feat: add event indexer service for PrivacyLayer contracts

indexer/.env.example

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+# PrivacyLayer Event Indexer Configuration
+
+# Server Configuration
+PORT=4000
+
+# Database Configuration
+DATABASE_URL="postgresql://user:password@localhost:5432/privacylayer_indexer?schema=public"
+
+# Stellar/Soroban Configuration
+SOROBAN_RPC_URL=https://soroban-testnet.stellar.org:443
+NETWORK_PASSPHRASE=Test SDF Network ; September 2015
+CONTRACT_ID=your_contract_id_here
+
+# Indexer Configuration
+POLL_INTERVAL=5000
+
+# For mainnet, use:
+# SOROBAN_RPC_URL=https://soroban.stellar.org:443
+# NETWORK_PASSPHRASE=Public Global Stellar Network ; September 2015

indexer/.gitignore

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+# Dependencies
+node_modules/
+
+# Build output
+dist/
+
+# Environment files
+.env
+.env.local
+.env.*.local
+
+# IDE
+.idea/
+.vscode/
+*.swp
+*.swo
+
+# OS files
+.DS_Store
+Thumbs.db
+
+# Logs
+logs/
+*.log
+npm-debug.log*
+
+# Test coverage
+coverage/
+
+# Prisma
+prisma/*.db
+prisma/*.db-journal

indexer/Dockerfile

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+FROM node:18-alpine
+
+WORKDIR /app
+
+# Install dependencies
+COPY package*.json ./
+RUN npm ci --only=production
+
+# Copy Prisma schema
+COPY prisma ./prisma/
+RUN npx prisma generate
+
+# Copy source code
+COPY dist ./dist/
+
+# Expose port
+EXPOSE 4000
+
+# Start the server
+CMD ["node", "dist/index.js"]

