// Copyright © Go Opus Authors (see AUTHORS file)
//
// License for use of this code is detailed in the LICENSE file

package opus

import (
	"errors"
	"fmt"
	"io"
	"runtime/cgo"
	"time"
	"unsafe"
)

/*
#cgo pkg-config: opus libopusenc
#include <opus.h>
#include <opusenc.h>

int
bridge_encoder_set_dtx(OggOpusEnc *st, opus_int32 use_dtx);

int
bridge_encoder_get_dtx(OggOpusEnc *st, opus_int32 *dtx);

int
bridge_encoder_get_sample_rate(OggOpusEnc *st, opus_int32 *sample_rate);

int
bridge_encoder_set_muxing_delay(OggOpusEnc *st, opus_int32 delay);

int
bridge_encoder_get_muxing_delay(OggOpusEnc *st, opus_int32 *delay);

int
bridge_encoder_set_bitrate(OggOpusEnc *st, opus_int32 bitrate);

int
bridge_encoder_get_bitrate(OggOpusEnc *st, opus_int32 *bitrate);

int
bridge_encoder_set_complexity(OggOpusEnc *st, opus_int32 complexity);

int
bridge_encoder_get_complexity(OggOpusEnc *st, opus_int32 *complexity);

int
bridge_encoder_set_max_bandwidth(OggOpusEnc *st, opus_int32 max_bw);

int
bridge_encoder_get_max_bandwidth(OggOpusEnc *st, opus_int32 *max_bw);

int
bridge_encoder_set_inband_fec(OggOpusEnc *st, opus_int32 fec);

int
bridge_encoder_get_inband_fec(OggOpusEnc *st, opus_int32 *fec);

int
bridge_encoder_set_packet_loss_perc(OggOpusEnc *st, opus_int32 loss_perc);

int
bridge_encoder_get_packet_loss_perc(OggOpusEnc *st, opus_int32 *loss_perc);

int
bridge_encoder_set_application(OggOpusEnc *st, opus_int32 application);

OpusEncCallbacks * my_write_callbacks();

OggOpusComments* my_empty_comment();

*/
import "C"

type Bandwidth int

const (
	// 4 kHz passband
	Narrowband = Bandwidth(C.OPUS_BANDWIDTH_NARROWBAND)
	// 6 kHz passband
	Mediumband = Bandwidth(C.OPUS_BANDWIDTH_MEDIUMBAND)
	// 8 kHz passband
	Wideband = Bandwidth(C.OPUS_BANDWIDTH_WIDEBAND)
	// 12 kHz passband
	SuperWideband = Bandwidth(C.OPUS_BANDWIDTH_SUPERWIDEBAND)
	// 20 kHz passband
	Fullband = Bandwidth(C.OPUS_BANDWIDTH_FULLBAND)
)

var errEncUninitialized = fmt.Errorf("opus encoder uninitialized")

// Encoder contains the state of an Opus encoder for libopus.
type Encoder struct {
	p        *C.struct_OggOpusEnc
	channels int
	handle   cgo.Handle
	writer   io.Writer
}

//export go_writecallback
func go_writecallback(p unsafe.Pointer, cbuf *C.uchar, length C.int) C.int {
	enc := ((*cgo.Handle)(p)).Value().(*Encoder)
	if enc == nil {
		// This is bad
		return 1
	}

	_, err := enc.writer.Write(unsafe.Slice((*byte)(cbuf), int(length)))

	if err != nil {
		return 1
	}
	return 0
}

// NewEncoder allocates a new Opus encoder and initializes it with the appropriate parameters.
func NewEncoder(sampleRate int, channels int, application Application, writer io.Writer) (*Encoder, error) {
	var enc Encoder
	err := enc.Init(sampleRate, channels, application, writer)
	if err != nil {
		return nil, err
	}
	return &enc, nil
}

