// SPDX-License-Identifier: agpl-3.0
pragma solidity ^0.8.0;

import {DistributionTypes} from './lib/DistributionTypes.sol';

/**
 * @title PegasysDistributionManager
 * @notice Accounting contract to manage multiple staking distributions
 */
contract PegasysDistributionManager {
  struct AssetData {
    uint128 emissionPerSecond;
    uint128 lastUpdateTimestamp;
    uint256 index;
    mapping(address => uint256) users;
  }

  uint256 public immutable DISTRIBUTION_END;

  address public immutable EMISSION_MANAGER;

  uint8 public constant PRECISION = 18;

  mapping(address => AssetData) public assets;

  event AssetConfigUpdated(address indexed asset, uint256 emission);
  event AssetIndexUpdated(address indexed asset, uint256 index);
  event UserIndexUpdated(
    address indexed user,
    address indexed asset,
    uint256 index
  );

  constructor(address emissionManager, uint256 distributionDuration) {
    DISTRIBUTION_END = block.timestamp + distributionDuration;
    EMISSION_MANAGER = emissionManager;
  }

  /**
   * @dev Configures the distribution of rewards for a list of assets
   * @param assetsConfigInput The list of configurations to apply
   */
  function _configureAssets(
    DistributionTypes.AssetConfigInput[] memory assetsConfigInput
  ) internal {
    for (uint256 i = 0; i < assetsConfigInput.length; i++) {
      AssetData storage assetConfig = assets[
        assetsConfigInput[i].underlyingAsset
      ];

      _updateAssetStateInternal(
        assetsConfigInput[i].underlyingAsset,
        assetConfig,
        assetsConfigInput[i].totalStaked
      );

      assetConfig.emissionPerSecond = assetsConfigInput[i].emissionPerSecond;

      emit AssetConfigUpdated(
        assetsConfigInput[i].underlyingAsset,
        assetsConfigInput[i].emissionPerSecond
      );
    }
  }

  /**
   * @dev Updates the state of one distribution, mainly rewards index and timestamp
   * @param underlyingAsset The address used as key in the distribution, for example sPSYS or the aTokens addresses on Pegasys
   * @param assetConfig Storage pointer to the distribution's config
   * @param totalStaked Current total of staked assets for this distribution
   * @return The new distribution index
   */
  function _updateAssetStateInternal(
    address underlyingAsset,
    AssetData storage assetConfig,
    uint256 totalStaked
  ) internal returns (uint256) {
    uint256 oldIndex = assetConfig.index;
    uint128 lastUpdateTimestamp = assetConfig.lastUpdateTimestamp;

    if (block.timestamp == lastUpdateTimestamp) {
      return oldIndex;
    }

    uint256 newIndex = _getAssetIndex(
      oldIndex,
      assetConfig.emissionPerSecond,
      lastUpdateTimestamp,
      totalStaked
    );

    if (newIndex != oldIndex) {
      assetConfig.index = newIndex;
      emit AssetIndexUpdated(underlyingAsset, newIndex);
    }

    assetConfig.lastUpdateTimestamp = uint128(block.timestamp);

    return newIndex;
  }

  /**
   * @dev Updates the state of an user in a distribution
   * @param user The user's address
   * @param asset The address of the reference asset of the distribution
   * @param stakedByUser Amount of tokens staked by the user in the distribution at the moment
   * @param totalStaked Total tokens staked in the distribution
   * @return The accrued rewards for the user until the moment
   */
  function _updateUserAssetInternal(
    address user,
    address asset,
    uint256 stakedByUser,
    uint256 totalStaked
  ) internal returns (uint256) {
    AssetData storage assetData = assets[asset];
    uint256 userIndex = assetData.users[user];
    uint256 accruedRewards = 0;

    uint256 newIndex = _updateAssetStateInternal(asset, assetData, totalStaked);

    if (userIndex != newIndex) {
      if (stakedByUser != 0) {
        accruedRewards = _getRewards(stakedByUser, newIndex, userIndex);
      }

