average.circuit.ts

import {
  add,
  sub,
  mul,
  div,
  checkLessThan,
  addToCallback,
  CircuitValue,
  CircuitValue256,
  constant,
  witness,
  getAccount,
} from "@axiom-crypto/client";

// For type safety, define the input types to your circuit here.
// These should be the _variable_ inputs to your circuit. Constants can be hard-coded into the circuit itself.
export interface CircuitInputs {
  blockNumber: CircuitValue;
  address: CircuitValue;
}

// Default inputs to use for compiling the circuit. These values should be different than the inputs fed into
// the circuit at proving time.
export const defaultInputs = {
  "blockNumber": 4000000,
  "address": "0xEaa455e4291742eC362Bc21a8C46E5F2b5ed4701"
}

// The function name `circuit` is searched for by default by our Axiom CLI; if you decide to 
// change the function name, you'll also need to ensure that you also pass the Axiom CLI flag 
// `-f <circuitFunctionName>` for it to work
export const circuit = async (inputs: CircuitInputs) => {
  // Number of samples to take. Note that this must be a constant value and NOT an input because the size of 
  // the circuit must be known at compile time.
  const samples = 8; 

  // Number of blocks between each sample.
  const spacing = 900;

  // Validate that the block number is greater than the number of samples times the spacing
  if (inputs.blockNumber.value() <= (samples * spacing)) {
    throw new Error("Block number must be greater than the number of samples times the spacing");
  }

  // Perform the block number validation in the circuit as well
  checkLessThan(mul(samples, spacing), inputs.blockNumber);

  // Get account balance at the sample block numbers
  let sampledAccounts = new Array(samples);
  for (let i = 0; i < samples; i++) {
    const sampleBlockNumber: CircuitValue = sub(inputs.blockNumber, mul(spacing, i));
    const account = getAccount(sampleBlockNumber, inputs.address);
    sampledAccounts[i] = account;
  }

  // Accumulate all of the balances to the `total` value
  let total = constant(0);
  for (const account of sampledAccounts) {
    const balance: CircuitValue256 = await account.balance();
    total = add(total, balance.lo());
  }

  // Divide the total amount by the number of samples to get the average value
  const average: CircuitValue = div(total, samples);

  // We call `addToCallback` on all values that we would like to be passed to our contract after the circuit has
  // been proven in ZK. The values can then be handled by our contract once the prover calls the callback function.
  addToCallback(inputs.blockNumber);
  addToCallback(inputs.address);
  addToCallback(average);
};