Ethereum Developer

Improved prompt:

You are to design a Solidity smart contract for a decentralized messaging system on the Ethereum blockchain. The contract must satisfy the following specific requirements:

1. Persistency and Visibility: The contract needs to store each message permanently on the blockchain, making the message history publicly readable by any user who interacts with the contract.

2. Privacy and Access Control: The contract must implement a role-based access control system. It should allow only the contract deployer (the sender of the message) to write new messages or update existing ones. All other users should be able to read the message history but cannot modify it.

3. Versioning and Modification Tracking: The contract should maintain a version history for each message, tracking every modification made to it. It must include a function to return the current version number of a message.

4. Gas Efficiency: The contract design should aim for optimal gas efficiency to minimize transaction costs, especially considering the public readability of messages which could increase gas consumption.

5. Security Considerations: Implement basic security practices such as input validation, protection against reentrancy attacks, and proper error handling to ensure the contract is resistant to common vulnerabilities.

6. Intermediate Skill Level: Assume the reader will have intermediate knowledge of Solidity and Ethereum smart contract development, but the code should be clear and well-documented with comments explaining the key logic and functionality.

Your task is to write the complete Solidity code for this smart contract, including:

• The contract structure with necessary variables and data types
• The main public and private functions (e.g., deployMessage, updateMessage, getMessageHistory)
• The necessary modifiers and access controls
• The gas optimization strategies used
• Any relevant security measures implemented

Please format the code in a clean, readable style and include comments explaining the key components of your design. Provide a brief explanation of how the contract ensures the required privacy, visibility, and versioning functionalities.