Tusker/Tusker/Screens/Preferences/Notifications/PushInstanceSettingsView.swift

//
//  PushInstanceSettingsView.swift
//  Tusker
//
//  Created by Shadowfacts on 4/7/24.
//  Copyright © 2024 Shadowfacts. All rights reserved.
//

import SwiftUI
import UserAccounts
import Pachyderm
import PushNotifications
import TuskerComponents

struct PushInstanceSettingsView: View {
    let account: UserAccountInfo
    let pushProxyRegistration: PushProxyRegistration
    @State private var mode: AsyncToggle.Mode
    @State private var error: Error?
    @State private var subscription: PushNotifications.PushSubscription?
    
    @MainActor
    init(account: UserAccountInfo, pushProxyRegistration: PushProxyRegistration) {
        self.account = account
        self.pushProxyRegistration = pushProxyRegistration
        let subscription = PushManager.shared.pushSubscription(account: account)
        self.subscription = subscription
        self.mode = subscription == nil ? .off : .on
    }
    
    var body: some View {
        VStack(alignment: .prefsAvatar) {
            HStack {
                PrefsAccountView(account: account)
                Spacer()
                AsyncToggle("\(account.instanceURL.host!) notifications enabled", labelHidden: true, mode: $mode, onChange: updateNotificationsEnabled(enabled:))
                    .labelsHidden()
            }
            PushSubscriptionView(account: account, subscription: subscription, updateSubscription: updateSubscription)
        }
        .alertWithData("An Error Occurred", data: $error) { data in
            Button("OK") {}
        } message: { data in
            Text(data.localizedDescription)
        }
    }
    
    private func updateNotificationsEnabled(enabled: Bool) async -> Bool {
        if enabled {
            do {
                try await enableNotifications()
            } catch {
                PushManager.logger.error("Error creating instance subscription: \(String(describing: error))")
                self.error = .enabling(error)
                return false
            }
        } else {
            do {
                try await disableNotifications()
            } catch {
                PushManager.logger.error("Error removing instance subscription: \(String(describing: error))")
                self.error = .disabling(error)
                return false
            }
        }
        return true
    }
    
    private func enableNotifications() async throws {
        let subscription = try await PushManager.shared.createSubscription(account: account)
        let req = Pachyderm.PushSubscription.create(
            endpoint: pushProxyRegistration.endpoint,
            // mastodon docs just say "Base64 encoded string of a public key from a ECDH keypair using the prime256v1 curve."
            // other apps use SecKeyCopyExternalRepresentation which is documented to use X9.63 for elliptic curve keys
            // and that seems to work
            publicKey: subscription.secretKey.publicKey.x963Representation,
            authSecret: subscription.authSecret,
            alerts: .init(subscription.alerts),
            policy: .init(subscription.policy)
        )
        let mastodonController = await MastodonController.getForAccount(account)
        do {
            let (result, _) = try await mastodonController.run(req)
            PushManager.logger.debug("Push subscription \(result.id) created on \(account.instanceURL)")
            self.subscription = subscription
        } catch {
            // if creation failed, remove the subscription locally as well
            await PushManager.shared.removeSubscription(account: account)
            throw error
        }
    }
    
    private func disableNotifications() async throws {
        let req = Pachyderm.PushSubscription.delete()
        let mastodonController = await MastodonController.getForAccount(account)
        _ = try await mastodonController.run(req)
        await PushManager.shared.removeSubscription(account: account)
        subscription = nil
        PushManager.logger.debug("Push subscription removed on \(account.instanceURL)")
    }
    
    private func updateSubscription(alerts: PushNotifications.PushSubscription.Alerts, policy: PushNotifications.PushSubscription.Policy) async -> Bool {
        let req = Pachyderm.PushSubscription.update(alerts: .init(alerts), policy: .init(policy))
        let mastodonController = await MastodonController.getForAccount(account)
        do {
            let (result, _) = try await mastodonController.run(req)
            PushManager.logger.debug("Push subscription \(result.id) updated on \(account.instanceURL)")
            subscription?.alerts = alerts
            subscription?.policy = policy
            return true
        } catch {
            PushManager.logger.error("Error updating subscription: \(String(describing: error))")
            self.error = .updating(error)
            return false
        }
    }
}

private enum Error: LocalizedError {
    case enabling(any Swift.Error)
    case disabling(any Swift.Error)
    case updating(any Swift.Error)

    var errorDescription: String? {
        switch self {
        case .enabling(let error):
            "Enabling push: \(error.localizedDescription)"
        case .disabling(let error):
            "Disabling push: \(error.localizedDescription)"
        case .updating(let error):
            "Updating settings: \(error.localizedDescription)"
        }
    }
}

private extension Pachyderm.PushSubscription.Alerts {
    init(_ alerts: PushNotifications.PushSubscription.Alerts) {
        self.init(
            mention: alerts.contains(.mention),
            status: alerts.contains(.status),
            reblog: alerts.contains(.reblog),
            follow: alerts.contains(.follow),
            followRequest: alerts.contains(.followRequest),
            favourite: alerts.contains(.favorite),
            poll: alerts.contains(.poll),
            update: alerts.contains(.update)
        )
    }
}

private extension Pachyderm.PushSubscription.Policy {
    init(_ policy: PushNotifications.PushSubscription.Policy) {
        switch policy {
        case .all:
            self = .all
        case .followers:
            self = .followers
        case .followed:
            self = .followed
        }
    }
}

//#Preview {
//    PushInstanceSettingsView()
//}