fix: Refactor XCM Contract: Enhanced Documentation, Error Handling, and Test Structure

[brawncode]

Description

This pull request refactors the XCM-based smart contract to improve code quality, readability, and maintainability. It includes enhancements to documentation, error handling, and test structure, ensuring that the contract adheres to modern ink! and Rust development practices.

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Key Changes

1. Unified Comments and Documentation

   • Detailed explanations are provided for each function, covering purpose, parameters, and potential failure scenarios.

2. Improved Error Handling

   • Added a new RuntimeError::UnexpectedEnvError variant to handle unexpected environment errors gracefully.
   • Enhanced the From<EnvError> implementation to catch and log unexpected errors.

3. Introduction of a Helper Function

   • Added a private build_xcm_message function to reduce code duplication when constructing XCM messages.
   • This function supports optional fee handling, increasing flexibility in message construction.

4. Code Style and Clarity

   • Improved variable naming for better understanding (e.g., beneficiary).
   • Reduced repetitive logic by consolidating shared functionality.
   • Used Option<Balance> to manage optional fees seamlessly.

5. Test Updates

   • Refactored test cases into clear Arrange, Act, and Assert sections for better structure and readability.
   • Added comments to explain each test step, ensuring clarity for future contributors.
   • Explicitly validated balances before and after XCM operations to ensure correctness.

6. Compatibility Enhancements

   • Ensured compatibility with ink! best practices by minimizing storage structures and using proper environment calls.
   • Simplified XCM message creation for greater versatility in cross-chain operations.

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Benefits of the Refactor

• Readability: Improved comments and modular design make the codebase easier to understand for new contributors.
• Maintainability: Reduced code duplication and enhanced structure simplify future updates and extensions.
• Resilience: Better error handling reduces runtime crashes in unexpected scenarios.
• Testing Clarity: Well-structured tests provide comprehensive validation and improve feedback during development.

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Checklist

• Updated comments and documentation.
• Added build_xcm_message helper function.
• Improved error handling with better fallback for unexpected cases.
• Refactored test cases for better structure and readability.
• Verified contract functionality with successful builds and tests.

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Testing Instructions

1. Build the contract:

   cargo +nightly contract build

2. Run the tests:

   cargo test  
   cargo +nightly test --features e2e-tests

3. Deploy the contract to a local Substrate node and verify XCM operations in the Polkadot JS Apps UI.