import Network

fileprivate let pipe = Character("|").asciiValue!

class PipeFramer: NWProtocolFramerImplementation {
    static let label = "Pipe framer"
    static let definition = NWProtocolFramer.Definition(implementation: PipeFramer.self)

    var minLengthUntilNextMessage = 1 {
        didSet { print("client: minLength set to", minLengthUntilNextMessage) }
    }

    required init(framer: NWProtocolFramer.Instance) {}

    func start(framer: NWProtocolFramer.Instance) -> NWProtocolFramer.StartResult { .ready }

    func handleInput(framer: NWProtocolFramer.Instance) -> Int {
        while true {
            var delimiterPosition: Int?
            _ = framer.parseInput(minimumIncompleteLength: minLengthUntilNextMessage, maximumLength: 65535) { buffer, endOfMessage in
                if let buffer = buffer {
                    print("client: parsing buffer: \"\(String(bytes: buffer, encoding: .utf8) ?? buffer.debugDescription)\"")
                    if let indexOfDelimiter = buffer.firstIndex(of: pipe) {
                        minLengthUntilNextMessage = 1
                        delimiterPosition = indexOfDelimiter
                    } else {
                        minLengthUntilNextMessage = buffer.count + 1
                    }
                } else {
                    print("client: no buffer")
                }
                return 0
            }

            if let length = delimiterPosition {
                guard framer.deliverInputNoCopy(length: length, message: .init(instance: framer), isComplete: true) else {
                    return 0
                }
                _ = framer.parseInput(minimumIncompleteLength: 1, maximumLength: 65535) { _,_ in 1 }
            } else {
                return minLengthUntilNextMessage
            }
        }
    }

    func handleOutput(framer: NWProtocolFramer.Instance, message: NWProtocolFramer.Message, messageLength: Int, isComplete: Bool) {
        try! framer.writeOutputNoCopy(length: messageLength)
        framer.writeOutput(data: [pipe])
    }

    func wakeup(framer: NWProtocolFramer.Instance) {}

    func stop(framer: NWProtocolFramer.Instance) -> Bool { return true }

    func cleanup(framer: NWProtocolFramer.Instance) { }
}