#include "itc.h"
#include "utils.h"

#include <semaphore.h>
#include <stdlib.h>
#include <sys/time.h>

struct itc {
        int nslots;
        void **slots;
        int inputidx;
        int outputidx;
        sem_t emptied;
        sem_t occupied;
};

itc *itc_alloc(int nslots)
{
        itc *ctx;

        if (nslots <= 0) {
                return NULL;
        }

        ctx = calloc(1, sizeof(*ctx));
        ctx->nslots = nslots;
        ctx->slots = calloc(nslots, sizeof(*ctx->slots));
        sem_init(&ctx->emptied, 0, nslots);
        sem_init(&ctx->occupied, 0, 0);

        return ctx;
}

void itc_free(itc **ctx, itc_free_element free_element)
{
        if (ctx == NULL || *ctx == NULL) {
                return;
        }

        itc_drop(*ctx, free_element);

        sem_destroy(&(*ctx)->emptied);
        sem_destroy(&(*ctx)->occupied);
        free((*ctx)->slots);
        free(*ctx);
        *ctx = NULL;
}

void *itc_retrive(itc *ctx, int timeout_ms)
{
        struct timespec ts;
        void *element;

        if (ctx == NULL) {
                return NULL;
        }

        timespec_add_ms(gettimespec(&ts), timeout_ms);

        if (sem_timedwait(&ctx->occupied, &ts)) {
                return NULL;
        }
        element = ctx->slots[ctx->outputidx];
        ctx->outputidx = (ctx->outputidx + 1) % ctx->nslots;
        sem_post(&ctx->emptied);

        return element;
}

int itc_inject(itc *ctx, int timeout_ms, void *element)
{
        struct timespec ts;

        if (ctx == NULL) {
                return -1;
        }

        timespec_add_ms(gettimespec(&ts), timeout_ms);

        if (sem_timedwait(&ctx->emptied, &ts)) {
                return -1;
        }
        ctx->slots[ctx->inputidx] = element;
        ctx->inputidx = (ctx->inputidx + 1) % ctx->nslots;
        sem_post(&ctx->occupied);

        return 0;
}

void itc_flush(itc *ctx)
{
        int i;

        if (ctx == NULL) {
                return;
        }

        for (i = 0; i < ctx->nslots; i++) {
                sem_wait(&ctx->emptied);
                sem_post(&ctx->emptied);
        }
}

void itc_drop(itc *ctx, itc_free_element free_element)
{
        void *element;

        if (ctx == NULL) {
                return;
        }

        while ((element = itc_retrive(ctx, 0)) != NULL) {
                if (free_element != NULL) {
                        free_element(element);
                }
        }
}