TON Blockchain Smart Contract Development for IDO (Token Claim and Refund) -- 2

We are seeking a skilled developer to create a smart contract on the TON blockchain for an Initial DEX Offering (IDO) with the following features:

1. Investment Functionality:
- Users can invest in the IDO using USDT or TON Coin (TON).
- Implement token acceptance and validation for both USDT and TON as investment currencies.

2. Token Claiming:
- Once the IDO ends, users should be able to claim their allocated tokens based on their investment.
- The contract should automatically handle token distribution upon claim.

3. Refund Mechanism:
- In case of unsuccessful funding (e.g., if the goal is not met), users should be able to request a refund.
- The contract should enable refunds in USDT or TON, depending on the user’s original investment.

Requirements:
- Knowledge of FunC and TON blockchain.
- Previous experience in writing and deploying smart contracts on the TON blockchain.
- Ability to integrate both USDT and TON Coin for investment purposes.

Please include examples of previous smart contracts you've worked on and your experience with the TON blockchain.