package mq_coder

import (
	"bytes"
	"io"

	"git.hpds.cc/Component/mq_coder/spec"
)

// Encoder is the tool for creating a packet easily
type Encoder struct {
	tag           spec.T
	len           *spec.L
	valReader     io.Reader
	valReaderSize int
	nodes         map[int]Packet
	state         int
	size          int32 // size of value
	isStreamMode  bool
	valBuf        *bytes.Buffer
	done          bool
	seqId         int
	isNodeMode    bool
}

// SetSeqId set sequenceId of a  packet, if this packet contains other
// packets, isNode should set to true
func (b *Encoder) SetSeqId(seqId int, isNode bool) {
	// init
	b.valBuf = new(bytes.Buffer)
	b.nodes = make(map[int]Packet)
	// set seqId
	b.seqId = seqId
	b.isNodeMode = isNode
}

// SetBytesV set bytes type as V
func (b *Encoder) SetBytesV(buf []byte) {
	b.size += int32(len(buf))
	b.valBuf.Write(buf)
	b.isStreamMode = false
	b.state |= 0x04
}

// SetReaderV set io.Reader type as V
func (b *Encoder) SetReaderV(r io.Reader, size int) {
	b.isStreamMode = true
	b.valReader = r
	b.state |= 0x04
	b.size += int32(size)
	b.valReaderSize = size
}

// AddPacket add a Packet child to this packet, this packet must be NodeMode
func (b *Encoder) AddPacket(child Packet) error {
	// only packet is in node mode can add other packets
	if !b.isNodeMode {
		return errNotNodeMode
	}

	if b.done {
		return errInvalidAdding
	}
	b.nodes[child.SeqId()] = child
	buf := child.Bytes()
	b.SetBytesV(buf)
	return nil
}

// AddStreamPacket will put a StreamPacket in chunked mode to current packet.
func (b *Encoder) AddStreamPacket(child Packet) (err error) {
	// if this packet is in stream mode, can not add any packets
	if b.done {
		return errInvalidAdding
	}

	// only accept packet in stream mode
	if !child.IsStreamMode() {
		return errNonStreamPacket
	}

	// set the valReader of this packet to the child's
	b.valReader = child.VReader()

	// valReaderSize will be the same as child's
	b.valReaderSize = child.VSize()
	// add this child packet
	b.nodes[child.SeqId()] = child
	// add the size of child's V to L of this packet
	b.size += int32(child.Size())
	// put the bytes of child to valBuf
	buf := child.Bytes()
	b.valBuf.Write(buf)
	// update state
	b.state |= 0x04
	b.isStreamMode = true
	b.done = true
	return nil
}

// Packet return a Packet instance.
func (b *Encoder) Packet() (Packet, error) {
	err := b.generateT()
	if err != nil {
		return nil, err
	}

	err = b.generateL()
	if err != nil {
		return nil, err
	}

	if b.state != 0x07 {
		return nil, errBuildIncomplete
	}

	if b.isStreamMode {
		return &StreamPacket{
			t:         b.tag,
			l:         *b.len,
			vr:        b.valReader,
			vBuf:      b.valBuf.Bytes(),
			chunkMode: true,
			chunkSize: b.valReaderSize,
		}, err
	}

	// not streaming mode
	return &StreamPacket{
		t:         b.tag,
		l:         *b.len,
		vBuf:      b.valBuf.Bytes(),
		chunkMode: false,
	}, err
}

// will generate T of a TLV.
func (b *Encoder) generateT() error {
	t, err := spec.NewT(b.seqId)
	t.SetNodeMode(b.isNodeMode)
	if err != nil {
		return err
	}
	b.tag = t
	b.state |= 0x01
	return nil
}

// will generate L of a TLV.
func (b *Encoder) generateL() error {
	l, err := spec.NewL(int(b.size))
	if err != nil {
		return err
	}
	b.len = &l
	b.state |= 0x02
	return nil
}