#ifndef OUTPUT_BUFFER_XFADE_H
#define OUTPUT_BUFFER_XFADE_H

#include "os_compat.h"
#include "audio.h"
#include "pcm_utils.h"

static struct ob_chunk *get_chunk(struct rbvec vec[2], size_t i);
static size_t calculate_xfade_chunks(struct rbvec vec[2])
{
	float xfade_time = ob.xfade_time; /* prevent race conditions */
	size_t chunks;
	struct ob_chunk *c;
	size_t nr;
	AudioFormat *af = &ob.audio_format;

	assert(pthread_equal(ob.thread, pthread_self()));

	if (xfade_time <= 0)
		return ob.bpp_cur;
	if (!isCurrentAudioFormat(af))
		return 0;

	if (!ob.total_time ||
	    (ob.elapsed_time + xfade_time) < ob.total_time)
		return ob.bpp_cur; /* too early, don't enable xfade yet */

	assert(af->bits > 0);
	assert(af->channels > 0);
	assert(af->sampleRate > 0);

	chunks = audio_format_time_to_size(af) / CHUNK_SIZE;
	chunks = chunks * (xfade_time + 0.5);
	assert(chunks);

	assert(ob.index->size >= ob.bpp_cur);
	if (chunks > (ob.index->size - ob.bpp_cur))
		chunks = ob.index->size - ob.bpp_cur;
	DEBUG("calculated xfade chunks: %d\n", chunks);
	nr = vec[0].len + vec[1].len;

	if (chunks <= nr) {
		c = get_chunk(vec, chunks);
		assert(c);
		if (c->seq != ob.seq_player) {
			do {
				c = get_chunk(vec, --chunks);
				assert(c);
			} while (chunks && c->seq == ob.seq_decoder);
			assert((c = get_chunk(vec, chunks)));
			if (!chunks && c->seq != ob.seq_decoder)
				return 0; /* nothing to xfade */
			++chunks;
			assert((c = get_chunk(vec, chunks)));
			assert(c->seq == ob.seq_decoder);
		}
		DEBUG("adjusted xfade chunks: %d\n", chunks);
	}

	ob.xfade_cur = chunks;
	ob.xfade_max = chunks;
	assert(ob.xfade_state == XFADE_DISABLED);
	ob.xfade_state = XFADE_ENABLED;
	return chunks;
}

static size_t xfade_chunks_needed(struct rbvec vec[2])
{
	assert(pthread_equal(ob.thread, pthread_self()));

	if (ob.xfade_state == XFADE_DISABLED)
		return calculate_xfade_chunks(vec);
	assert(ob.xfade_state == XFADE_ENABLED);
	return ob.xfade_max;
}

static void xfade_mix(struct ob_chunk *a, struct ob_chunk *b)
{
	assert(pthread_equal(ob.thread, pthread_self()));
	assert(ob.xfade_state == XFADE_ENABLED);
	assert(ob.xfade_cur <= ob.xfade_max);
	assert(b);
	assert(a != b);
	assert(a->len <= CHUNK_SIZE);
	assert(b->len <= CHUNK_SIZE);
	if (b->seq == a->seq) {
		/* deal with small rounding errors */
		DEBUG("seq_match: %d == %d\n", a->seq, b->seq);
		return;
	}

	/* as xfade_cur increases, b is scaled more and a is scaled less */
	pcm_mix(a->data, b->data, a->len, b->len,
	        &ob.audio_format, ((float)ob.xfade_cur) / ob.xfade_max);

	/* next time we fade more until we have nothing to fade */
	if (ob.xfade_cur)
		--ob.xfade_cur;
	if (b->len > a->len) {
		DEBUG("reassign len: %d => %d\n", a->len, b->len);
		a->len = b->len;
	}
	b->len = 0; /* invalidate the chunk we already mixed in */
}

#endif /* OUTPUT_BUFFER_XFADE_H */