sparkvault/server/nano_banana.js

import * as fs from "node:fs";
import * as path from "node:path";
import { GoogleGenAI } from "@google/genai";

export const NANO_BANANA_MODELS = [
  {
    id: "gemini-nano-banana-2.1",
    label: "Nano Banana 2.1 (Default High-Efficiency)",
    description: "gemini-nano-banana-2.1 — Fast, high-efficiency native image generation and conversational editing"
  },
  {
    id: "gemini-3-pro-image",
    label: "Nano Banana Pro (Studio Quality)",
    description: "gemini-3-pro-image — High-detail studio mockup generation and multi-turn editing"
  },
  {
    id: "gemini-3.1-flash-lite-image",
    label: "Nano Banana 2 Lite (Ultra-Fast)",
    description: "gemini-3.1-flash-lite-image — Rapid concept sketching and quick iterations"
  }
];

export const SURFACE_PRESETS = {
  "tshirt-front": {
    label: "👕 T-Shirt (Full Front Print)",
    buildPrompt: ({ prompt, garmentColorName, garmentHex }) =>
      `Photorealistic studio flat-lay apparel mockup of a heavyweight ${garmentColorName || "vintage cream"} (${garmentHex || "#F5E8D3"}) crewneck t-shirt. Centered full-front screenprint graphic design: ${prompt}. Crisp fabric texture, authentic screenprint ink detail, clean studio lighting.`
  },
  "tshirt-left-chest": {
    label: "👕 T-Shirt (5-inch Left-Chest Emblem)",
    buildPrompt: ({ prompt, garmentColorName, garmentHex }) =>
      `Photorealistic studio closeup & flat-lay apparel mockup of a heavyweight ${garmentColorName || "vintage cream"} (${garmentHex || "#F5E8D3"}) crewneck t-shirt featuring a compact 5-inch left-chest pocket-zone screenprinted emblem: ${prompt}. Clean vector-style spot-color ink on fabric, studio lighting.`
  },
  "isolated-graphic": {
    label: "🎨 Isolated Screenprint Artwork (Vector Style)",
    buildPrompt: ({ prompt, garmentColorName }) =>
      `Isolated flat vector screenprint t-shirt graphic emblem on a clean solid ${garmentColorName || "cream"} background, no shirt folds, bold spot-color illustration and outlined vintage typography: ${prompt}`
  },
  "sticker": {
    label: "🏷️ Die-Cut Vinyl Sticker / Patch",
    buildPrompt: ({ prompt }) =>
      `Photorealistic die-cut vinyl sticker with a crisp white contour border resting on a dark slate studio surface. Bold vector illustration and typography: ${prompt}`
  },
  "poster": {
    label: "🖼️ Framed Studio Art Poster",
    buildPrompt: ({ prompt }) =>
      `Gallery-framed vertical screenprint poster mockup in a minimalist studio interior. Bold editorial illustration and typography: ${prompt}`
  },
  "app-ui": {
    label: "💻 Product / App Interface Concept",
    buildPrompt: ({ prompt }) =>
      `High-craft modern product design and UI concept presentation mockup on a sleek dark desktop studio display: ${prompt}`
  }
};

export function buildNanoBananaPrompt({
  rawPrompt,
  ideaTitle,
  elevatorPitch,
  template = "tshirt-front",
  garmentColorName = "Vintage Cream",
  garmentHex = "#F5E8D3",
  whackCard = null,
  editInstruction = null
}) {
  if (editInstruction && editInstruction.trim()) {
    let editText = editInstruction.trim();
    if (whackCard) {
      editText += ` Incorporate creative twist from Card #${whackCard.number} (${whackCard.title}): ${whackCard.promptQuestion}`;
    }
    return editText;
  }

  const baseConcept = (rawPrompt && rawPrompt.trim())
    ? rawPrompt.trim()
    : `${ideaTitle}${elevatorPitch ? ` — ${elevatorPitch}` : ""}`;

  const surface = SURFACE_PRESETS[template] || SURFACE_PRESETS["tshirt-front"];
  let finalPrompt = surface.buildPrompt({
    prompt: baseConcept,
    garmentColorName,
    garmentHex
  });

  if (whackCard) {
    finalPrompt += ` Creative direction inspired by "${whackCard.title}": ${whackCard.promptQuestion}`;
  }
  return finalPrompt;
}

/**
 * Generates or edits an image using Google Gemini Nano Banana (`gemini-nano-banana-2.1`)
 * via the official `@google/genai` Interactions API (`ai.interactions.create`).
 */
export async function generateWithNanoBanana({
  apiKey,
  model = "gemini-nano-banana-2.1",
  prompt,
  referenceImagePath = null,
  referenceImageBase64 = null,
  referenceMimeType = "image/png",
  outputDir
}) {
  const resolvedKey = apiKey || process.env.GEMINI_API_KEY || process.env.GOOGLE_API_KEY;
  if (!resolvedKey) {
    const err = new Error(
      "No Gemini API key configured. Click '⚙️ Nano Banana API Key' in the Mockup Studio (or set GEMINI_API_KEY) to generate live images with Nano Banana 2.1, or use the Interactive T-Shirt Canvas Compositor."
    );
    err.code = "MISSING_API_KEY";
    throw err;
  }

  const validModel = NANO_BANANA_MODELS.some((m) => m.id === model)
    ? model
    : "gemini-nano-banana-2.1";

  const ai = new GoogleGenAI({ apiKey: resolvedKey });

  let inputPayload = prompt;

  // Check if we are performing conversational image-to-image editing
  let base64Data = referenceImageBase64;
  let mimeType = referenceMimeType || "image/png";

  if (!base64Data && referenceImagePath && fs.existsSync(referenceImagePath)) {
    const bytes = fs.readFileSync(referenceImagePath);
    base64Data = bytes.toString("base64");
    if (referenceImagePath.endsWith(".jpg") || referenceImagePath.endsWith(".jpeg")) {
      mimeType = "image/jpeg";
    }
  }

  if (base64Data) {
    // Strip data URL prefix if present
    const cleanedBase64 = base64Data.replace(/^data:image\/[a-zA-Z0-9+.-]+;base64,/, "");
    inputPayload = [
      { type: "text", text: prompt },
      {
        type: "image",
        mime_type: mimeType,
        data: cleanedBase64
      }
    ];
  }

  const interaction = await ai.interactions.create({
    model: validModel,
    input: inputPayload
  });

  const generatedImage = interaction.output_image;
  if (!generatedImage || !generatedImage.data) {
    throw new Error(
      interaction.output_text ||
        "Nano Banana completed the interaction without returning an image block. Try refining your visual prompt."
    );
  }

  const ext = (generatedImage.mime_type || "").includes("jpeg") ? "jpg" : "png";
  const filename = `nb-${Date.now()}-${Math.random().toString(36).slice(2, 7)}.${ext}`;
  const fullPath = path.join(outputDir, filename);

  fs.mkdirSync(outputDir, { recursive: true });
  fs.writeFileSync(fullPath, Buffer.from(generatedImage.data, "base64"));

  return {
    filename,
    imageUrl: `/mockups/${filename}`,
    mimeType: generatedImage.mime_type || `image/${ext}`,
    modelUsed: validModel,
    interactionId: interaction.id || null,
    textNotes: interaction.output_text || null
  };
}