/* SPDX-License-Identifier: GPL-2.0 */

/** \file flacdec_filter.c The flac decoder. */

#include <FLAC/stream_decoder.h>

#include "para.h"
#include "list.h"
#include "sched.h"
#include "buffer_tree.h"
#include "filter.h"
#include "error.h"
#include "string.h"

struct private_flacdec_data {
	FLAC__StreamDecoder *decoder;
	bool have_more;
	/*
	 * We can not consume directly what was copied by the read callback
	 * because we might need to feed unconsumend bytes to the decoder again
	 * after the read callback ran out of data and returned ABORT. So we
	 * track how many bytes have been fed to libflac but are unconsumed so far.
	 */
	size_t unconsumed;
};

static FLAC__StreamDecoderReadStatus read_cb(
		__a_unused const FLAC__StreamDecoder *decoder,
		FLAC__byte buffer[], size_t *bytes, void *client_data)
{
	struct filter_node *fn = client_data;
	struct private_flacdec_data *pfd = fn->private_data;
	struct btr_node *btrn = fn->btrn;
	char *btr_buf;
	size_t copy, want = *bytes, have;
	int ns;

	*bytes = 0;
	assert(want > 0);
	ns = btr_node_status(btrn, fn->min_iqs, BTR_NT_INTERNAL);
	if (ns < 0)
		return FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM;
	for (;;) {
		have = btr_next_buffer_omit(btrn, pfd->unconsumed, &btr_buf);
		if (have == 0)
			break;
		copy = PARA_MIN(want, have);
		//PARA_CRIT_LOG("want: %zu, have: %zu, unconsumed %zu\n",
		//	want, have, pfd->unconsumed);
		memcpy(buffer, btr_buf, copy);
		pfd->unconsumed += copy;
		*bytes += copy;
		buffer += copy;
		want -= copy;
		if (want == 0)
			break;
	}
	if (*bytes > 0)
		return FLAC__STREAM_DECODER_READ_STATUS_CONTINUE;
	/**
	* Nothing was copied. If the input queue of the btrn is smaller than
	* the minimal input queue size, our parent must have been gone, so
	* we're not going to get more input. Since our remaining data is not
	* sufficient do decode a single frame, we have an EOF condition.
	*/
	if (btr_get_input_queue_size(btrn) < fn->min_iqs) {
		assert(btr_no_parent(btrn));
		return FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM;
	}
	/*
	 * We are kind of screwed here. Returning CONTINUE with a byte count of
	 * zero leads to an endless loop, so we must return either EOF or
	 * ABORT. Unfortunately, both options require to flush the decoder
	 * afterwards because libFLAC refuses to resume decoding if the decoder
	 * is in EOF or ABORT state. But flushing implies dropping the decoder
	 * input queue, so buffered data is lost.
	 *
	 * We work around this shortcoming by remembering the number of
	 * unconsumed bytes in pfd->unconsumed. In the write/meta callbacks,
	 * this number is decreased whenever a frame has been decoded
	 * successfully and btr_consume() has been called to consume the bytes
	 * corresponding to the decoded frame.  After returning ABORT here, the
	 * decoder can be flushed, and we will feed the unconsumed bytes again.
	 */
	return FLAC__STREAM_DECODER_READ_STATUS_ABORT;
}

/*
 * The exact value does not really matter. It just has to be larger than the
 * size of the input buffer of the bitstream reader of libflac.
 */
#define TELL_CB_DUMMY_VAL 1000000

/*
 * FLAC__stream_decoder_get_decode_position() invokes this callback. The flac
 * library then gets the number of unconsumed bytes from the bitstream reader,
 * subtracts this number from the offset returned here and returns the
 * difference as the decode position.
 */
static FLAC__StreamDecoderTellStatus tell_cb(__a_unused const FLAC__StreamDecoder *decoder,
		FLAC__uint64 *absolute_byte_offset, __a_unused void *client_data)
{
	*absolute_byte_offset = TELL_CB_DUMMY_VAL;
	return FLAC__STREAM_DECODER_TELL_STATUS_OK;
}

/*
 * There is no API function that returns the number of unconsumed bytes
 * directly. The trick is to define a tell callback which always returns a
 * fixed dummy value and compute the number of unconsumed bytes from the return
 * value of FLAC__stream_decoder_get_decode_position().
 */
static void flac_consume(struct filter_node *fn)
{
	struct private_flacdec_data *pfd = fn->private_data;
	struct btr_node *btrn = fn->btrn;
	FLAC__uint64 x;

	FLAC__stream_decoder_get_decode_position(pfd->decoder, &x);
	assert(x <= TELL_CB_DUMMY_VAL);
	x = TELL_CB_DUMMY_VAL - x; /* number of unconsumed bytes */
	assert(x <= pfd->unconsumed);
	btr_consume(btrn, pfd->unconsumed - x);
	pfd->unconsumed = x;
}

static FLAC__StreamDecoderWriteStatus write_cb(
		const FLAC__StreamDecoder *decoder,
		const FLAC__Frame *frame,
		const FLAC__int32 *const buffer[],
		void *client_data)
{
	struct filter_node *fn = client_data;
	struct btr_node *btrn = fn->btrn;
	size_t k, n = frame->header.blocksize;
	unsigned channels = FLAC__stream_decoder_get_channels(decoder);
	char *outbuffer = arr_alloc(n, channels * 2);

