package inbound

import (
	"context"
	"encoding/base64"
	"fmt"
	cmpp "github.com/bigwhite/gocmpp"
	"log"
	"net"
	"strings"
	"sync"
	"time"
)

type authRequest struct {
	Account    string `json:"account"`
	AuthSource string `json:"authSource"`
	Timestamp  uint32 `json:"timestamp"`
	RemoteIP   string `json:"remoteIp,omitempty"`
}

type authResponse struct {
	PasswordCipher string `json:"passwordCipher"`
	ApplicationID  string `json:"applicationId"`
	TenantID       string `json:"tenantId"`
	Account        string `json:"account"`
	EnterpriseCode string `json:"enterpriseCode"`
	MaxConnections int    `json:"maxConnections"`
}

func (s Server) handleLogin(response *cmpp.Response, packet *cmpp.Packet, logger *log.Logger) (bool, error) {
	req, ok := packet.Packer.(*cmpp.CmppConnReqPkt)
	if !ok {
		return true, nil
	}
	account := strings.TrimRight(req.SrcAddr, "\x00")
	if account == "" {
		setInboundConnectResponse(response.Packer, cmpp.ErrnoConnInvalidSrcAddr, req.AuthSrc, "", req.Version)
		return false, cmpp.ConnRspStatusErrMap[cmpp.ErrnoConnInvalidSrcAddr]
	}
	if req.Version != cmpp.V20 && req.Version != cmpp.V21 && req.Version != cmpp.V30 {
		setInboundConnectResponse(response.Packer, cmpp.ErrnoConnVerTooHigh, req.AuthSrc, "", cmpp.V30)
		return false, cmpp.ConnRspStatusErrMap[cmpp.ErrnoConnVerTooHigh]
	}
	auth, err := s.authenticate(packet.Conn.Conn.RemoteAddr(), account, req.AuthSrc, req.Timestamp)
	if err != nil {
		logger.Printf("cmpp inbound auth failed account=%s remote=%s err=%v", account, packet.Conn.Conn.RemoteAddr(), err)
		setInboundConnectResponse(response.Packer, cmpp.ErrnoConnAuthFailed, req.AuthSrc, "", req.Version)
		return false, cmpp.ConnRspStatusErrMap[cmpp.ErrnoConnAuthFailed]
	}
	now := time.Now().UTC()
	session := &downstreamSession{
		account:        strings.TrimSpace(defaultString(auth.Account, account)),
		tenantID:       strings.TrimSpace(auth.TenantID),
		applicationID:  strings.TrimSpace(auth.ApplicationID),
		enterpriseCode: strings.TrimSpace(auth.EnterpriseCode),
		protocol:       cmppVersionName(req.Version),
		srcID:          strings.TrimSpace(auth.Account),
		remoteIP:       remoteIP(packet.Conn.Conn.RemoteAddr()),
		connectedAt:    now,
		connectionID:   fmt.Sprintf("%s-%d", s.gatewayInstanceID(), now.UnixNano()),
		conn:           packet.Conn,
		mu:             &sync.Mutex{},
		presence:       s.PresenceStore,
		instanceID:     s.gatewayInstanceID(),
		report:         s.reportConnection,
		deliveryReport: s.reportDownstreamDelivery,
		protocolLog:    s.emitProtocolLog,
	}
	if !rememberAccount(session, auth.MaxConnections) {
		logger.Printf("cmpp inbound auth failed account=%s remote=%s err=connection limit exceeded max=%d", account, packet.Conn.Conn.RemoteAddr(), auth.MaxConnections)
		setInboundConnectResponse(response.Packer, cmpp.ErrnoConnOthers, req.AuthSrc, "", req.Version)
		return false, cmpp.ConnRspStatusErrMap[cmpp.ErrnoConnOthers]
	}
	setInboundConnectResponse(response.Packer, 0, req.AuthSrc, auth.PasswordCipher, req.Version)
	go s.reportConnectionOrDisconnect(session, "connected", "")
	response.AfterSend = func(sendErr error) {
		if sendErr == nil {
			go s.flushPending(defaultString(auth.Account, account), logger)
		}
	}
	logger.Printf(
		"cmpp inbound event=login_accepted protocol=%s requested_version=0x%02x response_version=0x%02x account=%s remote=%s",
		cmppVersionName(req.Version), uint8(req.Version), uint8(req.Version), account, packet.Conn.Conn.RemoteAddr(),
	)
	return false, nil
}

func setInboundConnectResponse(packet any, status uint8, authSource string, secret string, version cmpp.Type) {
	switch resp := packet.(type) {
	case *cmpp.Cmpp2ConnRspPkt:
		resp.Status = status
		resp.AuthSrc = authSource
		resp.Secret = secret
		resp.Version = version
	case *cmpp.Cmpp3ConnRspPkt:
		resp.Status = uint32(status)
		resp.AuthSrc = authSource
		resp.Secret = secret
		resp.Version = version
	}
}

func cmppVersionName(version cmpp.Type) string {
	switch version {
	case cmpp.V20:
		return "cmpp20"
	case cmpp.V21:
		return "cmpp21"
	case cmpp.V30:
		return "cmpp30"
	default:
		return fmt.Sprintf("unknown_0x%02x", uint8(version))
	}
}

func (s Server) authenticate(remote net.Addr, account string, authSource string, timestamp uint32) (authResponse, error) {
	payload := authRequest{
		Account:    account,
		AuthSource: base64.StdEncoding.EncodeToString([]byte(authSource)),
		Timestamp:  timestamp,
		RemoteIP:   remoteIP(remote),
	}
	var result authResponse
	err := s.post(context.Background(), "/gateway/events/inbound/authenticate", payload, &result)
	return result, err
}