// SPDX-License-Identifier: GPL-3.0
pragma solidity ^0.8.10;

import {IERC20} from '@aave/core-v3/contracts/dependencies/openzeppelin/contracts/IERC20.sol';
import {IStreamable} from './interfaces/IStreamable.sol';
import {AdminControlledEcosystemReserve} from './AdminControlledEcosystemReserve.sol';
import {ReentrancyGuard} from './libs/ReentrancyGuard.sol';
import {SafeERC20} from './libs/SafeERC20.sol';

/**
 * @title AaveEcosystemReserve v2
 * @notice Stores ERC20 tokens of an ecosystem reserve, adding streaming capabilities.
 * Modification of Sablier https://github.com/sablierhq/sablier/blob/develop/packages/protocol/contracts/Sablier.sol
 * Original can be found also deployed on https://etherscan.io/address/0xCD18eAa163733Da39c232722cBC4E8940b1D8888
 * Modifications:
 * - Sablier "pulls" the funds from the creator of the stream at creation. In the Aave case, we already have the funds.
 * - Anybody can create streams on Sablier. Here, only the funds admin (Aave governance via controller) can
 * - Adapted codebase to Solidity 0.8.11, mainly removing SafeMath and CarefulMath to use native safe math
 * - Same as with creation, on Sablier the `sender` and `recipient` can cancel a stream. Here, only fund admin and recipient
 * @author BGD Labs
 **/
contract AaveEcosystemReserveV2 is AdminControlledEcosystemReserve, ReentrancyGuard, IStreamable {
  using SafeERC20 for IERC20;

  /*** Storage Properties ***/

  /**
   * @notice Counter for new stream ids.
   */
  uint256 private _nextStreamId;

  /**
   * @notice The stream objects identifiable by their unsigned integer ids.
   */
  mapping(uint256 => Stream) private _streams;

  /*** Modifiers ***/

  /**
   * @dev Throws if the caller is not the funds admin of the recipient of the stream.
   */
  modifier onlyAdminOrRecipient(uint256 streamId) {
    require(
      msg.sender == _fundsAdmin || msg.sender == _streams[streamId].recipient,
      'caller is not the funds admin or the recipient of the stream'
    );
    _;
  }

  /**
   * @dev Throws if the provided id does not point to a valid stream.
   */
  modifier streamExists(uint256 streamId) {
    require(_streams[streamId].isEntity, 'stream does not exist');
    _;
  }

  /*** Contract Logic Starts Here */

  function initialize(address fundsAdmin) external initializer {
    _nextStreamId = 100000;
    _setFundsAdmin(fundsAdmin);
  }

  /*** View Functions ***/

  /**
   * @notice Returns the next available stream id
   * @notice Returns the stream id.
   */
  function getNextStreamId() external view returns (uint256) {
    return _nextStreamId;
  }

  /**
   * @notice Returns the stream with all its properties.
   * @dev Throws if the id does not point to a valid stream.
   * @param streamId The id of the stream to query.
   * @notice Returns the stream object.
   */
  function getStream(
    uint256 streamId
  )
    external
    view
    streamExists(streamId)
    returns (
      address sender,
      address recipient,
      uint256 deposit,
      address tokenAddress,
      uint256 startTime,
      uint256 stopTime,
      uint256 remainingBalance,
      uint256 ratePerSecond
    )
  {
    sender = _streams[streamId].sender;
    recipient = _streams[streamId].recipient;
    deposit = _streams[streamId].deposit;
    tokenAddress = _streams[streamId].tokenAddress;
    startTime = _streams[streamId].startTime;
    stopTime = _streams[streamId].stopTime;
    remainingBalance = _streams[streamId].remainingBalance;
    ratePerSecond = _streams[streamId].ratePerSecond;
  }

  /**
   * @notice Returns either the delta in seconds between `block.timestamp` and `startTime` or
   *  between `stopTime` and `startTime, whichever is smaller. If `block.timestamp` is before
   *  `startTime`, it returns 0.
   * @dev Throws if the id does not point to a valid stream.
   * @param streamId The id of the stream for which to query the delta.
   * @notice Returns the time delta in seconds.
   */
  function deltaOf(uint256 streamId) public view streamExists(streamId) returns (uint256 delta) {
    Stream memory stream = _streams[streamId];
    if (block.timestamp <= stream.startTime) return 0;
    if (block.timestamp < stream.stopTime) return block.timestamp - stream.startTime;
    return stream.stopTime - stream.startTime;
  }

  struct BalanceOfLocalVars {
    uint256 recipientBalance;
    uint256 withdrawalAmount;
    uint256 senderBalance;
  }

  /**
   * @notice Returns the available funds for the given stream id and address.
   * @dev Throws if the id does not point to a valid stream.
   * @param streamId The id of the stream for which to query the balance.
   * @param who The address for which to query the balance.
   * @notice Returns the total funds allocated to `who` as uint256.
   */
  function balanceOf(
    uint256 streamId,
    address who
  ) public view streamExists(streamId) returns (uint256 balance) {
    Stream memory stream = _streams[streamId];
    BalanceOfLocalVars memory vars;

    uint256 delta = deltaOf(streamId);
    vars.recipientBalance = delta * stream.ratePerSecond;

