// @flow
import * as babelPlugins from "./generated/plugins";

export default (_: any, opts: Object): Object => {
  let loose = false;
  let modules = "commonjs";
  let spec = false;

  if (opts !== undefined) {
    if (opts.loose !== undefined) loose = opts.loose;
    if (opts.modules !== undefined) modules = opts.modules;
    if (opts.spec !== undefined) spec = opts.spec;
  }

  // be DRY
  const optsLoose = { loose };

  return {
    plugins: [
      [babelPlugins.transformTemplateLiterals, { loose, spec }],
      babelPlugins.transformLiterals,
      babelPlugins.transformFunctionName,
      [babelPlugins.transformArrowFunctions, { spec }],
      babelPlugins.transformBlockScopedFunctions,
      [babelPlugins.transformClasses, optsLoose],
      babelPlugins.transformObjectSuper,
      babelPlugins.transformShorthandProperties,
      babelPlugins.transformDuplicateKeys,
      [babelPlugins.transformComputedProperties, optsLoose],
      [babelPlugins.transformForOf, optsLoose],
      babelPlugins.transformStickyRegex,
      babelPlugins.transformUnicodeEscapes,
      babelPlugins.transformUnicodeRegex,
      [babelPlugins.transformSpread, optsLoose],
      [babelPlugins.transformParameters, optsLoose],
      [babelPlugins.transformDestructuring, optsLoose],
      babelPlugins.transformBlockScoping,
      babelPlugins.transformTypeofSymbol,
      babelPlugins.transformInstanceof,
      (modules === "commonjs" || modules === "cjs") && [
        babelPlugins.transformModulesCommonjs,
        optsLoose,
      ],
      modules === "systemjs" && [
        babelPlugins.transformModulesSystemjs,
        optsLoose,
      ],
      modules === "amd" && [babelPlugins.transformModulesAmd, optsLoose],
      modules === "umd" && [babelPlugins.transformModulesUmd, optsLoose],
      [
        babelPlugins.transformRegenerator,
        { async: false, asyncGenerators: false },
      ],
    ].filter(Boolean), // filter out falsy values
  };
};