package srpc

import (
	"bytes"
	"errors"
	"io"
	"net"
	"sync"
)

type RPCMsgType uint8

const (
	RPC_REQUEST   RPCMsgType = 0
	RPC_RESPONSE  RPCMsgType = 1
	RPC_HEARTBEAT RPCMsgType = 2
	RPC_CLOSE     RPCMsgType = 3
)

const RPCHeaderSize = 13

type RPCHeader struct {
	RPCType RPCMsgType
	Size    uint64
}

type RPCHeartbeat struct {
	OK bool
}

type RPCClose struct {
	OK bool
}

type RPCCall struct {
	Header  RPCHeader
	Payload interface{}
}

type IRPCConn interface {
	Send(payload interface{}) error
	Receive() (*RPCCall, error)
	Close()
}

type NetConn struct {
	sync.RWMutex
	conn net.Conn
	ed   IEncoderDecoder

	// interface
	IRPCConn
}

func (tc *NetConn) Send(payload interface{}) (err error) {
	var header RPCHeader
	var hb, b bytes.Buffer

	switch payload.(type) {
	case *RPCHeartbeat:
		header.RPCType = RPC_HEARTBEAT
		break
	case *RPCClose:
		header.RPCType = RPC_CLOSE
		break
	case *RPCRequest:
		header.RPCType = RPC_REQUEST
		break
	case *RPCResponse:
		header.RPCType = RPC_RESPONSE
		break
	default:
		return errors.New("srpc - Invalid RPC message type")
	}

	enc := tc.ed.NewEncoder(&b)
	if err = enc.Encode(payload); err != nil {
		return errors.New("srpc - Error: '" + err.Error() + "'")
	}
	header.Size = uint64(len(b.Bytes()))

	enc = tc.ed.NewEncoder(&hb)
	if err = enc.Encode(header); err != nil {
		return errors.New("srpc - Error: '" + err.Error() + "'")
	}

	data := append([]byte{}, hb.Bytes()...)
	data = append(data, b.Bytes()...)

	tc.Lock()
	defer tc.Unlock()

	if n, err := tc.conn.Write(data); err != nil || n != len(data) {
		return errors.New("srpc - Error writing message")
	}

	return nil
}

func (tc *NetConn) Receive() (ret *RPCCall, err error) {
	var header RPCHeader
	var payload interface{}
	hb := make([]byte, RPCHeaderSize)

	tc.Lock()
	defer tc.Unlock()

	if n, err := tc.conn.Read(hb); err != nil || n != RPCHeaderSize {
		if err != nil {
			if err == io.EOF {
				header.RPCType = RPC_CLOSE
				ret = &RPCCall{header, new(RPCClose)}
				return ret, nil
			}
		}
		return nil, errors.New("srpc - Error receiving message")
	}

	dec := tc.ed.NewDecoder(bytes.NewReader(hb))
	if err = dec.Decode(&header); err != nil {
		return nil, errors.New("srpc - Error: '" + err.Error() + "'")
	}

	switch header.RPCType {
	case RPC_HEARTBEAT:
		payload = new(RPCHeartbeat)
		break
	case RPC_CLOSE:
		payload = new(RPCClose)
		break
	case RPC_REQUEST:
		payload = new(RPCRequest)
		break
	case RPC_RESPONSE:
		payload = new(RPCResponse)
		break
	default:
		return nil, errors.New("srpc - Invalid RPC message type")
	}

	b := make([]byte, header.Size)
	if n, err := tc.conn.Read(b); err != nil || n != int(header.Size) {
		return nil, errors.New("srpc - Error receiving message")
	}

	dec = tc.ed.NewDecoder(bytes.NewReader(b))
	if err = dec.Decode(payload); err != nil {
		return nil, errors.New("srpc - Error: '" + err.Error() + "'")
	}

	ret = new(RPCCall)
	ret.Header = header
	ret.Payload = payload

	return ret, nil
}

func (tc *NetConn) Close() {
	tc.conn.Close()
}

func NewNetConn(conn net.Conn, ed IEncoderDecoder) *NetConn {
	ret := &NetConn{}
	ret.conn = conn
	ret.ed = ed

	return ret
}