	if (channels == 1) {
		for (k = 0; k < n; k++) {
			int sample = buffer[0][k];
			write_int16_host_endian(outbuffer + 2 * k, sample);
		}
	} else {
		for (k = 0; k < n; k++) {
			int left = buffer[0][k], right = buffer[1][k];
			write_int16_host_endian(outbuffer + 4 * k, left);
			write_int16_host_endian(outbuffer + 4 * k + 2, right);
		}
	}
	btr_add_output(outbuffer, n * channels * 2, btrn);
	flac_consume(fn);
	return FLAC__STREAM_DECODER_WRITE_STATUS_CONTINUE;
}

static void meta_cb (__a_unused const FLAC__StreamDecoder *decoder,
		__a_unused const FLAC__StreamMetadata *metadata,
		void *client_data)
{
	flac_consume(client_data);
}

static void error_cb( __a_unused const FLAC__StreamDecoder *decoder,
		FLAC__StreamDecoderErrorStatus status,
		__a_unused void *client_data)
{
	PARA_ERROR_LOG("%s\n", FLAC__StreamDecoderErrorStatusString[status]);
}

static int flacdec_init(struct filter_node *fn)
{
	struct private_flacdec_data *pfd = fn->private_data;
	FLAC__StreamDecoderInitStatus init_status;

	PARA_INFO_LOG("initializing flac decoder\n");
	pfd->decoder = FLAC__stream_decoder_new();
	if (!pfd->decoder)
		return -E_FLACDEC_DECODER_ALLOC;
	FLAC__stream_decoder_set_metadata_respond_all(pfd->decoder);
	init_status = FLAC__stream_decoder_init_stream(pfd->decoder, read_cb,
		NULL /* seek */, tell_cb, NULL /* length_cb */, NULL /* eof_cb */,
		write_cb, meta_cb, error_cb, fn);
	if (init_status == FLAC__STREAM_DECODER_INIT_STATUS_OK)
		return 1;
	FLAC__stream_decoder_delete(pfd->decoder);
	return -E_FLACDEC_DECODER_INIT;
}

static int flacdec_execute(const struct btr_node *btrn, const char *cmd,
		char **result)
{
	struct filter_node *fn = btr_context(btrn);
	struct private_flacdec_data *pfd = fn->private_data;
	unsigned sample_rate = FLAC__stream_decoder_get_sample_rate(pfd->decoder);
	unsigned channels = FLAC__stream_decoder_get_channels(pfd->decoder);

	return decoder_execute(cmd, sample_rate, channels, result);
}

#define FLACDEC_MAX_OUTPUT_SIZE (640 * 1024)

static bool output_queue_full(struct btr_node *btrn)
{
	return btr_get_output_queue_size(btrn) > FLACDEC_MAX_OUTPUT_SIZE;
}

static void flacdec_pre_monitor(struct sched *s, void *context)
{
	struct filter_node *fn = context;
	struct private_flacdec_data *pfd = fn->private_data;
	struct btr_node *btrn = fn->btrn;
	int ret;

	ret = btr_node_status(btrn, fn->min_iqs, BTR_NT_INTERNAL);
	if (ret < 0)
		return sched_min_delay(s);
	if (output_queue_full(btrn))
		return sched_request_timeout_ms(30, s);
	if (ret > 0 || pfd->have_more)
		return sched_min_delay(s);
}

static int flacdec_post_monitor(__a_unused struct sched *s, void *context)
{
	struct filter_node *fn = context;
	struct private_flacdec_data *pfd = fn->private_data;
	struct btr_node *btrn = fn->btrn;
	int ret;
	FLAC__StreamDecoderState state;

	if (output_queue_full(btrn))
		return 0;
	ret = btr_node_status(btrn, fn->min_iqs, BTR_NT_INTERNAL);
	if (ret < 0 && ret != -E_EOF) /* fatal error */
		goto out;
	if (ret <= 0 && !pfd->have_more) /* nothing to do */
		goto out;
	if (!pfd->decoder) {
		ret = flacdec_init(fn);
		goto out;
	}
	if (output_queue_full(btrn)) {
		pfd->have_more = true;
		ret = 1;
		goto out;
	}
	pfd->have_more = false;
	FLAC__stream_decoder_process_single(pfd->decoder);
	state = FLAC__stream_decoder_get_state(pfd->decoder);
	ret = -E_EOF;
	if (state == FLAC__STREAM_DECODER_END_OF_STREAM)
		goto out;
	if (state == FLAC__STREAM_DECODER_ABORTED) {
		FLAC__stream_decoder_flush(pfd->decoder);
		pfd->unconsumed = 0; /* feed unconsumed bytes again */
		fn->min_iqs = btr_get_input_queue_size(btrn) + 1;
		ret = 1;
		goto out;
	}
	pfd->have_more = true;
	fn->min_iqs = 0;
	ret = 1;
out:
	if (ret < 0)
		btr_remove_node(&fn->btrn);
	return ret;
}

static void flacdec_close(struct filter_node *fn)
{
	struct private_flacdec_data *pfd;

	if (!fn)
		return;
	pfd = fn->private_data;
	if (!pfd)
		return;
	if (pfd->decoder) {
		FLAC__stream_decoder_finish(pfd->decoder);
		FLAC__stream_decoder_delete(pfd->decoder);
	}
	free(pfd);
	fn->private_data = NULL;
}

static void flacdec_open(struct filter_node *fn)
{
	struct private_flacdec_data *pfd = zalloc(sizeof(*pfd));
	fn->private_data = pfd;
	fn->min_iqs = 0;
}

/** \cond doxygen_ignore */
const struct filter lsg_filter_cmd_com_flacdec_user_data = {
	.open = flacdec_open,
	.close = flacdec_close,
	.pre_monitor = flacdec_pre_monitor,
	.post_monitor = flacdec_post_monitor,
	.execute = flacdec_execute,
};
/** \endcond */