frontend/plugins/withCmakeJobLimit.js

const { withDangerousMod } = require('@expo/config-plugins');
const fs = require('fs');
const path = require('path');

const MAX_JOBS = '4';

// React Native's hermes-engine build hardcodes
//   Runtime.getRuntime().availableProcessors()
// for `cmake --build -j`, ignoring the CMAKE_BUILD_PARALLEL_LEVEL env var.
// On high-core CI runners this exhausts memory.
// This plugin caps it during prebuild.
const withCmakeJobLimit = (config) =>
  withDangerousMod(config, [
    'android',
    async (config) => {
      const root = config.modRequest.projectRoot;

      const hermesPath = path.join(
        root,
        'node_modules',
        'react-native',
        'ReactAndroid',
        'hermes-engine',
        'build.gradle.kts',
      );
      if (fs.existsSync(hermesPath)) {
        let content = fs.readFileSync(hermesPath, 'utf-8');
        content = content.replace(
          /Runtime\.getRuntime\(\)\.availableProcessors\(\)\.toString\(\)/,
          `"${MAX_JOBS}"`,
        );
        fs.writeFileSync(hermesPath, content);
        console.log(`[withCmakeJobLimit] capped hermes-engine jobs to ${MAX_JOBS}`);
      }

      return config;
    },
  ]);

module.exports = withCmakeJobLimit;