Oz impl

[Akshola00]

Summary of the PR:
The pull request titled "Oz impl" introduces a comprehensive and extensible payment processing module for the Chain-Library/chainlib-contract repository. The module supports both ERC-20 tokens and native currency payments, providing secure mechanisms for transaction validation, escrow management, fraud detection, and robust event tracking. This update aims to power the financial layer for purchase systems, ensuring flexibility, security, and reliability for payments across multiple token types.

Pull Request: Comprehensive Payment Processing Implementation

Overview

This PR closes #36 and introduces a robust, extensible payment processing module that underpins the financial layer of the purchase system. The module enables secure and flexible payments for content or asset purchases, supporting both ERC-20 tokens and native currency transfers. It features on-chain transaction validation, payment finality assurance, escrow handling, and fraud prevention mechanisms.

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✅ Features Implemented

1. Multi-Token Support

• Integrated ERC-20 token support via interface abstraction.
• Added support for native tokens (e.g., ETH or other EVM-based chains).
• Standardized token transfer logic using unified interfaces.

2. Transaction Validation

• On-chain validation against transaction hashes.
• Verified transaction receipts to confirm payment amount and status.
• Finality checks to ensure funds are irreversibly transferred.

3. Fraud Detection & Security

• Basic fraud detection:
  • Rejection of duplicate or manipulated transaction hashes.
  • Validation of sender and recipient addresses.
  • Safety checks for unexpected state transitions or missing confirmations.

4. Failure Recovery & Safety

• Retry logic for failed validations (e.g., network issues, delayed finality).
• Safety fallback for fund recovery from stuck or failed transactions.
• Emission of clear failure events for external monitoring or user feedback.

5. Event Emission & Monitoring

• Events emitted for:
  • PaymentReceived
  • PaymentConfirmed
  • PaymentFailed
  • EscrowReleased
• These events facilitate tracking, analytics, and UI updates.

6. Gas Optimization

• Minimized redundant token approval and transfer steps.
• Batched certain validation operations for on-chain gas savings.

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⚙️ Technical Design Notes

• ERC-20 interface (IERC20) is implemented and abstracted for easy integration of various tokens.
• The validateTransaction() function ensures:
  • Correct sender
  • Expected token and amount
• Fraud prevention is focused on predictable validation and rejection patterns.
• The code is modular and well-commented for easy extension and auditability.

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🧪 Testing & Validation

• Unit tests written for:
  • Token transfer correctness
  • Transaction hash validation
  • Escrow deposit and release
  • Event emission
• Manual test cases include:
  • Native token payments
  • ERC-20 token edge cases (e.g., low allowance, invalid hash)
  • Simulated failures and retry scenarios

[Akshola00]

@Pvsaint ptal