// SPDX-License-Identifier: MIT

pragma solidity 0.8.20;

import "../interfaces/IInterestModel.sol";

/**
 * @title TripleSlopeModel
 * @notice Triple slope interest rate model for bank
 * @dev Implements a three-tier interest rate model based on utilization
 */
contract TripleSlopeModel is IInterestModel {
    /// @dev Return the interest rate per second, using 1e18 as denom.
    function getInterestRate(uint256 debt, uint256 floating) external pure returns (uint256) {
        uint256 total = debt + floating;

        if (total == 0) return 0; // Prevent division by zero
        uint256 utilization = (debt * 100e18) / total;

        //Triple Slope Model
        if (utilization < 80e18) {
            // Less than 80% utilization -  % APY
            return (utilization * 8e16) / (80e18) / 365 days;
        } else if (utilization < 90e18) {
            // Between 80% and 90% - 8%-15% APY
            return (8e16 + ((utilization - 80e18) * 7e16) / 10e18) / 365 days;
        } else if (utilization < 100e18) {
            // Between 90% and 100% - 15%-50% APY
            return (15e16 + ((utilization - 90e18) * 35e16) / 10e18) / 365 days;
        } else {
            // Not possible, but just in case - 50% APY
            return uint256(50e16) / 365 days;
        }
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.20;

/**
 * @title IInterestModel
 * @notice Interface for interest rate model
 */
interface IInterestModel {
    /// @dev Return the interest rate per second, using 1e18 as denom.
    function getInterestRate(uint256 debt, uint256 floating) external view returns (uint256);
}

{
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "viaIR": true,
  "evmVersion": "paris",
  "outputSelection": {
    "*": {
      "*": [
        "evm.bytecode",
        "evm.deployedBytecode",
        "devdoc",
        "userdoc",
        "metadata",
        "abi"
      ]
    }
  },
  "metadata": {
    "useLiteralContent": true
  }
}

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[{"inputs":[{"internalType":"uint256","name":"debt","type":"uint256"},{"internalType":"uint256","name":"floating","type":"uint256"}],"name":"getInterestRate","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"pure","type":"function"}]

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