issue #23 - add roll dice chatroom support

foodgroup/chat.go

@@ -1,25 +1,55 @@
 package foodgroup
 
 import (
+	"bytes"
 	"context"
 	"errors"
+	"fmt"
+	"io"
 	"math"
+	"math/rand/v2"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"golang.org/x/net/html"
 
 	"github.com/mk6i/retro-aim-server/state"
 	"github.com/mk6i/retro-aim-server/wire"
 )
 
+var (
+	// sessOnlineHost represents the OnlineHost user that announcements die
+	// roll results.
+	sessOnlineHost = func() *state.Session {
+		sn := state.DisplayScreenName("OnlineHost")
+		sess := state.NewSession()
+		sess.SetDisplayScreenName(sn)
+		sess.SetIdentScreenName(sn.IdentScreenName())
+		return sess
+	}()
+
+	// rollDiceRgxp matches a roll dice chat command.
+	// ex: //roll //roll-sides3 //roll-dice2 //role-sides3-dice2
+	rollDiceRgxp = regexp.MustCompile(`^//roll(?:-(dice|sides)([0-9]{1,3}))?(?:-(dice|sides)([0-9]{1,3}))?\s*$`)
+)
+
 // NewChatService creates a new instance of ChatService.
 func NewChatService(chatMessageRelayer ChatMessageRelayer) *ChatService {
 	return &ChatService{
 		chatMessageRelayer: chatMessageRelayer,
+		randRollDie: func(sides int) int {
+			// generate random number between 1 and sides
+			return rand.IntN(sides) + 1
+		},
 	}
 }
 
 // ChatService provides functionality for the Chat food group, which is
 // responsible for sending and receiving chat messages.
 type ChatService struct {
 	chatMessageRelayer ChatMessageRelayer
+	randRollDie        func(sides int) int
 }
 
 // ChannelMsgToHost relays wire.ChatChannelMsgToClient SNAC sent from a user
@@ -31,31 +61,21 @@ func (s ChatService) ChannelMsgToHost(ctx context.Context, sess *state.Session,
 		FoodGroup: wire.Chat,
 		SubGroup:  wire.ChatChannelMsgToClient,
 	}
-
-	msg, hasMessage := inBody.Bytes(wire.ChatTLVMessageInformation)
-	if !hasMessage {
-		return nil, errors.New("SNAC(0x0E,0x05) does not contain a message TLV")
-	}
-
 	bodyOut := wire.SNAC_0x0E_0x06_ChatChannelMsgToClient{
 		Cookie:  inBody.Cookie,
 		Channel: inBody.Channel,
-		TLVRestBlock: wire.TLVRestBlock{
-			TLVList: wire.TLVList{
-				// The order of these TLVs matters for AIM 2.x. if out of
-				// order, screen names do not appear with each chat message.
-				wire.NewTLVBE(wire.ChatTLVSenderInformation, sess.TLVUserInfo()),
-				wire.NewTLVBE(wire.ChatTLVPublicWhisperFlag, []byte{}),
-				wire.NewTLVBE(wire.ChatTLVMessageInformation, msg),
-			},
-		},
 	}
-
 	if bodyOut.Channel == math.MaxUint16 {
-		// Fix incorrect channel bug in macOS client v4.0.9.
+		// fix incorrect channel bug in macOS client v4.0.9.
 		bodyOut.Channel = wire.ICBMChannelMIME
 	}
 
+	var err error
+	bodyOut.TLVRestBlock, err = s.transformChatMessage(inBody, sess)
+	if err != nil {
+		return nil, err
+	}
+
 	// send message to all the participants except sender
 	s.chatMessageRelayer.RelayToAllExcept(ctx, sess.ChatRoomCookie(), sess.IdentScreenName(), wire.SNACMessage{
 		Frame: frameOut,
@@ -75,6 +95,136 @@ func (s ChatService) ChannelMsgToHost(ctx context.Context, sess *state.Session,
 	return ret, nil
 }
 
