feat(bot): persist locale preferences across mini app and replies

apps/bot/src/bot-locale.ts

@@ -0,0 +1,45 @@
+import { normalizeSupportedLocale } from '@household/domain'
+import type { HouseholdConfigurationRepository, HouseholdMemberRecord } from '@household/ports'
+import type { Context } from 'grammy'
+
+import { resolveBotLocale, type BotLocale } from './i18n'
+
+function localeFromMember(member: HouseholdMemberRecord, fallback: BotLocale): BotLocale {
+  return member.preferredLocale ?? member.householdDefaultLocale ?? fallback
+}
+
+export async function resolveReplyLocale(options: {
+  ctx: Pick<Context, 'chat' | 'from'>
+  repository: HouseholdConfigurationRepository | undefined
+  householdId?: string
+}): Promise<BotLocale> {
+  const fallback = resolveBotLocale(options.ctx.from?.language_code)
+  const telegramUserId = options.ctx.from?.id?.toString()
+  const telegramChatId = options.ctx.chat?.id?.toString()
+
+  if (!options.repository) {
+    return fallback
+  }
+
+  if (options.ctx.chat && options.ctx.chat.type !== 'private' && telegramChatId) {
+    const household = await options.repository.getTelegramHouseholdChat(telegramChatId)
+    return household?.defaultLocale ?? fallback
+  }
+
+  if (!telegramUserId) {
+    return fallback
+  }
+
+  if (options.householdId) {
+    const member = await options.repository.getHouseholdMember(options.householdId, telegramUserId)
+    return member ? localeFromMember(member, fallback) : fallback
+  }
+
+  const members = await options.repository.listHouseholdMembersByTelegramUserId(telegramUserId)
+  if (members.length === 1) {
+    return localeFromMember(members[0]!, fallback)
+  }
+
+  const normalized = normalizeSupportedLocale(options.ctx.from?.language_code)
+  return normalized ?? fallback
+}