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Lottery Smart Contract

Overview

This document outlines the technical details and functionalities of the Lottery Smart Contract implemented in Go. The contract utilizes the KalpSDK to facilitate the creation, management, and execution of lottery events on a blockchain network. The contract enables authorized users to start a lottery, allows participants to buy tickets, and selects a winner randomly, awarding the prize pool to the winner.

Prerequisites

  • Familiarity with Go programming language: Understanding of basic Go syntax and constructs.

  • Basic understanding of blockchain concepts: Knowledge of smart contracts, state management, and transaction contexts.

  • Installation of the KalpSDK: The KalpSDK must be installed and set up to interact with the blockchain network.

Contract Initialization

StartLottery

Initializes a new lottery with a specified ticket price. Only authorized users can start a lottery.

  • Parameters:

    • lotteryID (string): Unique identifier for the lottery.

    • ticketPrice (int): Price of a single ticket in tokens.

  • Example API Invocation:

    func (s *SmartContract) StartLottery(ctx kalpsdk.TransactionContextInterface, lotteryID string, ticketPrice int) error {
    // Function implementation
}

  • Returns:

    • error: Error message if the operation fails.

Lottery Operations

BuyTicket

Allows a participant to purchase a ticket for an active lottery. The ticket price is deducted from the participant’s account balance, and the lottery’s prize pool is updated accordingly.

  • Parameters:

    • lotteryID (string): Unique identifier for the lottery.

  • Example API Invocation:

    func (s *SmartContract) BuyTicket(ctx kalpsdk.TransactionContextInterface, lotteryID string) error {
    // Function implementation
}

  • Returns:

    • error: Error message if the operation fails.

  • Authorization Required:

    • No, but the participant must have sufficient balance to purchase a ticket.

PickWinner

Randomly selects a winner from the participants of an active lottery and transfers the prize pool to the winner's account. The lottery is then marked as inactive.

  • Parameters:

    • lotteryID (string): Unique identifier for the lottery.

  • Example API Invocation: 

    func (s *SmartContract) PickWinner(ctx kalpsdk.TransactionContextInterface, lotteryID string) error {
    // Function implementation
}

  • Returns:

    • error: Error message if the operation fails.

GetLottery

Returns the details of a specified lottery, including the list of participants, ticket price, and prize pool.

  • Parameters:

    • lotteryID (string): Unique identifier for the lottery.

  • Example API Invocation:

    func (s *SmartContract) GetLottery(ctx kalpsdk.TransactionContextInterface, lotteryID string) (*Lottery, error) {
    // Function implementation
}

  • Returns:

    • *Lottery: A pointer to the Lottery structure containing the lottery details.

    • error: Error message if the operation fails.

Event Logging

The contract logs events for significant actions such as ticket purchases and winner announcements. These events can be used by off-chain applications to react to state changes.

  • Example Event:

    event := Event{Type: "TicketPurchased", Detail: fmt.Sprintf("Client %s purchased a ticket for lottery %s", clientID, lotteryID)}

Security Considerations

  • Access Control: Ensure that only authorized clients (e.g., users with specific MSP IDs) can perform sensitive operations like starting a lottery or picking a winner.

  • Input Validation: Validate input parameters to prevent issues such as insufficient funds when purchasing tickets or attempts to interact with inactive lotteries.

  • Randomness in Winner Selection: Use cryptographically secure methods to ensure the fairness of the winner selection process.

Conclusion

This Lottery Smart Contract implemented in Go provides a framework for creating and managing lotteries on a blockchain network using the KalpSDK. The contract includes functionalities for initializing lotteries, allowing participants to buy tickets, and selecting a random winner. With built-in event logging and strict access control, this contract ensures secure and transparent lottery operations.

Note

If you encounter any issues during development related to Kalp Studio, please raise a support ticket at care.kalp.studio. Our dedicated development team will assist you in finding the best possible solution.