#include "config.h"
#include <stdio.h>
#include "ev_dispatch.h"
#include "ev_http.h"

#define DEBUG

#ifdef DEBUG
#include <assert.h>
#define ASSERT_IS_D_THRAD\
  pthread_t tid = pthread_self();\
  assert( tid == this->m_tid );
#else
#define ASSERT_IS_D_THRAD
#endif

// ---
// TODO:
// libcurl: is used to handle the http requests
// sphinxclient: library for the search engine requests
// memcached: client library for the memcached requests
//

namespace EVD {

double Timer::elapsed_time( struct timeval *y )
{
  struct timeval duration;
  struct timeval now;
  current_time( &now );
  struct timeval *x = &now;
  struct timeval *result = &duration;

  // see: http://www.gnu.org/software/libtool/manual/libc/Elapsed-Time.html
  // Perform the carry for the later subtraction by updating y.
  if (x->tv_usec < y->tv_usec) {
    int nsec = (y->tv_usec - x->tv_usec) / 1000000 + 1;
    y->tv_usec -= 1000000 * nsec;
    y->tv_sec += nsec;
  }

  if (x->tv_usec - y->tv_usec > 1000000) {
    int nsec = (x->tv_usec - y->tv_usec) / 1000000;
    y->tv_usec += 1000000 * nsec;
    y->tv_sec -= nsec;
  }

  // Compute the time remaining to wait.
  // tv_usec is certainly positive.
  result->tv_sec = x->tv_sec - y->tv_sec;
  result->tv_usec = x->tv_usec - y->tv_usec;

  double elasped = ((double)duration.tv_sec + ((double)duration.tv_usec/1000000.0));
  // Return 1 if result is negative.
  if( x->tv_sec < y->tv_sec ){
    return (-1.0 * elasped);
  }
  return elasped;
}

Dispatch::Dispatch() : m_loop(NULL), m_counter(0), m_loop_started(false), m_http_client(NULL), m_pending(0)
{
  // zero everything out
  memset(&m_clock,0,sizeof(ev_timer));
  memset(&m_request_watcher,0,sizeof(ev_async));
  memset(&m_tid,0,sizeof(pthread_t));
  m_pid = getpid();
}

Dispatch::~Dispatch()
{
  if( m_http_client ) {
    delete m_http_client;
  }
}

// start up the background event listener
bool Dispatch::start()
{
  int rc;
  if( m_loop_started ){ return false; }

  rc = pthread_create( &m_tid, NULL, Dispatch::event_loop_start, this );
  if( rc ){ return false; }
   pthread_detach( m_tid );

  m_http_client = new HttpClient(this);

  // block until we get notified that the event thead is up and running
  Guard lock(m_lock);
  int count = 0;

  // wait until the event loop is started
  while( !m_loop_started && count < 100 ) { // never wait more then 100 iterations
    m_cond.timed_wait( m_lock, Timer(1,0) );
    //printf( "waiting another second\n" );
    ++count;
  }

  return (count < 100);
}

// tell the background event listener to terminate
void Dispatch::stop()
{
  if( !m_loop_started ){ return ; }

  //printf( "EVD::Dispatch stopping...\n" );
  m_loop_started = false;

  m_cond.broadcast();
  m_requests.signal();
  m_responses.signal();
  ev_unloop( m_loop, EVUNLOOP_ALL );
  if( m_http_client ) {
    delete m_http_client;
    m_http_client = NULL;
  }
}

// all event loop activity happens on this thread
void* Dispatch::event_loop_start( void *ptr )
{
  Dispatch *dis = (Dispatch*)ptr;
  dis->event_loop_main();
  //printf( "EVD::Dispatch event loop stopped\n" );
  return NULL;
}

static void
sigint_cb( struct ev_loop *loop, struct ev_signal *w, int revents )
{
  Dispatch *ptr = ((Dispatch*)w->data);
  ptr->stop();
}

// called when a new request was signaled from the main thread
void Dispatch::request_cb_start( struct ev_loop *loop, struct ev_async *w, int revents )
{
  Dispatch *ptr = (Dispatch*)w->data;
  ptr->request_cb( loop, w, revents );
}
void Dispatch::request_cb( struct ev_loop *loop, struct ev_async *w, int revents )
{
  ASSERT_IS_D_THRAD

  // create a new queue to store incoming requests
  std::queue<Request*> new_requests;
  // lock down the request queue
  m_requests.m_lock.lock();
  // lock and read as much as we can out of the queue
  new_requests = m_requests.m_queue;
  m_requests.m_queue = std::queue<Request*>(); // empty out the request queue
  m_requests.m_lock.unlock(); // unlock the queue

