mirror of
https://github.com/firebase/firebase-ios-sdk
synced 2026-11-11 22:55:59 +05:45
91 lines
3.2 KiB
Swift
91 lines
3.2 KiB
Swift
//
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// Copyright 2022 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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import Foundation
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private import FirebaseCoreInternal
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internal import FirebaseInstallations
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struct SessionInfo: Sendable {
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let sessionId: String
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let firstSessionId: String
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let shouldDispatchEvents: Bool
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let sessionIndex: Int32
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init(sessionId: String, firstSessionId: String, dispatchEvents: Bool, sessionIndex: Int32) {
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self.sessionId = sessionId
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self.firstSessionId = firstSessionId
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shouldDispatchEvents = dispatchEvents
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self.sessionIndex = sessionIndex
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}
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}
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///
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/// Generator is responsible for:
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/// 1) Generating the Session ID
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/// 2) Persisting and reading the Session ID from the last session
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/// (Maybe) 3) Persisting, reading, and incrementing an increasing index
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///
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/// Generation happens on whichever thread initiates a session (typically the
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/// main thread, via app lifecycle notifications), while `currentSession` is
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/// read by subscribers on their own threads. The mutable state is therefore
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/// guarded by a lock so this type can be safely `Sendable`.
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///
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final class SessionGenerator: Sendable {
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/// The generator's mutable state, only reachable while holding `state`.
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private struct State {
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var thisSession: SessionInfo?
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var firstSessionId: String = ""
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/// This will be incremented to 0 on the first generation.
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var sessionIndex: Int32 = -1
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}
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private let state = UnfairLock(State())
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private let collectEvents: Bool
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init(collectEvents: Bool) {
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self.collectEvents = collectEvents
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}
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// Generates a new Session ID. If there was already a generated Session ID
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// from the last session during the app's lifecycle, it will also set the last Session ID
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func generateNewSession() -> SessionInfo {
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// Generated outside the critical section: `UnfairLock` wraps
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// `os_unfair_lock`, which should be held only for the state
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// read-modify-write, never across allocations. The new ID is always
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// consumed, so there is no wasted work.
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let newSessionId = UUID().uuidString.replacingOccurrences(of: "-", with: "").lowercased()
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return state.withLock { state in
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// If firstSessionId is set, use it. Otherwise set it to the
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// first generated Session ID
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state.firstSessionId = state.firstSessionId.isEmpty ? newSessionId : state.firstSessionId
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state.sessionIndex += 1
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let newSession = SessionInfo(sessionId: newSessionId,
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firstSessionId: state.firstSessionId,
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dispatchEvents: collectEvents,
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sessionIndex: state.sessionIndex)
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state.thisSession = newSession
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return newSession
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}
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}
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var currentSession: SessionInfo? {
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state.withLock { $0.thisSession }
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}
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}
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