//
//  BTManager.swift
//  USB Meter
//
//  Created by Bogdan Timofte on 01/03/2020.
//  Copyright © 2020 Bogdan Timofte. All rights reserved.
//

import CoreBluetooth

class BluetoothManager : NSObject, ObservableObject {
    private var manager: CBCentralManager?
    private var isStarting = false
    private var advertisementDataCache = AdvertisementDataCache()
    @Published var managerState = CBManagerState.unknown
    @Published private(set) var scanStartedAt: Date?
    
    override init () {
        super.init()
    }
    
    func start() {
        guard manager == nil, !isStarting else {
            return
        }
        isStarting = true
        track("Starting Bluetooth manager and requesting authorization if needed")
        DispatchQueue.main.async { [weak self] in
            guard let self else { return }
            defer { self.isStarting = false }
            guard self.manager == nil else {
                return
            }
            self.manager = CBCentralManager(delegate: self, queue: nil)
        }
    }
    
    private func scanForMeters() {
        guard let manager else {
            track("Scan requested before Bluetooth manager was started")
            return
        }
        guard manager.state == .poweredOn else {
            track( "Scan requested but Bluetooth state is \(manager.state)")
            return
        }
        //manager.scanForPeripherals(withServices: allBluetoothRadioServices(), options: [ CBCentralManagerScanOptionAllowDuplicatesKey: true ])
        manager.scanForPeripherals(withServices: allBluetoothRadioServices(), options: [ CBCentralManagerScanOptionAllowDuplicatesKey: true ])
    }
    
    func discoveredMeter(peripheral: CBPeripheral, advertising advertismentData: [String : Any], rssi RSSI: NSNumber) {
        guard let peripheralName = resolvedPeripheralName(for: peripheral, advertising: advertismentData) else {
            return
        }
        guard let manufacturerData = resolvedManufacturerData(from: advertismentData), manufacturerData.count > 2 else {
            return
        }
        
        guard let model = Model.byPeripheralName[peripheralName] else {
            return
        }
        
        let macAddress = MACAddress(from: manufacturerData.suffix(from: 2))
        let macAddressString = macAddress.description
        appData.registerMeter(macAddress: macAddressString, modelName: model.canonicalName, advertisedName: peripheralName)
        appData.noteMeterSeen(at: Date(), macAddress: macAddressString)
        
        if appData.meters[peripheral.identifier] == nil {
            track("adding new USB Meter named '\(peripheralName)' with MAC Address: '\(macAddress)'")
            let btSerial = BluetoothSerial(peripheral: peripheral, radio: model.radio, with: macAddress, managedBy: manager!, RSSI: RSSI.intValue)
            var m = appData.meters
            m[peripheral.identifier] = Meter(model: model, with: btSerial)
            appData.meters = m
        } else if let meter = appData.meters[peripheral.identifier] {
            meter.lastSeen = Date()
            meter.btSerial.updateRSSI(RSSI.intValue)
            let macAddress = meter.btSerial.macAddress.description
            if meter.name == macAddress, let syncedName = appData.meterName(for: macAddress), syncedName != macAddress {
                meter.updateNameFromStore(syncedName)
            }
            if peripheral.delegate == nil {
                peripheral.delegate = meter.btSerial
            }
        }
    }
    
    private func resolvedPeripheralName(for peripheral: CBPeripheral, advertising advertismentData: [String : Any]) -> String? {
        let candidates = [
            (advertismentData[CBAdvertisementDataLocalNameKey] as? String),
            peripheral.name
        ]
        
        for candidate in candidates {
            if let trimmed = candidate?.trimmingCharacters(in: .whitespacesAndNewlines), !trimmed.isEmpty {
                return trimmed
            }
        }
        
        return nil
    }
    
    private func resolvedManufacturerData(from advertismentData: [String : Any]) -> Data? {
        if let data = advertismentData[CBAdvertisementDataManufacturerDataKey] as? Data {
            return data
        }
        if let data = advertismentData["kCBAdvDataManufacturerData"] as? Data {
            return data
        }
        return nil
    }
}

