// File: contracts/eNear.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

import "rainbow-bridge/contracts/eth/nearprover/contracts/ProofDecoder.sol";
import "rainbow-bridge/contracts/eth/nearbridge/contracts/Borsh.sol";
import "rainbow-bridge/contracts/eth/nearbridge/contracts/AdminControlled.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import { Bridge, INearProver } from "./Bridge.sol";

contract eNear is ERC20, Bridge, AdminControlled {

    uint constant PAUSE_FINALISE_FROM_NEAR = 1 << 0;
    uint constant PAUSE_TRANSFER_TO_NEAR = 1 << 1;

    event TransferToNearInitiated (
        address indexed sender,
        uint256 amount,
        string accountId
    );

    event NearToEthTransferFinalised (
        uint128 amount,
        address indexed recipient
    );

    struct BridgeResult {
        uint128 amount;
        address recipient;
    }

    /// @param _tokenName Name given to the token (can be admin updated)
    /// @param _tokenSymbol Symbol given to the token (can be admin updated)
    /// @param _nearConnector Near account ID of the near connector bridge
    /// @param _prover Address of the prover contract on ETH
    /// @param _minBlockAcceptanceHeight The contract will accept proofs from this block onwards
    /// @param _admin Address that can make admin changes to the contract
    /// @param _pausedFlags Flag settings which controls whether certain methods are paused or active
    constructor(
        string memory _tokenName,
        string memory _tokenSymbol,
        bytes memory _nearConnector,
        INearProver _prover,
        uint64 _minBlockAcceptanceHeight,
        address _admin,
        uint256 _pausedFlags
    ) public ERC20(_tokenName, _tokenSymbol) AdminControlled(_admin, _pausedFlags) Bridge(_prover, _nearConnector, _minBlockAcceptanceHeight) {
        // Match yocto Near
        _setupDecimals(24);
    }

    function finaliseNearToEthTransfer(bytes memory proofData, uint64 proofBlockHeight)
    external pausable (PAUSE_FINALISE_FROM_NEAR) {
        ProofDecoder.ExecutionStatus memory status = _parseAndConsumeProof(proofData, proofBlockHeight);
        BridgeResult memory result = _decodeBridgeResult(status.successValue);

        _mint(result.recipient, result.amount);

        emit NearToEthTransferFinalised(result.amount, result.recipient);
    }

    function transferToNear(uint256 _amount, string memory _nearReceiverAccountId)
    external pausable (PAUSE_TRANSFER_TO_NEAR) {
        _burn(msg.sender, _amount);
        emit TransferToNearInitiated(msg.sender, _amount, _nearReceiverAccountId);
    }

    function _decodeBridgeResult(bytes memory data) internal pure returns(BridgeResult memory result) {
        Borsh.Data memory borshData = Borsh.from(data);
        uint8 flag = borshData.decodeU8();
        require(flag == 0, "ERR_NOT_WITHDRAW_RESULT");
        result.amount = borshData.decodeU128();
        bytes20 recipient = borshData.decodeBytes20();
        result.recipient = address(uint160(recipient));
    }
}

// File: rainbow-bridge/contracts/eth/nearprover/contracts/ProofDecoder.sol



pragma solidity ^0.6;

import "../../nearbridge/contracts/Borsh.sol";
import "../../nearbridge/contracts/NearDecoder.sol";

library ProofDecoder {
    using Borsh for Borsh.Data;
    using ProofDecoder for Borsh.Data;
    using NearDecoder for Borsh.Data;

    struct FullOutcomeProof {
        ExecutionOutcomeWithIdAndProof outcome_proof;
        MerklePath outcome_root_proof; // TODO: now empty array
        BlockHeaderLight block_header_lite;
        MerklePath block_proof;
    }

