/* SPDX-License-Identifier: BSD-2-Clause */
/*
 * ffmpeg_loader.c — runtime FFmpeg loader.
 */
#include "ffmpeg_loader.h"
#include "log.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <dlfcn.h>

/*
 * SONAME versions match the Kwiboo ffmpeg-v4l2-request-fourier
 * fork (FFmpeg 8.1) installed at the /opt/fourier prefix.  The
 * fourier campaign's ld.so.conf.d/fourier.conf entry resolves
 * these sonames from /opt/fourier/lib via the ld cache, so
 * dlopen-by-soname works without LD_LIBRARY_PATH wrappers.
 *
 * Switched from Debian-stock soname 61/61/59 (FFmpeg 7.1.3) at
 * 2026-05-21 to land daedalus-fourier kernel substitution into
 * the production decode path via patches in the Kwiboo fork
 * (see daedalus-v4l2#11 substitution arc): we own the fork
 * source in marfrit-packages, so we can layer NEON-DSP
 * substitution patches there for libavcodec/aarch64/h264dsp_init
 * → daedalus_recipe_dispatch_* thunks.  The Debian-stock 7.1.3
 * is built outside the marfrit-packages source tree, which
 * would have made layering substitution patches awkward.
 *
 * Note: libavutil bumps soname 59 → 60 between FFmpeg 7.1 and
 * 8.1; libavformat + libavcodec each bump 61 → 62.  The public
 * API surface the daemon uses (avcodec_send_packet /
 * receive_frame / AVCodecContext flags / AVFrame fields) is
 * stable across the bump.
 */
#define LIBAVFORMAT_SONAME	"libavformat.so.62"
#define LIBAVCODEC_SONAME	"libavcodec.so.62"
#define LIBAVUTIL_SONAME	"libavutil.so.60"

/*
 * Resolve a symbol from a dlopen'd handle.  Logs the failure
 * and goto's `out_fail` if missing.  Use only inside
 * ffmpeg_loader_init.
 *
 * The `*(void **) &loader->sym = dlsym(...)` form is the
 * POSIX-recommended workaround for the ISO C "function pointer
 * is not a void pointer" rule (POSIX.1-2017 dlsym(3p), RATIONALE).
 * POSIX requires the conversion to work; ISO C does not.
 */
#define RESOLVE(handle_field, soname, sym)				\
	do {								\
		*(void **) &loader->sym =				\
			dlsym(loader->handle_field, #sym);		\
		if (!loader->sym) {					\
			log_err("dlsym(%s, %s): %s",			\
				soname, #sym, dlerror());		\
			goto out_fail;					\
		}							\
	} while (0)

int ffmpeg_loader_init(struct ffmpeg_loader *loader)
{
	memset(loader, 0, sizeof(*loader));

	loader->libavformat = dlopen(LIBAVFORMAT_SONAME, RTLD_LAZY);
	if (!loader->libavformat) {
		log_err("dlopen(%s): %s", LIBAVFORMAT_SONAME, dlerror());
		goto out_fail;
	}
	loader->libavcodec = dlopen(LIBAVCODEC_SONAME, RTLD_LAZY);
	if (!loader->libavcodec) {
		log_err("dlopen(%s): %s", LIBAVCODEC_SONAME, dlerror());
		goto out_fail;
	}
	loader->libavutil = dlopen(LIBAVUTIL_SONAME, RTLD_LAZY);
	if (!loader->libavutil) {
		log_err("dlopen(%s): %s", LIBAVUTIL_SONAME, dlerror());
		goto out_fail;
	}

	/* libavformat */
	RESOLVE(libavformat, LIBAVFORMAT_SONAME, avformat_alloc_context);
	RESOLVE(libavformat, LIBAVFORMAT_SONAME, avformat_free_context);
	RESOLVE(libavformat, LIBAVFORMAT_SONAME, avformat_open_input);
	RESOLVE(libavformat, LIBAVFORMAT_SONAME, avformat_close_input);
	RESOLVE(libavformat, LIBAVFORMAT_SONAME, avformat_find_stream_info);
	RESOLVE(libavformat, LIBAVFORMAT_SONAME, av_find_best_stream);
	RESOLVE(libavformat, LIBAVFORMAT_SONAME, av_read_frame);
	RESOLVE(libavformat, LIBAVFORMAT_SONAME, avformat_version);

	/* libavcodec */
	RESOLVE(libavcodec, LIBAVCODEC_SONAME, av_packet_alloc);
	RESOLVE(libavcodec, LIBAVCODEC_SONAME, av_packet_free);
	RESOLVE(libavcodec, LIBAVCODEC_SONAME, av_packet_unref);
	RESOLVE(libavcodec, LIBAVCODEC_SONAME, av_frame_alloc);
	RESOLVE(libavcodec, LIBAVCODEC_SONAME, av_frame_free);
	RESOLVE(libavcodec, LIBAVCODEC_SONAME, av_frame_unref);
	RESOLVE(libavcodec, LIBAVCODEC_SONAME, avcodec_find_decoder);
	RESOLVE(libavcodec, LIBAVCODEC_SONAME, avcodec_alloc_context3);
	RESOLVE(libavcodec, LIBAVCODEC_SONAME, avcodec_free_context);
	RESOLVE(libavcodec, LIBAVCODEC_SONAME, avcodec_parameters_to_context);
	RESOLVE(libavcodec, LIBAVCODEC_SONAME, avcodec_open2);
	RESOLVE(libavcodec, LIBAVCODEC_SONAME, avcodec_send_packet);
	RESOLVE(libavcodec, LIBAVCODEC_SONAME, avcodec_receive_frame);

	/* libavutil */
	RESOLVE(libavutil, LIBAVUTIL_SONAME, av_log_set_level);
	RESOLVE(libavutil, LIBAVUTIL_SONAME, av_get_media_type_string);
	RESOLVE(libavutil, LIBAVUTIL_SONAME, av_version_info);
	RESOLVE(libavutil, LIBAVUTIL_SONAME, av_pix_fmt_desc_get);

	{
		unsigned int v = loader->avformat_version();
		log_info("FFmpeg loaded: %s (libavformat %u.%u.%u)",
			 loader->av_version_info(),
			 (v >> 16) & 0xff, (v >> 8) & 0xff, v & 0xff);
	}
	return 0;

out_fail:
	ffmpeg_loader_cleanup(loader);
	return -1;
}

void ffmpeg_loader_cleanup(struct ffmpeg_loader *loader)
{
	if (!loader)
		return;
	if (loader->libavformat) dlclose(loader->libavformat);
	if (loader->libavcodec)  dlclose(loader->libavcodec);
	if (loader->libavutil)   dlclose(loader->libavutil);
	memset(loader, 0, sizeof(*loader));
}