truncateDiscordMessage

README.md

@@ -49,6 +49,8 @@ Albion Onlineのギルド [Dog The Boston](https://twitter.com/DogTheBoston) 用
 
 ## リリースノート
 
+- 2023-12-27 v1.8.1
+  - 修正: 応答がDiscordの文字数制限（2000字）を超えるときにエラーになる問題（省略するようにした）
 - 2023-12-26 v1.8.0
   - 機能: `ルートナビ` 確認用コマンド `/route-list` を追加
 - 2023-12-24 v1.7.0

pkg/handlers/common.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"math/rand"
 	"unicode"
+	"unicode/utf8"
 
 	"github.com/bwmarrin/discordgo"
 	"github.com/rs/zerolog"
@@ -145,3 +146,13 @@ func pickOne(choices []choice) string {
 func Ptr[T any](v T) *T {
 	return &v
 }
+
+// truncateDiscordMessage truncates a string to <2000 characters.
+func truncateDiscordMessage(s string, msg string) string {
+	const maxLen = 1950 // 2000 - 50 (for safety)
+	if utf8.RuneCountInString(s) <= maxLen {
+		return s
+	} else {
+		return s[:maxLen-1-utf8.RuneCountInString(msg)] + "\n" + msg
+	}
+}

pkg/handlers/reaction.go

@@ -157,10 +157,12 @@ func HandleReactionAddReactionRequired(s *discordgo.Session, r *discordgo.Messag
 			sb.WriteString(fmt.Sprintf("`%s` ", name))
 		}
 	}
+	resp := strings.TrimRight(sb.String(), " ")
+	resp = truncateDiscordMessage(resp, "...（省略）")
 
 	// Send the response.
 	msg, err := sendSilentMessage(s, r.ChannelID, &discordgo.MessageSend{
-		Content:   strings.TrimRight(sb.String(), " "),
+		Content:   resp,
 		Reference: parentMsg.Reference(),
 	})
 	if err != nil {

pkg/handlers/slashcmd_roanav.go

@@ -278,6 +278,7 @@ func (h *ROANavHandler) HandleCmdRouteList(s *discordgo.Session, i *discordgo.In
 	} else {
 		resp += smm
 	}
+	resp = truncateDiscordMessage(resp, "...長いので省略するわん！")
 
 	// Send response.
 	if mErr := respondEphemeralMessage(s, i, resp); mErr != nil {