    function decodeFullOutcomeProof(Borsh.Data memory data) internal view returns (FullOutcomeProof memory proof) {
        proof.outcome_proof = data.decodeExecutionOutcomeWithIdAndProof();
        proof.outcome_root_proof = data.decodeMerklePath();
        proof.block_header_lite = data.decodeBlockHeaderLight();
        proof.block_proof = data.decodeMerklePath();
    }

    struct BlockHeaderLight {
        bytes32 prev_block_hash;
        bytes32 inner_rest_hash;
        NearDecoder.BlockHeaderInnerLite inner_lite;
        bytes32 hash; // Computable
    }

    function decodeBlockHeaderLight(Borsh.Data memory data) internal view returns (BlockHeaderLight memory header) {
        header.prev_block_hash = data.decodeBytes32();
        header.inner_rest_hash = data.decodeBytes32();
        header.inner_lite = data.decodeBlockHeaderInnerLite();

        header.hash = sha256(
            abi.encodePacked(
                sha256(abi.encodePacked(header.inner_lite.hash, header.inner_rest_hash)),
                header.prev_block_hash
            )
        );
    }

    struct ExecutionStatus {
        uint8 enumIndex;
        bool unknown;
        bool failed;
        bytes successValue; /// The final action succeeded and returned some value or an empty vec.
        bytes32 successReceiptId; /// The final action of the receipt returned a promise or the signed
        /// transaction was converted to a receipt. Contains the receipt_id of the generated receipt.
    }

    function decodeExecutionStatus(Borsh.Data memory data)
        internal
        pure
        returns (ExecutionStatus memory executionStatus)
    {
        executionStatus.enumIndex = data.decodeU8();
        if (executionStatus.enumIndex == 0) {
            executionStatus.unknown = true;
        } else if (executionStatus.enumIndex == 1) {
            //revert("NearDecoder: decodeExecutionStatus failure case not implemented yet");
            // Can avoid revert since ExecutionStatus is latest field in all parent structures
            executionStatus.failed = true;
        } else if (executionStatus.enumIndex == 2) {
            executionStatus.successValue = data.decodeBytes();
        } else if (executionStatus.enumIndex == 3) {
            executionStatus.successReceiptId = data.decodeBytes32();
        } else {
            revert("NearDecoder: decodeExecutionStatus index out of range");
        }
    }

    struct ExecutionOutcome {
        bytes[] logs; /// Logs from this transaction or receipt.
        bytes32[] receipt_ids; /// Receipt IDs generated by this transaction or receipt.
        uint64 gas_burnt; /// The amount of the gas burnt by the given transaction or receipt.
        uint128 tokens_burnt; /// The total number of the tokens burnt by the given transaction or receipt.
        bytes executor_id; /// Hash of the transaction or receipt id that produced this outcome.
        ExecutionStatus status; /// Execution status. Contains the result in case of successful execution.
        bytes32[] merkelization_hashes;
    }

    function decodeExecutionOutcome(Borsh.Data memory data) internal view returns (ExecutionOutcome memory outcome) {
        outcome.logs = new bytes[](data.decodeU32());
        for (uint i = 0; i < outcome.logs.length; i++) {
            outcome.logs[i] = data.decodeBytes();
        }

        uint256 start = data.offset;
        outcome.receipt_ids = new bytes32[](data.decodeU32());
        for (uint i = 0; i < outcome.receipt_ids.length; i++) {
            outcome.receipt_ids[i] = data.decodeBytes32();
        }
        outcome.gas_burnt = data.decodeU64();
        outcome.tokens_burnt = data.decodeU128();
        outcome.executor_id = data.decodeBytes();
        outcome.status = data.decodeExecutionStatus();
        uint256 stop = data.offset;

        outcome.merkelization_hashes = new bytes32[](1 + outcome.logs.length);
        data.offset = start;
        outcome.merkelization_hashes[0] = data.peekSha256(stop - start);
        data.offset = stop;
        for (uint i = 0; i < outcome.logs.length; i++) {
            outcome.merkelization_hashes[i + 1] = sha256(outcome.logs[i]);
        }
    }

