/*
 * This file is part of mpv.
 *
 * Filter graph creation code taken from Libav avplay.c (LGPL 2.1 or later)
 *
 * mpv is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with mpv.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <inttypes.h>
#include <assert.h>

#include <libavutil/avstring.h>
#include <libavutil/mem.h>
#include <libavutil/mathematics.h>
#include <libavutil/rational.h>
#include <libavutil/pixdesc.h>
#include <libavutil/time.h>
#include <libswscale/swscale.h>
#include <libavfilter/avfilter.h>
#include <libavfilter/avfiltergraph.h>
#include <libavfilter/buffersink.h>
#include <libavfilter/buffersrc.h>

#include "core/mp_msg.h"
#include "core/m_option.h"
#include "core/m_struct.h"

#include "video/img_format.h"
#include "video/mp_image.h"
#include "video/sws_utils.h"
#include "video/fmt-conversion.h"
#include "vf.h"

#define IS_LIBAV_FORK (LIBAVFILTER_VERSION_MICRO < 100)

// FFmpeg and Libav have slightly different APIs, just enough to cause us
// unnecessary pain. <Expletive deleted.>
#if IS_LIBAV_FORK
#define graph_parse(graph, filters, inputs, outputs, log_ctx) \
    avfilter_graph_parse(graph, filters, inputs, outputs, log_ctx)
#else
#define graph_parse(graph, filters, inputs, outputs, log_ctx) \
    avfilter_graph_parse(graph, filters, &(inputs), &(outputs), log_ctx)
#endif

// ":" is deprecated, but "|" doesn't work in earlier versions.
#if (IS_LIBAV_FORK  && LIBAVFILTER_VERSION_INT >= AV_VERSION_INT(3, 7, 0)) || \
    (!IS_LIBAV_FORK && LIBAVFILTER_VERSION_INT >= AV_VERSION_INT(3, 50, 100))
#define FMTSEP "|"
#else
#define FMTSEP ":"
#endif

struct vf_priv_s {
    AVFilterGraph *graph;
    AVFilterContext *in;
    AVFilterContext *out;

    AVRational timebase_in;
    AVRational timebase_out;
    AVRational par_in;

    // options
    char *cfg_graph;
    int64_t cfg_sws_flags;
};

static const struct vf_priv_s vf_priv_dflt = {
    .cfg_sws_flags = SWS_BICUBIC,
};

static void destroy_graph(struct vf_instance *vf)
{
    struct vf_priv_s *p = vf->priv;
    avfilter_graph_free(&p->graph);
    p->in = p->out = NULL;
}

static AVRational par_from_sar_dar(int width, int height,
                                   int d_width, int d_height)
{
    return av_div_q((AVRational){d_width, d_height},
                    (AVRational){width, height});
}

static void dar_from_sar_par(int width, int height, AVRational par,
                             int *out_dw, int *out_dh)
{
    *out_dw = width;
    *out_dh = height;
    if (par.num != 0 && par.den != 0) {
        double d = av_q2d(par);
        if (d > 1.0) {
            *out_dw *= d;
        } else {
            *out_dh /= d;
        }
    }
}

static bool recreate_graph(struct vf_instance *vf, int width, int height,
                           int d_width, int d_height, unsigned int fmt)
{
    void *tmp = talloc_new(NULL);
    struct vf_priv_s *p = vf->priv;
    AVFilterContext *in = NULL, *out = NULL, *f_format = NULL;

    if (bstr0(p->cfg_graph).len == 0) {
        mp_msg(MSGT_VFILTER, MSGL_FATAL, "lavfi: no filter graph set\n");
        return false;
    }

    destroy_graph(vf);
    mp_msg(MSGT_VFILTER, MSGL_V, "lavfi: create graph: '%s'\n", p->cfg_graph);

    AVFilterGraph *graph = avfilter_graph_alloc();
    if (!graph)
        goto error;

    AVFilterInOut *outputs = avfilter_inout_alloc();
    AVFilterInOut *inputs  = avfilter_inout_alloc();
    if (!outputs || !inputs)
        goto error;

    // Build list of acceptable output pixel formats. libavfilter will insert
    // conversion filters if needed.
    char *fmtstr = talloc_strdup(tmp, "");
    for (int n = IMGFMT_START; n < IMGFMT_END; n++) {
        if (vf_next_query_format(vf, n)) {
            const char *name = av_get_pix_fmt_name(imgfmt2pixfmt(n));
            if (name) {
                const char *s = fmtstr[0] ? FMTSEP : "";
                fmtstr = talloc_asprintf_append_buffer(fmtstr, "%s%s", s, name);
            }
        }
    }

    char *sws_flags = talloc_asprintf(tmp, "flags=%"PRId64, p->cfg_sws_flags);
    graph->scale_sws_opts = av_strdup(sws_flags);

