letro-ios/ElementX/Sources/Services/Analytics/PostHogAnalyticsClient.swift

//
// Copyright 2021 New Vector Ltd
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

import AnalyticsEvents
import PostHog

/// An analytics client that reports events to a PostHog server.
class PostHogAnalyticsClient: AnalyticsClientProtocol {
    private var posthogFactory: PostHogFactory = DefaultPostHogFactory()
    
    init(posthogFactory: PostHogFactory? = nil) {
        if let factory = posthogFactory {
            self.posthogFactory = factory
        }
    }
    
    /// The PHGPostHog object used to report events.
    private var postHog: PHGPostHogProtocol?
    
    /// Any user properties to be included with the next captured event.
    private(set) var pendingUserProperties: AnalyticsEvent.UserProperties?
    
    /// Super Properties are properties associated with events that are set once and then sent with every capture call, be it a $screen, an autocaptured button click, or anything else.
    /// It is different from user properties that will be attached to the user and not events.
    /// Not persisted for now, should be set on start.
    private var superProperties: AnalyticsEvent.SuperProperties?
    
    var isRunning: Bool { postHog?.enabled ?? false }
    
    func start(analyticsConfiguration: AnalyticsConfiguration) {
        // Only start if analytics have been configured in BuildSettings
        guard let configuration = PHGPostHogConfiguration.standard(analyticsConfiguration: analyticsConfiguration) else { return }
        
        if postHog == nil {
            postHog = posthogFactory.createPostHog(config: configuration)
        }
        // Add super property cryptoSDK to the captured events, to allow easy
        // filtering of events across different client by using same filter.
        superProperties = AnalyticsEvent.SuperProperties(appPlatform: nil, cryptoSDK: .Rust, cryptoSDKVersion: nil)
        postHog?.enable()
    }
    
    func reset() {
        postHog?.reset()
        pendingUserProperties = nil
    }
    
    func stop() {
        postHog?.disable()
        
        // As of PostHog 1.4.4, setting the client to nil here doesn't release
        // it. Keep it around to avoid having multiple instances if the user re-enables
    }
    
    func capture(_ event: AnalyticsEventProtocol) {
        guard isRunning else { return }
        postHog?.capture(event.eventName, properties: attachUserProperties(to: attachSuperProperties(to: event.properties)))
    }
    
    func screen(_ event: AnalyticsScreenProtocol) {
        guard isRunning else { return }
        postHog?.screen(event.screenName.rawValue, properties: attachUserProperties(to: attachSuperProperties(to: event.properties)))
    }
    
    func updateUserProperties(_ userProperties: AnalyticsEvent.UserProperties) {
        guard let pendingUserProperties else {
            pendingUserProperties = userProperties
            return
        }
        
        // Merge the updated user properties with the existing ones
        self.pendingUserProperties = AnalyticsEvent.UserProperties(allChatsActiveFilter: userProperties.allChatsActiveFilter ?? pendingUserProperties.allChatsActiveFilter,
                                                                   ftueUseCaseSelection: userProperties.ftueUseCaseSelection ?? pendingUserProperties.ftueUseCaseSelection,
                                                                   numFavouriteRooms: userProperties.numFavouriteRooms ?? pendingUserProperties.numFavouriteRooms,
                                                                   numSpaces: userProperties.numSpaces ?? pendingUserProperties.numSpaces)
    }
    
    func updateSuperProperties(_ updatedProperties: AnalyticsEvent.SuperProperties) {
        guard let currentProperties = superProperties else {
            superProperties = updatedProperties
            return
        }
        
        superProperties = AnalyticsEvent.SuperProperties(appPlatform: updatedProperties.appPlatform ??
            currentProperties.appPlatform,
            cryptoSDK: updatedProperties.cryptoSDK ??
                currentProperties.cryptoSDK,
            cryptoSDKVersion: updatedProperties.cryptoSDKVersion ??
                currentProperties.cryptoSDKVersion)
    }
    
    // MARK: - Private
    
    /// Given a dictionary containing properties from an event, this method will return those properties
    /// with any pending user properties included under the `$set` key.
    /// - Parameter properties: A dictionary of properties from an event.
    /// - Returns: The `properties` dictionary with any user properties included.
    private func attachUserProperties(to properties: [String: Any]) -> [String: Any] {
        guard isRunning, let userProperties = pendingUserProperties else { return properties }
        
        var properties = properties
        
        // As user properties overwrite old ones via $set, compactMap the dictionary to avoid resetting any missing properties
        properties["$set"] = userProperties.properties.compactMapValues { $0 }
        pendingUserProperties = nil
        return properties
    }
    
    /// Attach super properties to events.
    /// If the property is already set on the event, the already set value will be kept.
    private func attachSuperProperties(to properties: [String: Any]) -> [String: Any] {
        guard isRunning, let superProperties else { return properties }
        
        var properties = properties
        
        superProperties.properties.forEach { (key: String, value: Any) in
            if properties[key] == nil {
                properties[key] = value
            }
        }
        return properties
    }
}