    struct ExecutionOutcomeWithId {
        bytes32 id; /// The transaction hash or the receipt ID.
        ExecutionOutcome outcome;
        bytes32 hash;
    }

    function decodeExecutionOutcomeWithId(Borsh.Data memory data)
        internal
        view
        returns (ExecutionOutcomeWithId memory outcome)
    {
        outcome.id = data.decodeBytes32();
        outcome.outcome = data.decodeExecutionOutcome();

        uint256 len = 1 + outcome.outcome.merkelization_hashes.length;
        outcome.hash = sha256(
            abi.encodePacked(
                uint8((len >> 0) & 0xFF),
                uint8((len >> 8) & 0xFF),
                uint8((len >> 16) & 0xFF),
                uint8((len >> 24) & 0xFF),
                outcome.id,
                outcome.outcome.merkelization_hashes
            )
        );
    }

    struct MerklePathItem {
        bytes32 hash;
        uint8 direction; // 0 = left, 1 = right
    }

    function decodeMerklePathItem(Borsh.Data memory data) internal pure returns (MerklePathItem memory item) {
        item.hash = data.decodeBytes32();
        item.direction = data.decodeU8();
        require(item.direction < 2, "ProofDecoder: MerklePathItem direction should be 0 or 1");
    }

    struct MerklePath {
        MerklePathItem[] items;
    }

    function decodeMerklePath(Borsh.Data memory data) internal pure returns (MerklePath memory path) {
        path.items = new MerklePathItem[](data.decodeU32());
        for (uint i = 0; i < path.items.length; i++) {
            path.items[i] = data.decodeMerklePathItem();
        }
    }

    struct ExecutionOutcomeWithIdAndProof {
        MerklePath proof;
        bytes32 block_hash;
        ExecutionOutcomeWithId outcome_with_id;
    }

    function decodeExecutionOutcomeWithIdAndProof(Borsh.Data memory data)
        internal
        view
        returns (ExecutionOutcomeWithIdAndProof memory outcome)
    {
        outcome.proof = data.decodeMerklePath();
        outcome.block_hash = data.decodeBytes32();
        outcome.outcome_with_id = data.decodeExecutionOutcomeWithId();
    }
}

// File: rainbow-bridge/contracts/eth/nearbridge/contracts/Borsh.sol



pragma solidity ^0.6;

import "@openzeppelin/contracts/math/SafeMath.sol";

library Borsh {
    using SafeMath for uint256;

    struct Data {
        uint256 offset;
        bytes raw;
    }

    function from(bytes memory data) internal pure returns (Data memory) {
        return Data({offset: 0, raw: data});
    }

    modifier shift(Data memory data, uint256 size) {
        require(data.raw.length >= data.offset + size, "Borsh: Out of range");
        _;
        data.offset += size;
    }

    function finished(Data memory data) internal pure returns (bool) {
        return data.offset == data.raw.length;
    }

    function peekKeccak256(Data memory data, uint256 length) internal pure returns (bytes32 res) {
        return bytesKeccak256(data.raw, data.offset, length);
    }

    function bytesKeccak256(
        bytes memory ptr,
        uint256 offset,
        uint256 length
    ) internal pure returns (bytes32 res) {
        // solium-disable-next-line security/no-inline-assembly
        assembly {
            res := keccak256(add(add(ptr, 32), offset), length)
        }
    }

    function peekSha256(Data memory data, uint256 length) internal view returns (bytes32) {
        return bytesSha256(data.raw, data.offset, length);
    }

    function bytesSha256(
        bytes memory ptr,
        uint256 offset,
        uint256 length
    ) internal view returns (bytes32) {
        bytes32[1] memory result;
        // solium-disable-next-line security/no-inline-assembly
        assembly {
            pop(staticcall(gas(), 0x02, add(add(ptr, 32), offset), length, result, 32))
        }
        return result[0];
    }

    function decodeU8(Data memory data) internal pure shift(data, 1) returns (uint8 value) {
        value = uint8(data.raw[data.offset]);
    }