    AVRational par = par_from_sar_dar(width, height, d_width, d_height);
    AVRational timebase = AV_TIME_BASE_Q;

    char *src_args = talloc_asprintf(tmp, "%d:%d:%d:%d:%d:%d:%d",
                                     width, height, imgfmt2pixfmt(fmt),
                                     timebase.num, timebase.den,
                                     par.num, par.den);

    if (avfilter_graph_create_filter(&in, avfilter_get_by_name("buffer"),
                                     "src", src_args, NULL, graph) < 0)
        goto error;

    if (avfilter_graph_create_filter(&out, avfilter_get_by_name("buffersink"),
                                     "out", NULL, NULL, graph) < 0)
        goto error;

    if (avfilter_graph_create_filter(&f_format, avfilter_get_by_name("format"),
                                     "format", fmtstr, NULL, graph) < 0)
        goto error;

    if (avfilter_link(f_format, 0, out, 0) < 0)
        goto error;

    outputs->name    = av_strdup("in");
    outputs->filter_ctx = in;

    inputs->name    = av_strdup("out");
    inputs->filter_ctx = f_format;

    if (graph_parse(graph, p->cfg_graph, inputs, outputs, NULL) < 0)
        goto error;

    if (avfilter_graph_config(graph, NULL) < 0)
        goto error;

    p->in = in;
    p->out = out;
    p->graph = graph;

    assert(out->nb_inputs == 1);
    assert(in->nb_outputs == 1);

    talloc_free(tmp);
    return true;

error:
    mp_msg(MSGT_VFILTER, MSGL_FATAL, "Can't configure libavfilter graph.\n");
    avfilter_graph_free(&graph);
    talloc_free(tmp);
    return false;
}

static int config(struct vf_instance *vf, int width, int height,
                  int d_width, int d_height, unsigned int flags,
                  unsigned int fmt)
{
    struct vf_priv_s *p = vf->priv;

    if (!recreate_graph(vf, width, height, d_width, d_height, fmt))
        return 0;

    AVFilterLink *l_out = p->out->inputs[0];
    AVFilterLink *l_in = p->in->outputs[0];

    p->timebase_in = l_in->time_base;
    p->timebase_out = l_out->time_base;

    p->par_in = l_in->sample_aspect_ratio;

    int dw, dh;
    dar_from_sar_par(l_out->w, l_out->h, l_out->sample_aspect_ratio, &dw, &dh);

    return vf_next_config(vf, l_out->w, l_out->h, dw, dh, flags,
                          pixfmt2imgfmt(l_out->format));

}

static int query_format(struct vf_instance *vf, unsigned int fmt)
{
    // We accept all sws-convertable formats as inputs. Output formats are
    // handled in config(). The current public libavfilter API doesn't really
    // allow us to do anything more sophisticated.
    // This breaks with filters which accept input pixel formats not
    // supported by libswscale.
    return mp_sws_supported_format(fmt) ? VFCAP_CSP_SUPPORTED : 0;
}

static AVFrame *mp_to_av(struct vf_instance *vf, struct mp_image *img)
{
    struct vf_priv_s *p = vf->priv;
    uint64_t pts = img->pts == MP_NOPTS_VALUE ?
                   AV_NOPTS_VALUE : img->pts * av_q2d(av_inv_q(p->timebase_in));
    AVFrame *frame = mp_image_to_av_frame_and_unref(img);
    frame->pts = pts;
    frame->sample_aspect_ratio = p->par_in;
    return frame;
}

static struct mp_image *av_to_mp(struct vf_instance *vf, AVFrame *av_frame)
{
    struct vf_priv_s *p = vf->priv;
    struct mp_image *img = mp_image_from_av_frame(av_frame);
    img->pts = av_frame->pts == AV_NOPTS_VALUE ?
               MP_NOPTS_VALUE : av_frame->pts * av_q2d(p->timebase_out);
    av_frame_free(&av_frame);
    return img;
}

static int filter_ext(struct vf_instance *vf, struct mp_image *mpi)
{
    struct vf_priv_s *p = vf->priv;

    if (!p->graph)
        return -1;

    AVFrame *frame = mp_to_av(vf, mpi);
    if (av_buffersrc_add_frame(p->in, frame) < 0) {
        av_frame_free(&frame);
        return -1;
    }
    av_frame_free(&frame);

    for (;;) {
        AVFrame *frame = av_frame_alloc();
        if (av_buffersink_get_frame(p->out, frame) < 0) {
            // Not an error situation - no more output buffers in queue.
            av_frame_free(&frame);
            break;
        }
        vf_add_output_frame(vf, av_to_mp(vf, frame));
    }

    return 0;
}

static int control(vf_instance_t *vf, int request, void *data)
{
    struct vf_priv_s *p = vf->priv;
    switch (request) {
    case VFCTRL_SEEK_RESET:
        if (p->graph) {
            struct vf_format *f = &vf->fmt_in;
            recreate_graph(vf, f->w, f->h, f->dw, f->dh, f->fmt);
        }
        break;
    }
    return vf_next_control(vf, request, data);
}

static void uninit(struct vf_instance *vf)
{
    if (!vf->priv)
        return;
    destroy_graph(vf);
}

static int vf_open(vf_instance_t *vf, char *args)
{
    vf->config = config;
    vf->filter_ext = filter_ext;
    vf->query_format = query_format;
    vf->control = control;
    vf->uninit = uninit;
    return 1;
}

#undef ST_OFF
#define ST_OFF(f) M_ST_OFF(struct vf_priv_s,f)
static const m_option_t vf_opts_fields[] = {
    {"graph", ST_OFF(cfg_graph), CONF_TYPE_STRING, CONF_MIN, 1},
    {"sws_flags", ST_OFF(cfg_sws_flags), CONF_TYPE_INT64},
    {0}
};

static const m_struct_t vf_opts = {
    "lavfi",
    sizeof(struct vf_priv_s),
    &vf_priv_dflt,
    vf_opts_fields
};

const vf_info_t vf_info_lavfi = {
    "libavfilter bridge",
    "lavfi",
    "",
    "",
    vf_open,
    &vf_opts
};