package notify

import (
	"context"
	"encoding/binary"
	"errors"
	"net"
	"sync"
	"time"
)

var (
	errBulkFastPayloadInvalid = errors.New("invalid bulk fast payload")
)

var bulkFastFrameScratchPool sync.Pool

const (
	bulkFastPayloadMagic         = "NBF1"
	bulkFastPayloadVersion       = 1
	bulkFastPayloadTypeData      = 1
	bulkFastPayloadTypeClose     = 2
	bulkFastPayloadTypeReset     = 3
	bulkFastPayloadTypeRelease   = 4
	bulkFastPayloadHeaderLen     = 28
	bulkFastPayloadFlagFullClose = 1 << 0
)

type bulkFastFrame struct {
	Type    uint8
	Flags   uint8
	DataID  uint64
	Seq     uint64
	Payload []byte
}

type bulkFastDataFrame = bulkFastFrame

func encodeBulkFastFrameHeader(dst []byte, frameType uint8, flags uint8, dataID uint64, seq uint64, payloadLen int) error {
	if dataID == 0 {
		return errBulkDataIDEmpty
	}
	if len(dst) < bulkFastPayloadHeaderLen {
		return errBulkFastPayloadInvalid
	}
	copy(dst[:4], bulkFastPayloadMagic)
	dst[4] = bulkFastPayloadVersion
	dst[5] = frameType
	dst[6] = flags
	dst[7] = 0
	binary.BigEndian.PutUint64(dst[8:16], dataID)
	binary.BigEndian.PutUint64(dst[16:24], seq)
	binary.BigEndian.PutUint32(dst[24:28], uint32(payloadLen))
	return nil
}

func encodeBulkFastDataFrameHeader(dst []byte, dataID uint64, seq uint64, payloadLen int) error {
	return encodeBulkFastFrameHeader(dst, bulkFastPayloadTypeData, 0, dataID, seq, payloadLen)
}

func encodeBulkFastDataFrame(dataID uint64, seq uint64, payload []byte) ([]byte, error) {
	frame := make([]byte, bulkFastPayloadHeaderLen+len(payload))
	if err := encodeBulkFastDataFrameHeader(frame, dataID, seq, len(payload)); err != nil {
		return nil, err
	}
	copy(frame[bulkFastPayloadHeaderLen:], payload)
	return frame, nil
}

func encodeBulkFastControlFrame(frameType uint8, flags uint8, dataID uint64, seq uint64, payload []byte) ([]byte, error) {
	frame := make([]byte, bulkFastPayloadHeaderLen+len(payload))
	if err := encodeBulkFastFrameHeader(frame, frameType, flags, dataID, seq, len(payload)); err != nil {
		return nil, err
	}
	copy(frame[bulkFastPayloadHeaderLen:], payload)
	return frame, nil
}

func decodeBulkFastFrame(payload []byte) (bulkFastFrame, bool, error) {
	if len(payload) < 4 || string(payload[:4]) != bulkFastPayloadMagic {
		return bulkFastFrame{}, false, nil
	}
	if len(payload) < bulkFastPayloadHeaderLen {
		return bulkFastFrame{}, true, errBulkFastPayloadInvalid
	}
	if payload[4] != bulkFastPayloadVersion {
		return bulkFastFrame{}, true, errBulkFastPayloadInvalid
	}
	switch payload[5] {
	case bulkFastPayloadTypeData, bulkFastPayloadTypeClose, bulkFastPayloadTypeReset, bulkFastPayloadTypeRelease:
	default:
		return bulkFastFrame{}, true, errBulkFastPayloadInvalid
	}
	dataLen := int(binary.BigEndian.Uint32(payload[24:28]))
	if dataLen < 0 || len(payload) != bulkFastPayloadHeaderLen+dataLen {
		return bulkFastFrame{}, true, errBulkFastPayloadInvalid
	}
	dataID := binary.BigEndian.Uint64(payload[8:16])
	if dataID == 0 {
		return bulkFastFrame{}, true, errBulkFastPayloadInvalid
	}
	return bulkFastFrame{
		Type:    payload[5],
		Flags:   payload[6],
		DataID:  dataID,
		Seq:     binary.BigEndian.Uint64(payload[16:24]),
		Payload: payload[bulkFastPayloadHeaderLen:],
	}, true, nil
}