+// transformChatMessage inspects and modifies the incoming chat message payload.
+//   - If message contains a properly formatted //roll command, return a roll
+//     die response.
+//   - Else return the unmodified incoming message.
+//
+// In the future, this function will validate the incoming message for correct form.
+func (s ChatService) transformChatMessage(inBody wire.SNAC_0x0E_0x05_ChatChannelMsgToHost, sender *state.Session) (wire.TLVRestBlock, error) {
+	messageBlob, hasMessage := inBody.Bytes(wire.ChatTLVMessageInfo)
+	if !hasMessage {
+		return wire.TLVRestBlock{}, errors.New("SNAC(0x0E,0x05) does not contain a message TLV")
+	}
+	messageText, err := textFromChatMsgBlob(messageBlob)
+	if err != nil {
+		return wire.TLVRestBlock{}, err
+	}
+
+	newMessageBlock := func(sess *state.Session, msg any) wire.TLVRestBlock {
+		block := wire.TLVRestBlock{}
+		// the order of these TLVs matters for AIM 2.x. if out of order, screen
+		// names do not appear with each chat message.
+		block.Append(wire.NewTLVBE(wire.ChatTLVSenderInformation, sess.TLVUserInfo()))
+		block.Append(wire.NewTLVBE(wire.ChatTLVPublicWhisperFlag, []byte{}))
+		block.Append(wire.NewTLVBE(wire.ChatTLVMessageInfo, msg))
+		return block
+	}
+
+	if doRoll, dice, sides := parseDiceCommand(messageText); doRoll {
+		payload := s.rollDice(sender, dice, sides)
+		// send die roll results from OnlineHost user
+		return newMessageBlock(sessOnlineHost, payload), nil
+	}
+
+	// return the incoming payload without modification
+	return newMessageBlock(sender, messageBlob), nil
+}
+
+// rollDice generates a chat response for the results of a die roll.
+func (s ChatService) rollDice(sess *state.Session, dice int, sides int) wire.TLVRestBlock {
+	sb := strings.Builder{}
+	sb.WriteString("<HTML><BODY BGCOLOR=\"#ffffff\"><FONT LANG=\"0\">")
+	sb.WriteString(fmt.Sprintf("%s rolled %d %d-sided dice:", sess.DisplayScreenName().String(), dice, sides))
+	for i := 0; i < dice; i++ {
+		sb.WriteString(fmt.Sprintf(" %d", s.randRollDie(sides)))
+	}
+	sb.WriteString("</FONT></BODY></HTML>")
+
+	block := wire.TLVRestBlock{}
+	block.Append(wire.NewTLVBE(wire.ChatTLVMessageInfoEncoding, "us-ascii"))
+	block.Append(wire.NewTLVBE(wire.ChatTLVMessageInfoLang, "en"))
+	block.Append(wire.NewTLVBE(wire.ChatTLVMessageInfoText, sb.String()))
+	return block
+}
+
+// textFromChatMsgBlob extracts plaintext message text from HTML located in
+// chat message info TLV(0x05).
+func textFromChatMsgBlob(msg []byte) ([]byte, error) {
+	block := wire.TLVRestBlock{}
+	if err := wire.UnmarshalBE(&block, bytes.NewBuffer(msg)); err != nil {
+		return nil, err
+	}
+
+	b, hasMsg := block.Bytes(wire.ChatTLVMessageInfoText)
+	if !hasMsg {
+		return nil, errors.New("SNAC(0x0E,0x05) has no chat msg text TLV")
+	}
+
+	tok := html.NewTokenizer(bytes.NewBuffer(b))
+	for {
+		switch tok.Next() {
+		case html.TextToken:
+			return tok.Text(), nil
+		case html.ErrorToken:
+			err := tok.Err()
+			if err == io.EOF {
+				err = nil
+			}
+			return nil, err
+		}
+	}
+}
+
+// parseDiceCommand gets the number of dice and sides from a die roll command.
+//
+// The roll command is activated with //roll followed by up to two arguments to
+// indicate die count and side count. By default, there are 2 dice and 6 sides.
+//
+//   - //roll               2x 6-sided dice
+//   - //roll-dice4         4x 6-sided dice
+//   - //roll-sides8        2x 8-sided dice
+//   - //roll-dice4-sides8  4x 8-sided dice
+//
+// The -dice param can not exceed 15 and -sides param cannot exceed 999.
+func parseDiceCommand(in []byte) (valid bool, dice int, sides int) {
+	matches := rollDiceRgxp.FindSubmatch(in)
+	if len(matches) == 0 {
+		return false, 0, 0
+	}
+
+	args := matches[1:]
+	if len(args[0]) > 0 && bytes.Equal(args[0], args[2]) {
+		// "sides" or "dice" appears twice
+		return false, 0, 0
+	}
+
+	dice = 2
+	sides = 6
+
+	for i := 0; i < len(args); i += 2 {
+		cmd := string(args[i])
+		val := string(args[i+1])
+
+		switch cmd {
+		case "sides":
+			var err error
+			sides, err = strconv.Atoi(val)
+			if err != nil || sides == 0 || sides > 999 {
+				return false, 0, 0
+			}
+		case "dice":
+			var err error
+			dice, err = strconv.Atoi(val)
+			if err != nil || dice == 0 || dice > 15 {
+				return false, 0, 0
+			}
+		}
+	}
+
+	return true, dice, sides
+}
+
 func setOnlineChatUsers(ctx context.Context, sess *state.Session, chatMessageRelayer ChatMessageRelayer) {
 	snacPayloadOut := wire.SNAC_0x0E_0x03_ChatUsersJoined{}
 	sessions := chatMessageRelayer.AllSessions(sess.ChatRoomCookie())