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Lottery Demo dApp Smart Contract

This smart contract allows users to participate in a demo lottery on the Casper blockchain. Users can purchase tickets to get a chance to win , which come from the prize pool accumulated from the ticket proceeds. Users can win either a jackpot (the whole prize pool) or a small consolation prize. When somebody wins the jackpot, a new lottery round starts, making the game indefinite.

This contract is written using the Odra smart contract framework for the Casper Network. Odra is Rust-based and encourages rapid development and clean, pragmatic design.

Entry Points (Contract Functions)

configure

Configures the essential lottery game settings. This entry point can only be called by the contract owner (designated during deployment).

Arguments Description
ticket_price Ticket price in CSPR
lottery_fee Lottery fee in percents
jackpot_probability Jackpot probability in percents
max_consolation_prize Max consolation prize amount in CSPR
consolation_prize_probability Consolation prize probability in percents

top_up_prize_pool

Adds funds to the prize pool. This entry point can only be called by the contract owner (designated during deployment).

Arguments Description
amount Amount in motes (1 CSPR is 1,000,000,000 motes)

transfer_fees_to_account

Transfers the requested amount from the fee purse to receiver`s account. Reverts if the requested amount bigger than collected fees. This entry point can only be called by the contract owner (designated during deployment).

Arguments Description
amount Amount in motes (1 CSPR is 1,000,000,000 motes)
receiver Receiver account hash

play_lottery

Participates in the current lottery round by purchasing a ticket. This is a Payable entry point that needs to be called using proxy_caller

Arguments Description
amount Ticket price in motes (1 CSPR is 1,000,000,000 motes)

Events

Play

The play_lottery entry point emits the following Play event, which is used to notify the Event Listener about new lottery plays:

Property Description
play_id Unique play ID that can be used to index plays
round_id Current lottery round ID
player Player account hash
timestamp Timestamp of the play
prize_amount Prize amount won by the player in motes (1 CSPR is 1,000,000,000 motes)
is_jackpot Flag that indicates whether the player won the jackpot
jackpot_amount The remaining prize pool balance after the play (0 if the player won the jackpot)

Usage

It's recommended to install cargo-odra first. You can find it here.

Build

make build

Test

To run tests on your local machine, you can simply execute the following command:

make test

To test actual WASM files against a backend

make test-wasm

Run locally

The most convenient way to run your smart contract locally would be by using NCTL in Docker:

docker run --rm -it --name casper-nctl -d \
    -p 11101:11101 \
    -p 14101:14101 \
    -p 18101:18101 \
    -v ${PWD}/wasm:/home/casper/contract \
    makesoftware/casper-nctl

Open the NCTL container terminal:

docker exec -it casper-nctl /bin/bash

Deploy the contract to the local NCTL:

casper-client put-deploy \
    --node-address http://127.0.0.1:11101 \
    --chain-name casper-net-1 \
    --payment-amount 200000000000 \
    --secret-key "/home/casper/casper-node/utils/nctl/assets/net-1/users/user-1/secret_key.pem" \
    --session-path /home/casper/contract/Lottery.wasm

Deploy to Casper Testnet

Copy and adjust .env file

cp .env.sample .env

Run the deploy command that uses Odra's Livenet backend:

cargo run --bin livenet --features=livenet