// file      : web/apache/service -*- C++ -*-
// copyright : Copyright (c) 2014-2015 Code Synthesis Tools CC
// license   : MIT; see accompanying LICENSE file

#ifndef WEB_APACHE_SERVICE
#define WEB_APACHE_SERVICE

#include <exception>
#include <string>
#include <cassert>

#include <httpd/httpd.h>
#include <httpd/http_config.h>

#include <web/module>

#include <web/apache/log>
#include <web/apache/request>

namespace web
{
  namespace apache
  {
    class service : ::module
    {
    public:
      // Note that the module exemplar is stored by-reference.
      //
      template <typename M>
      service (const std::string& name, const M& exemplar)
          : ::module
            {
              STANDARD20_MODULE_STUFF,
              nullptr,
              nullptr,
              nullptr,
              nullptr,
              nullptr,
              &register_hooks<M>
            },
            name_ (name),
            exemplar_ (exemplar)

// Doesn't look like handle_ member is required at all.
//          handle_ (&handle_impl<M>)
      {
        // instance<M> () invented to delegate processing from apache request
        // handler C function to service non static member function.
        // This appoach resticts number of service objects per module
        // implementation class with just one instance.
        //
        service*& srv = instance<M> ();
        assert (srv == nullptr);
        srv = this;
      }

      template <typename M>
      static service*&
      instance () noexcept
      {
        static service* instance;
        return instance;
      }

      template <typename M>
      static void
      register_hooks (apr_pool_t *pool) noexcept
      {
        ap_hook_handler (&request_handler<M>, NULL, NULL, APR_HOOK_LAST);
      }

      template <typename M>
      static int
      request_handler (request_rec* r) noexcept
      {
        auto srv = instance<M> ();

        if (!r->handler || srv->name_ != r->handler)
          return DECLINED;

        request req (r);
        log l(r);

        // As soons as M (), handle () and flush () can throw need to handle
        // exceptions here.
        //
        try
        {
          M m (static_cast<const M&> (srv->exemplar_));
          static_cast<module&> (m).handle (req, req, l);
          return req.flush();
        }
        catch (const std::exception& e)
        {
          l.write (nullptr, 0, __PRETTY_FUNCTION__, APLOG_ERR, e.what ());
        }
        catch (...)
        {
          l.write (nullptr,
                   0,
                   __PRETTY_FUNCTION__,
                   APLOG_ERR,
                   "unknown error");
        }

        return HTTP_INTERNAL_SERVER_ERROR;
      }

      //@@ Implementation calls handle_ function pointer below:
      //
      // handle_ (rq, rs, l, exemplar_);
      //

    private:
/*
      template <typename M>
      static void
      handle_impl (request& rq, response& rs, log& l, const module& exemplar)
      {
        M m (static_cast<const M&> (exemplar));
        static_cast<module&> (m).handle (rq, rs, l);
      }
*/
      std::string name_;
      const module& exemplar_;
//      void (*handle_) (request&, response&, log&, const module&);
    };
  }
}

#endif // WEB_APACHE_SERVICE