const fs = require('fs');
const path = require('path');

const StartServerPlugin = require('start-server-webpack-plugin');
const UglifyJsPlugin = require('uglifyjs-webpack-plugin');
const webpack = require('webpack');
const nodeExternals = require('webpack-node-externals');

const SOURCE_PATH = process.env.SOURCE_PATH || '/var/node/src';
const OUTPUT_PATH = process.env.OUTPUT_PATH || '/var/node/dist';

const hashFormat = {
  chunk: ('production' === process.env.NODE_ENV) ? '.[chunkhash:20]' : '',
}

function defaultConfig() {
  const config = {
    mode: 'production' !== process.env.NODE_ENV ? 'development' : 'production',
    entry: {
      index: [
        '@babel/polyfill',
        path.join(SOURCE_PATH, 'index.js'),
      ]
    },
    target: 'node',
    output: {
      filename: `[name]${hashFormat.chunk}.js`,
      chunkFilename: `[id]${hashFormat.chunk}.chunk.js`,
      path: OUTPUT_PATH,
    },
    optimization: {},
    externals: [nodeExternals({
      whitelist: [
        'webpack/hot/poll?1000',
        /^@truss/,
      ],
    })],
    module: {
      rules: [
        {
          test: /\.js$/,
          exclude: [
            'node_modules',
          ],
          use: {
            loader: 'babel-loader',
            options: {
              babelrcRoots: [
                OUTPUT_PATH,
              ],
              plugins: [
                ['@babel/plugin-proposal-decorators', {
                  legacy: true,
                }],
                '@babel/plugin-proposal-class-properties',
                '@babel/plugin-proposal-object-rest-spread',
              ],
              presets: [
                '@babel/preset-env',
              ],
            },
          },
        },
        {
          test: /\.css$/,
          use: [{
            loader: 'raw-loader'
          }],
        },
        {
          test: /\.scss$/,
          use: [{
            loader: 'raw-loader',
          }, {
            loader: 'sass-loader',
            options: {
              sourceMap: 'production' !== process.env.NODE_ENV,
            },
          }],
        },
      ],
    },
    plugins: [
      new StartServerPlugin({
        entryName: 'index',
        restartable: false,
      }),
    ],
    resolve: {
      alias: {},
      mainFields: ['module', 'main'],
      modules: [path.join(OUTPUT_PATH, 'node_modules')],
    },
    resolveLoader: {
      modules: [path.join(OUTPUT_PATH, 'node_modules')],
    },
  };

  if ('production' !== config.mode) {
    config.devtool = 'sourcemap';
    config.entry.whp = 'webpack/hot/poll?1000';
    config.plugins.push(new webpack.BannerPlugin({
      banner: 'require("source-map-support").install();',
      raw: true,
      entryOnly: false,
    }));
    config.plugins.push(new webpack.HotModuleReplacementPlugin());
  }
  else {
    config.optimization.minimizer = [
      new UglifyJsPlugin({cache: false})
    ];
    config.externals = [];
  }

  return config
}

module.exports = () => {
  const defaults = defaultConfig();
  try {
    const config = require(`${SOURCE_PATH}/webpack.config`);
    return typeof config === "function" ? config(defaults) : config;
  }
  catch (error) {
    if (`Cannot find module '${SOURCE_PATH}/webpack.config'` !== error.message) {
      throw error;
    }
    return defaults;
  }
}