import * as fs from "fs/promises";
import * as path from "path";
import { Alias } from "vite";

const pkgJsonCache = new Map();

const resolver: Alias = {
  find: /^(~\/.+)/,
  replacement: "$1",
  async customResolver(source, importer) {
    let root: null | string = null;

    const [_, sourcePath] = source.split("~/");

    if (importer!.includes("/src/")) {
      const [pkg] = importer!.split("/src/");

      root = `${pkg!}/src`;
    } else {
      let parent = importer!;

      while (parent !== "/") {
        parent = path.dirname(parent);

        let hasPkgJson = pkgJsonCache.get(parent);

        if (hasPkgJson === undefined)
          try {
            await fs.stat(`${parent}/package.json`);
            pkgJsonCache.set(parent, (hasPkgJson = true));
          } catch {
            pkgJsonCache.set(parent, (hasPkgJson = false));
          }

        if (hasPkgJson) {
          root = parent;
          break;
        }
      }

      if (root === null)
        throw new Error(
          `Failed to resolve import path ${source} in file ${importer}`
        );
    }

    const absolutePath = `${root}/${sourcePath}`;

    const folderItems = await fs.readdir(path.join(absolutePath, "../"));

    const item = folderItems.find((i) =>
      i.startsWith(sourcePath.split("/").at(-1)!)
    )!;

    const fullPath = absolutePath + path.extname(item);

    const stats = await fs.stat(fullPath);

    if (stats.isDirectory()) {
      const directoryItems = await fs.readdir(
        absolutePath + path.extname(item)
      );

      const indexFile = directoryItems.find((i) => i.startsWith("index"));

      return `${absolutePath}/${indexFile}`;
    } else {
      return fullPath;
    }
  },
};

export default resolver;