// Copyright 2021-2022, Offchain Labs, Inc.
// For license information, see https://github.com/OffchainLabs/nitro-contracts/blob/main/LICENSE
// SPDX-License-Identifier: BUSL-1.1

pragma solidity >=0.4.21 <0.9.0;

/**
 * @title Allows registering / retrieving addresses at uint indices, saving calldata.
 * @notice Precompiled contract that exists in every Arbitrum chain at 0x0000000000000000000000000000000000000066.
 */
interface ArbAddressTable {
    /**
     * @notice Check whether an address exists in the address table
     * @param addr address to check for presence in table
     * @return true if address is in table
     */
    function addressExists(
        address addr
    ) external view returns (bool);

    /**
     * @notice compress an address and return the result
     * @param addr address to compress
     * @return compressed address bytes
     */
    function compress(
        address addr
    ) external returns (bytes memory);

    /**
     * @notice read a compressed address from a bytes buffer
     * @param buf bytes buffer containing an address
     * @param offset offset of target address
     * @return resulting address and updated offset into the buffer (revert if buffer is too short)
     */
    function decompress(
        bytes calldata buf,
        uint256 offset
    ) external view returns (address, uint256);

    /**
     * @param addr address to lookup
     * @return index of an address in the address table (revert if address isn't in the table)
     */
    function lookup(
        address addr
    ) external view returns (uint256);

    /**
     * @param index index to lookup address
     * @return address at a given index in address table (revert if index is beyond end of table)
     */
    function lookupIndex(
        uint256 index
    ) external view returns (address);

    /**
     * @notice Register an address in the address table
     * @param addr address to register
     * @return index of the address (existing index, or newly created index if not already registered)
     */
    function register(
        address addr
    ) external returns (uint256);

    /**
     * @return size of address table (= first unused index)
     */
    function size() external view returns (uint256);
}