    function decodeI8(Data memory data) internal pure shift(data, 1) returns (int8 value) {
        value = int8(data.raw[data.offset]);
    }

    function decodeU16(Data memory data) internal pure returns (uint16 value) {
        value = uint16(decodeU8(data));
        value |= (uint16(decodeU8(data)) << 8);
    }

    function decodeI16(Data memory data) internal pure returns (int16 value) {
        value = int16(decodeI8(data));
        value |= (int16(decodeI8(data)) << 8);
    }

    function decodeU32(Data memory data) internal pure returns (uint32 value) {
        value = uint32(decodeU16(data));
        value |= (uint32(decodeU16(data)) << 16);
    }

    function decodeI32(Data memory data) internal pure returns (int32 value) {
        value = int32(decodeI16(data));
        value |= (int32(decodeI16(data)) << 16);
    }

    function decodeU64(Data memory data) internal pure returns (uint64 value) {
        value = uint64(decodeU32(data));
        value |= (uint64(decodeU32(data)) << 32);
    }

    function decodeI64(Data memory data) internal pure returns (int64 value) {
        value = int64(decodeI32(data));
        value |= (int64(decodeI32(data)) << 32);
    }

    function decodeU128(Data memory data) internal pure returns (uint128 value) {
        value = uint128(decodeU64(data));
        value |= (uint128(decodeU64(data)) << 64);
    }

    function decodeI128(Data memory data) internal pure returns (int128 value) {
        value = int128(decodeI64(data));
        value |= (int128(decodeI64(data)) << 64);
    }

    function decodeU256(Data memory data) internal pure returns (uint256 value) {
        value = uint256(decodeU128(data));
        value |= (uint256(decodeU128(data)) << 128);
    }

    function decodeI256(Data memory data) internal pure returns (int256 value) {
        value = int256(decodeI128(data));
        value |= (int256(decodeI128(data)) << 128);
    }

    function decodeBool(Data memory data) internal pure returns (bool value) {
        value = (decodeU8(data) != 0);
    }

    function decodeBytes(Data memory data) internal pure returns (bytes memory value) {
        value = new bytes(decodeU32(data));
        for (uint i = 0; i < value.length; i++) {
            value[i] = byte(decodeU8(data));
        }
    }

    function decodeBytes32(Data memory data) internal pure shift(data, 32) returns (bytes32 value) {
        bytes memory raw = data.raw;
        uint256 offset = data.offset;
        // solium-disable-next-line security/no-inline-assembly
        assembly {
            value := mload(add(add(raw, 32), offset))
        }
    }

    function decodeBytes20(Data memory data) internal pure returns (bytes20 value) {
        for (uint i = 0; i < 20; i++) {
            value |= bytes20(byte(decodeU8(data)) & 0xFF) >> (i * 8);
        }
    }

    // Public key

    struct SECP256K1PublicKey {
        uint256 x;
        uint256 y;
    }

    function decodeSECP256K1PublicKey(Borsh.Data memory data) internal pure returns (SECP256K1PublicKey memory key) {
        key.x = decodeU256(data);
        key.y = decodeU256(data);
    }

    struct ED25519PublicKey {
        bytes32 xy;
    }

    function decodeED25519PublicKey(Borsh.Data memory data) internal pure returns (ED25519PublicKey memory key) {
        key.xy = decodeBytes32(data);
    }

    // Signature

    struct SECP256K1Signature {
        bytes32 r;
        bytes32 s;
        uint8 v;
    }

    function decodeSECP256K1Signature(Borsh.Data memory data) internal pure returns (SECP256K1Signature memory sig) {
        sig.r = decodeBytes32(data);
        sig.s = decodeBytes32(data);
        sig.v = decodeU8(data);
    }

    struct ED25519Signature {
        bytes32[2] rs;
    }

    function decodeED25519Signature(Borsh.Data memory data) internal pure returns (ED25519Signature memory sig) {
        sig.rs[0] = decodeBytes32(data);
        sig.rs[1] = decodeBytes32(data);
    }
}

