// File: @openzeppelin/contracts/utils/math/Math.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (utils/math/Math.sol)

pragma solidity ^0.8.0;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    enum Rounding {
        Down, // Toward negative infinity
        Up, // Toward infinity
        Zero // Toward zero
    }

    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a > b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow.
        return (a & b) + (a ^ b) / 2;
    }

    /**
     * @dev Returns the ceiling of the division of two numbers.
     *
     * This differs from standard division with `/` in that it rounds up instead
     * of rounding down.
     */
    function ceilDiv(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b - 1) / b can overflow on addition, so we distribute.
        return a == 0 ? 0 : (a - 1) / b + 1;
    }

    /**
     * @notice Calculates floor(x * y / denominator) with full precision. Throws if result overflows a uint256 or denominator == 0
     * @dev Original credit to Remco Bloemen under MIT license (https://xn--2-umb.com/21/muldiv)
     * with further edits by Uniswap Labs also under MIT license.
     */
    function mulDiv(uint256 x, uint256 y, uint256 denominator) internal pure returns (uint256 result) {
        unchecked {
            // 512-bit multiply [prod1 prod0] = x * y. Compute the product mod 2^256 and mod 2^256 - 1, then use
            // use the Chinese Remainder Theorem to reconstruct the 512 bit result. The result is stored in two 256
            // variables such that product = prod1 * 2^256 + prod0.
            uint256 prod0; // Least significant 256 bits of the product
            uint256 prod1; // Most significant 256 bits of the product
            assembly {
                let mm := mulmod(x, y, not(0))
                prod0 := mul(x, y)
                prod1 := sub(sub(mm, prod0), lt(mm, prod0))
            }

            // Handle non-overflow cases, 256 by 256 division.
            if (prod1 == 0) {
                // Solidity will revert if denominator == 0, unlike the div opcode on its own.
                // The surrounding unchecked block does not change this fact.
                // See https://docs.soliditylang.org/en/latest/control-structures.html#checked-or-unchecked-arithmetic.
                return prod0 / denominator;
            }

            // Make sure the result is less than 2^256. Also prevents denominator == 0.
            require(denominator > prod1, "Math: mulDiv overflow");

            ///////////////////////////////////////////////
            // 512 by 256 division.
            ///////////////////////////////////////////////

            // Make division exact by subtracting the remainder from [prod1 prod0].
            uint256 remainder;
            assembly {
                // Compute remainder using mulmod.
                remainder := mulmod(x, y, denominator)

                // Subtract 256 bit number from 512 bit number.
                prod1 := sub(prod1, gt(remainder, prod0))
                prod0 := sub(prod0, remainder)
            }

            // Factor powers of two out of denominator and compute largest power of two divisor of denominator. Always >= 1.
            // See https://cs.stackexchange.com/q/138556/92363.

            // Does not overflow because the denominator cannot be zero at this stage in the function.
            uint256 twos = denominator & (~denominator + 1);
            assembly {
                // Divide denominator by twos.
                denominator := div(denominator, twos)

                // Divide [prod1 prod0] by twos.
                prod0 := div(prod0, twos)

                // Flip twos such that it is 2^256 / twos. If twos is zero, then it becomes one.
                twos := add(div(sub(0, twos), twos), 1)
            }

            // Shift in bits from prod1 into prod0.
            prod0 |= prod1 * twos;

            // Invert denominator mod 2^256. Now that denominator is an odd number, it has an inverse modulo 2^256 such
            // that denominator * inv = 1 mod 2^256. Compute the inverse by starting with a seed that is correct for
            // four bits. That is, denominator * inv = 1 mod 2^4.
            uint256 inverse = (3 * denominator) ^ 2;

            // Use the Newton-Raphson iteration to improve the precision. Thanks to Hensel's lifting lemma, this also works
            // in modular arithmetic, doubling the correct bits in each step.
            inverse *= 2 - denominator * inverse; // inverse mod 2^8
            inverse *= 2 - denominator * inverse; // inverse mod 2^16
            inverse *= 2 - denominator * inverse; // inverse mod 2^32
            inverse *= 2 - denominator * inverse; // inverse mod 2^64
            inverse *= 2 - denominator * inverse; // inverse mod 2^128
            inverse *= 2 - denominator * inverse; // inverse mod 2^256

