/**
 * 콘텐츠 스튜디오 이미지 생성 (Vercel 서버 함수). POST { channel, format, pillarId } → { ok, imageDataUrl, prompt }
 *
 * Gemini 키는 서버 환경변수 GEMINI_API_KEY 에만 둔다 (VITE_ 접두사·vite.config define 금지).
 * 프롬프트는 브라우저가 아니라 여기서 선택값으로 만든다. 배경은 api/_studio.js 주석.
 */
import { guard, readSelection } from './_studio.js';

// 이미지·렌더 요청은 외부 API 응답을 기다리므로 실행 시간 한도를 명시한다.
export const config = { maxDuration: 60 };

const MODEL = 'gemini-2.5-flash-image';

const PILLAR_DESCRIPTIONS = {
  safety: 'hospital safety systems, clean surgical rooms, CCTV monitoring, professional medical team, trust and reliability',
  expertise: 'medical expertise, advanced surgical equipment, professional doctors, medical certifications, precision and skill',
  results: 'natural beautiful results, before and after transformation, patient satisfaction, subtle elegant outcomes',
  care: 'patient-centered care, warm consultation, personalized treatment plan, caring medical staff, comfortable clinic interior',
};

const CHANNEL_HINTS = {
  youtube: 'YouTube thumbnail style, bold text overlay area, high contrast, eye-catching',
  instagram: 'Instagram aesthetic, clean minimalist, lifestyle photography style, warm tones',
  naver_blog: 'Korean blog header image, informative, medical illustration, clean layout',
  tiktok: 'TikTok cover image, vertical format, trendy, dynamic, youthful',
  facebook: 'Facebook ad creative, professional, compelling, clear messaging space',
};

function buildPrompt(sel) {
  return [
    'Generate a premium medical marketing image for a plastic surgery clinic.',
    `Theme: ${sel.pillarId ? PILLAR_DESCRIPTIONS[sel.pillarId] : ''}`,
    `Style: ${CHANNEL_HINTS[sel.channel] ?? ''}`,
    `Aspect ratio: ${sel.aspectRatio}`,
    'Color palette: soft purple (#7B2D8E), gold (#E8B931), warm white (#FAF8F5).',
    'Premium, luxurious, trustworthy aesthetic.',
    'No text or logos in the image.',
    'Photorealistic, high quality, professional medical marketing.',
  ].filter(Boolean).join(' ');
}

export default async function handler(req, res) {
  if (guard(req, res, ['POST'])) return;

  const key = process.env.GEMINI_API_KEY;
  if (!key) {
    console.error('[api/gemini-image] GEMINI_API_KEY 가 설정되지 않았습니다.');
    return res.status(500).json({ ok: false, error: 'unconfigured' });
  }
  const sel = readSelection(req.body);
  if (!sel) return res.status(400).json({ ok: false, error: 'bad selection' });

  const prompt = buildPrompt(sel);
  let upstream;
  try {
    upstream = await fetch(`https://generativelanguage.googleapis.com/v1beta/models/${MODEL}:generateContent`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json', 'x-goog-api-key': key },
      body: JSON.stringify({
        contents: [{ role: 'user', parts: [{ text: prompt }] }],
        generationConfig: { responseModalities: ['TEXT', 'IMAGE'] },
      }),
    });
  } catch (e) {
    console.error('[api/gemini-image] 연결 실패', e);
    return res.status(502).json({ ok: false, error: 'upstream unreachable' });
  }

  const data = await upstream.json().catch(() => null);
  if (!upstream.ok) {
    // 브라우저에는 상태만 넘기고, Google 의 상세 메시지는 서버 로그에만 남긴다.
    console.error('[api/gemini-image] 업스트림 오류', upstream.status, JSON.stringify(data?.error ?? {}).slice(0, 300));
    const status = upstream.status === 429 ? 429 : upstream.status === 400 ? 400 : 502;
    return res.status(status).json({ ok: false, error: status === 429 ? 'rate limited' : 'upstream error' });
  }

  const parts = data?.candidates?.[0]?.content?.parts ?? [];
  const image = parts.find((p) => p.inlineData?.mimeType?.startsWith('image/'))?.inlineData;
  if (!image) return res.status(502).json({ ok: false, error: 'no image' });

  return res.status(200).json({ ok: true, imageDataUrl: `data:${image.mimeType};base64,${image.data}`, prompt });
}