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72 lines
2.9 KiB
Kotlin
72 lines
2.9 KiB
Kotlin
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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package org.mozilla.fenix.perf
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import org.mozilla.fenix.perf.StartupTimelineStateMachine.StartupDestination.APP_LINK
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import org.mozilla.fenix.perf.StartupTimelineStateMachine.StartupDestination.HOMESCREEN
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import org.mozilla.fenix.perf.StartupTimelineStateMachine.StartupDestination.UNKNOWN
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/**
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* A state machine representing application startup for use with [StartupTimeline]. Android
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* application startup is complex so it's helpful to make all of our expected states explicit, e.g.
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* with a state machine, which helps check our assumptions. Unfortunately, because this state machine
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* is not used by the framework to determine possible startup scenarios, this is duplicating the
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* startup logic and is thus extremely fragile (especially because most devs won't know about this
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* class when they change the startup flow!). We may be able to mitigate this with assertions.
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*
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* To devs changing this class: by design as a state machine, this class should never hold any state
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* and should be 100% unit tested to validate assumptions.
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*/
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object StartupTimelineStateMachine {
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/**
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* The states the application passes through during startup. We define these states to help us
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* better understand Android startup. Note that these states are not 100% correlated to the
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* cold/warm/hot states Google Play Vitals uses.
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*/
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sealed class StartupState {
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/** The state when the application is starting up but is not in memory. */
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data class Cold(val destination: StartupDestination) : StartupState()
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}
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/**
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* The final screen the user will see during startup.
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*/
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enum class StartupDestination {
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HOMESCREEN,
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APP_LINK,
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UNKNOWN,
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}
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/**
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* A list of Activities supported by the app.
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*/
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enum class StartupActivity {
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HOME,
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INTENT_RECEIVER,
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}
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/**
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* Given the current state and any arguments, returns the next state of the state machine.
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*/
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fun getNextState(currentState: StartupState, startingActivity: StartupActivity): StartupState {
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return when (currentState) {
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is StartupState.Cold -> nextStateIsCold(currentState, startingActivity)
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}
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}
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private fun nextStateIsCold(currentState: StartupState.Cold, startingActivity: StartupActivity): StartupState {
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return when (currentState.destination) {
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UNKNOWN -> when (startingActivity) {
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StartupActivity.HOME -> StartupState.Cold(HOMESCREEN)
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StartupActivity.INTENT_RECEIVER -> StartupState.Cold(APP_LINK)
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}
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// We haven't defined the state machine after these states yet so we return the current state.
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else -> currentState
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}
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}
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}
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