/*
 * V4L2 mem2mem decoders
 *
 * Copyright (C) 2017 Alexis Ballier <aballier@gentoo.org>
 * Copyright (C) 2017 Jorge Ramirez <jorge.ramirez-ortiz@linaro.org>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg 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.
 *
 * FFmpeg 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 FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <linux/videodev2.h>
#include <sys/ioctl.h>
#include "libavutil/pixfmt.h"
#include "libavutil/pixdesc.h"
#include "libavutil/opt.h"
#include "libavcodec/avcodec.h"
#include "libavcodec/decode.h"

#include "v4l2_context.h"
#include "v4l2_m2m.h"
#include "v4l2_fmt.h"

static int v4l2_try_start(AVCodecContext *avctx)
{
    V4L2m2mContext *s = ((V4L2m2mPriv*)avctx->priv_data)->context;
    V4L2Context *const capture = &s->capture;
    V4L2Context *const output = &s->output;
    struct v4l2_selection selection;
    int ret;

    /* 1. start the output process */
    if (!output->streamon) {
        ret = ff_v4l2_context_set_status(output, VIDIOC_STREAMON);
        if (ret < 0) {
            av_log(avctx, AV_LOG_DEBUG, "VIDIOC_STREAMON on output context\n");
            return ret;
        }
    }

    if (capture->streamon)
        return 0;

    /* 2. get the capture format */
    capture->format.type = capture->type;
    ret = ioctl(s->fd, VIDIOC_G_FMT, &capture->format);
    if (ret) {
        av_log(avctx, AV_LOG_WARNING, "VIDIOC_G_FMT ioctl\n");
        return ret;
    }

    /* 2.1 update the AVCodecContext */
    avctx->pix_fmt = ff_v4l2_format_v4l2_to_avfmt(capture->format.fmt.pix_mp.pixelformat, AV_CODEC_ID_RAWVIDEO);
    capture->av_pix_fmt = avctx->pix_fmt;

    /* 3. set the crop parameters */
    selection.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    selection.r.height = avctx->coded_height;
    selection.r.width = avctx->coded_width;
    ret = ioctl(s->fd, VIDIOC_S_SELECTION, &selection);
    if (!ret) {
        ret = ioctl(s->fd, VIDIOC_G_SELECTION, &selection);
        if (ret) {
            av_log(avctx, AV_LOG_WARNING, "VIDIOC_G_SELECTION ioctl\n");
        } else {
            av_log(avctx, AV_LOG_DEBUG, "crop output %dx%d\n", selection.r.width, selection.r.height);
            /* update the size of the resulting frame */
            capture->height = selection.r.height;
            capture->width  = selection.r.width;
        }
    }

    /* 4. init the capture context now that we have the capture format */
    if (!capture->buffers) {
        ret = ff_v4l2_context_init(capture);
        if (ret) {
            av_log(avctx, AV_LOG_DEBUG, "can't request output buffers\n");
            return ret;
        }
    }

    /* 5. start the capture process */
    ret = ff_v4l2_context_set_status(capture, VIDIOC_STREAMON);
    if (ret) {
        av_log(avctx, AV_LOG_DEBUG, "VIDIOC_STREAMON, on capture context\n");
        return ret;
    }

    return 0;
}

static int v4l2_prepare_decoder(V4L2m2mContext *s)
{
    struct v4l2_event_subscription sub;
    V4L2Context *output = &s->output;
    int ret;

    /**
     * requirements
     */
    memset(&sub, 0, sizeof(sub));
    sub.type = V4L2_EVENT_SOURCE_CHANGE;
    ret = ioctl(s->fd, VIDIOC_SUBSCRIBE_EVENT, &sub);
    if ( ret < 0) {
        if (output->height == 0 || output->width == 0) {
            av_log(s->avctx, AV_LOG_ERROR,
                "the v4l2 driver does not support VIDIOC_SUBSCRIBE_EVENT\n"
                "you must provide codec_height and codec_width on input\n");
            return ret;
        }
    }

    return 0;
}

static int v4l2_receive_frame(AVCodecContext *avctx, AVFrame *frame)
{
    V4L2m2mContext *s = ((V4L2m2mPriv*)avctx->priv_data)->context;
    V4L2Context *const capture = &s->capture;
    V4L2Context *const output = &s->output;
    AVPacket avpkt = {0};
    int ret;

    ret = ff_decode_get_packet(avctx, &avpkt);
    if (ret < 0 && ret != AVERROR_EOF)
        return ret;