    /*
     * If the stream `balance` does not equal `deposit`, it means there have been withdrawals.
     * We have to subtract the total amount withdrawn from the amount of money that has been
     * streamed until now.
     */
    if (stream.deposit > stream.remainingBalance) {
      vars.withdrawalAmount = stream.deposit - stream.remainingBalance;
      vars.recipientBalance = vars.recipientBalance - vars.withdrawalAmount;
    }

    if (who == stream.recipient) return vars.recipientBalance;
    if (who == stream.sender) {
      vars.senderBalance = stream.remainingBalance - vars.recipientBalance;
      return vars.senderBalance;
    }
    return 0;
  }

  /*** Public Effects & Interactions Functions ***/

  struct CreateStreamLocalVars {
    uint256 duration;
    uint256 ratePerSecond;
  }

  /**
   * @notice Creates a new stream funded by this contracts itself and paid towards `recipient`.
   * @dev Throws if the recipient is the zero address, the contract itself or the caller.
   *  Throws if the deposit is 0.
   *  Throws if the start time is before `block.timestamp`.
   *  Throws if the stop time is before the start time.
   *  Throws if the duration calculation has a math error.
   *  Throws if the deposit is smaller than the duration.
   *  Throws if the deposit is not a multiple of the duration.
   *  Throws if the rate calculation has a math error.
   *  Throws if the next stream id calculation has a math error.
   *  Throws if the contract is not allowed to transfer enough tokens.
   *  Throws if there is a token transfer failure.
   * @param recipient The address towards which the money is streamed.
   * @param deposit The amount of money to be streamed.
   * @param tokenAddress The ERC20 token to use as streaming currency.
   * @param startTime The unix timestamp for when the stream starts.
   * @param stopTime The unix timestamp for when the stream stops.
   * @notice Returns the uint256 id of the newly created stream.
   */
  function createStream(
    address recipient,
    uint256 deposit,
    address tokenAddress,
    uint256 startTime,
    uint256 stopTime
  ) external onlyFundsAdmin returns (uint256) {
    require(recipient != address(0), 'stream to the zero address');
    require(recipient != address(this), 'stream to the contract itself');
    require(recipient != msg.sender, 'stream to the caller');
    require(deposit > 0, 'deposit is zero');
    require(startTime >= block.timestamp, 'start time before block.timestamp');
    require(stopTime > startTime, 'stop time before the start time');

    CreateStreamLocalVars memory vars;
    vars.duration = stopTime - startTime;

    /* Without this, the rate per second would be zero. */
    require(deposit >= vars.duration, 'deposit smaller than time delta');

    /* This condition avoids dealing with remainders */
    require(deposit % vars.duration == 0, 'deposit not multiple of time delta');

    vars.ratePerSecond = deposit / vars.duration;

    /* Create and store the stream object. */
    uint256 streamId = _nextStreamId;
    _streams[streamId] = Stream({
      remainingBalance: deposit,
      deposit: deposit,
      isEntity: true,
      ratePerSecond: vars.ratePerSecond,
      recipient: recipient,
      sender: address(this),
      startTime: startTime,
      stopTime: stopTime,
      tokenAddress: tokenAddress
    });

    /* Increment the next stream id. */
    _nextStreamId++;

    emit CreateStream(
      streamId,
      address(this),
      recipient,
      deposit,
      tokenAddress,
      startTime,
      stopTime
    );
    return streamId;
  }

  /**
   * @notice Withdraws from the contract to the recipient's account.
   * @dev Throws if the id does not point to a valid stream.
   *  Throws if the caller is not the funds admin or the recipient of the stream.
   *  Throws if the amount exceeds the available balance.
   *  Throws if there is a token transfer failure.
   * @param streamId The id of the stream to withdraw tokens from.
   * @param amount The amount of tokens to withdraw.
   */
  function withdrawFromStream(
    uint256 streamId,
    uint256 amount
  ) external nonReentrant streamExists(streamId) onlyAdminOrRecipient(streamId) returns (bool) {
    require(amount > 0, 'amount is zero');
    Stream memory stream = _streams[streamId];

    uint256 balance = balanceOf(streamId, stream.recipient);
    require(balance >= amount, 'amount exceeds the available balance');

    _streams[streamId].remainingBalance = stream.remainingBalance - amount;

    if (_streams[streamId].remainingBalance == 0) delete _streams[streamId];

    IERC20(stream.tokenAddress).safeTransfer(stream.recipient, amount);
    emit WithdrawFromStream(streamId, stream.recipient, amount);
    return true;
  }

  /**
   * @notice Cancels the stream and transfers the tokens back on a pro rata basis.
   * @dev Throws if the id does not point to a valid stream.
   *  Throws if the caller is not the funds admin or the recipient of the stream.
   *  Throws if there is a token transfer failure.
   * @param streamId The id of the stream to cancel.
   * @notice Returns bool true=success, otherwise false.
   */
  function cancelStream(
    uint256 streamId
  ) external nonReentrant streamExists(streamId) onlyAdminOrRecipient(streamId) returns (bool) {
    Stream memory stream = _streams[streamId];
    uint256 senderBalance = balanceOf(streamId, stream.sender);
    uint256 recipientBalance = balanceOf(streamId, stream.recipient);

    delete _streams[streamId];

    IERC20 token = IERC20(stream.tokenAddress);
    if (recipientBalance > 0) token.safeTransfer(stream.recipient, recipientBalance);

    emit CancelStream(streamId, stream.sender, stream.recipient, senderBalance, recipientBalance);
    return true;
  }
}