const fs = require('fs');
const path = require('path');
const config = require('../config');

const PATH = 'images/edits';
const TIMEOUT_MS = 180000;

/**
 * @param {string} imageUrl data:image/...;base64,... 或本地绝对/相对路径
 */
function parseImageInput (imageUrl) {
  const s = String(imageUrl || '').trim();
  const m = s.match(/^data:([^;]+);base64,([\s\S]+)$/i);
  if (m) {
    return {
      buffer: Buffer.from(m[2], 'base64'),
      filename: 'image.png',
      mime: (m[1] || 'image/png').split(';')[0].trim() || 'image/png',
    };
  }
  if (fs.existsSync(s)) {
    const buf = fs.readFileSync(s);
    const base = path.basename(s) || 'image.png';
    return { buffer: buf, filename: base, mime: 'image/png' };
  }
  throw new Error('img2img: image 需为 data URL 或存在的本地图片路径');
}

/**
 * OpenAI 官方 /v1/images/edits 要求 multipart/form-data（非 JSON）
 * 字段：prompt, image(文件), n, size；可选 model
 */
function buildFormData (prompt, imageUrl, modelOverride) {
  const form = new FormData();
  form.append('prompt', String(prompt || ''));
  form.append('n', '1');
  form.append('size', '1024x1024');
  const { buffer, filename, mime } = parseImageInput(imageUrl);
  const blob = new Blob([buffer], { type: mime });
  form.append('image', blob, filename.endsWith('.png') || filename.endsWith('.jpg') || filename.endsWith('.webp') ? filename : `${filename}.png`);
  if (modelOverride && String(modelOverride).trim()) {
    form.append('model', String(modelOverride).trim());
  }
  return form;
}

/** @deprecated 仅结构占位；真实请求请用 buildFormData + multipart */
function getBody (prompt, imageUrl) {
  return {
    prompt,
    image: typeof imageUrl === 'string' && imageUrl.length > 80 ? `${imageUrl.slice(0, 40)}…` : imageUrl,
    n: 1,
    size: '1024x1024',
  };
}

function getDoubaoBody (prompt, imageUrl, modelOverride) {
  const model =
    (modelOverride && String(modelOverride).trim()) || config.DOUBAO_MODEL;
  return {
    model,
    prompt,
    image: imageUrl,
    n: 1,
    size: '1024x1024',
  };
}

module.exports = {
  path: PATH,
  getBody,
  getDoubaoBody,
  buildFormData,
  timeoutMs: TIMEOUT_MS,
};