Revert "Remove all this pesky code (for review)"

src/TeleportConstantFee.sol

@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+// Copyright (C) 2021 Dai Foundation
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+pragma solidity 0.8.14;
+
+import {TeleportFees} from "./TeleportFees.sol";
+import {TeleportGUID} from "./TeleportGUID.sol";
+
+contract TeleportConstantFee is TeleportFees {
+    uint256 immutable public fee;
+    uint256 immutable public ttl;
+
+    /**
+    * @param _fee Constant fee in WAD
+    * @param _ttl Time in seconds to finalize flush (not teleport)
+    **/
+    constructor(uint256 _fee, uint256 _ttl) {
+        fee = _fee;
+        ttl = _ttl;
+    }
+
+    function getFee(TeleportGUID calldata guid, uint256, int256, uint256, uint256 amtToTake) override external view returns (uint256) {
+        // is slow withdrawal?
+        if (block.timestamp >= uint256(guid.timestamp) + ttl) {
+            return 0;
+        }
+
+        // is empty teleport?
+        if (guid.amount == 0) {
+            return 0;
+        }
+
+        return fee * amtToTake / guid.amount;
+    }
+}

src/TeleportFees.sol

@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+// Copyright (C) 2021 Dai Foundation
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+pragma solidity 0.8.14;
+
+import "./TeleportGUID.sol";
+
+// Calculate fees for a given Teleport GUID
+interface TeleportFees {
+    /**
+    * @dev Return fee for particular teleport. It should return 0 for teleports that are being slow withdrawn. 
+    * note: We define slow withdrawal as teleport older than x. x has to be enough to finalize flush (not teleport itself).
+    * @param teleportGUID Struct which contains the whole teleport data
+    * @param line Debt ceiling
+    * @param debt Current debt
+    * @param pending Amount left to withdraw
+    * @param amtToTake Amount to take. Can be less or equal to teleportGUID.amount b/c of debt ceiling or because it is pending
+    * @return fees Fee amount [WAD]
+    **/
+    function getFee(
+        TeleportGUID calldata teleportGUID, uint256 line, int256 debt, uint256 pending, uint256 amtToTake
+    ) external view returns (uint256 fees);
+}

src/TeleportGUID.sol

@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+// Copyright (C) 2021 Dai Foundation
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+pragma solidity 0.8.14;
+
+// Standard Maker Teleport GUID
+struct TeleportGUID {
+    bytes32 sourceDomain;
+    bytes32 targetDomain;
+    bytes32 receiver;
+    bytes32 operator;
+    uint128 amount;
+    uint80 nonce;
+    uint48 timestamp;
+}
+
+// solhint-disable-next-line func-visibility
+function bytes32ToAddress(bytes32 addr) pure returns (address) {
+    return address(uint160(uint256(addr)));
+}
+
+// solhint-disable-next-line func-visibility
+function addressToBytes32(address addr) pure returns (bytes32) {
+    return bytes32(uint256(uint160(addr)));
+}
+
+// solhint-disable-next-line func-visibility
+function getGUIDHash(TeleportGUID memory teleportGUID) pure returns (bytes32 guidHash) {
+    guidHash = keccak256(abi.encode(
+        teleportGUID.sourceDomain,
+        teleportGUID.targetDomain,
+        teleportGUID.receiver,
+        teleportGUID.operator,
+        teleportGUID.amount,
+        teleportGUID.nonce,
+        teleportGUID.timestamp
+    ));
+}