/* See LICENSE file for copyright and license details. */
#include "common.h"

USAGE("[-bs] bottom-stream ... top-stream")

#define PROCESS(TYPE, BLEND)\
	do {\
		TYPE x1, y1, z1, a1;\
		TYPE x2, y2, z2, a2;\
		size_t i, j;\
		for (i = 0; i < n; i += streams->pixel_size) {\
			x1 = ((TYPE *)(streams[0].buf + i))[0];\
			y1 = ((TYPE *)(streams[0].buf + i))[1];\
			z1 = ((TYPE *)(streams[0].buf + i))[2];\
			a1 = ((TYPE *)(streams[0].buf + i))[3];\
			for (j = 1; j < n_streams; j++) {\
				x2 = ((TYPE *)(streams[j].buf + i))[0];\
				y2 = ((TYPE *)(streams[j].buf + i))[1];\
				z2 = ((TYPE *)(streams[j].buf + i))[2];\
				a2 = ((TYPE *)(streams[j].buf + i))[3];\
				if (BLEND)\
					a2 /= (TYPE)(j + 1);\
				a1 *= 1 - a2;\
				x1 = x1 * a1 + x2 * a2;\
				y1 = y1 * a1 + y2 * a2;\
				z1 = z1 * a1 + z2 * a2;\
				a1 += a2;\
			}\
			((TYPE *)(streams[0].buf + i))[0] = x1;\
			((TYPE *)(streams[0].buf + i))[1] = y1;\
			((TYPE *)(streams[0].buf + i))[2] = z1;\
			((TYPE *)(streams[0].buf + i))[3] = a1;\
		}\
	} while (0)

static void process_lf  (struct stream *streams, size_t n_streams, size_t n) { PROCESS(double, 0); }
static void process_lf_b(struct stream *streams, size_t n_streams, size_t n) { PROCESS(double, 1); }
static void process_f   (struct stream *streams, size_t n_streams, size_t n) { PROCESS(float, 0); }
static void process_f_b (struct stream *streams, size_t n_streams, size_t n) { PROCESS(float, 1); }

int
main(int argc, char *argv[])
{
	struct stream *streams;
	size_t n_streams, i, frames = 0, tmp;
	int blend = 0, shortest = 0;
	void (*process)(struct stream *streams, size_t n_streams, size_t n);

	ARGBEGIN {
	case 'b':
		blend = 1;
		break;
	case 's':
		shortest = 1;
		frames = SIZE_MAX;
		break;
	default:
		usage();
	} ARGEND;

	if (argc < 2)
		usage();

	n_streams = (size_t)argc;
	streams = ecalloc(n_streams, sizeof(*streams));

	for (i = 0; i < n_streams; i++) {
		eopen_stream(streams + i, argv[i]);
		if (shortest ?
		    (streams[i].frames && streams[i].frames < frames) :
		    (streams[i].frames || streams[i].frames > frames))
			frames = streams[i].frames;
	}

	if (streams->encoding == DOUBLE)
		process = blend ? process_lf_b :process_lf;
	else if (streams->encoding == FLOAT)
		process = blend ? process_f_b : process_f;
	else
		eprintf("pixel format %s is not supported, try xyza\n", streams->pixfmt);
	CHECK_ALPHA_CHAN(streams);
	CHECK_N_CHAN(streams, 4, 4);

	tmp = streams->frames, streams->frames = frames;
	fprint_stream_head(stdout, streams);
	efflush(stdout, "<stdout>");
	streams->frames = tmp;
	process_multiple_streams(streams, n_streams, STDOUT_FILENO, "<stdout>", shortest, process);

	free(streams);
	return 0;
}