Implement PaymentIntent Contract in Cairo (StarkNet)

[nottherealalanturing]

📝 Description:

Create a basic Cairo 1.0 smart contract on StarkNet that supports the creation of a "payment intent". This contract will allow users to register a payment by specifying an amount, currency, and recipient. For now, this is a simple mockup – it won’t actually transfer funds, but will store intent data on-chain.

This is a foundational piece for integrating payments with smart contracts in a future release.

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✅ Requirements:

• Define a Cairo contract called PaymentIntent.

• Define a struct PaymentIntentData:

  • amount: u256
  • currency: felt252 (ISO code or symbol as felt252)
  • customer: ContractAddress
  • recipient: ContractAddress
  • status: felt252 (initially "created" as felt)

• Implement a function create_intent:

  • Parameters: amount, currency, customer, recipient
  • Generate a unique intent ID (e.g. counter or hash of inputs)
  • Store the PaymentIntentData in a mapping

• Implement a getter function get_intent(intent_id: felt252) to return stored data.

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🧪 Testing Requirements (Cairo Unit Tests):

• Test creation of a valid payment intent.
• Test that intent data is stored and retrieved correctly.
• Test edge cases (e.g., zero amount).

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🧱 Contract Storage:

• @storage_var payment_intents(intent_id: felt252) -> PaymentIntentData
• @storage_var intent_counter() -> u128 (for generating unique IDs)

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⚙️ Dependencies:

• Use Cairo 1.0 syntax
• Use starknet::ContractAddress for addresses

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