From 6b8cfe03daa8593a4d3c675e71cf6d6696758535 Mon Sep 17 00:00:00 2001
From: Yin Guanhao <sopium@mysterious.site>
Date: Sun, 17 Sep 2023 17:23:33 +0800
Subject: [PATCH] Add permissionless ICS20TransferERC20

---
 .../apps/20-transfer/ICS20TransferERC20.sol   | 106 ++++++++++++++++++
 test/ICS20TransferERC20.js                    |  25 +++++
 2 files changed, 131 insertions(+)
 create mode 100644 contracts/apps/20-transfer/ICS20TransferERC20.sol
 create mode 100644 test/ICS20TransferERC20.js

diff --git a/contracts/apps/20-transfer/ICS20TransferERC20.sol b/contracts/apps/20-transfer/ICS20TransferERC20.sol
new file mode 100644
index 0000000..10aed91
--- /dev/null
+++ b/contracts/apps/20-transfer/ICS20TransferERC20.sol
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: Apache-2.0
+pragma solidity ^0.8.9;
+
+import "./ICS20Transfer.sol";
+import "../../core/25-handler/IBCHandler.sol";
+import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+import "@openzeppelin/contracts/token/ERC20/presets/ERC20PresetMinterPauser.sol";
+
+// An ICS20 implementation that maps sink denoms to ERC20 contracts that's deployed and managed by this contract.
+//
+// Source denom is interpreted as ERC20 contract address in hex with the 0x prefix.
+contract ICS20TransferERC20 is ICS20Transfer {
+    // Map sink denom to ERC20.
+    mapping(string => ERC20PresetMinterPauser) public denomTokenContract;
+
+    constructor(IBCHandler ibcHandler_) ICS20Transfer(ibcHandler_) {
+    }
+
+    function _transferFrom(address sender, address receiver, string memory denom, uint256 amount)
+        internal
+        override
+        returns (bool)
+    {
+        IERC20 tokenContract = IERC20(parseAddr(denom));
+        // transferFrom returns a bool but it may also revert.
+        try tokenContract.transferFrom(sender, receiver, amount) returns (bool succeeded) {
+            return succeeded;
+        } catch (bytes memory) {
+            return false;
+        }
+    }
+
+    function _mint(address account, string memory denom, uint256 amount) internal override returns (bool) {
+        // Deploy an ERC20 contract for each (sink zone) denom seen.
+        if (address(denomTokenContract[denom]) == address(0)) {
+            string memory name = string.concat("IBC/", hexEncode(abi.encodePacked(sha256(bytes(denom)))));
+            denomTokenContract[denom] = new ERC20PresetMinterPauser(name, "");
+        }
+        denomTokenContract[denom].mint(account, amount);
+        return true;
+    }
+
+    function _burn(address account, string memory denom, uint256 amount) internal override returns (bool) {
+        if (address(denomTokenContract[denom]) == address(0)) {
+            return false;
+        }
+        try denomTokenContract[denom].burnFrom(account, amount) {
+            return true;
+        } catch (bytes memory) {
+            return false;
+        }
+    }
+
+    function hexEncode(bytes memory buffer) internal pure returns (string memory) {
+        // Fixed buffer size for hexadecimal convertion
+        bytes memory converted = new bytes(buffer.length * 2);
+
+        bytes memory _base = "0123456789ABCDEF";
+
+        for (uint256 i = 0; i < buffer.length; i++) {
+            converted[i * 2] = _base[uint8(buffer[i]) / _base.length];
+            converted[i * 2 + 1] = _base[uint8(buffer[i]) % _base.length];
+        }
+
+        return string(converted);
+    }
+
+    // a copy from https://github.com/provable-things/ethereum-api/blob/161552ebd4f77090d86482cff8c863cf903c6f5f/oraclizeAPI_0.6.sol
+    function parseAddr(string memory _a) internal pure returns (address _parsedAddress) {
+        bytes memory tmp = bytes(_a);
+        uint160 iaddr = 0;
+        uint160 b1;
+        uint160 b2;
+        for (uint256 i = 2; i < 2 + 2 * 20; i += 2) {
+            iaddr *= 256;
+            b1 = uint160(uint8(tmp[i]));
+            b2 = uint160(uint8(tmp[i + 1]));
+            if ((b1 >= 97) && (b1 <= 102)) {
+                b1 -= 87;
+            } else if ((b1 >= 65) && (b1 <= 70)) {
+                b1 -= 55;
+            } else if ((b1 >= 48) && (b1 <= 57)) {
+                b1 -= 48;
+            }
+            if ((b2 >= 97) && (b2 <= 102)) {
+                b2 -= 87;
+            } else if ((b2 >= 65) && (b2 <= 70)) {
+                b2 -= 55;
+            } else if ((b2 >= 48) && (b2 <= 57)) {
+                b2 -= 48;
+            }
+            iaddr += (b1 * 16 + b2);
+        }
+        return address(iaddr);
+    }
+}
+
+// Make external wrappers for testing.
+contract ICS20TransferERC20Test is ICS20TransferERC20 {
+    constructor(IBCHandler ibcHandler_) ICS20TransferERC20(ibcHandler_) {
+    }
+
+    function mint(address account, string memory denom, uint256 amount) external {
+        require(_mint(account, denom, amount));
+    }
+}
diff --git a/test/ICS20TransferERC20.js b/test/ICS20TransferERC20.js
new file mode 100644
index 0000000..fc5f2f0
--- /dev/null
+++ b/test/ICS20TransferERC20.js
@@ -0,0 +1,25 @@
+const IBCHandler = artifacts.require("IBCMockHandler");
+const ICS20TransferERC20 = artifacts.require("ICS20TransferERC20Test");
+const ERC20PresetMinterPauser = artifacts.require("ERC20PresetMinterPauser");
+
+contract("ICS20TransferERC20", ([account]) => {
+  it("should be able to mint/burn ERC20", async () => {
+    const ibcHandler = await IBCHandler.deployed();
+    const transfer = await ICS20TransferERC20.new(ibcHandler.address);
+
+    const denom = "/port-2/transfer-8/MY-TOKEN-TYPE-SCRIPT-HASH";
+
+    await transfer.mint(account, denom, 100);
+    await transfer.mint(account, denom, 51);
+    const myToken = await ERC20PresetMinterPauser.at(
+      await transfer.denomTokenContract(denom)
+    );
+
+    assert.equal(
+      await myToken.name(),
+      "IBC/A74473C8545D36443C16874E2A336A00016EF1C0EA489CE552A76EE1709CE50D"
+    );
+    assert.equal(await myToken.balanceOf(account), 151);
+    assert.equal(await myToken.totalSupply(), 151);
+  });
+});