extension BluetoothManager : CBCentralManagerDelegate {
    // MARK:  CBCentralManager state Changed
    func centralManagerDidUpdateState(_ central: CBCentralManager) {
        managerState = central.state;
        track("\(central.state)")
        
        switch central.state {
        case .poweredOff:
            scanStartedAt = nil
            track("Bluetooth is Off. How should I behave?")
        case .poweredOn:
            scanStartedAt = Date()
            track("Bluetooth is On... Start scanning...")
            // note that "didDisconnectPeripheral" won't be called if BLE is turned off while connected
            // connectedPeripheral = nil
            // pendingPeripheral = nil
            scanForMeters()
        case .resetting:
            scanStartedAt = nil
            track("Bluetooth is reseting... . Whatever that means.")
        case .unauthorized:
            scanStartedAt = nil
            track("Bluetooth is not authorized.")
        case .unknown:
            scanStartedAt = nil
            track("Bluetooth is in an unknown state.")
        case .unsupported:
            scanStartedAt = nil
            track("Bluetooth not supported by device")
        default:
            scanStartedAt = nil
            track("Bluetooth is in a state never seen before!")
        }
    }
    
    // MARK:  CBCentralManager didDiscover peripheral
    func centralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String : Any], rssi RSSI: NSNumber) {
        let completeAdvertisementData = self.advertisementDataCache.append(peripheral: peripheral, advertisementData: advertisementData)
        //track("Device discoverded UUID: '\(peripheral.identifier)' named '\(peripheral.name ?? "Unknown")'); RSSI: \(RSSI) dBm; Advertisment data: \(advertisementData)")
        discoveredMeter(peripheral: peripheral, advertising: completeAdvertisementData, rssi: RSSI )
    }
    
    // MARK:  CBCentralManager didConnect peripheral
    internal func centralManager(_ central: CBCentralManager, didConnect peripheral: CBPeripheral) {
        //track("Connected to peripheral: '\(peripheral.identifier)'")
        if let usbMeter = appData.meters[peripheral.identifier] {
            usbMeter.btSerial.connectionEstablished()
        }
        else {
            track("Connected to meter with UUID: '\(peripheral.identifier)'")
        }
    }
    
    // MARK:  CBCentralManager didDisconnectPeripheral peripheral
    internal func centralManager(_ central: CBCentralManager, didDisconnectPeripheral peripheral: CBPeripheral, error: Error?) {
        track("Disconnected from peripheral: '\(peripheral.identifier)' with error: \(error.debugDescription)")
        if let usbMeter = appData.meters[peripheral.identifier] {
            usbMeter.btSerial.connectionClosed()
        }
        else {
            track("Disconnected from meter with UUID: '\(peripheral.identifier)'")
        }
    }

    internal func centralManager(_ central: CBCentralManager, didFailToConnect peripheral: CBPeripheral, error: Error?) {
        track("Failed to connect to peripheral: '\(peripheral.identifier)' with error: \(error.debugDescription)")
        if let usbMeter = appData.meters[peripheral.identifier] {
            usbMeter.btSerial.connectionClosed()
        } else {
            track("Failed to connect to meter with UUID: '\(peripheral.identifier)'")
        }
    }
}

private class AdvertisementDataCache {
    
    private var map = [UUID: [String: Any]]()
    
    func append(peripheral: CBPeripheral, advertisementData: [String: Any]) -> [String: Any] {
        var ad = (map[peripheral.identifier]) ?? [String: Any]()
        if let localName = peripheral.name?.trimmingCharacters(in: .whitespacesAndNewlines), !localName.isEmpty {
            ad[CBAdvertisementDataLocalNameKey] = localName
        }
        for (key, value) in advertisementData {
            ad[key] = value
        }
        map[peripheral.identifier] = ad
        return ad
    }
    
    func clear() {
        map.removeAll()
    }
}