func decodeBulkFastDataFrame(payload []byte) (bulkFastDataFrame, bool, error) {
	frame, matched, err := decodeBulkFastFrame(payload)
	if !matched || err != nil {
		return frame, matched, err
	}
	if frame.Type != bulkFastPayloadTypeData {
		return bulkFastDataFrame{}, false, nil
	}
	return frame, true, nil
}

func (c *ClientCommon) encodeFastBulkDataPayload(dataID uint64, seq uint64, chunk []byte) ([]byte, error) {
	return c.encodeBulkFastPayload(bulkFastFrame{
		Type:    bulkFastPayloadTypeData,
		DataID:  dataID,
		Seq:     seq,
		Payload: chunk,
	})
}

func (c *ClientCommon) encodeBulkFastPayload(frame bulkFastFrame) ([]byte, error) {
	if c == nil {
		return nil, errBulkClientNil
	}
	if c.fastPlainEncode != nil {
		return encodeBulkFastFramePayloadFast(c.fastPlainEncode, c.SecretKey, frame)
	}
	plain, err := encodeBulkFastFramePayload(frame)
	if err != nil {
		return nil, err
	}
	return c.encryptTransportPayload(plain)
}

func (c *ClientCommon) encodeBulkFastBatchPayload(frames []bulkFastFrame) ([]byte, error) {
	if c == nil {
		return nil, errBulkClientNil
	}
	if c.fastPlainEncode != nil {
		return encodeBulkFastBatchPayloadFast(c.fastPlainEncode, c.SecretKey, frames)
	}
	plain, err := encodeBulkFastBatchPlain(frames)
	if err != nil {
		return nil, err
	}
	return c.encryptTransportPayload(plain)
}

func (c *ClientCommon) encodeBulkFastPayloadPooled(frame bulkFastFrame) ([]byte, func(), error) {
	if c == nil {
		return nil, nil, errBulkClientNil
	}
	if runtime := c.modernPSKRuntime; runtime != nil {
		return encodeBulkFastFramePayloadPooled(runtime, frame)
	}
	if c.fastPlainEncode != nil {
		payload, err := encodeBulkFastFramePayloadFast(c.fastPlainEncode, c.SecretKey, frame)
		return payload, nil, err
	}
	plain, err := encodeBulkFastFramePayload(frame)
	if err != nil {
		return nil, nil, err
	}
	payload, err := c.encryptTransportPayload(plain)
	return payload, nil, err
}

func (c *ClientCommon) encodeBulkFastBatchPayloadPooled(frames []bulkFastFrame) ([]byte, func(), error) {
	if c == nil {
		return nil, nil, errBulkClientNil
	}
	if runtime := c.modernPSKRuntime; runtime != nil {
		return encodeBulkFastBatchPayloadPooled(runtime, frames)
	}
	if c.fastPlainEncode != nil {
		payload, err := encodeBulkFastBatchPayloadFast(c.fastPlainEncode, c.SecretKey, frames)
		return payload, nil, err
	}
	plain, err := encodeBulkFastBatchPlain(frames)
	if err != nil {
		return nil, nil, err
	}
	payload, err := c.encryptTransportPayload(plain)
	return payload, nil, err
}

func (c *ClientCommon) sendFastBulkData(ctx context.Context, dataID uint64, seq uint64, chunk []byte, fastPathVersion uint8) error {
	binding := c.clientTransportBindingSnapshot()
	if binding == nil {
		return net.ErrClosed
	}
	if sender := binding.clientBulkBatchSenderSnapshot(c); sender != nil {
		return sender.submitData(ctx, dataID, seq, fastPathVersion, chunk)
	}
	payload, err := c.encodeFastBulkDataPayload(dataID, seq, chunk)
	if err != nil {
		return err
	}
	return c.writePayloadToTransport(payload)
}

