package hotline

import (
	"encoding/binary"
	"golang.org/x/crypto/bcrypt"
	"math/big"
	"net"
)

type byClientID []*ClientConn

func (s byClientID) Len() int {
	return len(s)
}

func (s byClientID) Swap(i, j int) {
	s[i], s[j] = s[j], s[i]
}

func (s byClientID) Less(i, j int) bool {
	return s[i].uint16ID() < s[j].uint16ID()
}

// ClientConn represents a client connected to a Server
type ClientConn struct {
	Connection net.Conn
	ID         *[]byte
	Icon       *[]byte
	Flags      *[]byte
	UserName   []byte
	Account    *Account
	IdleTime   int
	Server     *Server
	Version    *[]byte
	Idle       bool
	AutoReply  []byte
	Transfers  map[int][]*FileTransfer
	Agreed     bool
}

func (cc *ClientConn) sendAll(t int, fields ...Field) {
	for _, c := range sortedClients(cc.Server.Clients) {
		cc.Server.outbox <- *NewTransaction(t, c.ID, fields...)
	}
}

func (cc *ClientConn) handleTransaction(transaction *Transaction) error {
	requestNum := binary.BigEndian.Uint16(transaction.Type)
	if handler, ok := TransactionHandlers[requestNum]; ok {
		for _, reqField := range handler.RequiredFields {
			field := transaction.GetField(reqField.ID)

			// Validate that required field is present
			if field.ID == nil {
				cc.Server.Logger.Errorw(
					"Missing required field",
					"Account", cc.Account.Login, "UserName", string(cc.UserName), "RequestType", handler.Name, "FieldID", reqField.ID,
				)
				return nil
			}

			if len(field.Data) < reqField.minLen {
				cc.Server.Logger.Infow(
					"Field does not meet minLen",
					"Account", cc.Account.Login, "UserName", string(cc.UserName), "RequestType", handler.Name, "FieldID", reqField.ID,
				)
				return nil
			}
		}
		if !authorize(cc.Account.Access, handler.Access) {
			cc.Server.Logger.Infow(
				"Unauthorized Action",
				"Account", cc.Account.Login, "UserName", string(cc.UserName), "RequestType", handler.Name,
			)
			cc.Server.outbox <- cc.NewErrReply(transaction, handler.DenyMsg)

			return nil
		}

		cc.Server.Logger.Infow(
			"Received Transaction",
			"login", cc.Account.Login,
			"name", string(cc.UserName),
			"RequestType", handler.Name,
		)

		transactions, err := handler.Handler(cc, transaction)
		if err != nil {
			return err
		}
		for _, t := range transactions {
			cc.Server.outbox <- t
		}
	} else {
		cc.Server.Logger.Errorw(
			"Unimplemented transaction type received",
			"UserName", string(cc.UserName), "RequestID", requestNum,
		)
	}

	cc.Server.mux.Lock()
	defer cc.Server.mux.Unlock()

	if requestNum != tranKeepAlive {
		// reset the user idle timer
		cc.IdleTime = 0

		// if user was previously idle, mark as not idle and notify other connected clients that
		// the user is no longer away
		if cc.Idle {
			flagBitmap := big.NewInt(int64(binary.BigEndian.Uint16(*cc.Flags)))
			flagBitmap.SetBit(flagBitmap, userFlagAway, 0)
			binary.BigEndian.PutUint16(*cc.Flags, uint16(flagBitmap.Int64()))
			cc.Idle = false

			cc.sendAll(
				tranNotifyChangeUser,
				NewField(fieldUserID, *cc.ID),
				NewField(fieldUserFlags, *cc.Flags),
				NewField(fieldUserName, cc.UserName),
				NewField(fieldUserIconID, *cc.Icon),
			)
		}
	}

	return nil
}

func (cc *ClientConn) Authenticate(login string, password []byte) bool {
	if account, ok := cc.Server.Accounts[login]; ok {
		return bcrypt.CompareHashAndPassword([]byte(account.Password), password) == nil
	}

	return false
}

func (cc *ClientConn) uint16ID() uint16 {
	id, _ := byteToInt(*cc.ID)
	return uint16(id)
}

// Authorize checks if the user account has the specified permission
func (cc *ClientConn) Authorize(access int) bool {
	if access == 0 {
		return true
	}

	accessBitmap := big.NewInt(int64(binary.BigEndian.Uint64(*cc.Account.Access)))

	return accessBitmap.Bit(63-access) == 1
}

// Disconnect notifies other clients that a client has disconnected
func (cc ClientConn) Disconnect() {
	cc.Server.mux.Lock()
	defer cc.Server.mux.Unlock()

	delete(cc.Server.Clients, binary.BigEndian.Uint16(*cc.ID))

	cc.NotifyOthers(*NewTransaction(tranNotifyDeleteUser, nil, NewField(fieldUserID, *cc.ID)))

	if err := cc.Connection.Close(); err != nil {
		cc.Server.Logger.Errorw("error closing client connection", "RemoteAddr", cc.Connection.RemoteAddr())
	}
}

// NotifyOthers sends transaction t to other clients connected to the server
func (cc ClientConn) NotifyOthers(t Transaction) {
	for _, c := range sortedClients(cc.Server.Clients) {
		if c.ID != cc.ID && c.Agreed {
			t.clientID = c.ID
			cc.Server.outbox <- t
		}
	}
}

// NewReply returns a reply Transaction with fields for the ClientConn
func (cc *ClientConn) NewReply(t *Transaction, fields ...Field) Transaction {
	reply := Transaction{
		Flags:     0x00,
		IsReply:   0x01,
		Type:      t.Type,
		ID:        t.ID,
		clientID:  cc.ID,
		ErrorCode: []byte{0, 0, 0, 0},
		Fields:    fields,
	}

	return reply
}

// NewErrReply returns an error reply Transaction with errMsg
func (cc *ClientConn) NewErrReply(t *Transaction, errMsg string) Transaction {
	return Transaction{
		clientID:  cc.ID,
		Flags:     0x00,
		IsReply:   0x01,
		Type:      []byte{0, 0},
		ID:        t.ID,
		ErrorCode: []byte{0, 0, 0, 1},
		Fields: []Field{
			NewField(fieldError, []byte(errMsg)),
		},
	}
}