dynamic-import.ts

// Heavily inspired by
// https://github.com/airbnb/babel-plugin-dynamic-import-node/blob/master/src/utils.js

import { types as t, template } from "@babel/core";

if (!process.env.BABEL_8_BREAKING && !USE_ESM && !IS_STANDALONE) {
  // eslint-disable-next-line no-restricted-globals
  exports.getDynamicImportSource = function getDynamicImportSource(
    node: t.CallExpression,
  ): t.StringLiteral | t.TemplateLiteral {
    const [source] = node.arguments;

    return t.isStringLiteral(source) || t.isTemplateLiteral(source)
      ? source
      : (template.expression.ast`\`\${${source}}\`` as t.TemplateLiteral);
  };
}

export function buildDynamicImport(
  node: t.CallExpression | t.ImportExpression,
  deferToThen: boolean,
  wrapWithPromise: boolean,
  builder: (specifier: t.Expression) => t.Expression,
): t.Expression {
  const specifier = t.isCallExpression(node) ? node.arguments[0] : node.source;

  if (
    t.isStringLiteral(specifier) ||
    (t.isTemplateLiteral(specifier) && specifier.quasis.length === 0)
  ) {
    if (deferToThen) {
      return template.expression.ast`
        Promise.resolve().then(() => ${builder(specifier)})
      `;
    } else return builder(specifier);
  }

  const specifierToString = t.isTemplateLiteral(specifier)
    ? t.identifier("specifier")
    : t.templateLiteral(
        [t.templateElement({ raw: "" }), t.templateElement({ raw: "" })],
        [t.identifier("specifier")],
      );

  if (deferToThen) {
    return template.expression.ast`
      (specifier =>
        new Promise(r => r(${specifierToString}))
          .then(s => ${builder(t.identifier("s"))})
      )(${specifier})
    `;
  } else if (wrapWithPromise) {
    return template.expression.ast`
      (specifier =>
        new Promise(r => r(${builder(specifierToString)}))
      )(${specifier})
    `;
  } else {
    return template.expression.ast`
      (specifier => ${builder(specifierToString)})(${specifier})
    `;
  }
}