func (c *ClientCommon) sendFastBulkWrite(ctx context.Context, dataID uint64, startSeq uint64, chunkSize int, fastPathVersion uint8, payload []byte, payloadOwned bool) (int, error) {
	if len(payload) == 0 {
		return 0, nil
	}
	binding := c.clientTransportBindingSnapshot()
	if binding == nil {
		return 0, net.ErrClosed
	}
	if sender := binding.clientBulkBatchSenderSnapshot(c); sender != nil {
		return sender.submitWrite(ctx, dataID, startSeq, fastPathVersion, payload, chunkSize, payloadOwned)
	}
	if chunkSize <= 0 {
		chunkSize = defaultBulkChunkSize
	}
	written := 0
	seq := startSeq
	for written < len(payload) {
		end := written + chunkSize
		if end > len(payload) {
			end = len(payload)
		}
		if err := c.sendFastBulkData(ctx, dataID, seq, payload[written:end], fastPathVersion); err != nil {
			return written, err
		}
		seq++
		written = end
	}
	return written, nil
}

func (c *ClientCommon) sendFastBulkControl(ctx context.Context, frameType uint8, flags uint8, dataID uint64, seq uint64, fastPathVersion uint8, payload []byte) error {
	frame := bulkFastFrame{
		Type:    frameType,
		Flags:   flags,
		DataID:  dataID,
		Seq:     seq,
		Payload: payload,
	}
	binding := c.clientTransportBindingSnapshot()
	if binding == nil {
		return net.ErrClosed
	}
	if sender := binding.clientBulkBatchSenderSnapshot(c); sender != nil {
		return sender.submitControl(ctx, frameType, flags, dataID, seq, fastPathVersion, payload)
	}
	encoded, err := c.encodeBulkFastPayload(frame)
	if err != nil {
		return err
	}
	return c.writePayloadToTransport(encoded)
}

func (c *ClientCommon) encodeBulkFastControlPayload(frameType uint8, flags uint8, dataID uint64, seq uint64, payload []byte) ([]byte, error) {
	plain, err := encodeBulkFastControlFrame(frameType, flags, dataID, seq, payload)
	if err != nil {
		return nil, err
	}
	return c.encryptTransportPayload(plain)
}

func (s *ServerCommon) encodeFastBulkDataPayloadLogical(logical *LogicalConn, dataID uint64, seq uint64, chunk []byte) ([]byte, error) {
	return s.encodeBulkFastPayloadLogical(logical, bulkFastFrame{
		Type:    bulkFastPayloadTypeData,
		DataID:  dataID,
		Seq:     seq,
		Payload: chunk,
	})
}

func (s *ServerCommon) encodeBulkFastPayloadLogical(logical *LogicalConn, frame bulkFastFrame) ([]byte, error) {
	if logical == nil {
		return nil, errTransportDetached
	}
	if fastPlainEncode := logical.fastPlainEncodeSnapshot(); fastPlainEncode != nil {
		return encodeBulkFastFramePayloadFast(fastPlainEncode, logical.secretKeySnapshot(), frame)
	}
	plain, err := encodeBulkFastFramePayload(frame)
	if err != nil {
		return nil, err
	}
	return s.encryptTransportPayloadLogical(logical, plain)
}

func (s *ServerCommon) encodeBulkFastBatchPayloadLogical(logical *LogicalConn, frames []bulkFastFrame) ([]byte, error) {
	if logical == nil {
		return nil, errTransportDetached
	}
	if fastPlainEncode := logical.fastPlainEncodeSnapshot(); fastPlainEncode != nil {
		return encodeBulkFastBatchPayloadFast(fastPlainEncode, logical.secretKeySnapshot(), frames)
	}
	plain, err := encodeBulkFastBatchPlain(frames)
	if err != nil {
		return nil, err
	}
	return s.encryptTransportPayloadLogical(logical, plain)
}

