package json

import (
	"encoding/json"
	"io"
	"sync"

	"git.loafle.net/commons_go/rpc/codec"
	"git.loafle.net/commons_go/rpc/protocol"
)

var null = json.RawMessage([]byte("null"))

type serverMessage struct {
	// JSON-RPC protocol.
	Version     string               `json:"jsonrpc"`
	MessageType protocol.MessageType `json:"messageType"`
	Message     interface{}          `json:"message"`
}

// ----------------------------------------------------------------------------
// Codec
// ----------------------------------------------------------------------------

// NewCustomServerCodec returns a new JSON Codec based on passed encoder selector.
func NewCustomServerCodec(codecSel codec.CodecSelector) protocol.ServerCodec {
	return &ServerCodec{codecSel: codecSel}
}

// NewServerCodec returns a new JSON Codec.
func NewServerCodec() protocol.ServerCodec {
	return NewCustomServerCodec(codec.DefaultCodecSelector)
}

// ServerCodec creates a ServerRequestCodec to process each request.
type ServerCodec struct {
	codecSel codec.CodecSelector
}

// NewRequest returns a ServerRequestCodec.
func (sc *ServerCodec) NewRequest(r io.Reader) (protocol.ServerRequestCodec, error) {
	return newServerRequestCodec(r, sc.codecSel.SelectByReader(r))
}

// WriteNotification send a notification from server to client.
func (sc *ServerCodec) WriteNotification(w io.Writer, method string, args interface{}) error {
	noti := retainServerNotification(method, args)
	defer func() {
		releaseServerNotification(noti)
	}()
	msg := retainServerMessage(protocol.MessageTypeNotification, noti)
	defer func() {
		releaseServerMessage(msg)
	}()
	encoder := json.NewEncoder(sc.codecSel.SelectByWriter(w).Encode(w))
	// Not sure in which case will this happen. But seems harmless.
	if err := encoder.Encode(msg); nil != err {
		return err
	}
	return nil
}

var serverMessagePool sync.Pool

func retainServerMessage(msgType protocol.MessageType, msg interface{}) *serverMessage {
	var sm *serverMessage
	v := serverMessagePool.Get()
	if v == nil {
		sm = &serverMessage{}
	} else {
		sm = v.(*serverMessage)
	}

	sm.Version = Version
	sm.MessageType = msgType
	sm.Message = msg

	return sm
}

func releaseServerMessage(sm *serverMessage) {
	sm.Version = ""
	sm.MessageType = protocol.MessageTypeUnknown
	sm.Message = nil

	serverMessagePool.Put(sm)
}