// File: rainbow-bridge/contracts/eth/nearbridge/contracts/AdminControlled.sol



pragma solidity ^0.6;

contract AdminControlled {
    address public admin;
    uint public paused;

    constructor(address _admin, uint flags) public {
        admin = _admin;

        // Add the possibility to set pause flags on the initialization
        paused = flags;
    }

    modifier onlyAdmin {
        require(msg.sender == admin);
        _;
    }

    modifier pausable(uint flag) {
        require((paused & flag) == 0 || msg.sender == admin);
        _;
    }

    function adminPause(uint flags) public onlyAdmin {
        paused = flags;
    }

    function adminSstore(uint key, uint value) public onlyAdmin {
        assembly {
            sstore(key, value)
        }
    }

    function adminSendEth(address payable destination, uint amount) public onlyAdmin {
        destination.transfer(amount);
    }

    function adminReceiveEth() public payable onlyAdmin {}

    function adminDelegatecall(address target, bytes memory data) public payable onlyAdmin returns (bytes memory) {
        (bool success, bytes memory rdata) = target.delegatecall(data);
        require(success);
        return rdata;
    }
}

// File: @openzeppelin/contracts/token/ERC20/ERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "../../utils/Context.sol";
import "./IERC20.sol";
import "../../math/SafeMath.sol";

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of returning `false` on failure. This behavior is nonetheless conventional
 * and does not conflict with the expectations of ERC20 applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

    mapping (address => mapping (address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;
    uint8 private _decimals;

    /**
     * @dev Sets the values for {name} and {symbol}, initializes {decimals} with
     * a default value of 18.
     *
     * To select a different value for {decimals}, use {_setupDecimals}.
     *
     * All three of these values are immutable: they can only be set once during
     * construction.
     */
    constructor (string memory name_, string memory symbol_) public {
        _name = name_;
        _symbol = symbol_;
        _decimals = 18;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5,05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless {_setupDecimals} is
     * called.
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual returns (uint8) {
        return _decimals;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * Requirements:
     *
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
        return true;
    }

    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(address sender, address recipient, uint256 amount) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(sender, recipient, amount);

        _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(address owner, address spender, uint256 amount) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Sets {decimals} to a value other than the default one of 18.
     *
     * WARNING: This function should only be called from the constructor. Most
     * applications that interact with token contracts will not expect
     * {decimals} to ever change, and may work incorrectly if it does.
     */
    function _setupDecimals(uint8 decimals_) internal virtual {
        _decimals = decimals_;
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be to transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual { }
}

// File: contracts/Bridge.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

import "rainbow-bridge/contracts/eth/nearprover/contracts/INearProver.sol";
import "rainbow-bridge/contracts/eth/nearprover/contracts/ProofDecoder.sol";
import "rainbow-bridge/contracts/eth/nearbridge/contracts/Borsh.sol";

contract Bridge {
    using Borsh for Borsh.Data;
    using ProofDecoder for Borsh.Data;

    event ConsumedProof(bytes32 indexed _receiptId);

    INearProver public prover;
    bytes public nearConnector;

    /// Proofs from blocks that are below the acceptance height will be rejected.
    // If `minBlockAcceptanceHeight` value is zero - proofs from block with any height are accepted.
    uint64 public minBlockAcceptanceHeight;

    // OutcomeRecieptId -> Used
    mapping(bytes32 => bool) public usedProofs;

    constructor(INearProver _prover, bytes memory _nearConnector, uint64 _minBlockAcceptanceHeight) public {
        prover = _prover;
        nearConnector = _nearConnector;
        minBlockAcceptanceHeight = _minBlockAcceptanceHeight;
    }

