feat: US-014 - Migrate production chat from Gemini to OpenRouter

src/lib/llm.ts

@@ -0,0 +1,157 @@
+import { buildEmbeddingTexts } from '@/lib/search'
+
+export interface ChatMessage {
+  role: 'user' | 'assistant'
+  content: string
+}
+
+export const LLM_MODEL = 'z-ai/glm-5'
+export const LLM_DISPLAY_NAME = 'GLM-5'
+
+const OPENROUTER_API_URL = 'https://openrouter.ai/api/v1/chat/completions'
+
+function getApiKey(): string | undefined {
+  return import.meta.env.VITE_OPEN_ROUTER_API_KEY as string | undefined
+}
+
+export function isLLMAvailable(): boolean {
+  return !!getApiKey()
+}
+
+export function buildSystemPrompt(): string {
+  const texts = buildEmbeddingTexts()
+  const cvContent = texts.map((t) => `[${t.id}] ${t.text}`).join('\n')
+
+  return `You are a helpful assistant on Andy Charlwood's portfolio website.
+
+## Profile Data
+Each entry is prefixed with its ID in square brackets.
+
+${cvContent}
+
+## Response Rules
+- Answer ONLY from the profile data above. Never invent facts, roles, dates, or achievements.
+- Be concise: 2-4 sentences. Professional and friendly tone.
+- If the answer isn't in the profile, say so honestly.
+- Do not fabricate URLs, email addresses, or contact details.
+
+## Item References
+End your response with a single line listing relevant item IDs:
+[ITEMS: exp-nhs-nwicb, skill-python]
+Only include IDs that directly support your answer. Omit the line if none are relevant.`
+}
+
+function buildRequestBody(
+  messages: ChatMessage[],
+  systemPrompt: string,
+): object {
+  return {
+    model: LLM_MODEL,
+    stream: true,
+    temperature: 0.7,
+    max_tokens: 512,
+    messages: [
+      { role: 'system', content: systemPrompt },
+      ...messages.map((msg) => ({
+        role: msg.role,
+        content: msg.content,
+      })),
+    ],
+  }
+}
+
+export async function* sendChatMessage(
+  messages: ChatMessage[],
+): AsyncGenerator<string> {
+  const apiKey = getApiKey()
+  if (!apiKey) {
+    throw new Error('LLM API key not configured')
+  }
+
+  const systemPrompt = buildSystemPrompt()
+  const body = buildRequestBody(messages, systemPrompt)
+
+  const response = await fetch(OPENROUTER_API_URL, {
+    method: 'POST',
+    headers: {
+      'Content-Type': 'application/json',
+      'Authorization': `Bearer ${apiKey}`,
+      'HTTP-Referer': window.location.origin,
+      'X-Title': 'Andy Charlwood Portfolio',
+    },
+    body: JSON.stringify(body),
+  })
+
+  if (!response.ok) {
+    throw new Error(`LLM API error: ${response.status}`)
+  }
+
+  const reader = response.body?.getReader()
+  if (!reader) {
+    throw new Error('No response body')
+  }
+
+  const decoder = new TextDecoder()
+  let buffer = ''
+
+  try {
+    while (true) {
+      const { done, value } = await reader.read()
+      if (done) break
+
+      buffer += decoder.decode(value, { stream: true })
+
+      const lines = buffer.split('\n')
+      buffer = lines.pop() ?? ''
+
+      for (const line of lines) {
+        const trimmed = line.trim()
+        if (!trimmed.startsWith('data:')) continue
+
+        const jsonStr = trimmed.slice(5).trim()
+        if (!jsonStr || jsonStr === '[DONE]') continue
+
+        try {
+          const parsed = JSON.parse(jsonStr)
+          const text = parsed?.choices?.[0]?.delta?.content
+          if (text) {
+            yield text
+          }
+        } catch {
+          // Skip malformed JSON chunks
+        }
+      }
+    }
+
+    // Process any remaining buffer
+    if (buffer.trim().startsWith('data:')) {
+      const jsonStr = buffer.trim().slice(5).trim()
+      if (jsonStr && jsonStr !== '[DONE]') {
+        try {
+          const parsed = JSON.parse(jsonStr)
+          const text = parsed?.choices?.[0]?.delta?.content
+          if (text) {
+            yield text
+          }
+        } catch {
+          // Skip malformed final chunk
+        }
+      }
+    }
+  } finally {
+    reader.releaseLock()
+  }
+}
+
+export function parseItemIds(text: string): string[] {
+  const match = text.match(/\[ITEMS:\s*([^\]]+)\]/)
+  if (!match) return []
+  return match[1]
+    .split(',')
+    .map((id) => id.trim())
+    .filter(Boolean)
+}
+
+export function stripItemsSuffix(text: string): string {
+  return text.replace(/\n?\[ITEMS:[^\]]*\]\s*$/, '').trim()
+}