func (s *ServerCommon) encodeBulkFastPayloadLogicalPooled(logical *LogicalConn, frame bulkFastFrame) ([]byte, func(), error) {
	if logical == nil {
		return nil, nil, errTransportDetached
	}
	if runtime := logical.modernPSKRuntimeSnapshot(); runtime != nil {
		return encodeBulkFastFramePayloadPooled(runtime, frame)
	}
	if fastPlainEncode := logical.fastPlainEncodeSnapshot(); fastPlainEncode != nil {
		payload, err := encodeBulkFastFramePayloadFast(fastPlainEncode, logical.secretKeySnapshot(), frame)
		return payload, nil, err
	}
	plain, err := encodeBulkFastFramePayload(frame)
	if err != nil {
		return nil, nil, err
	}
	payload, err := s.encryptTransportPayloadLogical(logical, plain)
	return payload, nil, err
}

func (s *ServerCommon) encodeBulkFastBatchPayloadLogicalPooled(logical *LogicalConn, frames []bulkFastFrame) ([]byte, func(), error) {
	if logical == nil {
		return nil, nil, errTransportDetached
	}
	if runtime := logical.modernPSKRuntimeSnapshot(); runtime != nil {
		return encodeBulkFastBatchPayloadPooled(runtime, frames)
	}
	if fastPlainEncode := logical.fastPlainEncodeSnapshot(); fastPlainEncode != nil {
		payload, err := encodeBulkFastBatchPayloadFast(fastPlainEncode, logical.secretKeySnapshot(), frames)
		return payload, nil, err
	}
	plain, err := encodeBulkFastBatchPlain(frames)
	if err != nil {
		return nil, nil, err
	}
	payload, err := s.encryptTransportPayloadLogical(logical, plain)
	return payload, nil, err
}

func (s *ServerCommon) sendFastBulkDataTransport(ctx context.Context, logical *LogicalConn, transport *TransportConn, dataID uint64, seq uint64, chunk []byte, fastPathVersion uint8) error {
	if err := s.ensureServerTransportSendReady(transport); err != nil {
		return err
	}
	if logical == nil && transport != nil {
		logical = transport.logicalConnSnapshot()
	}
	if logical == nil {
		return errTransportDetached
	}
	if binding := logical.transportBindingSnapshot(); binding != nil {
		if binding.queueSnapshot() != nil {
			if sender := binding.serverBulkBatchSenderSnapshot(logical); sender != nil {
				return sender.submitData(ctx, dataID, seq, fastPathVersion, chunk)
			}
		}
	}
	payload, err := s.encodeFastBulkDataPayloadLogical(logical, dataID, seq, chunk)
	if err != nil {
		return err
	}
	return s.writeEnvelopePayload(logical, transport, nil, payload)
}

func (s *ServerCommon) sendFastBulkWriteTransport(ctx context.Context, logical *LogicalConn, transport *TransportConn, dataID uint64, startSeq uint64, chunkSize int, fastPathVersion uint8, payload []byte, payloadOwned bool) (int, error) {
	if len(payload) == 0 {
		return 0, nil
	}
	if err := s.ensureServerTransportSendReady(transport); err != nil {
		return 0, err
	}
	if logical == nil && transport != nil {
		logical = transport.logicalConnSnapshot()
	}
	if logical == nil {
		return 0, errTransportDetached
	}
	if binding := logical.transportBindingSnapshot(); binding != nil {
		if binding.queueSnapshot() != nil {
			if sender := binding.serverBulkBatchSenderSnapshot(logical); sender != nil {
				return sender.submitWrite(ctx, dataID, startSeq, fastPathVersion, payload, chunkSize, payloadOwned)
			}
		}
	}
	if chunkSize <= 0 {
		chunkSize = defaultBulkChunkSize
	}
	written := 0
	seq := startSeq
	for written < len(payload) {
		end := written + chunkSize
		if end > len(payload) {
			end = len(payload)
		}
		if err := s.sendFastBulkDataTransport(ctx, logical, transport, dataID, seq, payload[written:end], fastPathVersion); err != nil {
			return written, err
		}
		seq++
		written = end
	}
	return written, nil
}

