package rpc

import (
	"fmt"
	"math/rand"
	"reflect"
	"strings"
	"time"

	"src.dualinventive.com/go/dinet/ditime"
)

// CurrentDinetrpc is the current DI-Net RPC version
const CurrentDinetrpc = uint(1)

// DeferredDecoder is a type which is used for deferred decoding
type DeferredDecoder interface {
	Unmarshal(interface{}) error
	IsEmpty() bool
}

// Msg represents a single DI-Net RPC message
type Msg struct {
	Dinetrpc    uint            `json:"dinetrpc" msgpack:"dinetrpc"`
	Async       Async           `json:"async,omitempty" msgpack:"async,omitempty"`
	Rt          bool            `json:"rt,omitempty" msgpack:"rt,omitempty"`
	RtSeqnr     uint16          `json:"rt:seqnr,omitempty" msgpack:"rt:seqnr,omitempty"`
	ID          uint32          `json:"id,omitempty" msgpack:"id,omitempty"`
	DeviceUID   string          `json:"device:uid,omitempty" msgpack:"device:uid,omitempty"`
	ProjectID   uint            `json:"project:id,omitempty" msgpack:"project:id,omitempty"`
	UserID      uint            `json:"user:id,omitempty" msgpack:"user:id,omitempty"`
	Time        ditime.Time     `json:"time" msgpack:"time"`
	TimeRecv    ditime.Time     `json:"time:recv,omitempty" msgpack:"-"`
	Type        MsgType         `json:"-" msgpack:"-"`
	ClassMethod ClassMethod     `json:"-" msgpack:"-"`
	Error       *Error          `json:"error,omitempty" msgpack:"error,omitempty"`
	Result      DeferredDecoder `json:"result,omitempty" msgpack:"result,omitempty"`
	Params      DeferredDecoder `json:"params,omitempty" msgpack:"params,omitempty"`
	rawBytes    []byte
	class       string
	method      string
}

// NewParams allows for any datatype (not conforming the DeferredDecoder interface)
//  to be applied into Params
func NewParams(d interface{}) DeferredDecoder {
	return &deferredDecoder{out: d}
}

// NewResult allows for any datatype (not conforming the DeferredDecoder interface)
//  to be applied into Result
func NewResult(d interface{}) DeferredDecoder {
	return &deferredDecoder{out: d}
}

// CreateReply creates a copy of a message for replies
func (m *Msg) CreateReply() *Msg {
	msg := *m
	msg.Type = MsgTypeReply
	msg.Params = nil
	msg.Error = nil
	msg.Time = 0
	return &msg
}

// msgAlias is a helper struct for serialisation and deserialisation
type msgAlias Msg

// msgMeta is a helper struct for serialisation and deserialisation
type msgMeta struct {
	Req string `json:"req,omitempty" msgpack:"req,omitempty"`
	Rep string `json:"rep,omitempty" msgpack:"rep,omitempty"`
	Pub string `json:"pub,omitempty" msgpack:"pub,omitempty"`
	*msgAlias
}

// UnmarshalFinish is a helper function which must be called after deserialization
func (m *msgMeta) UnmarshalFinish() {
	switch {
	case m.Req != "":
		m.msgAlias.Type = MsgTypeRequest
		m.msgAlias.ClassMethod = ClassMethod(m.Req)
	case m.Rep != "":
		m.msgAlias.Type = MsgTypeReply
		m.msgAlias.ClassMethod = ClassMethod(m.Rep)
	case m.Pub != "":
		m.msgAlias.Type = MsgTypePublish
		m.msgAlias.ClassMethod = ClassMethod(m.Pub)
	}
}

func (m *msgMeta) detachDeferredDecoders() {
	if dec, ok := m.msgAlias.Result.(*deferredDecoder); ok {
		if len(dec.data) == 0 && dec.out == nil {
			m.msgAlias.Result = nil
		}
	}

	if dec, ok := m.msgAlias.Params.(*deferredDecoder); ok {
		if len(dec.data) == 0 && dec.out == nil {
			m.msgAlias.Params = nil
		}
	}
}

// MarshalPrepare is a helper function which must be called before serialization
func (m *msgMeta) MarshalPrepare() {
	m.detachDeferredDecoders()

	if m.msgAlias.Dinetrpc == 0 {
		m.msgAlias.Dinetrpc = CurrentDinetrpc
	}
	if m.msgAlias.Time == 0 {
		m.msgAlias.Time = ditime.Now()
	}

	switch m.msgAlias.Type {
	case MsgTypeRequest:
		m.Req = string(m.msgAlias.ClassMethod)
		if m.msgAlias.ID == 0 {
			m.msgAlias.ID = rand.Uint32()
		}
	case MsgTypeReply:
		m.Rep = string(m.msgAlias.ClassMethod)
	case MsgTypePublish:
		m.Pub = string(m.msgAlias.ClassMethod)
		m.msgAlias.ID = 0
	}
}

func (m *Msg) unmarshalGeneric(data []byte, f genericUnmarshaller) error {
	if m.Params == nil {
		m.Params = &deferredDecoder{}
	}

	if m.Result == nil {
		m.Result = &deferredDecoder{}
	}

	msg := &msgMeta{msgAlias: (*msgAlias)(m)}

	if err := f(data, &msg); err != nil {
		return err
	}

	msg.UnmarshalFinish()

	msg.rawBytes = data

	// When params is null, the Params is set to nil by the decoder
	//  we explicitly don't want that and assure that params is never nil
	if m.Params == nil {
		m.Params = &deferredDecoder{}
	}
	if m.Result == nil {
		m.Result = &deferredDecoder{}
	}
	return nil
}

