feat(boost-greeting): integrate greeting into guild member update and clean up handler

src/discord/bot.ts

@@ -5,6 +5,7 @@ import { BoosterRoleService } from "../services/boosterRoleService";
 import { DrizzleBoosterRoleStore } from "../services/drizzleBoosterRoleStore";
 import { DiscordRoleRepository } from "../services/discordRoleRepository";
 import { handleGuildMemberUpdate } from "./events/guildMemberUpdate";
+import { sendBoostGreeting } from "./events/boostGreeting";
 import { handleInteraction } from "./interactionHandler";
 
 export function attachBotHandlers(client: Client, config: AppConfig): void {
@@ -26,13 +27,25 @@ export function attachBotHandlers(client: Client, config: AppConfig): void {
   });
 
   client.on("guildMemberUpdate", async (oldMember, newMember) => {
+    const eligibilityRoleId = config.boosterEligibilityRoleId;
+
+    // Detect boost gain: member just acquired the booster eligibility role
+    const hadBooster = oldMember.roles.cache.has(eligibilityRoleId);
+    const hasBooster = newMember.roles.cache.has(eligibilityRoleId);
+    if (!hadBooster && hasBooster && config.boosterGreetingChannelId) {
+      await sendBoostGreeting(newMember, config.boosterGreetingChannelId).catch((err) => {
+        logger.error("Failed to send boost greeting", { error: String(err), userId: newMember.id });
+      });
+    }
+
+    // Handle boost loss (existing behaviour)
     const service = new BoosterRoleService(
       store,
       new DiscordRoleRepository(newMember.guild),
       { anchorPosition: resolveAnchorPosition(newMember.guild, config.boosterRoleAnchorRoleId) }
     );
 
-    await handleGuildMemberUpdate(oldMember, newMember, service, config.boosterEligibilityRoleId);
+    await handleGuildMemberUpdate(oldMember, newMember, service, eligibilityRoleId);
   });
 }
 

src/discord/events/boostGreeting.ts

@@ -4,8 +4,9 @@ type GuildTextChannel = {
   send(input: { content: string }): Promise<unknown>;
 };
 
-type GuildMember = {
+type GuildMemberLike = {
   id: string;
+  user?: { id: string };
   guild: {
     id: string;
     channels: {
@@ -14,46 +15,35 @@ type GuildMember = {
       };
     };
   };
-  user?: { id: string };
 };
 
 /**
- * Sends a welcome message to the configured greeting channel when a member
- * newly acquires the booster eligibility role (i.e. just boosted the server).
- *
- * Only fires on a *gain* transition (hadBoosterRole = false → hasBoosterRole = true).
- */
-export function handleBoostGreeting(
-  oldMember: GuildMember,
-  newMember: GuildMember,
-  greetingChannelId: string | null,
-): void {
-  if (!greetingChannelId) return;
-
-  const hadBoosterRole = oldMember.roles.cache.has(/** @type {any} */ (null) as any);
-  // Actually detect the gain: we need the actual role ID. The caller should pass it.
-}
-
-/**
- * Sends a welcome message when a member newly acquires the booster eligibility role.
- * Must be called with the booster eligibility role ID to check correctly.
+ * Sends a welcome message to the configured greeting channel.
+ * Call this after confirming the member newly gained the booster eligibility role.
  */
 export async function sendBoostGreeting(
-  member: { id: string; guild: { id: string; channels: { cache: { get(channelId: string): { send(input: { content: string }): Promise<unknown> } | undefined } } } },
+  member: GuildMemberLike,
   greetingChannelId: string,
 ): Promise<void> {
   const channel = member.guild.channels.cache.get(greetingChannelId);
+
   if (!channel) {
-    logger.warn("Boost greeting channel not found", { channelId: greetingChannelId, guildId: member.guild.id });
+    logger.warn("Boost greeting channel not found", {
+      channelId: greetingChannelId,
+      guildId: member.guild.id,
+    });
     return;
   }
 
-  await channel.send({
-    content: `🎉 Thank you for boosting <@${member.user?.id ?? member.id}>! You can now claim a custom role using \`/booster-role claim\` in <#${greetingChannelId}>.`
-  });
+  const mention = member.user?.id ?? member.id;
+  const message =
+    `🎉 Thank you for boosting <@${mention}>! ` +
+    `You can now claim a custom role using \`/booster-role claim\` in <#${greetingChannelId}>.`;
+
+  await channel.send({ content: message });
 
   logger.info("Boost greeting sent", {
-    userId: member.user?.id ?? member.id,
+    userId: member.id,
     guildId: member.guild.id,
     channelId: greetingChannelId,
   });