    /// Parses the provided proof and consumes it if it's not already used.
    /// The consumed event cannot be reused for future calls.
    function _parseAndConsumeProof(bytes memory proofData, uint64 proofBlockHeight)
    internal
    returns (ProofDecoder.ExecutionStatus memory result)
    {
        require(prover.proveOutcome(proofData, proofBlockHeight), "Proof should be valid");

        // Unpack the proof and extract the execution outcome.
        Borsh.Data memory borshData = Borsh.from(proofData);
        ProofDecoder.FullOutcomeProof memory fullOutcomeProof = borshData.decodeFullOutcomeProof();

        require(
            fullOutcomeProof.block_header_lite.inner_lite.height >= minBlockAcceptanceHeight,
            "Proof is from the ancient block"
        );

        require(borshData.finished(), "Argument should be exact borsh serialization");

        bytes32 receiptId = fullOutcomeProof.outcome_proof.outcome_with_id.outcome.receipt_ids[0];
        require(!usedProofs[receiptId], "The burn event proof cannot be reused");
        usedProofs[receiptId] = true;

        require(keccak256(fullOutcomeProof.outcome_proof.outcome_with_id.outcome.executor_id)
            == keccak256(nearConnector),
            "Can only unlock tokens from the linked proof producer on Near blockchain");

        result = fullOutcomeProof.outcome_proof.outcome_with_id.outcome.status;
        require(!result.failed, "Cannot use failed execution outcome for unlocking the tokens");
        require(!result.unknown, "Cannot use unknown execution outcome for unlocking the tokens");

        emit ConsumedProof(receiptId);
    }
}

// File: rainbow-bridge/contracts/eth/nearbridge/contracts/NearDecoder.sol



pragma solidity ^0.6;

import "@openzeppelin/contracts/math/SafeMath.sol";
import "./Borsh.sol";

library NearDecoder {
    using Borsh for Borsh.Data;
    using NearDecoder for Borsh.Data;

    struct PublicKey {
        uint8 enumIndex;
        Borsh.ED25519PublicKey ed25519;
        Borsh.SECP256K1PublicKey secp256k1;
    }

    function decodePublicKey(Borsh.Data memory data) internal pure returns (PublicKey memory key) {
        key.enumIndex = data.decodeU8();

        if (key.enumIndex == 0) {
            key.ed25519 = data.decodeED25519PublicKey();
        } else if (key.enumIndex == 1) {
            key.secp256k1 = data.decodeSECP256K1PublicKey();
        } else {
            revert("NearBridge: Only ED25519 and SECP256K1 public keys are supported");
        }
    }

    struct ValidatorStake {
        string account_id;
        PublicKey public_key;
        uint128 stake;
    }

    function decodeValidatorStake(Borsh.Data memory data) internal pure returns (ValidatorStake memory validatorStake) {
        validatorStake.account_id = string(data.decodeBytes());
        validatorStake.public_key = data.decodePublicKey();
        validatorStake.stake = data.decodeU128();
    }

    struct OptionalValidatorStakes {
        bool none;
        ValidatorStake[] validatorStakes;
        bytes32 hash; // Additional computable element
    }

    function decodeOptionalValidatorStakes(Borsh.Data memory data)
        internal
        view
        returns (OptionalValidatorStakes memory stakes)
    {
        stakes.none = (data.decodeU8() == 0);
        if (!stakes.none) {
            uint256 start = data.offset;

            stakes.validatorStakes = new ValidatorStake[](data.decodeU32());
            for (uint i = 0; i < stakes.validatorStakes.length; i++) {
                stakes.validatorStakes[i] = data.decodeValidatorStake();
            }

            uint256 stop = data.offset;
            data.offset = start;
            stakes.hash = data.peekSha256(stop - start);
            data.offset = stop;
        }
    }

    struct Signature {
        uint8 enumIndex;
        Borsh.ED25519Signature ed25519;
        Borsh.SECP256K1Signature secp256k1;
    }

    function decodeSignature(Borsh.Data memory data) internal pure returns (Signature memory sig) {
        sig.enumIndex = data.decodeU8();