      assetData.users[user] = newIndex;
      emit UserIndexUpdated(user, asset, newIndex);
    }

    return accruedRewards;
  }

  /**
   * @dev Used by "frontend" stake contracts to update the data of an user when claiming rewards from there
   * @param user The address of the user
   * @param stakes List of structs of the user data related with his stake
   * @return The accrued rewards for the user until the moment
   */
  function _claimRewards(
    address user,
    DistributionTypes.UserStakeInput[] memory stakes
  ) internal returns (uint256) {
    uint256 accruedRewards = 0;

    for (uint256 i = 0; i < stakes.length; i++) {
      accruedRewards =
        accruedRewards +
        _updateUserAssetInternal(
          user,
          stakes[i].underlyingAsset,
          stakes[i].stakedByUser,
          stakes[i].totalStaked
        );
    }

    return accruedRewards;
  }

  /**
   * @dev Return the accrued rewards for an user over a list of distribution
   * @param user The address of the user
   * @param stakes List of structs of the user data related with his stake
   * @return The accrued rewards for the user until the moment
   */
  function _getUnclaimedRewards(
    address user,
    DistributionTypes.UserStakeInput[] memory stakes
  ) internal view returns (uint256) {
    uint256 accruedRewards = 0;

    for (uint256 i = 0; i < stakes.length; i++) {
      AssetData storage assetConfig = assets[stakes[i].underlyingAsset];
      uint256 assetIndex = _getAssetIndex(
        assetConfig.index,
        assetConfig.emissionPerSecond,
        assetConfig.lastUpdateTimestamp,
        stakes[i].totalStaked
      );

      accruedRewards =
        accruedRewards +
        _getRewards(
          stakes[i].stakedByUser,
          assetIndex,
          assetConfig.users[user]
        );
    }
    return accruedRewards;
  }

  /**
   * @dev Internal function for the calculation of user's rewards on a distribution
   * @param principalUserBalance Amount staked by the user on a distribution
   * @param reserveIndex Current index of the distribution
   * @param userIndex Index stored for the user, representation his staking moment
   * @return The rewards
   */
  function _getRewards(
    uint256 principalUserBalance,
    uint256 reserveIndex,
    uint256 userIndex
  ) internal pure returns (uint256) {
    return
      (principalUserBalance * (reserveIndex - userIndex)) /
      (10**uint256(PRECISION));
  }

  /**
   * @dev Calculates the next value of an specific distribution index, with validations
   * @param currentIndex Current index of the distribution
   * @param emissionPerSecond Representing the total rewards distributed per second per asset unit, on the distribution
   * @param lastUpdateTimestamp Last moment this distribution was updated
   * @param totalBalance of tokens considered for the distribution
   * @return The new index.
   */
  function _getAssetIndex(
    uint256 currentIndex,
    uint256 emissionPerSecond,
    uint128 lastUpdateTimestamp,
    uint256 totalBalance
  ) internal view returns (uint256) {
    if (
      emissionPerSecond == 0 ||
      totalBalance == 0 ||
      lastUpdateTimestamp == block.timestamp ||
      lastUpdateTimestamp >= DISTRIBUTION_END
    ) {
      return currentIndex;
    }

    uint256 currentTimestamp = block.timestamp > DISTRIBUTION_END
      ? DISTRIBUTION_END
      : block.timestamp;
    uint256 timeDelta = currentTimestamp - lastUpdateTimestamp;
    return
      ((emissionPerSecond * timeDelta * (10**uint256(PRECISION))) /
        totalBalance) + currentIndex;
  }

  /**
   * @dev Returns the data of an user on a distribution
   * @param user Address of the user
   * @param asset The address of the reference asset of the distribution
   * @return The new index
   */
  function getUserAssetData(address user, address asset)
    public
    view
    returns (uint256)
  {
    return assets[asset].users[user];
  }
}