Initial commit

lib/ai/geminiClient.ts

@@ -0,0 +1,132 @@
+import { GoogleGenAI } from "@google/genai";
+
+export type SiteMenteMessage = {
+  role: "user" | "assistant" | "system";
+  content: string;
+};
+
+export type SiteMenteSpeechResult = {
+  audioBytes: Uint8Array;
+  mimeType: string;
+};
+
+const TEXT_MODEL = "gemini-2.5-flash";
+const SPEECH_MODEL = "gemini-2.5-flash-preview-tts";
+
+const getClient = () => {
+  const apiKey = process.env.GEMINI_API_KEY;
+  if (!apiKey) {
+    throw new Error("GEMINI_API_KEY is not set.");
+  }
+  return new GoogleGenAI({ apiKey });
+};
+
+const extractText = (response: unknown): string => {
+  const typed = response as {
+    candidates?: Array<{
+      content?: { parts?: Array<{ text?: string }> };
+    }>;
+  };
+  const text =
+    typed?.candidates?.[0]?.content?.parts
+      ?.map((part) => part.text ?? "")
+      .join("")
+      .trim() ?? "";
+
+  if (!text) {
+    throw new Error("Gemini returned an empty response.");
+  }
+
+  return text;
+};
+
+const extractAudio = (response: unknown): SiteMenteSpeechResult => {
+  const typed = response as {
+    candidates?: Array<{
+      content?: {
+        parts?: Array<{
+          inlineData?: { data?: string; mimeType?: string };
+        }>;
+      };
+    }>;
+  };
+  const inlineData =
+    typed?.candidates?.[0]?.content?.parts?.find((part) => part.inlineData)
+      ?.inlineData ?? null;
+
+  if (!inlineData?.data || !inlineData?.mimeType) {
+    throw new Error("Gemini did not return audio data.");
+  }
+
+  const audioBytes = Uint8Array.from(
+    Buffer.from(inlineData.data, "base64")
+  );
+
+  return { audioBytes, mimeType: inlineData.mimeType };
+};
+
+const buildContents = (messages: SiteMenteMessage[]) => {
+  return messages
+    .filter((message) => message.role !== "system")
+    .map((message) => ({
+      role: message.role === "assistant" ? "model" : "user",
+      parts: [{ text: message.content }],
+    }));
+};
+
+const buildSystemInstruction = (messages: SiteMenteMessage[]) => {
+  const systemText = messages
+    .filter((message) => message.role === "system")
+    .map((message) => message.content)
+    .join("\n")
+    .trim();
+
+  if (!systemText) {
+    return undefined;
+  }
+
+  return { parts: [{ text: systemText }] };
+};
+
+export const generateSiteMenteText = async (
+  messages: SiteMenteMessage[]
+): Promise<string> => {
+  try {
+    const client = getClient();
+    const response = await client.models.generateContent({
+      model: TEXT_MODEL,
+      contents: buildContents(messages),
+      systemInstruction: buildSystemInstruction(messages),
+    });
+    return extractText(response);
+  } catch (error) {
+    console.error("[SiteMente][Gemini] Text generation failed", error);
+    throw error;
+  }
+};
+
+export const generateSiteMenteSpeech = async (
+  text: string
+): Promise<SiteMenteSpeechResult> => {
+  try {
+    const client = getClient();
+    const response = await client.models.generateContent({
+      model: SPEECH_MODEL,
+      contents: [{ role: "user", parts: [{ text }] }],
+      config: {
+        responseModalities: ["AUDIO"],
+        speechConfig: {
+          voiceConfig: {
+            prebuiltVoiceConfig: {
+              voiceName: "Kore",
+            },
+          },
+        },
+      },
+    });
+    return extractAudio(response);
+  } catch (error) {
+    console.error("[SiteMente][Gemini] Speech generation failed", error);
+    throw error;
+  }
+};