Tip Jar Contract

# Tip Jar — Animica smart contract (vm_py / animica-python)
#
# A minimal on-chain tip jar: anyone can tip, only the owner can withdraw.
# Amounts are integer base units (nANM). This is a template — deploy and the
# real value transfer in withdraw() is wired to the Animica VM. In the current
# Forge phase the transfer is a MOCK (see the commented line below).

from animica import contract, public, view, msg, transfer


@contract
class TipJar:
    def __init__(self):
        # The account that deployed the contract owns it and can withdraw.
        self.owner = msg.sender
        # Running total of everything ever tipped (base units, nANM).
        self.total = 0
        # Current withdrawable balance held by the jar (base units, nANM).
        self.balance = 0
        # Ordered, de-duplicated list of addresses that have tipped.
        self._tippers = []
        # Per-address tip totals, for a simple leaderboard.
        self._by_sender = {}

    @public
    def tip(self, amount):
        """Add a tip. Records the sender and grows the running total."""
        assert amount > 0, "tip amount must be positive"
        sender = msg.sender
        if sender not in self._by_sender:
            self._tippers.append(sender)
            self._by_sender[sender] = 0
        self._by_sender[sender] += amount
        self.total += amount
        self.balance += amount
        return self.total

    @view
    def total_tips(self):
        """Total value tipped over the lifetime of the jar (base units)."""
        return self.total

    @view
    def tippers(self):
        """Every address that has tipped, in first-tip order."""
        return self._tippers

    @view
    def tipped_by(self, who):
        """How much a single address has tipped (base units)."""
        return self._by_sender.get(who, 0)

    @public
    def withdraw(self):
        """Owner-only. Zeroes the jar and sends the balance to the owner."""
        assert msg.sender == self.owner, "only the owner can withdraw"
        amount = self.balance
        assert amount > 0, "nothing to withdraw"
        self.balance = 0
        # MOCK (prepared for the next phase): the real value transfer runs on
        # deploy against the Animica VM. Uncomment when settlement is live.
        # transfer(self.owner, amount)
        return amount