🔐 Price-Locked ETH Vault

A single-user ETH vault smart contract that locks a user's deposited ETH and only allows withdrawal once the total USD value of the vault exceeds a minimum threshold.

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🧩 Overview

This contract enables a one-at-a-time exclusive ETH vault that:

• Accepts ETH deposits from a single user.
• Locks the deposited ETH — no one else can use the vault until it's withdrawn.
• Uses a Chainlink ETH/USD price feed to determine when the ETH value has appreciated.
• Only allows withdrawal when the USD value of the vault meets or exceeds a specified threshold.

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🛠️ Features

• ✅ Single user access: Only one user can interact with the vault at a time.
• 🔒 Lock mechanism: ETH is locked to that user until they withdraw.
• 💵 USD valuation: ETH value is converted to USD using a Chainlink oracle.
• ⛔ Withdraw blocked if value is below a set USD minimum.
• 🔁 Vault unlocks after withdrawal, allowing the next user to deposit.

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📄 Contract Flow

1. Deposit ETH

   • First user sends ETH to the contract.
   • Contract locks itself to that user's address.

2. Check Vault Value (USD)

   • The vault uses Chainlink’s ETH/USD price feed to calculate total USD value of ETH held.

3. Withdraw ETH

   • Only the locked user can withdraw.
   • Withdrawal only allowed if the vault's USD value ≥ MINIMUM_VAULT_USD_WITHDRAWAL_VALUE.

4. Reset

   • After withdrawal, the vault is open to new users again.

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🔧 Constructor Parameters

• AggregatorV3Interface _priceFeed: Chainlink price feed used to fetch ETH/USD price.

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