import CoreBluetooth
import Foundation

/// Hält die Verbindung zum Solarladeregler.
///
/// Einfacher noch als `LevelSession`: die Firmware bietet für keine
/// Charakteristik `notify` an (siehe `esp32_ble_solar.yaml`), es wird also
/// immer im Takt abgefragt statt abonniert.
final class VotronicSolarESPSession: NSObject {

    static let serviceUUID = CBUUID(string: VotronicSolarESPProtocol.serviceUUID)
    private static let batteryVoltageUUID = CBUUID(string: VotronicSolarESPProtocol.batteryVoltageUUID)
    private static let pvVoltageUUID = CBUUID(string: VotronicSolarESPProtocol.pvVoltageUUID)
    private static let pvCurrentUUID = CBUUID(string: VotronicSolarESPProtocol.pvCurrentUUID)
    private static let pvPowerUUID = CBUUID(string: VotronicSolarESPProtocol.pvPowerUUID)
    private static let controllerTempUUID = CBUUID(string: VotronicSolarESPProtocol.controllerTempUUID)
    private static let statusFlagsUUID = CBUUID(string: VotronicSolarESPProtocol.statusFlagsUUID)

    let deviceID: UUID
    private let queue: DispatchQueue
    private let peripheral: CBPeripheral
    private let onUpdate: (DeviceSnapshot) -> Void
    private let onStateChange: (DeviceLinkState) -> Void
    private let onVotronicSolarESPState: (VotronicSolarESPState) -> Void

    private var characteristics: [CBUUID: CBCharacteristic] = [:]
    private var state = VotronicSolarESPState()
    private var pollTimer: DispatchSourceTimer?

    /// Reicht für einen Solarregler, dessen Werte sich über Sekunden ändern –
    /// deutlich seltener als beim Ausrichten mit dem Neigungsmesser.
    var pollInterval: TimeInterval = 5

    init(deviceID: UUID,
         peripheral: CBPeripheral,
         queue: DispatchQueue,
         onUpdate: @escaping (DeviceSnapshot) -> Void,
         onStateChange: @escaping (DeviceLinkState) -> Void,
         onVotronicSolarESPState: @escaping (VotronicSolarESPState) -> Void) {
        self.deviceID = deviceID
        self.queue = queue
        self.peripheral = peripheral
        self.onUpdate = onUpdate
        self.onStateChange = onStateChange
        self.onVotronicSolarESPState = onVotronicSolarESPState
        super.init()
        peripheral.delegate = self
    }

    // MARK: - Lebenszyklus

    func start() {
        onStateChange(.connecting)
        peripheral.discoverServices([Self.serviceUUID])
    }

    func stop() {
        pollTimer?.cancel()
        pollTimer = nil
        characteristics.removeAll()
    }

    func handleDisconnect() {
        pollTimer?.cancel()
        pollTimer = nil
        characteristics.removeAll()
    }

    // MARK: - Abfrage

    private func startPolling() {
        guard pollTimer == nil else { return }
        let timer = DispatchSource.makeTimerSource(queue: queue)
        timer.schedule(deadline: .now(), repeating: pollInterval)
        timer.setEventHandler { [weak self] in self?.readAll() }
        timer.resume()
        pollTimer = timer
    }

    private func readAll() {
        guard peripheral.state == .connected else { return }
        for characteristic in characteristics.values where characteristic.properties.contains(.read) {
            peripheral.readValue(for: characteristic)
        }
    }

    private func publish() {
        guard state.hasReading else { return }
        onStateChange(.live)
        onVotronicSolarESPState(state)
        onUpdate(state.snapshot(deviceID: deviceID, rssi: nil))
    }
}

// MARK: - CBPeripheralDelegate

extension VotronicSolarESPSession: CBPeripheralDelegate {

    func peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?) {
        if let error {
            onStateChange(.failed(error.localizedDescription))
            return
        }
        guard let service = peripheral.services?.first(where: { $0.uuid == Self.serviceUUID }) else {
            onStateChange(.failed("Solarladeregler-Dienst nicht gefunden"))
            return
        }
        peripheral.discoverCharacteristics(
            [Self.batteryVoltageUUID, Self.pvVoltageUUID, Self.pvCurrentUUID,
             Self.pvPowerUUID, Self.controllerTempUUID, Self.statusFlagsUUID],
            for: service
        )
    }

    func peripheral(_ peripheral: CBPeripheral,
                    didDiscoverCharacteristicsFor service: CBService,
                    error: Error?) {
        guard error == nil, let found = service.characteristics else {
            onStateChange(.failed(error?.localizedDescription ?? "Keine Merkmale gefunden"))
            return
        }
        for characteristic in found {
            characteristics[characteristic.uuid] = characteristic
        }
        guard !characteristics.isEmpty else {
            onStateChange(.failed("Solarwerte nicht gefunden"))
            return
        }
        startPolling()
        readAll()
    }

    func peripheral(_ peripheral: CBPeripheral,
                    didUpdateValueFor characteristic: CBCharacteristic,
                    error: Error?) {
        guard error == nil, let value = characteristic.value else { return }

        switch characteristic.uuid {
        case Self.batteryVoltageUUID:
            state.batteryVoltage = VotronicSolarESPProtocol.float(from: value)
        case Self.pvVoltageUUID:
            state.pvVoltage = VotronicSolarESPProtocol.float(from: value)
        case Self.pvCurrentUUID:
            state.pvCurrent = VotronicSolarESPProtocol.float(from: value)
        case Self.pvPowerUUID:
            state.pvPower = VotronicSolarESPProtocol.float(from: value)
        case Self.controllerTempUUID:
            state.controllerTemperature = VotronicSolarESPProtocol.float(from: value)
        case Self.statusFlagsUUID:
            guard let flags = VotronicSolarESPProtocol.statusFlags(from: value) else { return }
            state.isBatteryCharging = flags.isBatteryCharging
            state.isBatteryDischarging = flags.isBatteryDischarging
            state.isControllerActive = flags.isControllerActive
            state.isCurrentLimited = flags.isCurrentLimited
        default:
            return
        }
        publish()
    }
}