// SPDX-License-Identifier: MIT

pragma solidity 0.8.19;

import {IBeacon} from "@openzeppelin/contracts/proxy/beacon/IBeacon.sol";

/**
 * @dev This contract implements a proxy that gets the implementation address for each call from an {UpgradeableBeacon}.
 *
 * The beacon address is stored in storage slot `uint256(keccak256('eip1967.proxy.beacon')) - 1`, so that it doesn't
 * conflict with the storage layout of the implementation behind the proxy.
 */
contract FairxyzBeaconProxy {
    /**
     * @dev Emitted when the beacon is upgraded.
     */
    event BeaconUpgraded(address indexed beacon);

    struct AddressSlot {
        address value;
    }

    /**
     * @dev The storage slot of the Beacon contract which defines the implementation for this proxy.
     * This is bytes32(uint256(keccak256('eip1967.proxy.beacon')) - 1)) and is validated in the constructor.
     */
    bytes32 internal constant _BEACON_SLOT =
        0xa3f0ad74e5423aebfd80d3ef4346578335a9a72aeaee59ff6cb3582b35133d50;

    /**
     * @dev Initializes the proxy, upgrading to beacon `beacon`.
     *
     * If `data` is nonempty, it's used as data in a delegate call to the implementation returned by the beacon. This
     * will typically be an encoded function call, and allows initializing the storage of the proxy like a Solidity
     * constructor.
     *
     * Requirements:
     *
     * - `beacon` must be a contract with the interface {IBeacon}.
     */
    constructor(address beacon, bytes memory data) payable {
        _upgradeBeaconToAndCall(beacon, data);
    }

    /**
     * @dev Fallback function that delegates calls to the address returned by `_implementation()`. Will run if no other
     * function in the contract matches the call data.
     */
    fallback() external payable virtual {
        _delegate(_implementation());
    }

    /**
     * @dev Fallback function that delegates calls to the address returned by `_implementation()`. Will run if call data
     * is empty.
     */
    receive() external payable virtual {
        _delegate(_implementation());
    }

    /**
     * @dev Delegates the current call to `implementation`.
     *
     * This function does not return to its internal call site, it will return directly to the external caller.
     */
    function _delegate(address implementation) internal virtual {
        assembly {
            // Copy msg.data. We take full control of memory in this inline assembly
            // block because it will not return to Solidity code. We overwrite the
            // Solidity scratch pad at memory position 0.
            calldatacopy(0, 0, calldatasize())

            // Call the implementation.
            // out and outsize are 0 because we don't know the size yet.
            let result := delegatecall(
                gas(),
                implementation,
                0,
                calldatasize(),
                0,
                0
            )

            // Copy the returned data.
            returndatacopy(0, 0, returndatasize())

            switch result
            // delegatecall returns 0 on error.
            case 0 {
                revert(0, returndatasize())
            }
            default {
                return(0, returndatasize())
            }
        }
    }

    /**
     * @dev Returns an `AddressSlot` with member `value` located at `slot`.
     */
    function _getAddressSlot(
        bytes32 slot
    ) internal pure returns (AddressSlot storage r) {
        /// @solidity memory-safe-assembly
        assembly {
            r.slot := slot
        }
    }

    /**
     * @dev Returns the current implementation address of the associated beacon.
     */
    function _implementation() internal view virtual returns (address) {
        return IBeacon(_getAddressSlot(_BEACON_SLOT).value).implementation();
    }

    /**
     * @dev Perform beacon upgrade with additional setup call. Note: This upgrades the address of the beacon, it does
     * not upgrade the implementation contained in the beacon (see {UpgradeableBeacon-_setImplementation} for that).
     *
     * Emits a {BeaconUpgraded} event.
     */
    function _upgradeBeaconToAndCall(
        address newBeacon,
        bytes memory data
    ) internal {
        require(
            newBeacon.code.length > 0,
            "ERC1967: new beacon is not a contract"
        );

        address implementation = IBeacon(newBeacon).implementation();

        require(
            implementation.code.length > 0,
            "ERC1967: beacon implementation is not a contract"
        );

        _getAddressSlot(_BEACON_SLOT).value = newBeacon;

        emit BeaconUpgraded(newBeacon);

        if (data.length > 0) {
            (bool success, bytes memory returndata) = implementation
                .delegatecall(data);

            if (!success) {
                if (returndata.length > 0) {
                    assembly {
                        let returndata_size := mload(returndata)
                        revert(add(32, returndata), returndata_size)
                    }
                } else {
                    revert("Address: low-level delegate call failed");
                }
            }
        }
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (proxy/beacon/IBeacon.sol)

pragma solidity ^0.8.0;

/**
 * @dev This is the interface that {BeaconProxy} expects of its beacon.
 */
interface IBeacon {
    /**
     * @dev Must return an address that can be used as a delegate call target.
     *
     * {BeaconProxy} will check that this address is a contract.
     */
    function implementation() external view returns (address);
}

{
  "compilationTarget": {
    "contracts/v2/Proxy/FairxyzBeaconProxy.sol": "FairxyzBeaconProxy"
  },
  "evmVersion": "paris",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": true,
    "runs": 10000
  },
  "remappings": []
}