# A/B Testing Service

Advanced A/B testing and experimentation service for the Telegram Marketing Intelligence Agent system.

## Overview

The A/B Testing service provides comprehensive experiment management, traffic allocation, and statistical analysis capabilities for optimizing marketing campaigns.

## Features

### Experiment Management
- Multiple experiment types (A/B, multivariate, bandit)
- Flexible variant configuration
- Target audience filtering
- Scheduled experiments
- Early stopping support

### Traffic Allocation Algorithms
- **Random**: Fixed percentage allocation
- **Epsilon-Greedy**: Balance exploration and exploitation
- **UCB (Upper Confidence Bound)**: Optimistic exploration strategy
- **Thompson Sampling**: Bayesian approach for optimal allocation

### Statistical Analysis
- Frequentist hypothesis testing
- Bayesian analysis
- Confidence intervals
- Power analysis
- Multiple testing correction

### Real-time Features
- Live metrics tracking
- Dynamic allocation updates
- Real-time results visualization
- Automated winner detection

## Architecture

```
┌─────────────────┐     ┌──────────────────┐     ┌─────────────────┐
│   API Gateway   │────▶│ A/B Testing Service│────▶│    MongoDB      │
└─────────────────┘     └──────────────────┘     └─────────────────┘
                               │                           │
                               ├───────────────────────────┤
                               ▼                           ▼
                        ┌─────────────┐           ┌──────────────┐
                        │    Redis    │           │   RabbitMQ   │
                        └─────────────┘           └──────────────┘
```

## API Endpoints

### Experiments
- `GET /api/experiments` - List experiments
- `POST /api/experiments` - Create experiment
- `GET /api/experiments/:id` - Get experiment details
- `PUT /api/experiments/:id` - Update experiment
- `DELETE /api/experiments/:id` - Delete experiment
- `POST /api/experiments/:id/start` - Start experiment
- `POST /api/experiments/:id/pause` - Pause experiment
- `POST /api/experiments/:id/complete` - Complete experiment

### Allocations
- `POST /api/allocations/allocate` - Allocate user to variant
- `GET /api/allocations/allocation/:experimentId/:userId` - Get user allocation
- `POST /api/allocations/conversion` - Record conversion
- `POST /api/allocations/event` - Record custom event
- `POST /api/allocations/batch/allocate` - Batch allocate users
- `GET /api/allocations/stats/:experimentId` - Get allocation statistics

### Results
- `GET /api/results/:experimentId` - Get experiment results
- `GET /api/results/:experimentId/metrics` - Get real-time metrics
- `GET /api/results/:experimentId/segments` - Get segment analysis
- `GET /api/results/:experimentId/funnel` - Get funnel analysis
- `GET /api/results/:experimentId/export` - Export results

## Configuration

### Environment Variables
- `PORT` - Service port (default: 3005)
- `MONGODB_URI` - MongoDB connection string
- `REDIS_URL` - Redis connection URL
- `RABBITMQ_URL` - RabbitMQ connection URL
- `JWT_SECRET` - JWT signing secret

### Experiment Configuration
- `DEFAULT_EXPERIMENT_DURATION` - Default duration in ms
- `MIN_SAMPLE_SIZE` - Minimum sample size per variant
- `CONFIDENCE_LEVEL` - Statistical confidence level
- `MDE` - Minimum detectable effect

### Allocation Configuration
- `ALLOCATION_ALGORITHM` - Default algorithm
- `EPSILON` - Epsilon for epsilon-greedy
- `UCB_C` - Exploration parameter for UCB

## Usage Examples

### Create an A/B Test
```javascript
const experiment = {
  name: "New CTA Button Test",
  type: "ab",
  targetMetric: {
    name: "conversion_rate",
    type: "conversion",
    goalDirection: "increase"
  },
  variants: [
    {
      variantId: "control",
      name: "Current Button",
      config: { buttonText: "Sign Up" },
      allocation: { percentage: 50 }
    },
    {
      variantId: "variant_a",
      name: "New Button",
      config: { buttonText: "Get Started Free" },
      allocation: { percentage: 50 }
    }
  ],
  control: "control",
  allocation: {
    method: "random"
  }
};

const response = await abTestingClient.createExperiment(experiment);
```

### Allocate User
```javascript
const allocation = await abTestingClient.allocate({
  experimentId: "exp_123",
  userId: "user_456",
  context: {
    deviceType: "mobile",
    platform: "iOS",
    location: {
      country: "US",
      region: "CA"
    }
  }
});

// Use variant configuration
if (allocation.variantId === "variant_a") {
  showNewButton();
} else {
  showCurrentButton();
}
```

### Record Conversion
```javascript
await abTestingClient.recordConversion({
  experimentId: "exp_123",
  userId: "user_456",
  value: 1,
  metadata: {
    revenue: 99.99,
    itemId: "premium_plan"
  }
});
```

### Get Results
```javascript
const results = await abTestingClient.getResults("exp_123");

// Check winner
if (results.analysis.summary.winner) {
  console.log(`Winner: ${results.analysis.summary.winner.name}`);
  console.log(`Improvement: ${results.analysis.summary.winner.improvement}%`);
}
```

## Adaptive Allocation

### Epsilon-Greedy
```javascript
const experiment = {
  allocation: {
    method: "epsilon-greedy",
    parameters: {
      epsilon: 0.1 // 10% exploration
    }
  }
};
```

### Thompson Sampling
```javascript
const experiment = {
  allocation: {
    method: "thompson"
  }
};
```

## Statistical Analysis

### Power Analysis
The service automatically calculates required sample sizes based on:
- Baseline conversion rate
- Minimum detectable effect
- Statistical power (default: 80%)
- Confidence level (default: 95%)

### Multiple Testing Correction
When running experiments with multiple variants:
- Bonferroni correction
- Benjamini-Hochberg procedure

## Best Practices

1. **Sample Size Planning**
   - Use power analysis to determine duration
   - Don't stop experiments too early
   - Account for weekly/seasonal patterns

2. **Metric Selection**
   - Choose primary metrics aligned with business goals
   - Monitor guardrail metrics
   - Consider long-term effects

3. **Audience Targeting**
   - Use consistent targeting criteria
   - Ensure sufficient traffic in each segment
   - Consider interaction effects

4. **Statistical Rigor**
   - Pre-register hypotheses
   - Avoid peeking at results
   - Use appropriate statistical tests

## Monitoring

### Health Check
```bash
curl http://localhost:3005/health
```

### Metrics
- Prometheus metrics at `/metrics`
- Key metrics:
  - Active experiments count
  - Allocation latency
  - Conversion rates by variant
  - Algorithm performance

## Development

### Setup
```bash
npm install
cp .env.example .env
npm run dev
```

### Testing
```bash
npm test
npm run test:integration
npm run test:statistical
```

### Docker
```bash
docker build -t ab-testing-service .
docker run -p 3005:3005 --env-file .env ab-testing-service
```

## Performance

- Allocation latency: <10ms p99
- Results calculation: <100ms for 100K users
- Real-time updates: <50ms latency
- Supports 10K allocations/second

## Security

- JWT authentication required
- Experiment isolation by account
- Rate limiting per account
- Audit logging for all changes

## Support

For issues and questions:
- Review the statistical methodology guide
- Check the troubleshooting section
- Contact the development team