const crypto = require("crypto");
const fs = require("fs");
const path = require("path");
const multer = require("multer");

const uploadDirectory = path.resolve(
  process.env.UPLOAD_DIR || path.join(process.cwd(), "uploads"),
);
const maxFileSize = Number.parseInt(process.env.MAX_UPLOAD_SIZE_BYTES, 10) || 5 * 1024 * 1024;
const extensionByMimeType = {
  "image/jpeg": ".jpg",
  "image/png": ".png",
  "image/gif": ".gif",
  "image/webp": ".webp",
};

fs.mkdirSync(uploadDirectory, { recursive: true });

const storage = multer.diskStorage({
  destination: uploadDirectory,
  filename: (req, file, callback) => {
    callback(null, `${crypto.randomUUID()}${extensionByMimeType[file.mimetype]}`);
  },
});

const uploadImage = multer({
  storage,
  limits: { fileSize: maxFileSize, files: 1 },
  fileFilter: (req, file, callback) => {
    if (!extensionByMimeType[file.mimetype]) {
      return callback(new Error("Only JPEG, PNG, GIF, and WebP images are allowed"));
    }
    callback(null, true);
  },
}).single("image");

function handlePostUpload(req, res, next) {
  uploadImage(req, res, (err) => {
    if (!err) return next();
    if (err.code === "LIMIT_FILE_SIZE") {
      return res.status(413).send("Image exceeds the maximum allowed size");
    }
    return res.status(400).send(err.message);
  });
}

function imageLinkForFile(file) {
  return file ? `/posts/image/${file.filename}` : null;
}

async function removeImageLink(imageLink) {
  if (!imageLink || !imageLink.startsWith("/posts/image/")) return;
  const filename = path.basename(imageLink);
  await fs.promises.unlink(path.join(uploadDirectory, filename)).catch((err) => {
    if (err.code !== "ENOENT") throw err;
  });
}

async function removeUploadedFile(file) {
  if (file) await removeImageLink(imageLinkForFile(file));
}

module.exports = {
  handlePostUpload,
  imageLinkForFile,
  removeImageLink,
  removeUploadedFile,
  uploadDirectory,
};