// SPDX-License-Identifier: Apache-2.0
/*

  Copyright 2020 ZeroEx Intl.

  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.

*/

pragma solidity ^0.6;
pragma experimental ABIEncoderV2;

import "./interfaces/IMooniswap.sol";
import "./ApproximateBuys.sol";
import "./SamplerUtils.sol";


contract MooniswapSampler is
    SamplerUtils,
    ApproximateBuys
{
    /// @dev Gas limit for Mooniswap calls.
    uint256 constant private MOONISWAP_CALL_GAS = 150e3; // 150k

    /// @dev Sample sell quotes from Mooniswap.
    /// @param registry Address of the Mooniswap Registry.
    /// @param takerToken Address of the taker token (what to sell).
    /// @param makerToken Address of the maker token (what to buy).
    /// @param takerTokenAmounts Taker token sell amount for each sample.
    /// @return pool The contract address for the pool
    /// @return makerTokenAmounts Maker amounts bought at each taker token
    ///         amount.
    function sampleSellsFromMooniswap(
        address registry,
        address takerToken,
        address makerToken,
        uint256[] memory takerTokenAmounts
    )
        public
        view
        returns (IMooniswap pool, uint256[] memory makerTokenAmounts)
    {
        _assertValidPair(makerToken, takerToken);
        uint256 numSamples = takerTokenAmounts.length;
        makerTokenAmounts = new uint256[](numSamples);

        for (uint256 i = 0; i < numSamples; i++) {
            uint256 buyAmount = sampleSingleSellFromMooniswapPool(
                registry,
                takerToken,
                makerToken,
                takerTokenAmounts[i]
            );
            makerTokenAmounts[i] = buyAmount;
            // Break early if there are 0 amounts
            if (makerTokenAmounts[i] == 0) {
                break;
            }
        }

        pool = IMooniswap(
            IMooniswapRegistry(registry).pools(takerToken, makerToken)
        );
    }

    function sampleSingleSellFromMooniswapPool(
        address registry,
        address mooniswapTakerToken,
        address mooniswapMakerToken,
        uint256 takerTokenAmount
    )
        public
        view
        returns (uint256)
    {
        // Find the pool for the pair.
        IMooniswap pool = IMooniswap(
            IMooniswapRegistry(registry).pools(mooniswapTakerToken, mooniswapMakerToken)
        );
        // If there is no pool then return early
        if (address(pool) == address(0)) {
            return 0;
        }
        uint256 poolBalance = mooniswapTakerToken == address(0)
            ? address(pool).balance
            : IERC20TokenV06(mooniswapTakerToken).balanceOf(address(pool));
        // If the pool balance is smaller than the sell amount
        // don't sample to avoid multiplication overflow in buys
        if (poolBalance < takerTokenAmount) {
            return 0;
        }
        try
            pool.getReturn
                {gas: MOONISWAP_CALL_GAS}
                (mooniswapTakerToken, mooniswapMakerToken, takerTokenAmount)
            returns (uint256 amount)
        {
            return amount;
        } catch (bytes memory) {
            // Swallow failures, leaving all results as zero.
            return 0;
        }
    }

    /// @dev Sample buy quotes from Mooniswap.
    /// @param registry Address of the Mooniswap Registry.
    /// @param takerToken Address of the taker token (what to sell).
    /// @param makerToken Address of the maker token (what to buy).
    /// @param makerTokenAmounts Maker token sell amount for each sample.
    /// @return pool The contract address for the pool
    /// @return takerTokenAmounts Taker amounts sold at each maker token
    ///         amount.
    function sampleBuysFromMooniswap(
        address registry,
        address takerToken,
        address makerToken,
        uint256[] memory makerTokenAmounts
    )
        public
        view
        returns (IMooniswap pool, uint256[] memory takerTokenAmounts)
    {
        _assertValidPair(makerToken, takerToken);
        uint256 numSamples = makerTokenAmounts.length;
        takerTokenAmounts = new uint256[](numSamples);

        takerTokenAmounts = _sampleApproximateBuys(
            ApproximateBuyQuoteOpts({
                makerTokenData: abi.encode(registry, makerToken),
                takerTokenData: abi.encode(registry, takerToken),
                getSellQuoteCallback: _sampleSellForApproximateBuyFromMooniswap
            }),
            makerTokenAmounts
        );

        pool = IMooniswap(
            IMooniswapRegistry(registry).pools(takerToken, makerToken)
        );
    }

    function _sampleSellForApproximateBuyFromMooniswap(
        bytes memory takerTokenData,
        bytes memory makerTokenData,
        uint256 sellAmount
    )
        private
        view
        returns (uint256 buyAmount)
    {
        (address registry, address mooniswapTakerToken) = abi.decode(takerTokenData, (address, address));
        (address _registry, address mooniswapMakerToken) = abi.decode(makerTokenData, (address, address));
        return sampleSingleSellFromMooniswapPool(
            registry,
            mooniswapTakerToken,
            mooniswapMakerToken,
            sellAmount
        );
    }
}