const path = require('path');
const WebpackCopyPlugin = require('copy-webpack-plugin');

module.exports = (webpackEnv, argv) => {
  const env = process.env;
  const mode = argv.mode || env.NODE_ENV || 'production';
  const isProd = mode === 'production';

  const tsconfig = require(path.resolve(__dirname, 'tsconfig.json'));
  const sourceDirName = 'src';
  const outDirectoryName = tsconfig.compilerOptions.outDir || 'dist';
  const outDirectory = path.resolve(__dirname, outDirectoryName);

  return {
    mode: mode,
    target: 'node',
    devtool: isProd ? 'source-map' : 'eval',
    entry: {
      [sourceDirName + '/index']: `./${sourceDirName}/index.ts`
    },
    output: {
      filename: '[name].js',
      path: outDirectory,
      libraryTarget: 'commonjs',
      clean: true
    },
    resolve: {
      extensions: ['.ts', '.js']
    },
    module: {
      rules: [
        {
          test: /\.ts$/,
          exclude: /node_modules/,
          use: {
            loader: 'babel-loader',
            options: require(path.resolve(__dirname, 'babel.config.js'))
          },
        }
      ]
    },
    plugins: [
      ...(isProd ? [
        new WebpackCopyPlugin({
          patterns: [{
            // Provide package.json without deps to avoid installing dependencies on vercel.com.
            from: 'package.json',
            to: 'package.json',
            transform (content) {
              const packageJson = JSON.parse(content.toString('utf8'));
              delete packageJson.scripts;
              delete packageJson.dependencies;
              delete packageJson.devDependencies;
              return Buffer.from(JSON.stringify(packageJson, null, 2));
            }
          }, {
            // Rewrite vercel.json with removed `dist` path.
            from: 'vercel.json',
            to: 'vercel.json',
            transform (content) {
              const vercelJson = JSON.parse(content.toString('utf8'));
              vercelJson.builds = vercelJson.builds.map((build) => (
                Object.assign(build, {
                  src: build.src.replace(outDirectoryName + path.sep, '')
                })
              ));
              vercelJson.rewrites = vercelJson.rewrites.map((rewrite) => (
                Object.assign(rewrite, {
                  destination: rewrite.destination.replace(path.sep + outDirectoryName, '')
                })
              ));
              return Buffer.from(JSON.stringify(vercelJson, null, 2));
            }
          }]
        })
      ] : [
        // isDev
      ])
    ]
  };
};