initial contract created from Yoav's pseudocode

.gitignore

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+node_modules
+
+#Hardhat files
+cache
+artifacts

README.md

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+# account-abstraction
+
+https://notes.ethereum.org/@vbuterin/alt_abstraction

contracts/Singleton.sol

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+// SPDX-License-Identifier: GPL-3.0
+pragma solidity >=0.7.0 <0.9.0;
+
+contract Singleton {
+
+    uint256 MAX_CHECK_GAS = 100_000;
+    uint256 POST_CALL_GAS_OVERHEAD = 50_000;
+
+    struct UserOperation {
+        bytes20 target;
+        uint64 callGas;
+        uint64 postCallGas;
+        uint256 gasPrice;
+        bytes callData;
+        bytes signature;
+    }
+
+    function handleOps(UserOperation[] calldata ops, uint256 minimumGasPrice) public {
+        //require(msg.sender == block.coinbase);
+        uint256 savedBalance = address(this).balance;
+        for(uint i=0;i<ops.length;i++){
+            UserOperation calldata op = ops[i];
+            if (gasleft() <= op.callGas + op.postCallGas + MAX_CHECK_GAS + POST_CALL_GAS_OVERHEAD){
+                break;
+            }
+            handleOp(op, minimumGasPrice);
+        }
+        payable(address(msg.sender)).transfer(address(this).balance-savedBalance);
+    }
+
+    function handleOp(UserOperation calldata op, uint256 minimumGasPrice) public {
+        uint256 savedGas = gasleft();
+
+        require(op.gasPrice >= minimumGasPrice);
+        require(gasleft()-op.callGas+op.postCallGas >= POST_CALL_GAS_OVERHEAD);
+
+        ISmartContractWallet smartContractWallet = ISmartContractWallet(address(op.target));
+        smartContractWallet.payForOp{gas:MAX_CHECK_GAS}(op.callGas, op.postCallGas, op.callData, op.signature);
+
+        require(address(this).balance >= op.gasPrice*(op.callGas+op.postCallGas));
+        (bool success,) = address(smartContractWallet).call{gas:op.callGas}(op.callData);
+        require(success);
+        smartContractWallet.handleRefundGas{gas:op.postCallGas,value:(savedGas-gasleft()-op.postCallGas)*tx.gasprice};
+    }
+}
+
+interface ISmartContractWallet {
+
+    // callGas, postCallGas, callData, signature
+    function payForOp(uint64, uint64, bytes calldata, bytes calldata) external;
+
+    function handleRefundGas() payable external;
+}

hardhat.config.js

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+require("@nomiclabs/hardhat-waffle");
+
+// This is a sample Hardhat task. To learn how to create your own go to
+// https://hardhat.org/guides/create-task.html
+task("accounts", "Prints the list of accounts", async (taskArgs, hre) => {
+  const accounts = await hre.ethers.getSigners();
+
+  for (const account of accounts) {
+    console.log(account.address);
+  }
+});
+
+// You need to export an object to set up your config
+// Go to https://hardhat.org/config/ to learn more
+
+/**
+ * @type import('hardhat/config').HardhatUserConfig
+ */
+module.exports = {
+  solidity: "0.8.4",
+};