package protocol

import (
	"encoding/json"
	"fmt"
)

type typePeek struct {
	V    int    `json:"v"`
	Type string `json:"type"`
}

// Decode 解析一帧 MQTT/应用 JSON，返回具体类型。
func Decode(data []byte) (any, error) {
	var peek typePeek
	if err := Unmarshal(data, &peek); err != nil {
		return nil, badRequest("invalid json")
	}
	if peek.V != 0 && peek.V != Version {
		return nil, badRequest("unsupported version")
	}
	if peek.Type == "" {
		return nil, badRequest("missing type")
	}

	var out any
	switch peek.Type {
	case TypeHello:
		out = &Hello{}
	case TypeResp:
		out = &Resp{}
	case TypeSend:
		out = &Send{}
	case TypeMsg:
		out = &Msg{}
	case TypeAck:
		out = &Ack{}
	case TypeRecall:
		out = &Recall{}
	case TypeStatus:
		out = &Status{}
	case TypeReceipt:
		out = &Receipt{}
	case TypeReceiptAck:
		out = &ReceiptAck{}
	case TypeRevoked:
		out = &Revoked{}
	case TypePresenceGet:
		out = &PresenceGet{}
	case TypeDirectoryList:
		out = &DirectoryList{}
	case TypePresenceWatch:
		out = &PresenceWatch{}
	case TypePresence:
		out = &Presence{}
	case TypeUnlock:
		out = &Unlock{}
	case TypeSelfGet:
		out = &SelfGet{}
	case TypeSelfUpdate:
		out = &SelfUpdate{}
	case TypeSelfTalkPassword:
		out = &SelfTalkPassword{}
	case TypeSelfLoginPassword:
		out = &SelfLoginPassword{}
	case TypeSelfLogout:
		out = &SelfLogout{}
	case TypeGroupCreate:
		out = &GroupCreate{}
	case TypeGroupAdd:
		out = &GroupAdd{}
	case TypeGroupRemove:
		out = &GroupRemove{}
	case TypeGroupLeave:
		out = &GroupLeave{}
	case TypeGroupTransfer:
		out = &GroupTransfer{}
	case TypeGroupRename:
		out = &GroupRename{}
	case TypeGroupDissolve:
		out = &GroupDissolve{}
	case TypeGroupList:
		out = &GroupList{}
	case TypeGroupGet:
		out = &GroupGet{}
	case TypeGroupEvent:
		out = &GroupEvent{}
	case TypeFatal:
		out = &Fatal{}
	default:
		return nil, badRequest(fmt.Sprintf("unknown type %q", peek.Type))
	}
	if err := Unmarshal(data, out); err != nil {
		return nil, badRequest("invalid json for type")
	}
	return out, nil
}

// DecodeRegister 解析注册 HTTP 请求体。
func DecodeRegister(data []byte) (*RegisterRequest, error) {
	var req RegisterRequest
	if err := Unmarshal(data, &req); err != nil {
		return nil, badRequest("invalid json")
	}
	return &req, nil
}

// MustRaw 将值编码为 json.RawMessage（用于填 Resp.Data）。
func MustRaw(v any) json.RawMessage {
	b, err := Marshal(v)
	if err != nil {
		panic(err)
	}
	return b
}