#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <errno.h>

#include <hexagram/schedule.h>

static int _slot_cmp(const void *item_a, const void *item_b) {
    hexagram_schedule_slot *a = (hexagram_schedule_slot *)item_a,
                           *b = (hexagram_schedule_slot *)item_b;

    return a->interval_us < b->interval_us? -1:
           a->interval_us > b->interval_us?  1: 0;
}

static inline hexagram_schedule_slot *_slot(hexagram_schedule *schedule, size_t i) {
    return &((hexagram_schedule_slot *)(schedule + 1))[i];
};

static inline time_t _slot_interval_ns(hexagram_schedule *schedule, size_t i) {
    return 1000 * _slot(schedule, i)->interval_us;
}

static inline int _set_interval(hexagram_schedule *schedule, time_t int_nsec) {
    schedule->ts.it_value.tv_sec     = 0;
    schedule->ts.it_value.tv_nsec    = int_nsec;
    schedule->ts.it_interval.tv_sec  = 0;
    schedule->ts.it_interval.tv_nsec = int_nsec;

    return timer_settime(schedule->timer, 0, &schedule->ts, NULL);
}

static inline int _slot_set_interval(hexagram_schedule *schedule, size_t i) {
    return _set_interval(schedule, _slot_interval_ns(schedule, i));
}

static void _ev_notify(union sigval sv) {
    hexagram_schedule *schedule = sv.sival_ptr;
    time_t last = -1;

    while (schedule->current < schedule->count) {
        hexagram_schedule_slot *slot = _slot(schedule, schedule->current);
        hexagram_schedule_table_entry *entry = slot->entry;
        time_t delay = slot->interval_us;

        if (entry->handler(&entry->frame, schedule->ctx) < 0) {
            schedule->error = errno;

            break;
        }

        schedule->current++;

        if (last >= 0 && last != delay) {
            _slot_set_interval(schedule, schedule->current);

            return;
        }

        last = delay;
    }

    schedule->current = 0;

    _slot_set_interval(schedule, schedule->current);
}

hexagram_schedule *hexagram_schedule_create(hexagram_schedule_table_entry *table,
                                            size_t count,
                                            void *ctx) {
    hexagram_schedule *schedule;
    size_t i;

    if ((schedule = malloc(sizeof(*schedule) + count * sizeof(hexagram_schedule_slot))) == 0) {
        goto error_malloc_schedule;
    }

    memset(schedule, '\0', sizeof(*schedule));

    schedule->current = 0;
    schedule->error   = 0;
    schedule->count   = count;
    schedule->table   = table;
    schedule->ctx     = ctx;

    schedule->ev.sigev_notify          = SIGEV_THREAD;
    schedule->ev.sigev_notify_function = _ev_notify;
    schedule->ev.sigev_value.sival_ptr = schedule;

    if (timer_create(CLOCK_REALTIME, &schedule->ev, &schedule->timer) < 0) {
        goto error_timer_create;
    }

    for (i=0; i<count; i++) {
        hexagram_schedule_slot *slot = _slot(schedule, i);

        slot->interval_us = table[i].interval_us;
        slot->entry       = &table[i];
    }

    qsort(schedule + 1, count, sizeof(hexagram_schedule_slot), _slot_cmp);

    return schedule;

error_timer_create:
    free(schedule);

error_malloc_schedule:
    return NULL;
}

void hexagram_schedule_destroy(hexagram_schedule *schedule) {
    if (schedule->timer) {
        timer_delete(schedule->timer);
    }

    free(schedule);
}

void hexagram_schedule_reset(hexagram_schedule *schedule) {
    schedule->current = 0;
    schedule->error   = 0;
}

int hexagram_schedule_run(hexagram_schedule *schedule) {
    return _slot_set_interval(schedule, schedule->current);
}

int hexagram_schedule_stop(hexagram_schedule *schedule) {
    return _set_interval(schedule, 0);
}

int hexagram_schedule_error(hexagram_schedule *schedule) {
    return schedule->error;
}