  // process the new requests 
  while( !new_requests.empty() ) {
    Request *req = new_requests.front();
    new_requests.pop();
    //printf( "Request: %s, time since requested: %.2f\n", req->url.c_str(), difftime(time(NULL),req->start_time) );
 
    // inc before we enable the request, since the time to enable and push to responses queue may
    // be long enough for a context switch to allow someone to check request, response and pending count all be zero.
    ++m_pending;
    if( !req->enable() ) { // XXX: if using DNS in requests expect this method to block while dns resolves
      --m_pending;
      printf("EVD::Dispatch request error\n");
      // for some reason we couldn't enable the request cleanup the request and continue
      delete req;
    }
  }

}

// the main event loop
void Dispatch::event_loop_main()
{
//  struct ev_signal signal_exit_watcher;
  m_loop = ev_loop_new(0); //ev_default_loop(0);

//  m_clock.data = this;

  // every 100s of a second we'll check the queue for requests
//  ev_timer_init( &m_clock, timeout_cb_start, 0.5, 0.5 );
//  ev_timer_again( m_loop, &m_clock ); // start timer

  // trap sigint to ensure we clean up the event loop before exit
//  signal_exit_watcher.data = this;
//  ev_signal_init( &signal_exit_watcher, sigint_cb, SIGINT );
//  ev_signal_start( m_loop, &signal_exit_watcher );

  m_request_watcher.data = this;
  ev_async_init( &m_request_watcher, request_cb_start );
  ev_async_start( m_loop, &m_request_watcher );

  // start the main event loop

  m_lock.lock();
  m_loop_started = true;
  m_cond.signal(); // let the world know we're ready for them
  m_lock.unlock();

  ev_loop( m_loop, 0 );
  ev_loop_destroy( m_loop );
  pthread_exit(NULL);
}
void Dispatch::timeout_cb_start(struct ev_loop *loop, struct ev_timer *w, int revents)
{
  Dispatch *ptr = ((Dispatch*)w->data);
  ptr->timeout_cb( loop, w, revents );
}

// called on the event loop thread
void Dispatch::timeout_cb(struct ev_loop *loop, struct ev_timer *w, int revents)
{
  ASSERT_IS_D_THRAD
  //printf("timeout cb\n");
}

// called on the main thread, not the event loop thread
request_t Dispatch::request( Request *req )
{
  request_t key = m_counter++;
  req->set_key( key );
  m_requests.push( req ); // load the request into the request queue
  ev_async_send( m_loop, &m_request_watcher ); // signal to the event loop we have new requests pending
  return key; // return to the client a unique identifier for matching up the response to this request
}

Response *Dispatch::response_for( request_t id )
{
  RespondedTable::iterator loc = m_responded.find(id);
  if( loc == m_responded.end() ){ return NULL; }
  Response *res = loc->second;
  m_responded.erase(loc);
  return res;
}

Queue<Response>::POP_STATE Dispatch::wait_for_response_by_id( request_t id, Timer timeout )
{
  // first check if the response is loaded 
  Response *rep = NULL;
  Queue<Response>::POP_STATE rstate;
  RespondedTable::iterator loc = m_responded.find(id);

  if( loc != m_responded.end() ){ return Queue<Response>::POPPED; }

  while( (rep = m_responses.pop_or_wait( &rstate, m_loop_started, timeout )) ) {
    //printf( "rep: %s, id: %d\n", rep->name.c_str(), rep->id );
    m_responded[rep->id] = rep;
    if( rep->id == id ){ return rstate; }
  }

  return rstate;
}

Response *Dispatch::get_next_response( Timer timer )
{
  Response *rep = NULL;
  Queue<Response>::POP_STATE  rstate;

  do {
    rep = m_responses.pop_or_wait( &rstate, m_loop_started, timer );
    if( rstate == Queue<Response>::EXITING ){ rep = NULL; break; }
    if( !rep && rstate == Queue<Response>::EXPIRED ) {
      int pending_count = m_pending;
      if( pending_count == 0 ) { // if pending is zero then acquire locks on the request and response queue 
        int request_count = m_requests.size();
        int response_count = m_responses.size();
        //printf( "pending: %d, request: %d, response: %d\n", pending_count, request_count, response_count );
        if( pending_count == 0 && request_count == 0 && response_count == 0 ) {
          return NULL;
        }
      }
    }
    else if( rep ) {
      --m_pending;
    }

  } while( !rep && rstate == Queue<Response>::EXPIRED );

  return rep;
}

}// end namespace EVD