Checking total amount sent to a contract (ever) within the contract execution

Question

I'd like to create a contract that behaves a certain way based on how much total tez has been sent to the contract.

How should I track and check the total amount ever sent to a contract?

Example:

• User A is the first to send 1 tez to the contract, the contract does something with the information that 1 tez has been sent (1 tez now and 0 tez previously).
• User B sends 1 tez to the contract, the contract does something with the information that 2 tez has been sent to the contract (1 tez now and 1 tez previously).

Answer 1

In SmartPy you can do this: code

The IDE has an output panel that you can use to check all the calls and updated storage, hope it helps :)

import smartpy as sp

class MyContract(sp.Contract):
    def __init__(self, **kargs):
        self.init(**kargs)

    @sp.entry_point
    def send_tez(self):
        # Do some stuff
        self.data.previousAmount = self.data.latestAmount;
        self.data.latestAmount = sp.amount
    
    @sp.entry_point
    def dont_allow_amount(self):
        sp.verify(sp.amount == sp.tez(0), message = "Entrypoint doesn't allow amount.")

@sp.add_test(name = "Amount recording")
def test():
    scenario = sp.test_scenario()
    scenario.h1("Amount recording")
    c1 = MyContract(latestAmount = sp.tez(0), previousAmount = sp.tez(0))
    scenario += c1
    scenario += c1.send_tez().run(amount = sp.tez(1))
    scenario += c1.send_tez().run(amount = sp.tez(2))
    scenario += c1.send_tez().run(amount = sp.tez(3))
    
    # amount > 0 is rejected in the other entrypoint
    scenario += c1.dont_allow_amount().run(amount = sp.tez(1), valid = False)
    # amount = 0 is fine
    scenario += c1.dont_allow_amount().run(amount = sp.tez(0))