            // Because the division is now exact we can divide by multiplying with the modular inverse of denominator.
            // This will give us the correct result modulo 2^256. Since the preconditions guarantee that the outcome is
            // less than 2^256, this is the final result. We don't need to compute the high bits of the result and prod1
            // is no longer required.
            result = prod0 * inverse;
            return result;
        }
    }

    /**
     * @notice Calculates x * y / denominator with full precision, following the selected rounding direction.
     */
    function mulDiv(uint256 x, uint256 y, uint256 denominator, Rounding rounding) internal pure returns (uint256) {
        uint256 result = mulDiv(x, y, denominator);
        if (rounding == Rounding.Up && mulmod(x, y, denominator) > 0) {
            result += 1;
        }
        return result;
    }

    /**
     * @dev Returns the square root of a number. If the number is not a perfect square, the value is rounded down.
     *
     * Inspired by Henry S. Warren, Jr.'s "Hacker's Delight" (Chapter 11).
     */
    function sqrt(uint256 a) internal pure returns (uint256) {
        if (a == 0) {
            return 0;
        }

        // For our first guess, we get the biggest power of 2 which is smaller than the square root of the target.
        //
        // We know that the "msb" (most significant bit) of our target number `a` is a power of 2 such that we have
        // `msb(a) <= a < 2*msb(a)`. This value can be written `msb(a)=2**k` with `k=log2(a)`.
        //
        // This can be rewritten `2**log2(a) <= a < 2**(log2(a) + 1)`
        // → `sqrt(2**k) <= sqrt(a) < sqrt(2**(k+1))`
        // → `2**(k/2) <= sqrt(a) < 2**((k+1)/2) <= 2**(k/2 + 1)`
        //
        // Consequently, `2**(log2(a) / 2)` is a good first approximation of `sqrt(a)` with at least 1 correct bit.
        uint256 result = 1 << (log2(a) >> 1);

        // At this point `result` is an estimation with one bit of precision. We know the true value is a uint128,
        // since it is the square root of a uint256. Newton's method converges quadratically (precision doubles at
        // every iteration). We thus need at most 7 iteration to turn our partial result with one bit of precision
        // into the expected uint128 result.
        unchecked {
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            return min(result, a / result);
        }
    }

    /**
     * @notice Calculates sqrt(a), following the selected rounding direction.
     */
    function sqrt(uint256 a, Rounding rounding) internal pure returns (uint256) {
        unchecked {
            uint256 result = sqrt(a);
            return result + (rounding == Rounding.Up && result * result < a ? 1 : 0);
        }
    }

    /**
     * @dev Return the log in base 2, rounded down, of a positive value.
     * Returns 0 if given 0.
     */
    function log2(uint256 value) internal pure returns (uint256) {
        uint256 result = 0;
        unchecked {
            if (value >> 128 > 0) {
                value >>= 128;
                result += 128;
            }
            if (value >> 64 > 0) {
                value >>= 64;
                result += 64;
            }
            if (value >> 32 > 0) {
                value >>= 32;
                result += 32;
            }
            if (value >> 16 > 0) {
                value >>= 16;
                result += 16;
            }
            if (value >> 8 > 0) {
                value >>= 8;
                result += 8;
            }
            if (value >> 4 > 0) {
                value >>= 4;
                result += 4;
            }
            if (value >> 2 > 0) {
                value >>= 2;
                result += 2;
            }
            if (value >> 1 > 0) {
                result += 1;
            }
        }
        return result;
    }

    /**
     * @dev Return the log in base 2, following the selected rounding direction, of a positive value.
     * Returns 0 if given 0.
     */
    function log2(uint256 value, Rounding rounding) internal pure returns (uint256) {
        unchecked {
            uint256 result = log2(value);
            return result + (rounding == Rounding.Up && 1 << result < value ? 1 : 0);
        }
    }

    /**
     * @dev Return the log in base 10, rounded down, of a positive value.
     * Returns 0 if given 0.
     */
    function log10(uint256 value) internal pure returns (uint256) {
        uint256 result = 0;
        unchecked {
            if (value >= 10 ** 64) {
                value /= 10 ** 64;
                result += 64;
            }
            if (value >= 10 ** 32) {
                value /= 10 ** 32;
                result += 32;
            }
            if (value >= 10 ** 16) {
                value /= 10 ** 16;
                result += 16;
            }
            if (value >= 10 ** 8) {
                value /= 10 ** 8;
                result += 8;
            }
            if (value >= 10 ** 4) {
                value /= 10 ** 4;
                result += 4;
            }
            if (value >= 10 ** 2) {
                value /= 10 ** 2;
                result += 2;
            }
            if (value >= 10 ** 1) {
                result += 1;
            }
        }
        return result;
    }

