pragma solidity 0.5.10;
pragma experimental "ABIEncoderV2";

import "../interfaces/CounterfactualApp.sol";
import "../ChallengeRegistry.sol";


/// @notice TimeLockedPassThrough - Before `switchesOutcomeAt`, this contract
/// should return the exact same outcome as the outcome `targetAppIdentityHash`
///  returns, allowing it to "pass through" unaltered.
///
/// However, after `switchesOutcomeAt`, it should return `defaultOutcome`.
/// `challengeRegistryAddress` is used to look up the outcome.
///
/// This contract is applied to virtual apps for two reasons:
///
/// 1. After the pre-agreed intermediation period elapses, the outcome
///    must be fixed to the default (cannot be changed without
///    the intermediary's consent) to allow them to safely get back their
///    collateral.
///
/// 2. During the installation and uninstallation of the virtual app,
///    this contract must be set to the default outcome, so that if funding
///    fails halfway, the intermediary can dispute both channels safely
contract TimeLockedPassThrough {

  struct AppState {
    address challengeRegistryAddress;
    bytes32 targetAppIdentityHash;
    uint256 switchesOutcomeAt;
    bytes defaultOutcome;
  }

  function computeOutcome(bytes calldata encodedState)
    external
    view
    returns (bytes memory)
  {
    AppState memory appState = abi.decode(encodedState, (AppState));

    if (block.number >= appState.switchesOutcomeAt)
      return appState.defaultOutcome;

    return ChallengeRegistry(
      appState.challengeRegistryAddress
    ).getOutcome(
      appState.targetAppIdentityHash
    );
  }
}