Trio/FreeAPS/Sources/APS/FetchGlucoseManager.swift

import Combine
import Foundation
import SwiftDate
import Swinject

protocol FetchGlucoseManager {}

final class BaseFetchGlucoseManager: FetchGlucoseManager, Injectable {
    private let processQueue = DispatchQueue(label: "BaseGlucoseManager.processQueue")
    @Injected() var glucoseStorage: GlucoseStorage!
    @Injected() var nightscoutManager: NightscoutManager!
    @Injected() var apsManager: APSManager!
    @Injected() var settingsManager: SettingsManager!

    private var lifetime = Lifetime()
    private let timer = DispatchTimer(timeInterval: 1.minutes.timeInterval)

    private lazy var appGroupSource = AppGroupSource()

    init(resolver: Resolver) {
        injectServices(resolver)
        subscribe()
    }

    var glucoseSource: AnyPublisher<[BloodGlucose], Never> {
        switch settingsManager.settings.cgm {
        case .xdrip:
            return appGroupSource.fetch()
        default:
            return nightscoutManager.fetchGlucose()
        }
    }

    private func subscribe() {
        timer.publisher
            .receive(on: processQueue)
            .flatMap { date -> AnyPublisher<(Date, Date, [BloodGlucose]), Never> in
                debug(.nightscout, "FetchGlucoseManager heartbeat")
                debug(.nightscout, "Start fetching glucose")
                return Publishers.CombineLatest3(
                    Just(date),
                    Just(self.glucoseStorage.syncDate()),
                    self.glucoseSource
                )
                .eraseToAnyPublisher()
            }
            .sink { date, syncDate, glucose in
                // Because of Spike dosn't respect a date query
                let filteredByDate = glucose.filter { $0.dateString > syncDate }
                let filtered = self.glucoseStorage.filterTooFrequentGlucose(filteredByDate, at: syncDate)
                if !filtered.isEmpty {
                    debug(.nightscout, "New glucose found")
                    self.glucoseStorage.storeGlucose(filtered)
                    self.apsManager.heartbeat(date: date, force: false)
                }
            }
            .store(in: &lifetime)
        timer.fire()
        timer.resume()
    }
}