add spl20 contract

src/spl20.sol

@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.13;
+
+struct Mint {
+  uint8 decimals;
+  uint256 supply;
+  address mintAuthority;
+  address freezeAuthority;
+  address mintAddress;
+}
+
+struct TokenAccount {
+  address mintAddress;
+  address owner;
+  uint256 balance;
+  bool isFrozen;
+}
+
+contract Spl20 {
+
+  mapping(address => Mint) public mints;
+  mapping(address => TokenAccount) public tokenAccounts;
+  address[] public mintAddresses;
+  address[] public tokenAddresses;
+
+  function initializeMint(
+    uint8 decimals, 
+    uint256 supply,
+    address mintAuthority, 
+    address freezeAuthority,
+    address mintAddress
+  ) public returns (Mint memory) {
+    require(mints[mintAddress].mintAuthority == address(0), "Mint already exists");
+    mints[mintAddress] = Mint(decimals, supply, mintAuthority, freezeAuthority, mintAddress);
+    mintAddresses.push(mintAddress);
+    return Mint(decimals, supply, mintAuthority, freezeAuthority, mintAddress);
+  }
+
+  function mintTokens(address mintAddress, uint256 amount) public {
+    require(mints[mintAddress].mintAuthority == msg.sender, "Only the mint authority can mint tokens");
+    require(mints[mintAddress].mintAddress != address(0), "Token does not exist");
+    require(mints[mintAddress].supply + amount <= type(uint256).max, "Supply overflow");
+
+    mints[mintAddress].supply += amount;
+
+    address tokenAddress = address(uint160(uint(keccak256(abi.encodePacked(msg.sender, mintAddress)))));
+
+    if (tokenAccounts[tokenAddress].mintAddress == address(0)) {
+      tokenAccounts[tokenAddress] = TokenAccount(mintAddress, msg.sender, 0, false);
+      tokenAddresses.push(tokenAddress);
+    }
+
+    tokenAccounts[tokenAddress].balance += amount;    
+  }
+
+  function transfer(address to, address mintAddress, uint256 amount) public {
+    address toTokenAddress = address(uint160(uint(keccak256(abi.encodePacked(to, mintAddress)))));
+    address fromTokenAddress = address(uint160(uint(keccak256(abi.encodePacked(msg.sender, mintAddress)))));
+
+    require(tokenAccounts[fromTokenAddress].balance >= amount, "Insufficient balance");
+    require(tokenAccounts[toTokenAddress].balance + amount <= type(uint256).max, "Supply overflow");
+    require(tokenAccounts[fromTokenAddress].isFrozen == false, "Token is frozen");
+
+    if (tokenAccounts[toTokenAddress].mintAddress == address(0)) {
+      tokenAccounts[toTokenAddress] = TokenAccount(mintAddress, to, 0, false);
+      tokenAddresses.push(toTokenAddress);
+    }
+
+    tokenAccounts[fromTokenAddress].balance -= amount;
+    tokenAccounts[toTokenAddress].balance += amount;
+  }
+
+  function getMint(address token) public view returns (Mint memory) {
+    return mints[token];
+  }
+
+  function getTokenAccount(address owner, address token) public view returns (TokenAccount memory) {
+    return tokenAccounts[address(uint160(uint(keccak256(abi.encodePacked(owner, token)))))];
+  }
+}