/*
	Bow / bow back
	Multi-threaded.
	Locks placed within bower struct
	but locking them within the bowing function.

	Original idea from Java Puzzlers
*/

#include <string.h>
#include <pthread.h> 	// pthread_t, pthread_create
#include <stdio.h>	// printf
#include <unistd.h>     // sleep

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

pthread_mutex_t io_mutex = PTHREAD_MUTEX_INITIALIZER;

typedef struct {
  char name[20];
  pthread_mutex_t mutex;
} Friend;

void initFriend(Friend* friendP, char* name) {
  strcpy(friendP->name, name);
  pthread_mutex_init(&(friendP->mutex), NULL);
}
void bowBack(Friend* bower, Friend* bowie);

void bow(Friend* bower, Friend* bowie) {
  //  pthread_mutex_lock(&io_mutex);
  printf("%s: I bow to %s.\n", bower->name, bowie->name);
  //  pthread_mutex_unlock(&io_mutex);
  bowBack(bowie, bower);
}

void bowBack(Friend* bower, Friend* bowie) {
  //  pthread_mutex_lock(&io_mutex);
  printf("%s: I bow back to %s.\n", bower->name, bowie->name);
  //  pthread_mutex_unlock(&io_mutex);
}

void* bowing(void* p) {
  Friend** friends = (Friend**)p;
  //  printf("In bowing\n");

  //pthread_mutex_lock(&mutex);
  pthread_mutex_lock(&friends[0]->mutex);
  // pthread_yield();
  sleep(1);
  pthread_mutex_lock(&friends[1]->mutex);
  //  pthread_mutex_unlock(&mutex);

  bow(friends[0], friends[1]);
  pthread_mutex_unlock(&friends[0]->mutex);
  pthread_mutex_unlock(&friends[1]->mutex);
  return NULL;
}

int main() {
  Friend alphonse;
  initFriend(&alphonse, "Alphonse");
  Friend gaston;
  initFriend(&gaston, "Gaston");
  pthread_t tid1, tid2;

  Friend* ag[] = {&alphonse, &gaston};
  Friend* ga[] = {&gaston, &alphonse};
  pthread_create(&tid1, NULL, bowing, (void*)ag);
  pthread_create(&tid2, NULL, bowing, (void*)ga);
  //  pthread_exit(0);
  pthread_join(tid1, NULL);
  pthread_join(tid2, NULL);
}