// SPDX-License-Identifier: AGPL-3.0-only
pragma solidity ^0.8.24;

/// @title EveryChannelWitnessRegistry
/// @notice Minimal registry-backed witness set for observation consensus. This is intentionally
/// simple for the first testnet tranche: explicit membership, no staking, no slashing.
contract EveryChannelWitnessRegistry {
    address public owner;
    mapping(address => bool) public isWitness;
    uint256 public witnessCount;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
    event WitnessAdded(address indexed witness);
    event WitnessRemoved(address indexed witness);

    error NotOwner();
    error ZeroAddress();
    error WitnessAlreadyRegistered(address witness);
    error WitnessNotRegistered(address witness);

    constructor(address initialOwner) {
        if (initialOwner == address(0)) revert ZeroAddress();
        owner = initialOwner;
        emit OwnershipTransferred(address(0), initialOwner);
    }

    modifier onlyOwner() {
        if (msg.sender != owner) revert NotOwner();
        _;
    }

    function transferOwnership(address newOwner) external onlyOwner {
        if (newOwner == address(0)) revert ZeroAddress();
        address previous = owner;
        owner = newOwner;
        emit OwnershipTransferred(previous, newOwner);
    }

    function addWitness(address witness) external onlyOwner {
        if (witness == address(0)) revert ZeroAddress();
        if (isWitness[witness]) revert WitnessAlreadyRegistered(witness);
        isWitness[witness] = true;
        witnessCount += 1;
        emit WitnessAdded(witness);
    }

    function removeWitness(address witness) external onlyOwner {
        if (!isWitness[witness]) revert WitnessNotRegistered(witness);
        isWitness[witness] = false;
        witnessCount -= 1;
        emit WitnessRemoved(witness);
    }
}