import type { NextApiRequest, NextApiResponse } from "next";
import sharp from "sharp";
import { authorizeDocuments, documentApiError } from "@/lib/documents-api";
import { saveDocumentImage } from "@/lib/document-images";

const maxUploadBytes = 8 * 1024 * 1024;
const maxStoredBytes = 2 * 1024 * 1024;
const imageTypes = new Set(["image/png", "image/jpeg", "image/webp"]);
const imageFormats = new Set(["png", "jpeg", "webp"]);

export const config = { api: { bodyParser: false } };

export default async function handler(request: NextApiRequest, response: NextApiResponse) {
  try {
    if (request.method !== "POST") {
      response.setHeader("Allow", "POST");
      return response.status(405).end();
    }
    if (!authorizeDocuments(request, response, true)) return;

    const type = request.headers["content-type"]?.split(";")[0].trim().toLowerCase();
    if (!type || !imageTypes.has(type)) {
      return response.status(415).json({ error: "请上传 PNG、JPEG 或 WebP 图片" });
    }
    if (Number(request.headers["content-length"]) > maxUploadBytes) {
      return response.status(413).json({ error: "图片上传上限为 8 MiB" });
    }

    const chunks: Buffer[] = [];
    let length = 0;
    for await (const chunk of request.iterator({ destroyOnReturn: false })) {
      const bytes = Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk);
      length += bytes.length;
      if (length > maxUploadBytes) {
        return response.status(413).json({ error: "图片上传上限为 8 MiB" });
      }
      chunks.push(bytes);
    }

    let encoded: Buffer;
    try {
      const input = sharp(Buffer.concat(chunks), { limitInputPixels: 25_000_000 });
      const { format, pages } = await input.metadata();
      if (!format || !imageFormats.has(format) || type !== `image/${format}` || (pages ?? 1) > 1) {
        return response.status(415).json({ error: "图片格式需与声明一致，且只支持静态图片" });
      }
      encoded = await input.rotate()
        .resize({ width: 2000, height: 4000, fit: "inside", withoutEnlargement: true })
        .webp({ quality: 85 })
        .toBuffer();
    } catch {
      return response.status(400).json({ error: "无法解码图片，或像素数量超过限制" });
    }
    if (encoded.length > maxStoredBytes) {
      return response.status(413).json({ error: "处理后的图片超过 2 MiB，请缩小后重试" });
    }

    const id = saveDocumentImage(encoded);
    const url = `/api/documents/images/${id}`;
    return response.status(200).json({ id, url, contentType: "image/webp", size: encoded.length });
  } catch (error) {
    return documentApiError(response, error);
  }
}