const { getDefaultConfig, mergeConfig } = require(
  '@react-native/metro-config'
);

const defaultConfig = getDefaultConfig(__dirname);

/**
 * Metro configuration for Hermes + OTA
 *
 * Key points:
 * 1. Hermes bytecode compilation is handled by the
 * RN build pipeline (Xcode / Gradle), NOT Metro.
 * 2. For OTA, you need to compile bytecode yourself
 * using hermesc AFTER Metro bundles.
 * 3. Source maps need two-stage composition.
 */
const config = {
  transformer: {
    // Enable Hermes-compatible output
    hermesParser: true,

    // Minify for production OTA bundles
    minifierPath: 'metro-minify-terser',
    minifierConfig: {
      compress: {
        drop_console: true,   // Strip console.log
        dead_code: true,
        passes: 2,
      },
    },
  },

  serializer: {
    // Generate source maps for OTA debugging
    sourceMapUrl: 'index.map',

    // For Hermes: use "plain" output (not RAM bundles)
    // RAM bundles are incompatible with hermesc
    createModuleIdFactory:
      defaultConfig.serializer.createModuleIdFactory,
  },

  resolver: {
    // Ensure .hbc files aren't treated as assets
    assetExts: defaultConfig.resolver.assetExts.filter(
      (ext) => ext !== 'hbc'
    ),
    sourceExts: [
      ...defaultConfig.resolver.sourceExts,
      'cjs',
    ],
  },
};

module.exports = mergeConfig(defaultConfig, config);

# Step 1: Bundle with Metro (plain JS + source map)
npx react-native bundle \
  --platform ios \
  --dev false \
  --entry-file index.js \
  --bundle-output ./build/index.bundle.js \
  --sourcemap-output ./build/index.bundle.js.map

# Step 2: Compile to Hermes bytecode
# Use the hermesc that ships with your RN version!
node_modules/react-native/sdks/hermesc/osx-bin/hermesc \
  -emit-binary \
  -O \
  -output-source-map \
  -out ./build/index.bundle.hbc \
  ./build/index.bundle.js

# Step 3: Compose source maps (bytecode → JS → source)
node_modules/react-native/scripts/compose-source-maps.js \
  ./build/index.bundle.js.map \
  ./build/index.bundle.hbc.map \
  -o ./build/index.bundle.composed.map

# Step 4: Upload to your OTA provider
# The bundle is .hbc, the map is .composed.map