eth-address-index/solidity/AddressDeclarator.sol

pragma solidity >=0.6.12;

// SPDX-License-Identifier: GPL-3.0-or-later

contract AddressDeclarator {

	struct declaratorItem {
		address signer;
		bytes32[] content;
	}

	mapping( address => uint256[] ) declaratorItemsIndex;
	mapping( address => uint256 ) public declaratorCount;
	mapping( address => mapping ( address => declaratorItem ) ) declarationByDeclaratorIndex;
 	declaratorItem[] declaratorItems;

	constructor(bytes32[] memory _descriptions) {
		for (uint i; i < _descriptions.length; i++) {
			addDeclaration(msg.sender, _descriptions[i]);
		}
	}

	function addDeclaration(address _subject, bytes32 _proof) public returns ( bool ) {
		declaratorItem storage item;

		item = declarationByDeclaratorIndex[msg.sender][_subject];
		if (item.signer == address(0)) {
			item.signer = msg.sender;
			declaratorItemsIndex[_subject].push(declaratorItems.length);
			declaratorItems.push(item);
			declaratorCount[_subject]++;
		}
		item.content.push(_proof);

		return true;
	}

	function declarator(address _target, uint256 _idx) public view returns ( address ) {
		uint256 idx;
		declaratorItem storage item;
		
		idx = declaratorItemsIndex[_target][_idx];
		item = declaratorItems[idx];

		return item.signer;
	}

	function declaration(address _declarator, address _target) public view returns ( bytes32[] memory ) {
		declaratorItem storage item;
		
		item = declarationByDeclaratorIndex[_declarator][_target];

		return item.content;
	}
}