    /**
     * @dev Return the log in base 10, following the selected rounding direction, of a positive value.
     * Returns 0 if given 0.
     */
    function log10(uint256 value, Rounding rounding) internal pure returns (uint256) {
        unchecked {
            uint256 result = log10(value);
            return result + (rounding == Rounding.Up && 10 ** result < value ? 1 : 0);
        }
    }

    /**
     * @dev Return the log in base 256, rounded down, of a positive value.
     * Returns 0 if given 0.
     *
     * Adding one to the result gives the number of pairs of hex symbols needed to represent `value` as a hex string.
     */
    function log256(uint256 value) internal pure returns (uint256) {
        uint256 result = 0;
        unchecked {
            if (value >> 128 > 0) {
                value >>= 128;
                result += 16;
            }
            if (value >> 64 > 0) {
                value >>= 64;
                result += 8;
            }
            if (value >> 32 > 0) {
                value >>= 32;
                result += 4;
            }
            if (value >> 16 > 0) {
                value >>= 16;
                result += 2;
            }
            if (value >> 8 > 0) {
                result += 1;
            }
        }
        return result;
    }

    /**
     * @dev Return the log in base 256, following the selected rounding direction, of a positive value.
     * Returns 0 if given 0.
     */
    function log256(uint256 value, Rounding rounding) internal pure returns (uint256) {
        unchecked {
            uint256 result = log256(value);
            return result + (rounding == Rounding.Up && 1 << (result << 3) < value ? 1 : 0);
        }
    }
}

// File: @openzeppelin/contracts/utils/math/SignedMath.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (utils/math/SignedMath.sol)

pragma solidity ^0.8.0;

/**
 * @dev Standard signed math utilities missing in the Solidity language.
 */
library SignedMath {
    /**
     * @dev Returns the largest of two signed numbers.
     */
    function max(int256 a, int256 b) internal pure returns (int256) {
        return a > b ? a : b;
    }

    /**
     * @dev Returns the smallest of two signed numbers.
     */
    function min(int256 a, int256 b) internal pure returns (int256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two signed numbers without overflow.
     * The result is rounded towards zero.
     */
    function average(int256 a, int256 b) internal pure returns (int256) {
        // Formula from the book "Hacker's Delight"
        int256 x = (a & b) + ((a ^ b) >> 1);
        return x + (int256(uint256(x) >> 255) & (a ^ b));
    }

    /**
     * @dev Returns the absolute unsigned value of a signed value.
     */
    function abs(int256 n) internal pure returns (uint256) {
        unchecked {
            // must be unchecked in order to support `n = type(int256).min`
            return uint256(n >= 0 ? n : -n);
        }
    }
}

// File: @openzeppelin/contracts/utils/Strings.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (utils/Strings.sol)

pragma solidity ^0.8.0;

import "./math/Math.sol";
import "./math/SignedMath.sol";

/**
 * @dev String operations.
 */
library Strings {
    bytes16 private constant _SYMBOLS = "0123456789abcdef";
    uint8 private constant _ADDRESS_LENGTH = 20;

    /**
     * @dev Converts a `uint256` to its ASCII `string` decimal representation.
     */
    function toString(uint256 value) internal pure returns (string memory) {
        unchecked {
            uint256 length = Math.log10(value) + 1;
            string memory buffer = new string(length);
            uint256 ptr;
            /// @solidity memory-safe-assembly
            assembly {
                ptr := add(buffer, add(32, length))
            }
            while (true) {
                ptr--;
                /// @solidity memory-safe-assembly
                assembly {
                    mstore8(ptr, byte(mod(value, 10), _SYMBOLS))
                }
                value /= 10;
                if (value == 0) break;
            }
            return buffer;
        }
    }

    /**
     * @dev Converts a `int256` to its ASCII `string` decimal representation.
     */
    function toString(int256 value) internal pure returns (string memory) {
        return string(abi.encodePacked(value < 0 ? "-" : "", toString(SignedMath.abs(value))));
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
     */
    function toHexString(uint256 value) internal pure returns (string memory) {
        unchecked {
            return toHexString(value, Math.log256(value) + 1);
        }
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
     */
    function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
        bytes memory buffer = new bytes(2 * length + 2);
        buffer[0] = "0";
        buffer[1] = "x";
        for (uint256 i = 2 * length + 1; i > 1; --i) {
            buffer[i] = _SYMBOLS[value & 0xf];
            value >>= 4;
        }
        require(value == 0, "Strings: hex length insufficient");
        return string(buffer);
    }

    /**
     * @dev Converts an `address` with fixed length of 20 bytes to its not checksummed ASCII `string` hexadecimal representation.
     */
    function toHexString(address addr) internal pure returns (string memory) {
        return toHexString(uint256(uint160(addr)), _ADDRESS_LENGTH);
    }

    /**
     * @dev Returns true if the two strings are equal.
     */
    function equal(string memory a, string memory b) internal pure returns (bool) {
        return keccak256(bytes(a)) == keccak256(bytes(b));
    }
}

// File: contracts/Multisender.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import {Strings} from "@openzeppelin/contracts/utils/Strings.sol";

/**
 * @dev Send ERC20/ERC721 to multiple account at once
 *
 * Features:
 *  - No transaction fees
 *  - Protection against gas griefing
 *  - User-friendly error messages: Lists each address if transfer fails
 *  - Audited using the reputable tool(=`slither`)
 *
 */
contract Multisender {
    using Strings for uint256;
    using Strings for address;

    // Fixed gas consumption when `transfer` is called
    uint256 public constant TRANSFER_GAS = 2300;

    // Default gas consumption when utilizing Openzeppelin mesured by `GasMeter.sol`
    uint256 public constant BASE_ERC20_TRANSFER_GAS = 28384;
    uint256 public constant BASE_ERC721_TRANSFER_GAS = 37573;

    // The multiplier to calculate max consumable gas
    uint256 public constant MAX_GAS_MULTIPLIER = 3;

    error FailedInnerCall();
    error MesuredGas(uint256 sum, uint256 avarage);

    /**
     * @dev Transfer native token to multiple receipients
     * Revert if the transferring operation consume larger gas then standard
     * The native opcode `transfer` consume 2300 gas, but the actual gas consumption
     * become larger than it when the receipient is a contract.
     * Ref: https://consensys.io/diligence/blog/2019/09/stop-using-soliditys-transfer-now/
     *
     * @param tos list of receipient addresses
     * @param amounts list of amounts
     * @param baseGas_ the basic gas consumption of transferring operation
     */
    function multisend(
        address[] calldata tos,
        uint256[] calldata amounts,
        uint256 baseGas_
    ) public payable {
        require(tos.length == amounts.length, "tos and amounts must have the same length");

        uint256 baseGas = baseGas_ != 0 ? baseGas_ : TRANSFER_GAS;

        string memory failedList = "";
        uint256 sum = 0;
        for (uint256 i = 0; i < tos.length; i++) {
            sum += amounts[i];
            if (!_transfer(tos[i], amounts[i], baseGas)) {
                failedList = string.concat(failedList, tos[i].toHexString(), ",");
            }
        }

        require(sum == msg.value, "sum of amounts must be equal to msg.value");

        _assertFailedList(failedList);
    }

    /**
     * @dev Transfer erc20 to multiple receipients
     * Revert if the transferring operation consume `MAX_GAS_MULTIPLIER` times larger gas then standard
     *
     * @param token address of token
     * @param tos list of receipient addresses
     * @param amounts list of amounts
     * @param baseGas_ the basic gas consumption of transferring operation
     */
    function multisendERC20(
        address token,
        address[] calldata tos,
        uint256[] calldata amounts,
        uint256 baseGas_
    ) public {
        require(token != address(0), "token address cannot be 0");
        require(tos.length == amounts.length, "tos and amounts must have the same length");

        uint256 baseGas = baseGas_ != 0 ? baseGas_ : BASE_ERC20_TRANSFER_GAS;

        string memory failedList = "";
        for (uint256 i = 0; i < tos.length; i++) {
            if (
                !_transferGeneric(
                    token,
                    baseGas,
                    "transferFrom(address,address,uint256)",
                    abi.encode(msg.sender, tos[i], amounts[i])
                )
            ) {
                failedList = string.concat(failedList, tos[i].toHexString(), ",");
            }
        }

        _assertFailedList(failedList);
    }

    /**
     * @dev Transfer erc721 to multiple receipients
     * Revert if the transferring operation consume `MAX_GAS_MULTIPLIER` times larger gas then standard
     *
     * @param token address of token
     * @param tos list of receipient addresses
     * @param tokenIds list of tokenIds
     * @param data list of data
     * @param baseGas_ the basic gas consumption of transferring operation
     */
    function multisendERC721(
        address token,
        address[] calldata tos,
        uint256[] calldata tokenIds,
        bytes[] calldata data,
        uint256 baseGas_
    ) public {
        require(token != address(0), "token address cannot be 0");
        require(tos.length == tokenIds.length, "tos and tokenIds must have the same length");
        require(tos.length == data.length, "tos and data must have the same length");

        uint256 baseGas = baseGas_ != 0 ? baseGas_ : BASE_ERC721_TRANSFER_GAS;

        string memory failedList = "";
        for (uint256 i = 0; i < tos.length; i++) {
            if (
                !_transferGeneric(
                    token,
                    baseGas,
                    "safeTransferFrom(address,address,uint256,bytes)",
                    abi.encode(msg.sender, tos[i], tokenIds[i], data[i])
                )
            ) {
                failedList = string.concat(failedList, tos[i].toHexString(), ",");
            }
        }

        _assertFailedList(failedList);
    }

    function mesureAverageGas(
        address token,
        address[] calldata tos,
        uint256[] calldata tokenIds,
        bytes[] calldata data
    ) public payable returns (uint256) {
        uint256 sum = 0;
        for (uint256 i = 0; i < tos.length; i++) {
            uint256 startGas = gasleft();
            _transferGenericWithErrMesage(
                token,
                "safeTransferFrom(address,address,uint256,bytes)",
                abi.encode(msg.sender, tos[i], tokenIds[i], data[i])
            );
            uint256 endGas = gasleft();
            sum += startGas - endGas;
        }

        revert MesuredGas(sum, sum / tos.length);
    }

    // function _validateLeftgas(uint256 i, uint256 total, uint256 requiredGas) internal view {
    //     if (gasleft() < requiredGas) {
    //         revert(
    //             string.concat(
    //                 "will run out of gas at index ",
    //                 (i + 1).toString(),
    //                 " in ",
    //                 total.toString(),
    //                 ", left: ",
    //                 gasleft().toString(),
    //                 " required: ",
    //                 requiredGas.toString()
    //             )
    //         );
    //     }
    // }

    function _assertFailedList(string memory failedList) internal pure {
        uint256 length = bytes(failedList).length;

        if (length > 0) {
            revert(
                string.concat(
                    "failed to transfer to ",
                    // NOTE: 43 length = address + ","
                    (length / 43).toString(),
                    " addresses: ",
                    failedList
                )
            );
        }
    }

    function _transfer(address to, uint256 amount, uint256 baseGas) internal returns (bool) {
        // NOTE: call transferFrom with gas limit to avoid gas greefing
        // slither-disable-next-line arbitrary-send-eth
        (bool success, ) = to.call{gas: baseGas, value: amount}("");
        return success;
    }

    function _transferGeneric(
        address target,
        uint256 baseGas,
        string memory functionSignature,
        bytes memory args
    ) internal returns (bool) {
        // NOTE: call with gas limit to avoid gas greefing
        // slither-disable-next-line low-level-calls
        (bool success, bytes memory data) = target.call{gas: baseGas * MAX_GAS_MULTIPLIER}(
            abi.encodePacked(bytes4(keccak256(bytes(functionSignature))), args)
        );

        // If the function returns a boolean, decode it. Otherwise, just return the success flag.
        if (data.length == 32) {
            return success && abi.decode(data, (bool));
        }
        return success;
    }

    function _transferGenericWithErrMesage(
        address target,
        string memory functionSignature,
        bytes memory args
    ) internal {
        // NOTE: call with gas limit to avoid gas greefing
        // slither-disable-next-line low-level-calls
        (bool success, bytes memory data) = target.call(
            abi.encodePacked(bytes4(keccak256(bytes(functionSignature))), args)
        );

        if (success) return;

        if (data.length > 0) {
            assembly {
                let returndata_size := mload(data)
                revert(add(32, data), returndata_size)
            }
        } else {
            revert FailedInnerCall();
        }
    }
}