import { randomUUID } from "node:crypto";
import { mkdir, writeFile } from "node:fs/promises";
import path from "node:path";

/**
 * Editor image uploads land in ./uploads/ (gitignored) and are served by
 * the GET /uploads/[name] route handler — Next.js only serves public/
 * files that existed at build time, so runtime uploads need their own
 * route. Filenames are random UUIDs with an extension derived from the
 * MIME type — client filenames never touch the filesystem. Swapping this
 * for object storage later only means changing saveUploadedImage and the
 * returned URL.
 */

export const MAX_UPLOAD_BYTES = 8 * 1024 * 1024; // 8 MB

const EXTENSION_BY_MIME: Record<string, string> = {
  "image/png": "png",
  "image/jpeg": "jpg",
  "image/webp": "webp",
  "image/gif": "gif",
  "image/avif": "avif",
};

export const MIME_BY_EXTENSION: Record<string, string> = Object.fromEntries(
  Object.entries(EXTENSION_BY_MIME).map(([mime, ext]) => [ext, mime]),
);

/** Matches the filenames saveUploadedImage generates — nothing else. */
export const UPLOAD_NAME_PATTERN = /^[0-9a-f]{8}(?:-[0-9a-f]{4}){3}-[0-9a-f]{12}\.(png|jpg|webp|gif|avif)$/;

export function defaultUploadsDir(): string {
  return path.join(process.cwd(), "uploads");
}

export type UploadResult =
  | { ok: true; filename: string }
  | { ok: false; error: string; status: 400 | 413 };

export async function saveUploadedImage(file: File): Promise<UploadResult> {
  const extension = EXTENSION_BY_MIME[file.type];
  if (!extension) {
    return {
      ok: false,
      status: 400,
      error: "Unsupported image type. Use PNG, JPEG, WebP, GIF, or AVIF.",
    };
  }
  if (file.size > MAX_UPLOAD_BYTES) {
    return {
      ok: false,
      status: 413,
      error: `Image is too large (max ${MAX_UPLOAD_BYTES / 1024 / 1024} MB).`,
    };
  }
  if (file.size === 0) {
    return { ok: false, status: 400, error: "The uploaded file is empty." };
  }

  const filename = `${randomUUID()}.${extension}`;
  await mkdir(path.join(process.cwd(), "uploads"), { recursive: true });
  await writeFile(
    path.join(process.cwd(), "uploads", filename),
    Buffer.from(await file.arrayBuffer()),
  );
  return { ok: true, filename };
}