Validator Querier Precompile

[ceyonur]

We currently expose validator sets through AccessibleState.GetSnowContext().ValidatorState in stateful precompile function. Meaning that we can actually perform a query for subnet validators (and even other subnet validators) and provide this functionality to smart contracts. This could be very handy for governance, delegations, rewards and staking operations.

[ceyonur]

I sketched an interface:

//SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

interface IValidatorQuerier {
  // Returns the validator ID list of the current subnet and the height at which it was fetched.
  // The order of the list is lexicographically sorted by validator ID.
  function getCurrentValidatorList() external view returns (bytes20[] calldata validatorList, uint64 pChainHeight);

  // Returns the validator ID list of the subnet with [subnetID] and the height at [pChainHeight].
  // The order of the list is lexicographically sorted by validator ID.
  function getValidatorListAt(
    bytes32 subnetID,
    uint64 pChainHeight
  ) external view returns (bytes20[] calldata validatorIDs);

  // Returns the stake weight of the validator with [validatorID] in the subnet with [subnetID] at [pChainHeight].
  function getWeight(bytes32 subnetID, bytes20 validatorID, uint64 pChainHeight) external view returns (uint64 weight);

  // Returns the BLS public key of the validator with [validatorID] in the subnet with [subnetID] at [pChainHeight].
  function getBLSPublicKey(
    bytes32 subnetID,
    bytes20 validatorID,
    uint64 pChainHeight
  ) external view returns (bytes calldata blsPublicKey);

  // Returns the subnet ID of the current subnet.
  function getCurrentSubnetID() external view returns (bytes32 subnetID);

  // Returns the current height of the P-Chain.
  function getCurrentPChainHeight() external view returns (uint64 pChainHeight);
}