/**
 * Please note this code is just a proof of concept and should not
 * be used in production!
 * 
 * Based on https://github.com/airbnb/babel-plugin-dynamic-import-node
 */
 
import syntax from 'babel-plugin-syntax-dynamic-import';

export default function ({ template, types: t }) {
  // Uses a hacky "thennable" return object that invokes the callbacks synchronusly,
  // Will not work if the import function does follow up `.then/.catch`
  //
  // i.e. 
  //     import().then(...) // <-- Should be fine
  //     import().then(...).then(...) // <-- Nope
  const buildImport = template(` (function(modulePath) {
    var e;
    try {
        var m = require(modulePath);
    } catch (err) {
        e = err;
    }
    return {
        then: function(cb, errCb) {
            if (e && errCb) {
                errCb(e);
            } else {
                cb(m);
            }
        },
        catch: function(cb) {
            if (e) {
                cb(e); 
            }
        }
    };
})(SOURCE);`);

  return {
    inherits: syntax,

    visitor: {
      Import(path) {
        const importArguments = path.parentPath.node.arguments;
        const isString = t.isStringLiteral(importArguments[0])
                        || t.isTemplateLiteral(importArguments[0]);
        if (isString) {
          t.removeComments(importArguments[0]);
        }
        const newImport = buildImport({
          SOURCE: (isString)
            ? importArguments
            : t.templateLiteral([
              t.templateElement({ raw: '', cooked: '' }),
              t.templateElement({ raw: '', cooked: '' }, true),
            ], importArguments),
        });
        path.parentPath.replaceWith(newImport);
      },
    },
  };
}