indexer/README.md

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+# PrivacyLayer Event Indexer
+
+A high-performance event indexer for the PrivacyLayer smart contract on Stellar/Soroban.
+
+## Features
+
+- **Real-time Event Indexing**: Automatically indexes all PrivacyLayer contract events
+- **GraphQL API**: Query deposits, withdrawals, and admin events efficiently
+- **WebSocket Subscriptions**: Real-time updates via GraphQL subscriptions
+- **PostgreSQL Storage**: Persistent, indexed storage for historical queries
+- **Docker Support**: Easy deployment with Docker Compose
+
+## Events Indexed
+
+| Event | Description | Fields |
+|-------|-------------|--------|
+| `DepositEvent` | Emitted on deposit | commitment, leafIndex, root |
+| `WithdrawEvent` | Emitted on withdrawal | nullifierHash, recipient, relayer, fee, amount |
+| `PoolPausedEvent` | Emitted when pool is paused | admin |
+| `PoolUnpausedEvent` | Emitted when pool is unpaused | admin |
+| `VkUpdatedEvent` | Emitted when verifying key is updated | admin |
+
+## Quick Start
+
+### Prerequisites
+
+- Node.js 18+
+- PostgreSQL 15+
+- npm or yarn
+
+### Installation
+
+```bash
+# Clone the repository
+git clone https://github.com/ANAVHEOBA/PrivacyLayer.git
+cd PrivacyLayer/indexer
+
+# Install dependencies
+npm install
+
+# Copy environment file
+cp .env.example .env
+
+# Edit .env with your configuration
+# - DATABASE_URL: PostgreSQL connection string
+# - CONTRACT_ID: Your deployed PrivacyLayer contract ID
+# - SOROBAN_RPC_URL: Soroban RPC endpoint
+```
+
+### Database Setup
+
+```bash
+# Run migrations
+npx prisma migrate dev --name init
+
+# (Optional) Open Prisma Studio to view data
+npx prisma studio
+```
+
+### Running the Indexer
+
+```bash
+# Development mode with auto-reload
+npm run dev
+
+# Production build
+npm run build
+npm start
+```
+
+### Docker Deployment
+
+```bash
+# Build and run with Docker Compose
+docker-compose up -d
+
+# View logs
+docker-compose logs -f indexer
+```
+
+## API Documentation
+
+### GraphQL Endpoint
+
+The indexer exposes a GraphQL API at `http://localhost:4000/graphql`.
+
+### Example Queries
+
+#### Get recent deposits
+
+```graphql
+query {
+  deposits(pagination: { skip: 0, take: 10 }) {
+    id
+    commitment
+    leafIndex
+    root
+    txHash
+    timestamp
+    ledger
+  }
+}
+```
+
+#### Get withdrawals by recipient
+
+```graphql
+query {
+  withdrawals(filter: { recipient: "G..." }) {
+    id
+    nullifierHash
+    recipient
+    amount
+    timestamp
+  }
+}
+```
+
+#### Check if commitment is used
+
+```graphql
+query {
+  isCommitmentUsed(commitment: "0x...")
+}
+```
+
+#### Get current Merkle tree state
+
+```graphql
+query {
+  merkleTreeState {
+    currentRoot
+    leafCount
+    lastUpdated
+  }
+}
+```
+
+### Real-time Subscriptions
+
+#### Subscribe to new deposits
+
+```graphql
+subscription {
+  onDeposit {
+    commitment
+    leafIndex
+    root
+    timestamp
+  }
+}
+```
+
+#### Subscribe to Merkle tree updates
+
+```graphql
+subscription {
+  onMerkleTreeUpdate {
+    currentRoot
+    leafCount
+    lastUpdated
+  }
+}
+```
+
+## Configuration
+
+| Environment Variable | Description | Default |
+|---------------------|-------------|---------|
+| `PORT` | API server port | `4000` |
+| `DATABASE_URL` | PostgreSQL connection string | Required |
+| `SOROBAN_RPC_URL` | Soroban RPC endpoint | `https://soroban-testnet.stellar.org:443` |
+| `NETWORK_PASSPHRASE` | Stellar network passphrase | Testnet |
+| `CONTRACT_ID` | PrivacyLayer contract ID | Required |
+| `POLL_INTERVAL` | Event polling interval (ms) | `5000` |
+
+## Architecture
+
+```
+┌─────────────────────────────────────────────────────────────┐
+│                      GraphQL API                            │
+│  ┌─────────────┐  ┌─────────────┐  ┌─────────────────────┐ │
+│  │   Queries   │  │ Mutations   │  │   Subscriptions     │ │
+│  └─────────────┘  └─────────────┘  └─────────────────────┘ │
+└─────────────────────────────────────────────────────────────┘
+                           │
+                           ▼
+┌─────────────────────────────────────────────────────────────┐
+│                    Event Indexer                            │
+│  ┌─────────────┐  ┌─────────────┐  ┌─────────────────────┐ │
+│  │   Parser    │  │  Processor  │  │   Merkle Sync       │ │
+│  └─────────────┘  └─────────────┘  └─────────────────────┘ │
+└─────────────────────────────────────────────────────────────┘
+         │                    │                    │
+         ▼                    ▼                    ▼
+┌─────────────────┐  ┌─────────────────┐  ┌─────────────────┐
+│   Soroban RPC   │  │   PostgreSQL    │  │    PubSub       │
+│   (Events)      │  │   (Storage)     │  │  (WebSocket)    │
+└─────────────────┘  └─────────────────┘  └─────────────────┘
+```
+
+## Development
+
+### Project Structure
+
+```
+indexer/
+├── src/
+│   ├── index.ts          # Main entry point
+│   ├── indexer.ts        # Event indexing logic
+│   ├── parsers.ts        # Event parsing utilities
+│   ├── resolvers.ts      # GraphQL resolvers
+│   └── schema.graphql    # GraphQL schema
+├── prisma/
+│   └── schema.prisma     # Database schema
+├── package.json
+├── tsconfig.json
+├── Dockerfile
+├── docker-compose.yml
+└── README.md
+```
+
+### Running Tests
+
+```bash
+npm test
+```
+
+## License
+
+MIT License - See LICENSE file for details.
+
+## Contributing
+
+Contributions are welcome! Please see the main [CONTRIBUTING.md](../CONTRIBUTING.md) for guidelines.
+
+## Support
+
+For issues and feature requests, please open a GitHub issue.

indexer/docker-compose.yml

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+version: '3.8'
+
+services:
+  postgres:
+    image: postgres:15-alpine
+    environment:
+      POSTGRES_USER: privacylayer
+      POSTGRES_PASSWORD: privacylayer_secret
+      POSTGRES_DB: privacylayer_indexer
+    volumes:
+      - postgres_data:/var/lib/postgresql/data
+    ports:
+      - "5432:5432"
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U privacylayer -d privacylayer_indexer"]
+      interval: 5s
+      timeout: 5s
+      retries: 5
+
+  indexer:
+    build: .
+    environment:
+      DATABASE_URL: "postgresql://privacylayer:privacylayer_secret@postgres:5432/privacylayer_indexer?schema=public"
+      SOROBAN_RPC_URL: ${SOROBAN_RPC_URL:-https://soroban-testnet.stellar.org:443}
+      NETWORK_PASSPHRASE: ${NETWORK_PASSPHRASE:-Test SDF Network ; September 2015}
+      CONTRACT_ID: ${CONTRACT_ID}
+      PORT: 4000
+      POLL_INTERVAL: 5000
+    ports:
+      - "4000:4000"
+    depends_on:
+      postgres:
+        condition: service_healthy
+    restart: unless-stopped
+
+volumes:
+  postgres_data: