// SPDX-FileCopyrightText: 2023 Lido <info@lido.fi>
// SPDX-License-Identifier: GPL-3.0

// See contracts/COMPILERS.md
pragma solidity 0.8.9;

import {MemUtils} from "../common/lib/MemUtils.sol";

interface IDepositContract {
    function get_deposit_root() external view returns (bytes32 rootHash);

    function deposit(
        bytes calldata pubkey, // 48 bytes
        bytes calldata withdrawal_credentials, // 32 bytes
        bytes calldata signature, // 96 bytes
        bytes32 deposit_data_root
    ) external payable;
}

contract BeaconChainDepositor {
    uint256 internal constant PUBLIC_KEY_LENGTH = 48;
    uint256 internal constant SIGNATURE_LENGTH = 96;
    uint256 internal constant DEPOSIT_SIZE = 32 ether;

    /// @dev deposit amount 32eth in gweis converted to little endian uint64
    /// DEPOSIT_SIZE_IN_GWEI_LE64 = toLittleEndian64(32 ether / 1 gwei)
    uint64 internal constant DEPOSIT_SIZE_IN_GWEI_LE64 = 0x0040597307000000;

    IDepositContract public immutable DEPOSIT_CONTRACT;

    constructor(address _depositContract) {
        if (_depositContract == address(0)) revert DepositContractZeroAddress();
        DEPOSIT_CONTRACT = IDepositContract(_depositContract);
    }

    /// @dev Invokes a deposit call to the official Beacon Deposit contract
    /// @param _keysCount amount of keys to deposit
    /// @param _withdrawalCredentials Commitment to a public key for withdrawals
    /// @param _publicKeysBatch A BLS12-381 public keys batch
    /// @param _signaturesBatch A BLS12-381 signatures batch
    function _makeBeaconChainDeposits32ETH(
        uint256 _keysCount,
        bytes memory _withdrawalCredentials,
        bytes memory _publicKeysBatch,
        bytes memory _signaturesBatch
    ) internal {
        if (_publicKeysBatch.length != PUBLIC_KEY_LENGTH * _keysCount) {
            revert InvalidPublicKeysBatchLength(_publicKeysBatch.length, PUBLIC_KEY_LENGTH * _keysCount);
        }
        if (_signaturesBatch.length != SIGNATURE_LENGTH * _keysCount) {
            revert InvalidSignaturesBatchLength(_signaturesBatch.length, SIGNATURE_LENGTH * _keysCount);
        }

        bytes memory publicKey = MemUtils.unsafeAllocateBytes(PUBLIC_KEY_LENGTH);
        bytes memory signature = MemUtils.unsafeAllocateBytes(SIGNATURE_LENGTH);

        for (uint256 i; i < _keysCount;) {
            MemUtils.copyBytes(_publicKeysBatch, publicKey, i * PUBLIC_KEY_LENGTH, 0, PUBLIC_KEY_LENGTH);
            MemUtils.copyBytes(_signaturesBatch, signature, i * SIGNATURE_LENGTH, 0, SIGNATURE_LENGTH);

            DEPOSIT_CONTRACT.deposit{value: DEPOSIT_SIZE}(
                publicKey, _withdrawalCredentials, signature, _computeDepositDataRoot(_withdrawalCredentials, publicKey, signature)
            );

            unchecked {
                ++i;
            }
        }
    }

    /// @dev computes the deposit_root_hash required by official Beacon Deposit contract
    /// @param _publicKey A BLS12-381 public key.
    /// @param _signature A BLS12-381 signature
    function _computeDepositDataRoot(bytes memory _withdrawalCredentials, bytes memory _publicKey, bytes memory _signature)
        private
        pure
        returns (bytes32)
    {
        // Compute deposit data root (`DepositData` hash tree root) according to deposit_contract.sol
        bytes memory sigPart1 = MemUtils.unsafeAllocateBytes(64);
        bytes memory sigPart2 = MemUtils.unsafeAllocateBytes(SIGNATURE_LENGTH - 64);
        MemUtils.copyBytes(_signature, sigPart1, 0, 0, 64);
        MemUtils.copyBytes(_signature, sigPart2, 64, 0, SIGNATURE_LENGTH - 64);

        bytes32 publicKeyRoot = sha256(abi.encodePacked(_publicKey, bytes16(0)));
        bytes32 signatureRoot = sha256(abi.encodePacked(sha256(abi.encodePacked(sigPart1)), sha256(abi.encodePacked(sigPart2, bytes32(0)))));

        return sha256(
                abi.encodePacked(
                    sha256(abi.encodePacked(publicKeyRoot, _withdrawalCredentials)),
                    sha256(abi.encodePacked(DEPOSIT_SIZE_IN_GWEI_LE64, bytes24(0), signatureRoot))
                )
            );
    }

    error DepositContractZeroAddress();
    error InvalidPublicKeysBatchLength(uint256 actual, uint256 expected);
    error InvalidSignaturesBatchLength(uint256 actual, uint256 expected);
}