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Lottery Demo dApp

This is an example of a decentralized application (or dApp) built on the Casper Network, a layer 1 proof-of-stake (PoS) blockchain. Lottery game logic implemented on-chain aims to demonstrate the value of blockchain, which is the increased trust to the outcome since nobody can manipulate the results.

To participate in the lottery, you need to buy a ticket using the native token of the Casper Network. After collecting a fee, the application puts the proceeds into the prize pool, which is used to reward the players. When somebody wins the jackpot, a new lottery round starts, making the game indefinite.

You can try it by playing the lottery deployed to Casper Testnet at https://lottery-demo.casper.network. Please use the Faucet to obtain the test tokens.

Lottery Application

Toolset

This application was created to onboard software engineers to the Casper blockchain and the Web3 architecture in general. Unlike traditional Web2 applications, in Web3, users may interact with blockchain directly. It changes the traditional paradigm of how information flows between users and the application and forces the application to observe the network activity and react correspondingly.

To ease the integration, this example was developed with the help of higher-level abstractions that address those specific challenges of Web3 development and elevate the developer experience.

Casper Development Ecosystem

  • CSPR.click is a Web3 authentication layer that covers the end-user interaction with the blockchain. It provides integration with all the wallets in the Casper Ecosystem and greets users with a well-known Single-Sign-On like experience
  • Odra is a smart contract framework written in Rust that abstracts the chain-specific details behind a familiar OOP interface
  • CSPR.cloud is a middleware layer for the Casper Network. It observes and indexes the network activity and provides access to it via a scalable REST API and real-time WebSocket subscriptions

Architecture

Lottery Demo is a Web that consists of four primary components interacting with each other:

  • Smart Contract runs on the Casper Network and implements the lottery logic
  • Event Listener listens to the contract on-chain activity and aggregates it to the database for faster access via the API
  • API reads aggregated on-chain data and serves it to the Web Client. It also acts as a proxy to the CSPR.cloud APIs to make it possible for the Web Client to access CSPR.cloud without exposing the access key
  • Web Client allows users to play the lottery by directly calling the smart contract and displaying information about past plays. It fetches the lottery data from the API and general blockchain data (e.g. account balance) from CSPR.cloud via the CSPR.cloud proxy endpoints exposed by the API

Architecture

Each component's code resides in a corresponding separate directory of this mono-repository. Event Listener and API are both parts of the server infrastructure.

Run

You can run the demo application using Docker compose.

First, build the applications:

docker compose -f infra/local/docker-compose.yaml --project-name lottery build

Then, run using the following command:

docker compose -f infra/local/docker-compose.yaml --project-name lottery up -d

There are shortcuts available in the Makefile:

make build-demo
make run-demo

Develop

Please, do the following steps if you want to play with the code, or if you want to use it as a starting point for your own dApp.

CSPR.build

Register a free CSPR.build account to create CSPR.click and CSPR.cloud access keys.

Smart contract

Build and deploy the smart contract to Casper Testnet as described here. You can skip this step and use the existing Testnet smart contract package hash 8efc85466cf4054f47eb009b683b611fa63cccd14f074bf78f1e9404dc52a347, which is already provided in the default configuration.

If you want to write and test your own smart contracts, check the smart contract documentation.

Server

Follow the Server instructions to configure, build, and run the Event Listener and API.

Web Client

Follow the Web Client instructions to configure, build, and run the application.

About Casper

Casper is a layer 1 proof-of-stake (PoS) blockchain that prioritizes security and decentralization. Casper was built with developer needs in mind and supports features such as upgradable smart contracts or multi-signature transactions on the protocol level. Casper smart contracts are run in a WASM virtual machine, creating the possibility of using a wider variety of languages for smart contract development.

Community

Join Casper Developers Telegram channel to connect with other developers.