feat: US-009 - Chat widget — Gemini Flash integration

src/lib/gemini.ts

@@ -0,0 +1,152 @@
+import { buildEmbeddingTexts } from '@/lib/search'
+
+export interface ChatMessage {
+  role: 'user' | 'assistant'
+  content: string
+}
+
+const GEMINI_API_BASE = 'https://generativelanguage.googleapis.com/v1beta/models/gemini-2.0-flash'
+
+function getApiKey(): string | undefined {
+  return import.meta.env.VITE_GEMINI_API_KEY as string | undefined
+}
+
+export function isGeminiAvailable(): boolean {
+  return !!getApiKey()
+}
+
+function buildSystemPrompt(): string {
+  const texts = buildEmbeddingTexts()
+  const cvContent = texts.map((t) => `- ${t.text}`).join('\n')
+
+  return `You are an AI assistant embedded in Andy Charlwood's professional portfolio website. Your role is to answer questions about Andy's professional experience, skills, projects, and qualifications accurately and concisely.
+
+Here is Andy's complete professional profile:
+
+${cvContent}
+
+Instructions:
+- Answer questions based ONLY on the information above. Do not invent roles, dates, or achievements.
+- Be concise — 2-4 sentences for most answers.
+- Be professional but friendly in tone.
+- If asked something not covered by the profile data, say you don't have that information.
+- At the end of your response, on a new line, include relevant portfolio item IDs in this format: [ITEMS: id1, id2, id3]
+- Only include item IDs that are directly relevant to your answer. The available IDs are the ones listed above (e.g., exp-*, skill-*, proj-*, ach-*, edu-*, action-*).
+- If no items are particularly relevant, omit the [ITEMS: ...] line entirely.`
+}
+
+function buildRequestBody(
+  messages: ChatMessage[],
+  systemPrompt: string,
+): object {
+  const contents = messages.map((msg) => ({
+    role: msg.role === 'assistant' ? 'model' : 'user',
+    parts: [{ text: msg.content }],
+  }))
+
+  return {
+    system_instruction: {
+      parts: [{ text: systemPrompt }],
+    },
+    contents,
+    generationConfig: {
+      temperature: 0.7,
+      maxOutputTokens: 512,
+    },
+  }
+}
+
+export async function* sendChatMessage(
+  messages: ChatMessage[],
+): AsyncGenerator<string> {
+  const apiKey = getApiKey()
+  if (!apiKey) {
+    throw new Error('Gemini API key not configured')
+  }
+
+  const systemPrompt = buildSystemPrompt()
+  const body = buildRequestBody(messages, systemPrompt)
+
+  const response = await fetch(
+    `${GEMINI_API_BASE}:streamGenerateContent?alt=sse&key=${apiKey}`,
+    {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify(body),
+    },
+  )
+
+  if (!response.ok) {
+    throw new Error(`Gemini 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')
+      // Keep the last potentially incomplete line in the buffer
+      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?.candidates?.[0]?.content?.parts?.[0]?.text
+          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?.candidates?.[0]?.content?.parts?.[0]?.text
+          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()
+}