/* eslint-disable global-require */
/* eslint-env node */

const validEnv = ["development", "test", "production"]
const currentEnv = process.env.NODE_ENV || "unknown"
const isDevelopmentEnv  = currentEnv === "development"
const isProductionEnv   = currentEnv === "production"
const isTestEnv         = currentEnv === "test"

if (!validEnv.includes(currentEnv)) {
  throw new Error(
    "Please specify a valid `NODE_ENV` or " +
    "`BABEL_ENV` environment variables. Valid values are \"development\", " +
    "\"test\", and \"production\". Instead, received: " +
    JSON.stringify(currentEnv) +
    "."
  )
}

module.exports = (targets, extra_options={}) => {
  const generated_options = {
    babelrc: false,
    presets: [
      isTestEnv && [
        require("@babel/preset-env").default,
        {
          targets: {
            node: "current",
          },
        },
      ],
      (isProductionEnv || isDevelopmentEnv) && [
        require("@babel/preset-env").default,
        {
          modules: false,
          targets: targets,

          forceAllTransforms: false,
          useBuiltIns:        false,
          exclude:            ["transform-typeof-symbol"],

          // We are specifying mutiple browser target sets
          ignoreBrowserslistConfig: true,
        },
      ],
      "@babel/preset-flow",
    ].filter(Boolean),
    plugins: [
      // require("babel-plugin-macros"),
      require("@babel/plugin-syntax-dynamic-import").default,
      isTestEnv && require("babel-plugin-dynamic-import-node"),
      require("@babel/plugin-transform-exponentiation-operator").default,
      require("@babel/plugin-transform-destructuring").default,
      [
        require("@babel/plugin-proposal-class-properties").default,
        {
          loose: true,
        },
      ],
      [
        require("@babel/plugin-proposal-object-rest-spread").default,
        {
          useBuiltIns: true,
        },
      ],
      [
        require("@babel/plugin-transform-runtime").default,
        {
          helpers:     false,
          regenerator: true,
        },
      ],
      [
        require("@babel/plugin-transform-regenerator").default,
        {
          async: false,
        },
      ],
      "syntax-trailing-function-commas",
    ].filter(Boolean),
  }

  return {
    loader:  "babel-loader",
    options: Object.assign({}, generated_options, extra_options),
  }
}