// Init initializes a pre-allocated opus encoder. Unless the encoder has been
// created using NewEncoder, this method must be called exactly once in the
// life-time of this object, before calling any other methods.
func (enc *Encoder) Init(sampleRate int, channels int, application Application, writer io.Writer) error {
	if enc.p != nil {
		return fmt.Errorf("opus encoder already initialized")
	}
	if channels != 1 && channels != 2 {
		return fmt.Errorf("number of channels must be 1 or 2: %d", channels)
	}

	enc.channels = channels
	enc.writer = writer
	enc.handle = cgo.NewHandle(enc)

	var errno C.int
	if channels > 8 {
		enc.p = C.ope_encoder_create_callbacks(C.my_write_callbacks(), unsafe.Pointer(&enc.handle), C.my_empty_comment(), C.opus_int32(sampleRate), C.int(channels), C.int(255), &errno)
	} else if channels > 2 {
		enc.p = C.ope_encoder_create_callbacks(C.my_write_callbacks(), unsafe.Pointer(&enc.handle), C.my_empty_comment(), C.opus_int32(sampleRate), C.int(channels), C.int(1), &errno)
	} else {
		enc.p = C.ope_encoder_create_callbacks(C.my_write_callbacks(), unsafe.Pointer(&enc.handle), C.my_empty_comment(), C.opus_int32(sampleRate), C.int(channels), C.int(0), &errno)
	}

	if errno != 0 {
		return Error(int(errno))
	}
	C.bridge_encoder_set_application(enc.p, C.int(application))
	return nil
}

// Encode raw PCM data
func (enc *Encoder) Encode(pcm []int16) error {
	if enc.p == nil {
		return errEncUninitialized
	}
	if len(pcm) == 0 {
		return fmt.Errorf("opus: no data supplied")
	}

	if len(pcm)%enc.channels != 0 {
		return fmt.Errorf("opus: input buffer length must be multiple of channels")
	}
	samples := len(pcm) / enc.channels

	n := int(C.ope_encoder_write(enc.p, (*C.opus_int16)(&pcm[0]), C.int(samples)))
	if n != 0 {
		return Error(n)
	}
	return nil
}

// FlushHeaders Write out the header now rather than wait for audio to begin.
func (enc *Encoder) FlushHeaders() error {
	res := C.ope_encoder_flush_header(enc.p)
	if res != C.OPUS_OK {
		return Error(res)
	}
	return nil
}

// Close finishes stream, then frees allocated resources
func (enc *Encoder) Close() error {
	if enc.p != nil {
		res := C.ope_encoder_drain(enc.p)
		if res != C.OPUS_OK {
			return Error(res)
		}
		C.ope_encoder_destroy(enc.p)
		enc.p = nil
		enc.handle.Delete()
	}
	return nil
}

// EncodeFloat32 raw PCM data
func (enc *Encoder) EncodeFloat32(pcm []float32) error {
	if enc.p == nil {
		return errEncUninitialized
	}
	if len(pcm) == 0 {
		return fmt.Errorf("opus: no data supplied")
	}

	if len(pcm)%enc.channels != 0 {
		return fmt.Errorf("opus: input buffer length must be multiple of channels")
	}
	samples := len(pcm) / enc.channels

	n := int(C.ope_encoder_write_float(enc.p, (*C.float)(&pcm[0]), C.int(samples)))
	if n != 0 {
		return Error(n)
	}
	return nil
}

// SetDTX configures the encoder's use of discontinuous transmission (DTX).
func (enc *Encoder) SetDTX(dtx bool) error {
	i := 0
	if dtx {
		i = 1
	}
	res := C.bridge_encoder_set_dtx(enc.p, C.opus_int32(i))
	if res != C.OPUS_OK {
		return Error(res)
	}
	return nil
}

// DTX reports whether this encoder is configured to use discontinuous
// transmission (DTX).
func (enc *Encoder) DTX() (bool, error) {
	var dtx C.opus_int32
	res := C.bridge_encoder_get_dtx(enc.p, &dtx)
	if res != C.OPUS_OK {
		return false, Error(res)
	}
	return dtx != 0, nil
}

// SampleRate returns the encoder sample rate in Hz.
func (enc *Encoder) SampleRate() (int, error) {
	var sr C.opus_int32
	res := C.bridge_encoder_get_sample_rate(enc.p, &sr)
	if res != C.OPUS_OK {
		return 0, Error(res)
	}
	return int(sr), nil
}

// SetBitrate sets the bitrate of the Encoder
func (enc *Encoder) SetBitrate(bitrate int) error {
	res := C.bridge_encoder_set_bitrate(enc.p, C.opus_int32(bitrate))
	if res != C.OPUS_OK {
		return Error(res)
	}
	return nil
}

// SetBitrateToAuto will allow the encoder to automatically set the bitrate
func (enc *Encoder) SetBitrateToAuto() error {
	res := C.bridge_encoder_set_bitrate(enc.p, C.opus_int32(C.OPUS_AUTO))
	if res != C.OPUS_OK {
		return Error(res)
	}
	return nil
}

