/*
	Bow / bow back
	Multi-threaded.
	Locks placed within bower struct

	Idea from Java Puzzlers
*/

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

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(&(bower->mutex));
    printf("%s: I bow to %s.\n", bower->name, bowie->name);
    bowBack(bowie, bower);
    pthread_mutex_unlock(&(bower->mutex));
}

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

void* bowing(void* p) {
    FRIEND** friends = (FRIEND**)p;
    bow(friends[0], friends[1]);
    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);
}