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PaymentChannel.sol

pragma solidity >=0.5.0 <0.6.0;

interface Token { 
    function approve(address _spender, uint256 _value) external returns (bool success);
    function allowance(address _owner, address _spender) external view returns (uint256 remaining);
    function transferFrom(address _from, address _to, uint256 _value) external returns (bool success);
}

interface PaymentChannel {}

contract PaymentChannelERC20 is PaymentChannel {
    constructor(Token _token, address _recipient, uint256 _duration) public {}
}

contract PaymentChannelETH is PaymentChannel {
    constructor(address payable _recipient, uint256 _duration) public payable {}
}

contract ChannelFactory {
    function newChannel(address payable _recipient, uint256 _duration) external payable returns(PaymentChannel _channel){
        _channel = (new PaymentChannelETH).value(msg.value)(_recipient, _duration);
    }
    function newChannel(Token _token, address _recipient, uint256 _duration) external returns(PaymentChannel _channel) {
        _channel = new PaymentChannelERC20(_token, _recipient, _duration);
        _token.transferFrom(msg.sender, address(_channel), _token.allowance(msg.sender, address(this)));
    }
}

contract Account {
    function openChannel(ChannelFactory _factory, Token _token, address payable _recipient, uint256 _duration, uint256 _amount) external {
        _token.approve(address(_factory), _amount);
        _factory.newChannel(_token, _recipient, _duration);   
    }
    function openChannel(ChannelFactory _factory,  address payable _recipient, uint256 _duration, uint256 _amount) external {
        _factory.newChannel.value(_amount)(_recipient, _duration);   
    }
}