// SPDX-License-Identifier: GPL-2.0-only
// Copyright (c) 2025 Šerif Rami <ramiserifpersia@gmail.com>

#include "us144mkii.h"

/**
 * tascam_playback_open() - Opens the PCM playback substream.
 * @substream: The ALSA PCM substream to open.
 *
 * This function sets the hardware parameters for the playback substream
 * and stores a reference to the substream in the driver's private data.
 *
 * Return: 0 on success.
 */
static int tascam_playback_open(struct snd_pcm_substream *substream) {
  struct tascam_card *tascam = snd_pcm_substream_chip(substream);

  substream->runtime->hw = tascam_pcm_hw;
  tascam->playback_substream = substream;
  atomic_set(&tascam->playback_active, 0);

  return 0;
}

/**
 * tascam_playback_close() - Closes the PCM playback substream.
 * @substream: The ALSA PCM substream to close.
 *
 * This function clears the reference to the playback substream in the
 * driver's private data.
 *
 * Return: 0 on success.
 */
static int tascam_playback_close(struct snd_pcm_substream *substream) {
  struct tascam_card *tascam = snd_pcm_substream_chip(substream);

  tascam->playback_substream = NULL;

  return 0;
}

/**
 * tascam_playback_prepare() - Prepares the PCM playback substream for use.
 * @substream: The ALSA PCM substream to prepare.
 *
 * This function initializes playback-related counters.
 *
 * Return: 0 on success.
 */
static int tascam_playback_prepare(struct snd_pcm_substream *substream) {
  struct tascam_card *tascam = snd_pcm_substream_chip(substream);

  tascam->driver_playback_pos = 0;
  tascam->playback_frames_consumed = 0;

  return 0;
}

/**
 * tascam_playback_pointer() - Returns the current playback pointer position.
 * @substream: The ALSA PCM substream.
 *
 * This function returns the current position of the playback pointer within
 * the ALSA ring buffer, in frames.
 *
 * Return: The current playback pointer position in frames.
 */
static snd_pcm_uframes_t
tascam_playback_pointer(struct snd_pcm_substream *substream) {
  struct tascam_card *tascam = snd_pcm_substream_chip(substream);
  struct snd_pcm_runtime *runtime = substream->runtime;
  u64 pos;

  if (!atomic_read(&tascam->playback_active))
    return 0;

  guard(spinlock_irqsave)(&tascam->lock);
  pos = tascam->playback_frames_consumed;

  if (runtime->buffer_size == 0)
    return 0;

  u64 remainder = do_div(pos, runtime->buffer_size);
  return runtime ? remainder : 0;
}

/**
 * tascam_playback_ops - ALSA PCM operations for playback.
 *
 * This structure defines the callback functions for playback stream operations,
 * including open, close, ioctl, hardware parameters, hardware free, prepare,
 * trigger, and pointer.
 */
const struct snd_pcm_ops tascam_playback_ops = {
    .open = tascam_playback_open,
    .close = tascam_playback_close,
    .ioctl = snd_pcm_lib_ioctl,
    .hw_params = tascam_pcm_hw_params,
    .hw_free = tascam_pcm_hw_free,
    .prepare = tascam_playback_prepare,
    .trigger = tascam_pcm_trigger,
    .pointer = tascam_playback_pointer,
};