    if (s->draining)
        goto dequeue;

    ret = ff_v4l2_context_enqueue_packet(output, &avpkt);
    if (ret < 0) {
        if (ret != AVERROR(ENOMEM))
           return ret;
        /* no input buffers available, continue dequeing */
    }

    if (avpkt.size) {
        ret = v4l2_try_start(avctx);
        if (ret) {
            av_packet_unref(&avpkt);
            return 0;
        }
    }

dequeue:
    av_packet_unref(&avpkt);
    return ff_v4l2_context_dequeue_frame(capture, frame);
}

static av_cold int v4l2_decode_init(AVCodecContext *avctx)
{
    V4L2Context *capture, *output;
    V4L2m2mContext *s;
    int ret;

    ret = ff_v4l2_m2m_create_context(avctx, &s);
    if (ret < 0)
        return ret;

    capture = &s->capture;
    output = &s->output;

    /* if these dimensions are invalid (ie, 0 or too small) an event will be raised
     * by the v4l2 driver; this event will trigger a full pipeline reconfig and
     * the proper values will be retrieved from the kernel driver.
     */
    output->height = capture->height = avctx->coded_height;
    output->width = capture->width = avctx->coded_width;

    output->av_codec_id = avctx->codec_id;
    output->av_pix_fmt  = AV_PIX_FMT_NONE;

    capture->av_codec_id = AV_CODEC_ID_RAWVIDEO;
    capture->av_pix_fmt = avctx->pix_fmt;

    ret = ff_v4l2_m2m_codec_init(avctx);
    if (ret) {
        av_log(avctx, AV_LOG_ERROR, "can't configure decoder\n");
        return ret;
    }

    return v4l2_prepare_decoder(s);
}

#define OFFSET(x) offsetof(V4L2m2mPriv, x)
#define FLAGS AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_DECODING_PARAM

static const AVOption options[] = {
    V4L_M2M_DEFAULT_OPTS,
    { "num_capture_buffers", "Number of buffers in the capture context",
        OFFSET(num_capture_buffers), AV_OPT_TYPE_INT, {.i64 = 20}, 20, INT_MAX, FLAGS },
    { NULL},
};

#define M2MDEC(NAME, LONGNAME, CODEC, bsf_name) \
static const AVClass v4l2_m2m_ ## NAME ## _dec_class = {\
    .class_name = #NAME "_v4l2_m2m_decoder",\
    .item_name  = av_default_item_name,\
    .option     = options,\
    .version    = LIBAVUTIL_VERSION_INT,\
};\
\
AVCodec ff_ ## NAME ## _v4l2m2m_decoder = { \
    .name           = #NAME "_v4l2m2m" ,\
    .long_name      = NULL_IF_CONFIG_SMALL("V4L2 mem2mem " LONGNAME " decoder wrapper"),\
    .type           = AVMEDIA_TYPE_VIDEO,\
    .id             = CODEC ,\
    .priv_data_size = sizeof(V4L2m2mPriv),\
    .priv_class     = &v4l2_m2m_ ## NAME ## _dec_class,\
    .init           = v4l2_decode_init,\
    .receive_frame  = v4l2_receive_frame,\
    .close          = ff_v4l2_m2m_codec_end,\
    .bsfs           = bsf_name, \
    .capabilities   = AV_CODEC_CAP_HARDWARE | AV_CODEC_CAP_DELAY | \
                      AV_CODEC_CAP_AVOID_PROBING, \
    .wrapper_name   = "v4l2m2m", \
};

M2MDEC(h264,  "H.264", AV_CODEC_ID_H264,       "h264_mp4toannexb");
M2MDEC(hevc,  "HEVC",  AV_CODEC_ID_HEVC,       "hevc_mp4toannexb");
M2MDEC(mpeg1, "MPEG1", AV_CODEC_ID_MPEG1VIDEO, NULL);
M2MDEC(mpeg2, "MPEG2", AV_CODEC_ID_MPEG2VIDEO, NULL);
M2MDEC(mpeg4, "MPEG4", AV_CODEC_ID_MPEG4,      NULL);
M2MDEC(h263,  "H.263", AV_CODEC_ID_H263,       NULL);
M2MDEC(vc1 ,  "VC1",   AV_CODEC_ID_VC1,        NULL);
M2MDEC(vp8,   "VP8",   AV_CODEC_ID_VP8,        NULL);
M2MDEC(vp9,   "VP9",   AV_CODEC_ID_VP9,        NULL);
