Initial API scaffold: Elysia + Bun + Drizzle + BetterAuth + LangChain

src/services/ai.ts

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+import { ChatAnthropic } from '@langchain/anthropic';
+import { ChatPromptTemplate } from '@langchain/core/prompts';
+import { StringOutputParser } from '@langchain/core/output_parsers';
+
+export type AIProvider = 'anthropic' | 'openai';
+
+// Get model based on provider
+function getModel(provider: AIProvider = 'anthropic') {
+  if (provider === 'anthropic') {
+    return new ChatAnthropic({
+      modelName: 'claude-sonnet-4-20250514',
+      anthropicApiKey: process.env.ANTHROPIC_API_KEY,
+    });
+  }
+  
+  // Add OpenAI support later
+  throw new Error(`Provider ${provider} not yet supported`);
+}
+
+// Email generation prompt
+const emailPrompt = ChatPromptTemplate.fromMessages([
+  ['system', `You are a professional wealth advisor writing to a valued client.
+Maintain a warm but professional tone. Incorporate personal details naturally.
+Keep emails concise (3-4 paragraphs max).
+Do not include subject line - just the body.`],
+  ['human', `Advisor: {advisorName}
+Client: {clientName}
+Their interests: {interests}
+Recent notes: {notes}
+Purpose: {purpose}
+
+Generate a personalized email that feels genuine, not templated.`],
+]);
+
+export interface GenerateEmailParams {
+  advisorName: string;
+  clientName: string;
+  interests: string[];
+  notes: string;
+  purpose: string;
+  provider?: AIProvider;
+}
+
+export async function generateEmail(params: GenerateEmailParams): Promise<string> {
+  const model = getModel(params.provider);
+  const parser = new StringOutputParser();
+  const chain = emailPrompt.pipe(model).pipe(parser);
+  
+  const response = await chain.invoke({
+    advisorName: params.advisorName,
+    clientName: params.clientName,
+    interests: params.interests.join(', ') || 'not specified',
+    notes: params.notes || 'No recent notes',
+    purpose: params.purpose,
+  });
+  
+  return response;
+}
+
+// Birthday message generation
+const birthdayPrompt = ChatPromptTemplate.fromMessages([
+  ['system', `Generate a thoughtful birthday message from a wealth advisor to their client.
+Should feel personal, not generic. Keep it brief (2-3 sentences) and sincere.`],
+  ['human', `Client: {clientName}
+Years as client: {yearsAsClient}
+Interests: {interests}
+
+Generate a warm birthday message.`],
+]);
+
+export interface GenerateBirthdayMessageParams {
+  clientName: string;
+  yearsAsClient: number;
+  interests: string[];
+  provider?: AIProvider;
+}
+
+export async function generateBirthdayMessage(params: GenerateBirthdayMessageParams): Promise<string> {
+  const model = getModel(params.provider);
+  const parser = new StringOutputParser();
+  const chain = birthdayPrompt.pipe(model).pipe(parser);
+  
+  const response = await chain.invoke({
+    clientName: params.clientName,
+    yearsAsClient: params.yearsAsClient.toString(),
+    interests: params.interests.join(', ') || 'not specified',
+  });
+  
+  return response;
+}
+
+// Email subject generation
+const subjectPrompt = ChatPromptTemplate.fromMessages([
+  ['system', `Generate a professional but warm email subject line for a wealth advisor's email.
+Keep it short (under 50 characters). Do not use quotes.`],
+  ['human', `Purpose: {purpose}
+Client name: {clientName}
+
+Generate just the subject line, nothing else.`],
+]);
+
+export async function generateSubject(purpose: string, clientName: string, provider?: AIProvider): Promise<string> {
+  const model = getModel(provider);
+  const parser = new StringOutputParser();
+  const chain = subjectPrompt.pipe(model).pipe(parser);
+  
+  const response = await chain.invoke({ purpose, clientName });
+  return response.trim();
+}