Add pay function

contracts/DateTimeUtils.sol

@@ -33,6 +33,23 @@ type Year is uint256;
 type Timestamp is uint256;
 
 using DateTimeUtils for Timestamp global;
+using {
+    monthsLess as <,
+    monthsEqual as ==,
+    monthsGreater as >
+} for Months global;
+
+function monthsLess(Months left, Months right) pure returns (bool result) {
+    return Months.unwrap(left) < Months.unwrap(right);
+}
+
+function monthsEqual(Months a, Months b) pure returns (bool result) {
+    return !(a < b) && !(b < a);
+}
+
+function monthsGreater(Months left, Months right) pure returns (bool result) {
+    return !(left < right) && !(left == right);
+}
 
 library DateTimeUtils {
     function timestamp() internal view returns (Timestamp timestampValue) {

contracts/Paymaster.sol

@@ -19,21 +19,39 @@
     along with Paymaster.  If not, see <https://www.gnu.org/licenses/>.
 */
 
-pragma solidity ^0.8.18;
+pragma solidity ^0.8.19;
 
-// cspell:words structs
+// cspell:words structs IERC20
 
+import {IERC20} from "@openzeppelin/contracts/interfaces/IERC20.sol";
 import {EnumerableSet} from "@openzeppelin/contracts/utils/structs/EnumerableSet.sol";
 import {Math} from "@openzeppelin/contracts/utils/math/Math.sol";
 import {AccessManagedUpgradeable}
 from "@openzeppelin/contracts-upgradeable/access/manager/AccessManagedUpgradeable.sol";
 
+import {
+    SchainPriceIsNotSet,
+    SkaleTokenIsNotSet,
+    SklPriceIsNotSet
+} from "./errors/Parameters.sol";
+import {
+    ReplenishmentPeriodIsTooBig,
+    TooSmallAllowance,
+    TransferFailure
+} from "./errors/Replenishment.sol";
 import {SchainNotFound, SchainAddingError, SchainDeletionError} from "./errors/Schain.sol";
 import {ValidatorNotFound, ValidatorAddingError, ValidatorDeletionError} from "./errors/Validator.sol";
-import {IPaymaster, SchainHash, ValidatorId} from "./interfaces/IPaymaster.sol";
+import {
+    IPaymaster,
+    SchainHash,
+    USD,
+    ValidatorId
+} from "./interfaces/IPaymaster.sol";
+import {SKL} from "./types/Skl.sol";
 import {
     DateTimeUtils,
-    Timestamp
+    Timestamp,
+    Months
 } from "./DateTimeUtils.sol";
 
 
@@ -59,6 +77,11 @@ contract Paymaster is AccessManagedUpgradeable, IPaymaster {
     mapping(ValidatorId => Validator) public validators;
     EnumerableSet.UintSet private _validatorIds;
 
+    Months public maxReplenishmentPeriod;
+    USD public schainPricePerMonth;
+    USD public oneSklPrice;
+    IERC20 public skaleToken;
+
     function addSchain(string calldata name) external override restricted {
         SchainHash schainHash = SchainHash.wrap(keccak256(abi.encodePacked(name)));
         Schain memory schain = Schain({
@@ -97,9 +120,50 @@ contract Paymaster is AccessManagedUpgradeable, IPaymaster {
         validator.activeNodesAmount = Math.min(amount, validator.nodesAmount);
     }
 
-    // function pay(SchainHash schainHash, Months duration) external {
+    function setMaxReplenishmentPeriod(Months months) external override restricted {
+        maxReplenishmentPeriod = months;
+    }
+
+    function setSchainPrice(USD price) external override restricted {
+        schainPricePerMonth = price;
+    }
+
+    function setSklPrice(USD price) external override restricted {
+        oneSklPrice = price;
+    }
+
+    function setSkaleToken(IERC20 token) external override restricted {
+        skaleToken = token;
+    }
+
+    function pay(SchainHash schainHash, Months duration) external override {
+        if (duration > maxReplenishmentPeriod) {
+            revert ReplenishmentPeriodIsTooBig();
+        }
+
+        Schain storage schain = _getSchain(schainHash);
+        SKL cost = _toSKL(_getCost(duration));
+
+        if (address(skaleToken) == address(0)) {
+            revert SkaleTokenIsNotSet();
+        }
+        SKL allowance = SKL.wrap(
+            skaleToken.allowance(_msgSender(), address(this))
+        );
+        if (allowance < cost) {
+            revert TooSmallAllowance({
+                spender: address(this),
+                required: SKL.unwrap(cost),
+                allowed: SKL.unwrap(allowance)
+            });
+        }
 
