/* Copyright (c) 2026 Storm Dragon
 * SPDX-License-Identifier: GPL-3.0-or-later
 * Test-only preload for cninjam configured with ALSA null input/output at 48kHz.
 * Null capture is not clocked and need not initialize its buffer. Supply silence
 * and real-time pacing without accessing a microphone or playback device.
 */
#define _GNU_SOURCE
#include <alsa/asoundlib.h>
#include <dlfcn.h>
#include <errno.h>
#include <pthread.h>
#include <string.h>
#include <time.h>

static pthread_once_t readOnce = PTHREAD_ONCE_INIT;
static snd_pcm_sframes_t (*realRead)(snd_pcm_t *, void *, snd_pcm_uframes_t);

static void resolve_read(void) {
    *(void **)(&realRead) = dlsym(RTLD_NEXT, "snd_pcm_readi");
}

snd_pcm_sframes_t snd_pcm_readi(snd_pcm_t *pcm, void *buffer, snd_pcm_uframes_t frames) {
    pthread_once(&readOnce, resolve_read);
    if (!realRead) return -ENOSYS;
    snd_pcm_sframes_t count = realRead(pcm, buffer, frames);
    if (count > 0) {
        memset(buffer, 0, snd_pcm_frames_to_bytes(pcm, count));
        struct timespec delay = {
            .tv_sec = count / 48000,
            .tv_nsec = (count % 48000) * 1000000000LL / 48000,
        };
        while (nanosleep(&delay, &delay) < 0 && errno == EINTR) {}
    }
    return count;
}