*operator<<*/

  } /*namespace web*/
} /*namespace xo*/

/* end StreamEndpointDescr.hpp */