// SetBitrateToMax causes the encoder to use as much rate as it can. This can be
// useful for controlling the rate by adjusting the output buffer size.
func (enc *Encoder) SetBitrateToMax() error {
	res := C.bridge_encoder_set_bitrate(enc.p, C.opus_int32(C.OPUS_BITRATE_MAX))
	if res != C.OPUS_OK {
		return Error(res)
	}
	return nil
}

// Bitrate returns the bitrate of the Encoder
func (enc *Encoder) Bitrate() (int, error) {
	var bitrate C.opus_int32
	res := C.bridge_encoder_get_bitrate(enc.p, &bitrate)
	if res != C.OPUS_OK {
		return 0, Error(res)
	}
	return int(bitrate), nil
}

// SetMuxingDelay sets maximum container delay
func (enc *Encoder) SetMuxingDelay(delay time.Duration) error {
	if delay < 0 || delay > time.Millisecond*1000 {
		return errors.New("value must be between 0 to 1000 milliseconds")
	}
	res := C.bridge_encoder_set_muxing_delay(enc.p, C.opus_int32(delay.Milliseconds()*48))
	if res != C.OPUS_OK {
		return Error(res)
	}
	return nil
}

// MuxingDelay returns the maximum container delay
func (enc *Encoder) MuxingDelay() (time.Duration, error) {
	var delay C.opus_int32
	res := C.bridge_encoder_get_muxing_delay(enc.p, &delay)
	if res != C.OPUS_OK {
		return 0, Error(res)
	}
	return time.Millisecond * time.Duration(int(delay)/48), nil
}

// SetComplexity sets the encoder's computational complexity
func (enc *Encoder) SetComplexity(complexity int) error {
	res := C.bridge_encoder_set_complexity(enc.p, C.opus_int32(complexity))
	if res != C.OPUS_OK {
		return Error(res)
	}
	return nil
}

// Complexity returns the computational complexity used by the encoder
func (enc *Encoder) Complexity() (int, error) {
	var complexity C.opus_int32
	res := C.bridge_encoder_get_complexity(enc.p, &complexity)
	if res != C.OPUS_OK {
		return 0, Error(res)
	}
	return int(complexity), nil
}

// SetMaxBandwidth configures the maximum bandpass that the encoder will select
// automatically
func (enc *Encoder) SetMaxBandwidth(maxBw Bandwidth) error {
	res := C.bridge_encoder_set_max_bandwidth(enc.p, C.opus_int32(maxBw))
	if res != C.OPUS_OK {
		return Error(res)
	}
	return nil
}

// MaxBandwidth gets the encoder's configured maximum allowed bandpass.
func (enc *Encoder) MaxBandwidth() (Bandwidth, error) {
	var maxBw C.opus_int32
	res := C.bridge_encoder_get_max_bandwidth(enc.p, &maxBw)
	if res != C.OPUS_OK {
		return 0, Error(res)
	}
	return Bandwidth(maxBw), nil
}

// SetInBandFEC configures the encoder's use of inband forward error
// correction (FEC)
func (enc *Encoder) SetInBandFEC(fec bool) error {
	i := 0
	if fec {
		i = 1
	}
	res := C.bridge_encoder_set_inband_fec(enc.p, C.opus_int32(i))
	if res != C.OPUS_OK {
		return Error(res)
	}
	return nil
}

// InBandFEC gets the encoder's configured inband forward error correction (FEC)
func (enc *Encoder) InBandFEC() (bool, error) {
	var fec C.opus_int32
	res := C.bridge_encoder_get_inband_fec(enc.p, &fec)
	if res != C.OPUS_OK {
		return false, Error(res)
	}
	return fec != 0, nil
}

// SetPacketLossPerc configures the encoder's expected packet loss percentage.
func (enc *Encoder) SetPacketLossPerc(lossPerc int) error {
	res := C.bridge_encoder_set_packet_loss_perc(enc.p, C.opus_int32(lossPerc))
	if res != C.OPUS_OK {
		return Error(res)
	}
	return nil
}

// PacketLossPerc gets the encoder's configured packet loss percentage.
func (enc *Encoder) PacketLossPerc() (int, error) {
	var lossPerc C.opus_int32
	res := C.bridge_encoder_get_packet_loss_perc(enc.p, &lossPerc)
	if res != C.OPUS_OK {
		return 0, Error(res)
	}
	return int(lossPerc), nil
}