// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity >=0.8.22;

import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import { UD21x18 } from "@prb/math/src/UD21x18.sol";

library Flow {
    /// @notice Enum representing the different statuses of a stream.
    /// @custom:value0 PENDING Stream scheduled to start in the future.
    /// @custom:value1 STREAMING_SOLVENT Streaming stream with no uncovered debt.
    /// @custom:value2 STREAMING_INSOLVENT Streaming stream with uncovered debt.
    /// @custom:value3 PAUSED_SOLVENT Paused stream with no uncovered debt.
    /// @custom:value4 PAUSED_INSOLVENT Paused stream with uncovered debt.
    /// @custom:value5 VOIDED Paused stream with no uncovered debt, which cannot be restarted.
    enum Status {
        PENDING,
        STREAMING_SOLVENT,
        STREAMING_INSOLVENT,
        PAUSED_SOLVENT,
        PAUSED_INSOLVENT,
        VOIDED
    }

    /// @notice Struct representing Flow streams.
    ///
    /// @dev The fields are arranged like this to save gas via tight variable packing.
    ///
    /// @param balance The amount of tokens that are currently available in the stream, denoted in the token's decimals.
    /// This is the sum of deposited amounts minus the sum of withdrawn amounts.
    /// @param ratePerSecond The payment rate per second, denoted as a fixed-point number where 1e18 is 1 token per
    /// second. For example, to stream 1000 tokens per week, this parameter would have the value $(1000 * 10^18) / (7
    /// days in seconds)$.
    /// @param sender The address streaming the tokens, with the ability to pause the stream.
    /// @param snapshotTime The Unix timestamp used for the ongoing debt calculation.
    /// @param isStream Boolean indicating if the struct entity exists.
    /// @param isTransferable Boolean indicating if the stream NFT is transferable.
    /// @param isVoided Boolean indicating if the stream is voided. Voiding any stream is non-reversible and it cannot
    /// be restarted. Voiding an insolvent stream sets its uncovered debt to zero.
    /// @param token The contract address of the ERC-20 token to stream.
    /// @param tokenDecimals The decimals of the ERC-20 token to stream.
    /// @param snapshotDebtScaled The amount of tokens that the sender owed to the recipient at snapshot time, denoted
    /// as a 18-decimals fixed-point number. This, along with the ongoing debt, can be used to calculate the total debt
    /// at any given point in time.
    struct Stream {
        // slot 0
        uint128 balance;
        UD21x18 ratePerSecond;
        // slot 1
        address sender;
        uint40 snapshotTime;
        bool isStream;
        bool isTransferable;
        bool isVoided;
        // slot 2
        IERC20 token;
        uint8 tokenDecimals;
        // slot 3
        uint256 snapshotDebtScaled;
    }
}