// Bytes returns the raw message bytes after successful Marshal or Unmarshal
//  it returns an empty slice when the message is incorrect
func (m *Msg) Bytes() []byte {
	return m.rawBytes
}

// IsError checks if the message is an Error reply message
func (m *Msg) IsError() bool {
	if m.Error == nil {
		return false
	}
	return m.Error.Code != Ok && m.Type == MsgTypeReply
}

// SetError sets the ErrorCode in the message
func (m *Msg) SetError(err ErrorCode) *Msg {
	if m.Error == nil {
		m.Error = GetError(err)
		return m
	}
	m.Error = GetError(err, m.Error.Data)
	return m
}

// Valid checks if the RPC message is valid
func (m *Msg) Valid() error {
	// check dinet rpc
	if m.Dinetrpc != CurrentDinetrpc {
		return &InvalidMsgError{ErrMsgInvalidDinetrpc, m}
	}

	if err := m.validClassMethod(); err != nil {
		return err
	}

	// when the error message is set, it must contain an error
	if m.Type == MsgTypeReply && m.Error != nil && m.Error.Code == Ok {
		return &InvalidMsgError{ErrMsgErrorWithOk, m}
	}

	// check time
	if m.Time == 0 {
		return &InvalidMsgError{ErrMsgEmptyTime, m}
	}
	return nil
}

func (m *Msg) validClassMethod() error {
	// device must be empty or valid
	if len(m.DeviceUID) > 0 && !ValidDeviceUID(m.DeviceUID) {
		return &InvalidMsgError{ErrMsgInvalidDeviceUID, m}
	}

	// message must contain either device UID, project ID or user ID
	if !ValidDeviceUID(m.DeviceUID) && !ValidProjectID(m.ProjectID) && !ValidUserID(m.UserID) {
		return &InvalidMsgError{ErrMsgEmptyDeviceProjectUser, m}
	}

	// no class method is invalid
	if len(m.ClassMethod) == 0 {
		return &InvalidMsgError{ErrMsgInvalidClassMethod, m}
	}
	return nil
}

// Class calculates the RPC message class from the ClassMethod property
func (m *Msg) Class() Class {
	if m.class == "" {
		m.splitClassMethod()
	}
	return Class(m.class)
}

// Method calculates the RPC message method from the ClassMethod property
func (m *Msg) Method() string {
	if m.method == "" {
		m.splitClassMethod()
	}
	return m.method
}

// splitClassMethod splits the class:method and caches it in m.method, and m.class
func (m *Msg) splitClassMethod() {
	s := strings.SplitN(string(m.ClassMethod), ":", 2)
	if len(s) > 1 {
		m.class = s[0]
		m.method = s[1]
	}
}

// String from the DI-Net RPC message
func (m *Msg) String() string {
	prefix := m.Time.Format(time.StampMilli)

	if m.DeviceUID != "" {
		prefix += " device:" + m.DeviceUID
	} else if m.ProjectID != 0 {
		prefix += fmt.Sprintf(" project:%d", m.ProjectID)
	}

	if m.UserID != 0 {
		prefix += fmt.Sprintf(" user:%d", m.UserID)
	}

	prefix += fmt.Sprintf(" %s %s", m.Type.String(), m.ClassMethod)

	if m.IsError() {
		return prefix + fmt.Sprintf(" ERROR %v", m.Error.Code)
	}
	if m.Type == MsgTypeRequest {
		return prefix + fmt.Sprintf(" %v", m.Params)
	}
	return prefix + fmt.Sprintf(" %v", m.Result)
}

// Compare checks if the given message is the same. It ignores non relevant data e.g. time, ID
func (m *Msg) Compare(msg2 *Msg) bool {
	return CompareMsg(m, msg2)
}

// CompareMsg checks if the two messages are the same. It ignores non relevant data e.g. time, ID
func CompareMsg(msg1 *Msg, msg2 *Msg) bool {
	if !CompareMsgHeader(msg1, msg2) {
		return false
	}
	if !CompareError(msg1.Error, msg2.Error) {
		return false
	}
	if !reflect.DeepEqual(msg1.Result, msg2.Result) {
		return false
	}
	if !reflect.DeepEqual(msg1.Params, msg2.Params) {
		return false
	}
	return true
}

// CompareMsgHeader checks if the two message headers are the same. It ignores non relevant data e.g. time, ID
func CompareMsgHeader(msg1 *Msg, msg2 *Msg) bool {
	if msg1.Dinetrpc != msg2.Dinetrpc {
		return false
	}
	if msg1.Async != msg2.Async {
		return false
	}
	if msg1.DeviceUID != msg2.DeviceUID {
		return false
	}
	if msg1.ProjectID != msg2.ProjectID {
		return false
	}
	if msg1.UserID != msg2.UserID {
		return false
	}
	if msg1.Type != msg2.Type {
		return false
	}
	if msg1.ClassMethod != msg2.ClassMethod {
		return false
	}
	return true
}