/* oggrecode: re-encode an Ogg Vorbis file at a lower VBR quality, deterministically (fixed stream serial,
 * no tags). Used by build-edgar.sh to shrink the music and sound effects of The Legend of Edgar.
 * Part of the build scripts published with the game's source. Public domain / CC0.
 *   oggrecode <quality -0.1..1.0> <in.ogg> <out.ogg> [mono]
 * Links against libogg, libvorbis, libvorbisenc and libvorbisfile. */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <vorbis/vorbisfile.h>
#include <vorbis/vorbisenc.h>

static void flush(ogg_stream_state *os, ogg_page *og, FILE *out, int force)
{
	while ((force ? ogg_stream_flush(os, og) : ogg_stream_pageout(os, og)) > 0)
	{
		fwrite(og->header, 1, og->header_len, out);
		fwrite(og->body, 1, og->body_len, out);
	}
}

int main(int argc, char **argv)
{
	OggVorbis_File vf;
	vorbis_info vi, *src;
	vorbis_comment vc;
	vorbis_dsp_state vd;
	vorbis_block vb;
	ogg_stream_state os;
	ogg_page og;
	ogg_packet op, h1, h2, h3;
	FILE *in, *out;
	int bitstream, channels, mono, i, j;
	long rate;

	if (argc < 4) return 2;
	mono = argc > 4 && strcmp(argv[4], "mono") == 0;
	in = fopen(argv[2], "rb");
	if (!in || ov_open_callbacks(in, &vf, NULL, 0, OV_CALLBACKS_NOCLOSE) < 0) { fprintf(stderr, "bad input %s\n", argv[2]); return 1; }
	src = ov_info(&vf, -1);
	rate = src->rate;
	channels = mono ? 1 : src->channels;

	vorbis_info_init(&vi);
	if (vorbis_encode_init_vbr(&vi, channels, rate, (float)atof(argv[1])) != 0) return 1;
	vorbis_comment_init(&vc);
	vorbis_analysis_init(&vd, &vi);
	vorbis_block_init(&vd, &vb);
	ogg_stream_init(&os, 1);
	out = fopen(argv[3], "wb");
	vorbis_analysis_headerout(&vd, &vc, &h1, &h2, &h3);
	ogg_stream_packetin(&os, &h1);
	ogg_stream_packetin(&os, &h2);
	ogg_stream_packetin(&os, &h3);
	flush(&os, &og, out, 1);

	while (1)
	{
		float **pcm;
		long got = ov_read_float(&vf, &pcm, 4096, &bitstream);
		if (got <= 0)
		{
			vorbis_analysis_wrote(&vd, 0);
		}
		else
		{
			float **dst = vorbis_analysis_buffer(&vd, got);
			int sch = ov_info(&vf, -1)->channels;
			for (j = 0; j < got; j++)
			{
				if (mono)
				{
					float s = 0;
					for (i = 0; i < sch; i++) s += pcm[i][j];
					dst[0][j] = s / sch;
				}
				else
				{
					for (i = 0; i < channels; i++) dst[i][j] = pcm[i < sch ? i : 0][j];
				}
			}
			vorbis_analysis_wrote(&vd, got);
		}
		while (vorbis_analysis_blockout(&vd, &vb) == 1)
		{
			vorbis_analysis(&vb, NULL);
			vorbis_bitrate_addblock(&vb);
			while (vorbis_bitrate_flushpacket(&vd, &op))
			{
				ogg_stream_packetin(&os, &op);
				flush(&os, &og, out, 0);
			}
		}
		if (got <= 0) break;
	}
	flush(&os, &og, out, 1);
	fclose(out);
	ov_clear(&vf);
	fclose(in);
	return 0;
}