        if (sig.enumIndex == 0) {
            sig.ed25519 = data.decodeED25519Signature();
        } else if (sig.enumIndex == 1) {
            sig.secp256k1 = data.decodeSECP256K1Signature();
        } else {
            revert("NearBridge: Only ED25519 and SECP256K1 signatures are supported");
        }
    }

    struct OptionalSignature {
        bool none;
        Signature signature;
    }

    function decodeOptionalSignature(Borsh.Data memory data) internal pure returns (OptionalSignature memory sig) {
        sig.none = (data.decodeU8() == 0);
        if (!sig.none) {
            sig.signature = data.decodeSignature();
        }
    }

    struct LightClientBlock {
        bytes32 prev_block_hash;
        bytes32 next_block_inner_hash;
        BlockHeaderInnerLite inner_lite;
        bytes32 inner_rest_hash;
        OptionalValidatorStakes next_bps;
        OptionalSignature[] approvals_after_next;
        bytes32 hash;
        bytes32 next_hash;
    }

    struct InitialValidators {
        ValidatorStake[] validator_stakes;
    }

    function decodeInitialValidators(Borsh.Data memory data)
        internal
        view
        returns (InitialValidators memory validators)
    {
        validators.validator_stakes = new ValidatorStake[](data.decodeU32());
        for (uint i = 0; i < validators.validator_stakes.length; i++) {
            validators.validator_stakes[i] = data.decodeValidatorStake();
        }
    }

    function decodeLightClientBlock(Borsh.Data memory data) internal view returns (LightClientBlock memory header) {
        header.prev_block_hash = data.decodeBytes32();
        header.next_block_inner_hash = data.decodeBytes32();
        header.inner_lite = data.decodeBlockHeaderInnerLite();
        header.inner_rest_hash = data.decodeBytes32();
        header.next_bps = data.decodeOptionalValidatorStakes();

        header.approvals_after_next = new OptionalSignature[](data.decodeU32());
        for (uint i = 0; i < header.approvals_after_next.length; i++) {
            header.approvals_after_next[i] = data.decodeOptionalSignature();
        }

        header.hash = sha256(
            abi.encodePacked(
                sha256(abi.encodePacked(header.inner_lite.hash, header.inner_rest_hash)),
                header.prev_block_hash
            )
        );

        header.next_hash = sha256(abi.encodePacked(header.next_block_inner_hash, header.hash));
    }

    struct BlockHeaderInnerLite {
        uint64 height; /// Height of this block since the genesis block (height 0).
        bytes32 epoch_id; /// Epoch start hash of this block's epoch. Used for retrieving validator information
        bytes32 next_epoch_id;
        bytes32 prev_state_root; /// Root hash of the state at the previous block.
        bytes32 outcome_root; /// Root of the outcomes of transactions and receipts.
        uint64 timestamp; /// Timestamp at which the block was built.
        bytes32 next_bp_hash; /// Hash of the next epoch block producers set
        bytes32 block_merkle_root;
        bytes32 hash; // Additional computable element
    }

    function decodeBlockHeaderInnerLite(Borsh.Data memory data)
        internal
        view
        returns (BlockHeaderInnerLite memory header)
    {
        header.hash = data.peekSha256(208);
        header.height = data.decodeU64();
        header.epoch_id = data.decodeBytes32();
        header.next_epoch_id = data.decodeBytes32();
        header.prev_state_root = data.decodeBytes32();
        header.outcome_root = data.decodeBytes32();
        header.timestamp = data.decodeU64();
        header.next_bp_hash = data.decodeBytes32();
        header.block_merkle_root = data.decodeBytes32();
    }
}

// File: @openzeppelin/contracts/math/SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

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



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: rainbow-bridge/contracts/eth/nearprover/contracts/INearProver.sol



pragma solidity ^0.6;

interface INearProver {
    function proveOutcome(bytes calldata proofData, uint64 blockHeight) external view returns (bool);
}