pragma solidity >=0.6.12;

// Author:	Louis Holbrook <dev@holbrook.no> 0826EDA1702D1E87C6E2875121D2E7BB88C2A746
// SPDX-License-Identifier:	AGPL-3.0-or-later
// File-version: 1


interface IOffline {
	// Verify signer and data
	// Check input assuming signature is valid against contract instance.
	function isOfflineValid(address _signer, bytes memory _data) external view returns(bool);

	// Verify signature against data, and isOfflineValid() against data and signer (as validator)
	// Signature must be ERC191 version 0x00 with contract instance as validator.
	function verifyOfflineRequest(bytes memory _data, bytes memory _signature) external view returns(bool);

	// Change state if signature and signer is valid.
	// Call verifyOfflineRequest and:
        // - revert if it returns false.
	// - return 0 if state is changed according to the request.
	// - return any other valid to indicate an application specific error.
	function executeOfflineRequest(bytes memory _data, bytes memory _signature) external returns(uint256);
}