background-execution-demo.js

#!/usr/bin/env node
// background-execution-demo.js - Demonstration of non-blocking background execution

console.log('🚀 Background Execution System Demo\n');

// Simulate the key concepts of our background execution system
class BackgroundExecutionDemo {
  constructor() {
    this.activeJobs = new Map();
    this.jobQueue = [];
    this.maxConcurrentJobs = 3;
    this.jobIdCounter = 0;
  }

  // Simulate starting a background job (non-blocking)
  async *startBackgroundJob(taskName, duration = 2000) {
    const jobId = `job_${++this.jobIdCounter}`;
    
    console.log(`📋 Queuing job: ${taskName} (ID: ${jobId})`);
    
    // Immediate response - UI not blocked
    yield {
      type: 'job_queued',
      jobId,
      taskName,
      status: 'queued',
      message: `Job ${taskName} queued for background processing`
    };

    // Start background execution
    const jobPromise = this.executeInBackground(jobId, taskName, duration);
    this.activeJobs.set(jobId, {
      id: jobId,
      taskName,
      promise: jobPromise,
      startTime: Date.now()
    });

    // Stream status updates
    yield* this.streamJobStatus(jobId);
  }

  // Background execution (doesn't block UI)
  async executeInBackground(jobId, taskName, duration) {
    console.log(`🔧 Background: Starting execution of ${taskName}`);
    
    // Simulate work with progress updates
    const steps = 5;
    const stepDuration = duration / steps;
    
    for (let i = 1; i <= steps; i++) {
      await new Promise(resolve => setTimeout(resolve, stepDuration));
      
      // Notify of progress (would trigger UI updates)
      this.notifyProgress(jobId, i, steps, `Step ${i}/${steps} completed`);
    }
    
    console.log(`✅ Background: Completed execution of ${taskName}`);
    return { success: true, result: `${taskName} completed successfully` };
  }

  // Stream job status updates to UI
  async *streamJobStatus(jobId) {
    const maxWait = 10000; // 10 seconds
    const pollInterval = 200; // 200ms
    let elapsed = 0;

    while (elapsed < maxWait) {
      const job = this.activeJobs.get(jobId);
      
      if (!job) {
        yield {
          type: 'job_completed',
          jobId,
          status: 'completed',
          message: 'Background job completed'
        };
        return;
      }

      // Check if job is done
      try {
        const result = await Promise.race([
          job.promise,
          new Promise(resolve => setTimeout(() => resolve(null), pollInterval))
        ]);

        if (result !== null) {
          // Job completed
          this.activeJobs.delete(jobId);
          yield {
            type: 'job_completed',
            jobId,
            status: 'completed',
            result,
            message: `Job completed: ${job.taskName}`
          };
          return;
        }
      } catch (error) {
        // Job failed
        this.activeJobs.delete(jobId);
        yield {
          type: 'job_failed',
          jobId,
          status: 'failed',
          error: error.message,
          message: `Job failed: ${job.taskName}`
        };
        return;
      }

      elapsed += pollInterval;
    }

    // Timeout - job continues in background
    yield {
      type: 'job_timeout',
      jobId,
      status: 'running',
      message: 'UI timeout - job continues in background'
    };
  }

  // Simulate progress notifications
  notifyProgress(jobId, current, total, message) {
    const progress = (current / total) * 100;
    console.log(`📊 Progress [${jobId}]: ${progress.toFixed(0)}% - ${message}`);
  }

  // Get status of all background jobs
  getJobsStatus() {
    return Array.from(this.activeJobs.values()).map(job => ({
      id: job.id,
      taskName: job.taskName,
      runningTime: Date.now() - job.startTime
    }));
  }
}

// Demonstration function
async function demonstrateBackgroundExecution() {
  const executor = new BackgroundExecutionDemo();
  
  console.log('🎯 Demonstrating non-blocking execution:\n');

  // Start multiple background jobs
  const jobs = [
    executor.startBackgroundJob('Write Fibonacci File', 1500),
    executor.startBackgroundJob('Process Data', 2000),
    executor.startBackgroundJob('Generate Report', 1000)
  ];

  // Simulate UI responsiveness while jobs run
  const uiSimulation = async () => {
    for (let i = 1; i <= 8; i++) {
      console.log(`🖱️  UI Action ${i}: User interaction processed immediately`);
      await new Promise(resolve => setTimeout(resolve, 300));
    }
  };

  // Process all jobs concurrently while maintaining UI responsiveness
  const jobPromises = jobs.map(async (jobGenerator, index) => {
    console.log(`\n--- Job ${index + 1} Status Updates ---`);
    for await (const status of jobGenerator) {
      console.log(`📡 Job ${index + 1} Update:`, status.message);
      if (status.type === 'job_completed' || status.type === 'job_failed') {
        break;
      }
    }
  });

  // Run everything concurrently
  await Promise.all([
    ...jobPromises,
    uiSimulation()
  ]);

  console.log('\n🎊 All jobs completed! UI remained responsive throughout.');
  console.log('\n📊 Final job status:', executor.getJobsStatus());
}

// Key benefits demonstration
function explainBenefits() {
  console.log('\n🌟 Key Benefits of Background Execution System:');
  console.log('');
  console.log('1. 🚫 Non-Blocking: UI never freezes during tool execution');
  console.log('2. 📡 Streaming Updates: Real-time progress without polling');
  console.log('3. 🔄 Concurrent Jobs: Multiple tools can run simultaneously');
  console.log('4. 💾 Persistence: Jobs survive UI disconnections');
  console.log('5. 🎛️  Control: Jobs can be paused, resumed, or cancelled');
  console.log('6. 📊 Monitoring: Full visibility into job status and progress');
  console.log('');
  console.log('🎯 Result: Smooth, responsive user experience even with long-running tasks!');
}

// Run the demonstration
demonstrateBackgroundExecution()
  .then(() => explainBenefits())
  .catch(error => {
    console.error('❌ Demo failed:', error);
    process.exit(1);
  });

export { BackgroundExecutionDemo };