import { readFileSync } from "node:fs";
import { extname } from "node:path";

import type babel from "@babel/core";
import { transformSync } from "@babel/core";
import type * as esbuild from "esbuild";
import { once } from "lodash-es";

/**
 * An esbuild plugin that processes files with Babel if `plugins` is not empty.
 */
export const babelPlugin = ({
  filter = /\.[jt]sx?$/,
  plugins: getPlugins,
}: {
  filter?: RegExp;
  plugins:
    | babel.PluginItem[]
    | ((file: { path: string; contents: string }) => babel.PluginItem[]);
}): esbuild.Plugin => ({
  name: "babel-plugin",
  setup(build) {
    build.onLoad({ filter, namespace: "file" }, ({ path }) => {
      const load = once(() => readFileSync(path, "utf-8"));
      const plugins = Array.isArray(getPlugins)
        ? getPlugins
        : getPlugins({
            path,
            get contents() {
              return load();
            },
          });

      if (!plugins.length) {
        return;
      }

      const { code } = transformSync(load(), {
        assumptions: {
          noDocumentAll: true,
          noClassCalls: true,
        },
        parserOpts: {
          createImportExpressions: true,
          plugins: [
            "jsx",
            "decorators",
            "typescript",
            "importAttributes",
            "explicitResourceManagement",
            "v8intrinsic",
          ],
        },
        filename: path,
        plugins,
        sourceType: "module",
      })!;

      return {
        contents: code!,
        loader: extname(path).slice(1) as "js" | "ts",
      };
    });
  },
});