/*

 * null audio output driver

 *

 * This file is part of mpv.

 *

 * mpv is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * mpv is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.

 */

/*

 * Note: this does much more than just ignoring audio output. It simulates

 *       (to some degree) an ideal AO.

 */

#include <stdio.h>

#include <stdlib.h>

#include <math.h>

#include "mpv_talloc.h"

#include "osdep/timer.h"

#include "options/m_option.h"

#include "common/common.h"

#include "common/msg.h"

#include "audio/format.h"

#include "ao.h"

#include "internal.h"

struct priv {

    bool paused;

    double last_time;

    float buffered;     // samples

    int buffersize;     // samples

    bool playing;

    bool untimed;

    float bufferlen;    // seconds

    float speed;        // multiplier

    float latency_sec;  // seconds

    float latency;      // samples

    bool broken_eof;

    bool broken_delay;

    // Minimal unit of audio samples that can be written at once. If play() is

    // called with sizes not aligned to this, a rounded size will be returned.

    // (This is not needed by the AO API, but many AOs behave this way.)

    int outburst;       // samples

    struct m_channels channel_layouts;

    int format;

};

static void drain(struct ao *ao)

{

    struct priv *priv = ao->priv;

    if (ao->untimed) {

        priv->buffered = 0;

        return;

    }

    if (priv->paused)

        return;

    double now = mp_time_sec();

    if (priv->buffered > 0) {

        priv->buffered -= (now - priv->last_time) * ao->samplerate * priv->speed;

        if (priv->buffered < 0)

            priv->buffered = 0;

    }

    priv->last_time = now;

}

static int init(struct ao *ao)

{

    struct priv *priv = ao->priv;

    if (priv->format)

        ao->format = priv->format;

    ao->untimed = priv->untimed;

    struct mp_chmap_sel sel = {.tmp = ao};

    if (priv->channel_layouts.num_chmaps) {

        for (int n = 0; n < priv->channel_layouts.num_chmaps; n++)

            mp_chmap_sel_add_map(&sel, &priv->channel_layouts.chmaps[n]);

    } else {

        mp_chmap_sel_add_any(&sel);

    }

    if (!ao_chmap_sel_adjust(ao, &sel, &ao->channels))

        mp_chmap_from_channels(&ao->channels, 2);

    priv->latency = priv->latency_sec * ao->samplerate;

    // A "buffer" for this many seconds of audio

    int bursts = (int)(ao->samplerate * priv->bufferlen + 1) / priv->outburst;

    ao->device_buffer = priv->outburst * bursts + priv->latency;

    priv->last_time = mp_time_sec();

    return 0;

}

// close audio device

static void uninit(struct ao *ao)

{

}

// stop playing and empty buffers (for seeking)

static void reset(struct ao *ao)

{

    struct priv *priv = ao->priv;

    priv->paused = false;

    priv->buffered = 0;

    priv->playing = false;

}

static void start(struct ao *ao)

{

    struct priv *priv = ao->priv;

    if (priv->paused)

        MP_ERR(ao, "illegal state: start() while paused\n");

    drain(ao);

    priv->paused = false;

    priv->last_time = mp_time_sec();

    priv->playing = true;

}

static bool set_pause(struct ao *ao, bool paused)

{

    struct priv *priv = ao->priv;

    if (!priv->playing)

        MP_ERR(ao, "illegal state: set_pause() while not playing\n");

    if (priv->paused != paused) {

        drain(ao);

        priv->paused = paused;

        if (!priv->paused)

            priv->last_time = mp_time_sec();

    }

    return true;

}

static bool audio_write(struct ao *ao, void **data, int samples)

{

    struct priv *priv = ao->priv;

    if (priv->buffered <= 0)

        priv->buffered = priv->latency; // emulate fixed latency

    priv->buffered += samples;

    return true;

}

static void get_state(struct ao *ao, struct mp_pcm_state *state)

{

    struct priv *priv = ao->priv;

    drain(ao);

    state->free_samples = ao->device_buffer - priv->latency - priv->buffered;

    state->free_samples = state->free_samples / priv->outburst * priv->outburst;

    state->queued_samples = priv->buffered;

    // Note how get_state returns the delay in audio device time (instead of

    // adjusting for speed), since most AOs seem to also do that.

    state->delay = priv->buffered;

    // Drivers with broken EOF handling usually always report the same device-

    // level delay that is additional to the buffer time.

    if (priv->broken_eof && priv->buffered < priv->latency)

        state->delay = priv->latency;

    state->delay /= ao->samplerate;

    if (priv->broken_delay) { // Report only multiples of outburst

        double q = priv->outburst / (double)ao->samplerate;

        if (state->delay > 0)

            state->delay = (int)(state->delay / q) * q;

    }

    state->playing = priv->playing && priv->buffered > 0;

}

#define OPT_BASE_STRUCT struct priv

const struct ao_driver audio_out_null = {

    .description = "Null audio output",

    .name      = "null",

    .init      = init,

    .uninit    = uninit,

    .reset     = reset,

    .get_state = get_state,

    .set_pause = set_pause,

    .write     = audio_write,

    .start     = start,

    .priv_size = sizeof(struct priv),

    .priv_defaults = &(const struct priv) {

        .bufferlen = 0.2,

        .outburst = 256,

        .speed = 1,

    },

    .options = (const struct m_option[]) {

        {"untimed", OPT_BOOL(untimed)},

        {"buffer", OPT_FLOAT(bufferlen), M_RANGE(0, 100)},

        {"outburst", OPT_INT(outburst), M_RANGE(1, 100000)},

        {"speed", OPT_FLOAT(speed), M_RANGE(0, 10000)},

        {"latency", OPT_FLOAT(latency_sec), M_RANGE(0, 100)},

        {"broken-eof", OPT_BOOL(broken_eof)},

        {"broken-delay", OPT_BOOL(broken_delay)},

        {"channel-layouts", OPT_CHANNELS(channel_layouts)},

        {"format", OPT_AUDIOFORMAT(format)},

        {0}

    },

    .options_prefix = "ao-null",

};