upgrade packages and add uniswap v2 core

.gitignore

@@ -18,3 +18,4 @@ deployments
 .article.md 
 contracts/stablecoins/README.md
 
+yarn-error.log

.prettierignore

@@ -7,6 +7,5 @@ package.json
 img
 .env
 .*
-README.md
 coverage.json
-deployments
+deployments

.prettierrc

@@ -1,8 +1,22 @@
 {
     "tabWidth": 4,
+    "trailingComma": "es5",
     "useTabs": false,
     "semi": false,
     "singleQuote": false,
-    "printWidth": 100
+    "printWidth": 100,
+    "overrides": [
+      {
+        "files": "*.sol",
+        "options": {
+          "printWidth": 80,
+          "tabWidth": 4,
+          "useTabs": false,
+          "singleQuote": false,
+          "bracketSpacing": false,
+          "explicitTypes": "always"
+        }
+      }
+    ]
   }
 

.vscode/extensions.json

@@ -0,0 +1,9 @@
+{
+    // See https://go.microsoft.com/fwlink/?LinkId=827846 to learn about workspace recommendations.
+    // Extension identifier format: ${publisher}.${name}. Example: vscode.csharp
+
+    // List of extensions which should be recommended for users of this workspace.
+    "recommendations": ["dbaeumer.vscode-eslint", "esbenp.prettier-vscode", "NomicFoundation.hardhat-solidity"],
+    // List of extensions recommended by VS Code that should not be recommended for users of this workspace.
+    "unwantedRecommendations": []
+  }

.vscode/settings.json

@@ -0,0 +1,10 @@
+{
+    "editor.formatOnSave": true,
+    "solidity.formatter": "prettier", // This is the default so it might be missing.
+    "[solidity]": {
+      "editor.defaultFormatter": "NomicFoundation.hardhat-solidity"
+    },
+    "eslint.enable": true,
+    "eslint.validate": ["javascript", "typescript"],
+    "eslint.alwaysShowStatus": true
+  }

README.md

@@ -11,6 +11,7 @@ This repo is dedicated to making minimal repos of existing defi primatives.
 - `Staking.sol`: Based off [Synthetix](https://synthetix.io/)
 - `RewardToken.sol`: Based off [Synthetix](https://synthetix.io/)
 - `Exchange.sol` , `Factory.sol` , `Token.sol` : Based off [Uniswap v1](https://docs.uniswap.org/protocol/V1/introduction). The used pricing formula is documented [here](./docs/uniswap-v1/)
+-  Uniswap-v2:  [core and periphery](./docs/uniswap-v2/)
 - `DecentralizedStableCoin`: Based off DAI
 - `CentralizedStableCoin`: Based off USDC
 

contracts/amm/uniswap-v2/core/UniswapV2ERC20.sol

@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: Unlicense
+pragma solidity ^0.8.7;
+
+import "./interfaces/IUniswapV2ERC20.sol";
+import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+
+contract UniswapV2ERC20 is IUniswapV2ERC20, ERC20 {
+    error EXPIRED(uint256 deadline, uint256 blockTimestamp);
+    error InvalidSignature(address recoveredAddress, address owner);
+    bytes32 public override DOMAIN_SEPARATOR;
+    // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
+    bytes32 public constant override PERMIT_TYPEHASH =
+        0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;
+    mapping(address => uint256) public override nonces;
+
+    constructor() ERC20("Uniswap V2", "UNI-V2") {
+        uint256 chainId;
+        assembly {
+            chainId := chainid()
+        }
+        DOMAIN_SEPARATOR = keccak256(
+            abi.encode(
+                keccak256(
+                    "EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"
+                ),
+                keccak256(bytes("Uniswap V2")),
+                keccak256(bytes("1")),
+                chainId,
+                address(this)
+            )
+        );
+    }
+
+    function permit(
+        address owner,
+        address spender,
+        uint256 value,
+        uint256 deadline,
+        uint8 v,
+        bytes32 r,
+        bytes32 s
+    ) external override {
+        if (deadline < block.timestamp) revert EXPIRED(deadline, block.timestamp);
+        bytes32 digest = keccak256(
+            abi.encodePacked(
+                "\x19\x01",
+                DOMAIN_SEPARATOR,
+                keccak256(
+                    abi.encode(PERMIT_TYPEHASH, owner, spender, value, nonces[owner]++, deadline)
+                )
+            )
+        );
+        address recoveredAddress = ecrecover(digest, v, r, s);
+        if (recoveredAddress == address(0) || recoveredAddress != owner)
+            revert InvalidSignature(recoveredAddress, owner);
+        _approve(owner, spender, value);
+    }
+}

contracts/amm/uniswap-v2/core/UniswapV2Factory.sol

@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: Unlicense
+pragma solidity ^0.8.7;
+
+import "./interfaces/IUniswapV2Factory.sol";
+import "./UniswapV2Pair.sol";
+
+contract UniswapV2Factory is IUniswapV2Factory {
+    error IdenticalAddresses();
+    error PairExists();
+    error ZeroAddress();
+    error Forbidden(address feeTo, address feeToSetter);
+
+    address public override feeTo;
+    address public override feeToSetter;
+
+    mapping(address => mapping(address => address)) public override getPair;
+    address[] public override allPairs;
+
+    constructor(address _feeToSetter) {
+        feeToSetter = _feeToSetter;
+    }
+
+    function allPairsLength() external view override returns (uint256) {
+        return allPairs.length;
+    }
+
+    function createPair(address tokenA, address tokenB) external override returns (address pair) {
+        if (tokenA == tokenB) revert IdenticalAddresses();
+
+        (address token0, address token1) = tokenA < tokenB ? (tokenA, tokenB) : (tokenB, tokenA);
+
+        if (token0 == address(0)) revert ZeroAddress();
+
+        if (getPair[token0][token1] != address(0)) revert PairExists();
+
+        bytes memory bytecode = type(UniswapV2Pair).creationCode;
+        bytes32 salt = keccak256(abi.encodePacked(token0, token1));
+        assembly {
+            pair := create2(0, add(bytecode, 32), mload(bytecode), salt)
+        }
+
+        IUniswapV2Pair(pair).initialize(token0, token1);
+
+        getPair[token0][token1] = pair;
+        getPair[token1][token0] = pair;
+        allPairs.push(pair);
+
+        emit PairCreated(token0, token1, pair, allPairs.length);
+    }
+
+    function setFeeTo(address _feeTo) external override {
+        if (msg.sender != feeToSetter) revert Forbidden(msg.sender, feeToSetter);
+        feeTo = _feeTo;
+    }
+
+    function setFeeToSetter(address _feeToSetter) external override {
+        if (msg.sender != feeToSetter) revert Forbidden(msg.sender, feeToSetter);
+        feeToSetter = _feeToSetter;
+    }
+}