// @flow

/**
 * Copyright (c) 2018-present, SourceCred Authors.
 * Copyright (c) 2015-2018, Facebook, Inc.
 *
 * Forked from babel-preset-react-app/index.js, which is released under
 * the MIT license.
 */

const plugins = [
  // Necessary to include regardless of the environment because
  // in practice some other transforms (such as object-rest-spread)
  // don't work without it: https://github.com/babel/babel/issues/7215
  require.resolve("babel-plugin-transform-es2015-destructuring"),
  // class { handleClick = () => { } }
  require.resolve("babel-plugin-transform-class-properties"),
  // The following two plugins use Object.assign directly, instead of Babel's
  // extends helper. Note that this assumes `Object.assign` is available.
  // { ...todo, completed: true }
  [
    require.resolve("babel-plugin-transform-object-rest-spread"),
    {
      useBuiltIns: true,
    },
  ],
  // Transforms JSX
  [
    require.resolve("babel-plugin-transform-react-jsx"),
    {
      useBuiltIns: true,
    },
  ],
  // Polyfills the runtime needed for async/await and generators
  [
    require.resolve("babel-plugin-transform-runtime"),
    {
      helpers: false,
      polyfill: false,
      regenerator: true,
    },
  ],
];

// This is similar to how `env` works in Babel:
// https://babeljs.io/docs/usage/babelrc/#env-option
// We are not using `env` because it’s ignored in versions > babel-core@6.10.4:
// https://github.com/babel/babel/issues/4539
// https://github.com/facebookincubator/create-react-app/issues/720
// It’s also nice that we can enforce `NODE_ENV` being specified.
var env = process.env.BABEL_ENV || process.env.NODE_ENV;
var backend = process.env.SOURCECRED_BACKEND === "true";
if (env !== "development" && env !== "test" && env !== "production") {
  throw new Error(
    "Using `babel-preset-react-app` requires that you specify `NODE_ENV` or " +
      '`BABEL_ENV` environment variables. Valid values are "development", ' +
      '"test", and "production". Instead, received: ' +
      JSON.stringify(env) +
      "."
  );
}

if (env === "development" || env === "test") {
  // The following two plugins are currently necessary to make React warnings
  // include more valuable information. They are included here because they are
  // currently not enabled in babel-preset-react. See the below threads for more info:
  // https://github.com/babel/babel/issues/4702
  // https://github.com/babel/babel/pull/3540#issuecomment-228673661
  // https://github.com/facebookincubator/create-react-app/issues/989
  plugins.push.apply(plugins, [
    // Adds component stack to warning messages
    require.resolve("babel-plugin-transform-react-jsx-source"),
    // Adds __self attribute to JSX which React will use for some warnings
    require.resolve("babel-plugin-transform-react-jsx-self"),
  ]);
}

if (env === "test") {
  module.exports = {
    presets: [
      // ES features necessary for user's Node version
      [
        require("babel-preset-env").default,
        {
          targets: {
            node: "current",
          },
        },
      ],
      // JSX, Flow
      require.resolve("babel-preset-react"),
    ],
    plugins: plugins.concat([
      // Compiles import() to a deferred require()
      require.resolve("babel-plugin-dynamic-import-node"),
    ]),
  };
} else {
  module.exports = {
    presets: [
      // Latest stable ECMAScript features
      [
        require.resolve("babel-preset-env"),
        {
          targets: backend
            ? {
                node: "current",
              }
            : {
                ie: 9,
                uglify: true,
              },
          // Disable polyfill transforms
          useBuiltIns: false,
          // Do not transform modules to CJS
          modules: false,
        },
      ],
      // JSX, Flow
      require.resolve("babel-preset-react"),
    ],
    plugins: plugins.concat(
      backend
        ? [
            // Must come before `babel-plugin-transform-regenerator`.
            require.resolve("babel-plugin-transform-es2015-for-of"),
          ]
        : [],
      [
        // function* () { yield 42; yield 43; }
        [
          require.resolve("babel-plugin-transform-regenerator"),
          {
            // Async functions are converted to generators by babel-preset-env
            async: false,
          },
        ],
        // Adds syntax support for import()
        require.resolve("babel-plugin-syntax-dynamic-import"),
      ]
    ),
  };

  if (env === "production") {
    // Optimization: hoist JSX that never changes out of render()
    // Disabled because of issues: https://github.com/facebookincubator/create-react-app/issues/553
    // TODO: Enable again when these issues are resolved.
    // plugins.push.apply(plugins, [
    //   require.resolve('babel-plugin-transform-react-constant-elements')
    // ]);
  }
}