Algolotto

A fully on-chain lottery built for the Algorand blockchain using pyTEAL.

Main smart contract can be found at: /assets/lotto.py, the flow consists of the following key stages:

• Initialisation: initialize contract and global variables.
• Ticket Purchase: allow participants to purchase tickets while using their local storage to storage ticket numbers. If user has tickets for previous draw, then erase their local storage.
• Commit randomness: requirement to interact with randomness beacon.
• Trigger draw and identify winner: retrieve pseudo-randomness and draw winning ticket.
• Dispense reward: send lottery pot to winner and reward bot that triggered the command.
• Restart draw: Reset relevant variables and start a new lottery.

Development Environment

Sandbox

1. Clone the sandbox repository from here.
2. Modify docker-compose.yml by adding a volume that maps to our compiled contracts, as so:

    volumes:
      - type: bind
        source: /home/moataz/projects/crypto/algolotto/algolotto/build
        target: /data

3. Initialize the docker containers by running ./sandbox up.

Running a Smart Contract Locally

1. Build the smart contract module folder by running ./build.sh assets.lotto.
2. Enter the algod container by running ./sandbox enter algod. The smart contract TEAL files should now be available in the container in the /data directory.
3. Deploy program to local sandbox environment using the command:

goal app create --creator <owner address> --approval-prog /data/approval.teal --clear-prog /data/clear.teal --global-byteslices <n> --global-ints <n> --local-byteslices <n> --local-ints <n>

Testing Operations

• To opt-in to the app:

goal app optin --app-id 1 --from $TWO 

• To purchase a ticket:

goal app call --app-id 1 --from $TWO --app-arg "str:purchase" --app-arg "int:1"

• To dump transaction for inspection

goal app call ... --dryrun-dump -o tx.dr

• To launch debugger for a given transaction dump

tealdbg debug -d tx.dr --listen 0.0.0.0

• To view local storage of an account

goal app read --app-id 1 -f $TWO --local

• To view all available accounts

goal account list

• To check balance of an account

goal account balance -a $TWO

• To send algo between accounts

goal clerk send -a 100000 -f $ONE -t $TWO

Deployment Operations

• To retrieve application address using application id

python3 -c "import algosdk.encoding as e; print(e.encode_address(e.checksum(b'appID'+(<app id>).to_bytes(8, 'big'))))"

• To run local randomness beacon

export VRF_LOG_LEVEL=debug;
export AF_ALGOD_ADDRESS=http://localhost:4001;
export AF_ALGOD_TOKEN=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa;

go run ./cmd run-daemon \
  --vrf-mnemonic "boil frequent harvest donkey outside start thought road insane wine tooth fame assault any advice belt walk again proud debate culture omit diary able treat" \
  --service-mnemonic "chat glory west mobile desk coin hockey swallow tilt chunk task model hidden helmet toddler tortoise always afraid absorb valve bar distance history absorb exercise"\
  --app-creator-mnemonic "chat glory west mobile desk coin hockey swallow tilt chunk task model hidden helmet toddler tortoise always afraid absorb valve bar distance history absorb exercise"\
  --approval-program pyteal/vrf_beacon_abi_approval.teal --clear-program pyteal/vrf_beacon_abi_clear.teal --starting-round 8

Notes

• Integer arguments still have to be converted using Btoi as specifying "int:x" as an argument only tells TEAL how to encode the argument but it is still passed as a byte.