// SPDX-License-Identifier: GPL-3.0-or-later

pragma solidity >=0.5.0;
pragma experimental ABIEncoderV2;

/// @notice Trident pool interface.
interface IPool {
    /// @notice Executes a swap from one token to another.
    /// @dev The input tokens must've already been sent to the pool.
    /// @param data ABI-encoded params that the pool requires.
    /// @return finalAmountOut The amount of output tokens that were sent to the user.
    function swap(bytes calldata data) external returns (uint256 finalAmountOut);

    /// @notice Executes a swap from one token to another with a callback.
    /// @dev This function allows borrowing the output tokens and sending the input tokens in the callback.
    /// @param data ABI-encoded params that the pool requires.
    /// @return finalAmountOut The amount of output tokens that were sent to the user.
    function flashSwap(bytes calldata data) external returns (uint256 finalAmountOut);

    /// @notice Mints liquidity tokens.
    /// @param data ABI-encoded params that the pool requires.
    /// @return liquidity The amount of liquidity tokens that were minted for the user.
    function mint(bytes calldata data) external returns (uint256 liquidity);

    /// @notice Burns liquidity tokens.
    /// @dev The input LP tokens must've already been sent to the pool.
    /// @param data ABI-encoded params that the pool requires.
    /// @return withdrawnAmounts The amount of various output tokens that were sent to the user.
    function burn(bytes calldata data) external returns (TokenAmount[] memory withdrawnAmounts);

    /// @notice Burns liquidity tokens for a single output token.
    /// @dev The input LP tokens must've already been sent to the pool.
    /// @param data ABI-encoded params that the pool requires.
    /// @return amountOut The amount of output tokens that were sent to the user.
    function burnSingle(bytes calldata data) external returns (uint256 amountOut);

    /// @return A unique identifier for the pool type.
    function poolIdentifier() external pure returns (bytes32);

    /// @return An array of tokens supported by the pool.
    function getAssets() external view returns (address[] memory);

    /// @notice Simulates a trade and returns the expected output.
    /// @dev The pool does not need to include a trade simulator directly in itself - it can use a library.
    /// @param data ABI-encoded params that the pool requires.
    /// @return finalAmountOut The amount of output tokens that will be sent to the user if the trade is executed.
    function getAmountOut(bytes calldata data) external view returns (uint256 finalAmountOut);

    /// @notice Simulates a trade and returns the expected output.
    /// @dev The pool does not need to include a trade simulator directly in itself - it can use a library.
    /// @param data ABI-encoded params that the pool requires.
    /// @return finalAmountIn The amount of input tokens that are required from the user if the trade is executed.
    function getAmountIn(bytes calldata data) external view returns (uint256 finalAmountIn);

    /// @dev This event must be emitted on all swaps.
    event Swap(address indexed recipient, address indexed tokenIn, address indexed tokenOut, uint256 amountIn, uint256 amountOut);

    /// @dev This struct frames output tokens for burns.
    struct TokenAmount {
        address token;
        uint256 amount;
    }
}