/*
 OMSManager.swift

 Created by Takuto Nakamura on 2024/03/02.
*/

import Combine
import OpenMultitouchSupportXCF
import os

public final class OMSManager: Sendable {
    public static let shared = OMSManager()

    private let protectedManager: OSAllocatedUnfairLock<OpenMTManager?>
    private let protectedListener = OSAllocatedUnfairLock<OpenMTListener?>(uncheckedState: nil)
    private let dateFormatter = DateFormatter()

    private let touchDataSubject = PassthroughSubject<[OMSTouchData], Never>()
    public var touchDataStream: AsyncStream<[OMSTouchData]> {
        AsyncStream { continuation in
            let cancellable = touchDataSubject.sink { value in
                continuation.yield(value)
            }
            continuation.onTermination = { _ in
                cancellable.cancel()
            }
        }
    }

    public var isListening: Bool {
        protectedListener.withLockUnchecked { $0 != nil }
    }

    private init() {
        protectedManager = .init(uncheckedState: OpenMTManager.shared())
        dateFormatter.dateFormat = "HH:mm:ss.SSSS"
    }

    @discardableResult
    public func startListening() -> Bool {
        guard let xcfManager = protectedManager.withLockUnchecked(\.self),
              protectedListener.withLockUnchecked({ $0 == nil }) else {
            return false
        }
        let listener = xcfManager.addListener(
            withTarget: self,
            selector: #selector(listen)
        )
        protectedListener.withLockUnchecked { $0 = listener }
        return true
    }

    @discardableResult
    public func stopListening() -> Bool {
        guard let xcfManager = protectedManager.withLockUnchecked(\.self),
              let listener = protectedListener.withLockUnchecked(\.self) else {
            return false
        }
        xcfManager.remove(listener)
        protectedListener.withLockUnchecked { $0 = nil }
        return true
    }

    @objc func listen(_ event: OpenMTEvent) {
        guard let touches = (event.touches as NSArray) as? [OpenMTTouch] else { return }
        if touches.isEmpty {
            touchDataSubject.send([])
        } else {
            let array = touches.compactMap { touch -> OMSTouchData? in
                guard let state = OMSState(touch.state) else { return nil }
                return OMSTouchData(
                    id: touch.identifier,
                    position: OMSPosition(x: touch.posX, y: touch.posY),
                    total: touch.total,
                    pressure: touch.pressure,
                    axis: OMSAxis(major: touch.majorAxis, minor: touch.minorAxis),
                    angle: touch.angle,
                    density: touch.density,
                    state: state,
                    timestamp: dateFormatter.string(from: Date.now)
                )
            }
            touchDataSubject.send(array)
        }
    }
}

extension AnyCancellable: @retroactive @unchecked Sendable {}
extension PassthroughSubject: @retroactive @unchecked Sendable {}