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

#ifndef BREP_MODULE
#define BREP_MODULE

#include <brep/diagnostics>

namespace brep
{
  // This exception is used to signal that the request is invalid
  // (4XX codes) rather than that it could not be processed (5XX).
  // By default 422 is returned, which means the request was
  // semantically invalid.
  //
  struct invalid_request
  {
    web::status_code status {422};
    std::string description;

    //@@ Maybe optional "try again" link?
    //
  };

  // And this exception indicated a server error (5XX). In particular,
  // it is thrown by the fail diagnostics stream and is caught by the
  // module implementation where it is both logged as an error and
  // returned to the user with the 5XX status code.
  //
  struct server_error
  {
    diag_data data;
  };

  // Every module member function that needs to produce any diagnostics
  // shall begin with:
  //
  // MODULE_DIAG;
  //
  // This will instantiate the fail, error, warn, info, and trace
  // diagnostics streams with the function's name.
  //
#define MODULE_DIAG                                                     \
  const fail_mark<server_error> fail (__PRETTY_FUNCTION__);             \
  const basic_mark error (severity::error,                              \
                          this->log_writer_,                            \
                          __PRETTY_FUNCTION__);                         \
  const basic_mark warn (severity::warn,                                \
                         this->log_writer_,                             \
                         __PRETTY_FUNCTION__);                          \
  const basic_mark info (severity::info,                                \
                         this->log_writer_,                             \
                         __PRETTY_FUNCTION__);                          \
  const basic_mark trace (severity::info,                               \
                          this->log_writer_,                            \
                          __PRETTY_FUNCTION__)

  // Adaptation of the web::module to our needs.
  //
  class module: public web::module
  {
  public:
    virtual void
    handle (request&, response&) = 0;

    // Diagnostics.
    //
  protected:
    // Trace verbosity level.
    //
    // 0 - tracing disabled.
    // 1 - @@ TODO: document
    // 2 - @@ TODO: document
    //
    // While uint8 is more than enough, use uint16 for the ease of printing.
    //
    std::uint16_t verb_ {0};

    template <class F> static void level1 (const F& f) {if (verb_ >= 1) f ();}
    template <class F> static void level2 (const F& f) {if (verb_ >= 2) f ();}

    // Implementation details.
    //
  protected:
    module ();

    virtual void
    handle (request&, response&, log&);

    // Diagnostics implementation details.
    //
  private:
    log* log_ {nullptr}; // Diagnostics backend provided by the web server.

    void
    log_write (diag_data&&) const;

    const diag_epilogue log_writer_;
  };
}

#endif // BREP_MODULE