#include "channel.h"

#include "value.h"

#include <stdlib.h>

#include <string.h>

LatChannel *channel_new(void) {

    LatChannel *ch = calloc(1, sizeof(LatChannel));

    ch->buffer = lat_vec_new(sizeof(LatValue));

    ch->closed = false;

    ch->refcount = 1;

#ifndef __EMSCRIPTEN__

    pthread_mutex_init(&ch->mutex, NULL);

    pthread_cond_init(&ch->cond_notempty, NULL);

#endif

    return ch;

}

void channel_retain(LatChannel *ch) {

    __atomic_add_fetch(&ch->refcount, 1, __ATOMIC_SEQ_CST);

}

void channel_release(LatChannel *ch) {

    size_t prev = __atomic_sub_fetch(&ch->refcount, 1, __ATOMIC_SEQ_CST);

    if (prev == 0) {

        /* Free any remaining buffered values */

        for (size_t i = 0; i < ch->buffer.len; i++) {

            LatValue *v = lat_vec_get(&ch->buffer, i);

            value_free(v);

        }

        lat_vec_free(&ch->buffer);

#ifndef __EMSCRIPTEN__

        pthread_mutex_destroy(&ch->mutex);

        pthread_cond_destroy(&ch->cond_notempty);

#endif

        free(ch);

    }

}

bool channel_send(LatChannel *ch, LatValue val) {

#ifndef __EMSCRIPTEN__

    pthread_mutex_lock(&ch->mutex);

#endif

    if (ch->closed) {

#ifndef __EMSCRIPTEN__

        pthread_mutex_unlock(&ch->mutex);

#endif

        value_free(&val);

        return false;

    }

    lat_vec_push(&ch->buffer, &val);

#ifndef __EMSCRIPTEN__

    pthread_cond_signal(&ch->cond_notempty);

    /* Wake any select waiters */

    for (LatSelectWaiter *w = ch->waiters; w; w = w->next) {

        pthread_mutex_lock(w->mutex);

        pthread_cond_signal(w->cond);

        pthread_mutex_unlock(w->mutex);

    }

    pthread_mutex_unlock(&ch->mutex);

#endif

    return true;

}

LatValue channel_recv(LatChannel *ch, bool *ok) {

#ifndef __EMSCRIPTEN__

    pthread_mutex_lock(&ch->mutex);

    while (ch->buffer.len == 0 && !ch->closed) {

        pthread_cond_wait(&ch->cond_notempty, &ch->mutex);

    }

#endif

    if (ch->buffer.len == 0) {

        /* closed + empty */

#ifndef __EMSCRIPTEN__

        pthread_mutex_unlock(&ch->mutex);

#endif

        *ok = false;

        return value_unit();

    }

    /* Shift front element */

    LatValue val;

    memcpy(&val, lat_vec_get(&ch->buffer, 0), sizeof(LatValue));

    /* Shift remaining elements forward */

    if (ch->buffer.len > 1) {

        memmove(ch->buffer.data,

                (char *)ch->buffer.data + ch->buffer.elem_size,

                (ch->buffer.len - 1) * ch->buffer.elem_size);

    }

    ch->buffer.len--;

#ifndef __EMSCRIPTEN__

    pthread_mutex_unlock(&ch->mutex);

#endif

    *ok = true;

    return val;

}

void channel_close(LatChannel *ch) {

#ifndef __EMSCRIPTEN__

    pthread_mutex_lock(&ch->mutex);

#endif

    ch->closed = true;

#ifndef __EMSCRIPTEN__

    pthread_cond_broadcast(&ch->cond_notempty);

    /* Wake any select waiters */

    for (LatSelectWaiter *w = ch->waiters; w; w = w->next) {

        pthread_mutex_lock(w->mutex);

        pthread_cond_signal(w->cond);

        pthread_mutex_unlock(w->mutex);

    }

    pthread_mutex_unlock(&ch->mutex);

#endif

}

bool channel_try_recv(LatChannel *ch, LatValue *out, bool *closed_out) {

#ifndef __EMSCRIPTEN__

    pthread_mutex_lock(&ch->mutex);

#endif

    if (ch->buffer.len == 0) {

        if (closed_out) *closed_out = ch->closed;

#ifndef __EMSCRIPTEN__

        pthread_mutex_unlock(&ch->mutex);

#endif

        return false;

    }

    memcpy(out, lat_vec_get(&ch->buffer, 0), sizeof(LatValue));

    if (ch->buffer.len > 1) {

        memmove(ch->buffer.data,

                (char *)ch->buffer.data + ch->buffer.elem_size,

                (ch->buffer.len - 1) * ch->buffer.elem_size);

    }

    ch->buffer.len--;

    if (closed_out) *closed_out = false;

#ifndef __EMSCRIPTEN__

    pthread_mutex_unlock(&ch->mutex);

#endif

    return true;

}

void channel_add_waiter(LatChannel *ch, LatSelectWaiter *w) {

#ifndef __EMSCRIPTEN__

    pthread_mutex_lock(&ch->mutex);

    w->next = ch->waiters;

    ch->waiters = w;

    pthread_mutex_unlock(&ch->mutex);

#else

    (void)ch; (void)w;

#endif

}

void channel_remove_waiter(LatChannel *ch, LatSelectWaiter *w) {

#ifndef __EMSCRIPTEN__

    pthread_mutex_lock(&ch->mutex);

    LatSelectWaiter **pp = &ch->waiters;

    while (*pp) {

        if (*pp == w) { *pp = w->next; break; }

        pp = &(*pp)->next;

    }

    pthread_mutex_unlock(&ch->mutex);

#else

    (void)ch; (void)w;

#endif

}