func (s *ServerCommon) sendFastBulkControlTransport(ctx context.Context, logical *LogicalConn, transport *TransportConn, frameType uint8, flags uint8, dataID uint64, seq uint64, fastPathVersion uint8, payload []byte) error {
	if err := s.ensureServerTransportSendReady(transport); err != nil {
		return err
	}
	if logical == nil && transport != nil {
		logical = transport.logicalConnSnapshot()
	}
	if logical == nil {
		return errTransportDetached
	}
	if binding := logical.transportBindingSnapshot(); binding != nil {
		if binding.queueSnapshot() != nil {
			if sender := binding.serverBulkBatchSenderSnapshot(logical); sender != nil {
				return sender.submitControl(ctx, frameType, flags, dataID, seq, fastPathVersion, payload)
			}
		}
	}
	encoded, err := s.encodeBulkFastPayloadLogical(logical, bulkFastFrame{
		Type:    frameType,
		Flags:   flags,
		DataID:  dataID,
		Seq:     seq,
		Payload: payload,
	})
	if err != nil {
		return err
	}
	return s.writeEnvelopePayload(logical, transport, nil, encoded)
}

func (s *ServerCommon) encodeBulkFastControlPayloadLogical(logical *LogicalConn, frameType uint8, flags uint8, dataID uint64, seq uint64, payload []byte) ([]byte, error) {
	plain, err := encodeBulkFastControlFrame(frameType, flags, dataID, seq, payload)
	if err != nil {
		return nil, err
	}
	return s.encryptTransportPayloadLogical(logical, plain)
}

func getBulkFastFrameScratch(payloadLen int) []byte {
	need := bulkFastPayloadHeaderLen + payloadLen
	if buf, ok := bulkFastFrameScratchPool.Get().([]byte); ok && cap(buf) >= need {
		return buf[:need]
	}
	return make([]byte, need)
}

func putBulkFastFrameScratch(buf []byte) {
	if cap(buf) == 0 || cap(buf) > 4*1024*1024 {
		return
	}
	bulkFastFrameScratchPool.Put(buf[:0])
}

func (c *ClientCommon) dispatchInboundTransportPayload(payload []byte, now time.Time) error {
	plain, err := c.decryptTransportPayload(payload)
	if err != nil {
		return err
	}
	if frames, matched, err := decodeBulkFastFrames(plain); matched {
		if err != nil {
			return err
		}
		for _, frame := range frames {
			c.dispatchFastBulkFrame(frame)
		}
		return nil
	}
	if frames, matched, err := decodeStreamFastDataFrames(plain); matched {
		if err != nil {
			return err
		}
		for _, frame := range frames {
			c.dispatchFastStreamData(frame)
		}
		return nil
	}
	env, err := c.decodeEnvelopePlain(plain)
	if err != nil {
		return err
	}
	c.dispatchEnvelope(env, now)
	return nil
}

func (s *ServerCommon) dispatchInboundTransportPayload(logical *LogicalConn, transport *TransportConn, conn net.Conn, payload []byte, now time.Time) error {
	if logical == nil && transport != nil {
		logical = transport.logicalConnSnapshot()
	}
	if logical == nil {
		return errTransportDetached
	}
	plain, err := s.decryptTransportPayloadLogical(logical, payload)
	if err != nil {
		return err
	}
	if frames, matched, err := decodeBulkFastFrames(plain); matched {
		if err != nil {
			return err
		}
		for _, frame := range frames {
			s.dispatchFastBulkFrame(logical, transport, conn, frame)
		}
		return nil
	}
	if frames, matched, err := decodeStreamFastDataFrames(plain); matched {
		if err != nil {
			return err
		}
		for _, frame := range frames {
			s.dispatchFastStreamData(logical, transport, conn, frame)
		}
		return nil
	}
	env, err := s.decodeEnvelopePlain(plain)
	if err != nil {
		return err
	}
	s.dispatchEnvelope(logical, transport, conn, env, now)
	return nil
}