# LangHook Demo Playground Implementation

This document summarizes the implementation of the LangHook Demo Playground as requested in issue #79.

## Overview

The demo playground provides an interactive experience showing how LangHook transforms natural language subscription sentences into event filters and applies intelligent LLM gating.

## Implementation Details

### Backend Changes

1. **New Routes Added to `langhook/app.py`:**
   - `/demo` - Serves the React demo application
   - `/demo/{path:path}` - Handles React Router paths for the demo

### Frontend Changes

1. **New Components:**
   - `frontend/src/Demo.tsx` - Main demo playground component (650+ lines)

2. **Updated Components:**
   - `frontend/src/App.tsx` - Added Demo tab routing
   - `frontend/src/Sidebar.tsx` - Added Demo navigation item with PlayCircle icon

3. **Navigation Structure:**
   - Demo tab placed prominently as second item in sidebar
   - Accessible at `/demo` path

## Demo Features

### Step 1: Choose Subscription Sentence
Interactive selection of 5 predefined scenarios:
1. **GitHub PR Approval**: "Notify me when PR 1374 is approved"
2. **Stripe High-Value Refunds**: "Alert me when a high-value Stripe refund is issued"
3. **Jira Ticket Completion**: "Tell me when a Jira ticket is moved to Done"
4. **Slack File Uploads**: "Ping me when someone uploads a file to Slack"
5. **Important Email Alerts**: "Let me know if an important email arrives"

### Step 2: Send Sample Events
Each subscription includes 3 mock events demonstrating:
- ❌ **No Match**: Event doesn't match the subscription pattern
- 🚫 **LLM Rejected**: Matches pattern but rejected by AI gate as unimportant
- ✅ **Approved**: Matches pattern and approved by AI gate

### Visual Processing Timeline
Animated 5-step breakdown showing:
1. Natural Language → Subject Filter conversion
2. Raw payload → Canonical event transformation
3. Pattern matching evaluation
4. LLM gate evaluation (when applicable)
5. Final decision and action

## Technical Implementation

### Data Structure
- Comprehensive demo data with realistic scenarios
- Mock canonical events matching LangHook's event schema
- Proper outcome categorization and reasoning

### User Experience
- Fully responsive design for mobile and desktop
- Smooth animations and transitions
- Consistent styling with existing LangHook UI
- Interactive elements with hover states and feedback

### Integration
- Seamlessly integrated into existing app architecture
- Uses same routing patterns as other tabs
- Maintains consistent navigation experience

## Testing

The implementation has been verified to:
- ✅ Build successfully with React build process
- ✅ Serve correctly from FastAPI backend
- ✅ Handle routing for both `/demo` and React Router paths
- ✅ Provide responsive experience across screen sizes
- ✅ Integrate properly with existing navigation

## Files Changed

```
frontend/src/App.tsx          - Added Demo import and routing
frontend/src/Sidebar.tsx      - Added Demo navigation item  
frontend/src/Demo.tsx         - New comprehensive demo component
langhook/app.py              - Added /demo route handlers
```

## Usage

1. Start the LangHook application
2. Navigate to the Demo tab in the sidebar, or visit `/demo` directly
3. Select a subscription sentence from the provided options
4. Click "Process Event" on any mock event to see the processing pipeline
5. Watch the animated timeline showing LangHook's internal processing steps

The demo provides an educational and interactive way to understand LangHook's core functionality without requiring actual webhook setup or LLM API keys.