Nexus/packages/api/src/gemini-client.ts

import { logger } from "./lib/logger.js";

type GeminiSettings = {
  geminiApiKey?: string | null;
  geminiModel?: string | null;
};

/** Returns true if the settings have a Gemini API key configured. */
export function isGeminiConfigured(settings: GeminiSettings | null | undefined): boolean {
  return !!settings?.geminiApiKey;
}

/**
 * Generates an image using the Google Gemini API.
 * @returns A base64 data URL of the generated image.
 */
export async function generateGeminiImage(
  apiKey: string,
  prompt: string,
  model = "gemini-2.5-flash-image",
): Promise<string> {
  const fullPrompt = `Generate a professional, cinematic cover image for a 3D production project. ${prompt}`;
  const start = performance.now();

  const response = await fetch(
    `https://generativelanguage.googleapis.com/v1beta/models/${model}:generateContent?key=${apiKey}`,
    {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({
        contents: [{ parts: [{ text: fullPrompt }] }],
        generationConfig: { responseModalities: ["TEXT", "IMAGE"] },
      }),
    },
  );

  if (!response.ok) {
    const responseTimeMs = Math.round(performance.now() - start);
    const body = await response.text();
    let msg = body;
    try {
      const parsed = JSON.parse(body) as { error?: { message?: string } };
      if (parsed.error?.message) msg = parsed.error.message;
    } catch {
      /* keep raw */
    }
    logger.warn({ provider: "gemini", model, promptLength: fullPrompt.length, responseTimeMs, status: response.status }, "External API call failed");
    throw new Error(`HTTP ${response.status}: ${msg}`);
  }

  const data = (await response.json()) as {
    candidates?: Array<{
      content?: {
        parts?: Array<{
          inlineData?: { data: string; mimeType: string };
          text?: string;
        }>;
      };
    }>;
  };

  const imagePart = data.candidates?.[0]?.content?.parts?.find(
    (p) => p.inlineData,
  );

  if (!imagePart?.inlineData?.data) {
    throw new Error("No image data returned from Gemini");
  }

  const responseTimeMs = Math.round(performance.now() - start);
  logger.info({ provider: "gemini", model, promptLength: fullPrompt.length, responseTimeMs }, "External API call");

  const base64 = imagePart.inlineData.data;
  const mimeType = imagePart.inlineData.mimeType ?? "image/png";
  return `data:${mimeType};base64,${base64}`;
}

/** Turns Gemini API errors into actionable human-readable messages. */
export function parseGeminiError(err: unknown): string {
  const msg = err instanceof Error ? err.message : String(err);
  const lower = msg.toLowerCase();

  if (lower.includes("400") || lower.includes("invalid")) {
    return "Invalid request — check the Gemini model name and prompt.";
  }
  if (lower.includes("401") || lower.includes("unauthorized") || lower.includes("api_key_invalid") || lower.includes("api key not valid")) {
    return "Invalid API key — make sure you copied it correctly from Google AI Studio.";
  }
  if (lower.includes("403") || lower.includes("forbidden") || lower.includes("permission")) {
    return "Access denied — your API key may not have permission to use image generation.";
  }
  if (lower.includes("404") || lower.includes("not found")) {
    return "Model not found — verify the Gemini model name is correct.";
  }
  if (lower.includes("429") || lower.includes("rate limit") || lower.includes("quota")) {
    return "Rate limit or quota exceeded — wait a moment and try again.";
  }
  if (lower.includes("econnrefused") || lower.includes("enotfound") || lower.includes("fetch failed")) {
    return "Cannot reach the Gemini API — check your network connection.";
  }
  return msg.replace(/^Error: /, "").slice(0, 300);
}