-    // }
+        if (!skaleToken.transferFrom(_msgSender(), address(this), SKL.unwrap(cost))) {
+            revert TransferFailure();
+        }
+
+        schain.paidUntil = schain.paidUntil.add(duration);
+    }
 
     // Private
 
@@ -146,4 +210,20 @@ contract Paymaster is AccessManagedUpgradeable, IPaymaster {
             revert ValidatorNotFound(id);
         }
     }
+
+    function _toSKL(USD amount) private view returns (SKL result) {
+        if (oneSklPrice == USD.wrap(0)) {
+            revert SklPriceIsNotSet();
+        }
+        result = SKL.wrap(
+            USD.unwrap(amount) * 1e18 / USD.unwrap(oneSklPrice)
+        );
+    }
+
+    function _getCost(Months period) private view returns (USD cost) {
+        if (schainPricePerMonth == USD.wrap(0)) {
+            revert SchainPriceIsNotSet();
+        }
+        cost = USD.wrap(Months.unwrap(period) * USD.unwrap(schainPricePerMonth));
+    }
 }

contracts/errors/Parameters.sol

@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+/*
+    Parameters.sol - Paymaster
+    Copyright (C) 2023-Present SKALE Labs
+    @author Dmytro Stebaiev
+
+    Paymaster 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.
+
+    Paymaster 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 Paymaster.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+pragma solidity ^0.8.18;
+
+
+error SchainPriceIsNotSet();
+error SkaleTokenIsNotSet();
+error SklPriceIsNotSet();

contracts/errors/Replenishment.sol

@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+/*
+    Replenishment.sol - Paymaster
+    Copyright (C) 2023-Present SKALE Labs
+    @author Dmytro Stebaiev
+
+    Paymaster 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.
+
+    Paymaster 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 Paymaster.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+pragma solidity ^0.8.18;
+
+
+error ReplenishmentPeriodIsTooBig();
+error TooSmallAllowance(
+    address spender,
+    uint256 required,
+    uint256 allowed
+);
+error TransferFailure();

contracts/interfaces/IPaymaster.sol

@@ -21,6 +21,13 @@
 
 pragma solidity ^0.8.18;
 
+// cspell:words IERC20
+
+import {IERC20} from "@openzeppelin/contracts/interfaces/IERC20.sol";
+
+import {Months} from "../DateTimeUtils.sol";
+import {USD} from "../types/Usd.sol";
+
 
 type SchainHash is bytes32;
 type ValidatorId is uint256;
@@ -32,4 +39,9 @@ interface IPaymaster {
     function removeValidator(ValidatorId id) external;
     function setNodesAmount(ValidatorId id, uint256 amount) external;
     function setActiveNodes(ValidatorId id, uint256 amount) external;
+    function setMaxReplenishmentPeriod(Months months) external;
+    function setSchainPrice(USD price) external;
+    function setSklPrice(USD price) external;
+    function setSkaleToken(IERC20 token) external;
+    function pay(SchainHash schainHash, Months duration) external;
 }

contracts/types/Skl.sol

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+/*
+    Skl.sol - Paymaster
+    Copyright (C) 2023-Present SKALE Labs
+    @author Dmytro Stebaiev
+
+    Paymaster 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.
+
+    Paymaster 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 Paymaster.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+pragma solidity ^0.8.18;
+
+
+type SKL is uint256;
+
+using {
+    sklLess as <
+} for SKL global;
+
+function sklLess(SKL left, SKL right) pure returns (bool result) {
+    return SKL.unwrap(left) < SKL.unwrap(right);
+}

contracts/types/Usd.sol

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+/*
+    Usd.sol - Paymaster
+    Copyright (C) 2023-Present SKALE Labs
+    @author Dmytro Stebaiev
+
+    Paymaster 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.
+
+    Paymaster 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 Paymaster.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+pragma solidity ^0.8.18;
+
+
+type USD is uint256;
+
+function usdEquals(USD a, USD b) pure returns (bool result) {
+    return USD.unwrap(a) == USD.unwrap(b);
+}
+
+using {
+    usdEquals as ==
+} for USD global;