refactor: remove IntegrationState and simplify IntegrationPlugin

android/src/main/kotlin/com/rudderstack/sdk/kotlin/android/Analytics.kt

@@ -14,7 +14,6 @@ import com.rudderstack.sdk.kotlin.android.plugins.NetworkInfoPlugin
 import com.rudderstack.sdk.kotlin.android.plugins.OSInfoPlugin
 import com.rudderstack.sdk.kotlin.android.plugins.ScreenInfoPlugin
 import com.rudderstack.sdk.kotlin.android.plugins.TimezoneInfoPlugin
-import com.rudderstack.sdk.kotlin.android.plugins.devicemode.DestinationResult
 import com.rudderstack.sdk.kotlin.android.plugins.devicemode.IntegrationPlugin
 import com.rudderstack.sdk.kotlin.android.plugins.devicemode.IntegrationsManagementPlugin
 import com.rudderstack.sdk.kotlin.android.plugins.lifecyclemanagment.ActivityLifecycleManagementPlugin
@@ -80,7 +79,7 @@ class Analytics(
 
     internal val activityLifecycleManagementPlugin = ActivityLifecycleManagementPlugin()
     internal val processLifecycleManagementPlugin = ProcessLifecycleManagementPlugin()
-    private var integrationsManagementPlugin: IntegrationsManagementPlugin? = null
+    private var integrationsManagementPlugin = IntegrationsManagementPlugin()
     private val sessionTrackingPlugin = SessionTrackingPlugin()
 
     init {
@@ -134,15 +133,15 @@ class Analytics(
         super.reset(clearAnonymousId)
 
         sessionTrackingPlugin.refreshSession()
-        this.integrationsManagementPlugin?.reset()
+        integrationsManagementPlugin.reset()
     }
 
     override fun flush() {
         if (!isAnalyticsActive()) return
 
         super.flush()
 
-        this.integrationsManagementPlugin?.flush()
+        integrationsManagementPlugin.flush()
     }
 
     /**
@@ -227,9 +226,7 @@ class Analytics(
     fun addIntegration(plugin: IntegrationPlugin) {
         if (!isAnalyticsActive()) return
 
-        initIntegrationsManagementPlugin()
-
-        integrationsManagementPlugin?.addIntegration(plugin)
+        integrationsManagementPlugin.addIntegration(plugin)
     }
 
     /**
@@ -240,29 +237,7 @@ class Analytics(
     fun removeIntegration(plugin: IntegrationPlugin) {
         if (!isAnalyticsActive()) return
 
-        integrationsManagementPlugin?.removeIntegration(plugin)
-    }
-
-    /**
-     * Registers a callback to be invoked when the destination of the [plugin] is ready.
-     *
-     * @param plugin The [IntegrationPlugin] for which the callback needs to be invoked.
-     * @param onReady The callback to be invoked when the destination is ready.
-     */
-    fun onDestinationReady(plugin: IntegrationPlugin, onReady: (Any?, DestinationResult) -> Unit) {
-        if (!isAnalyticsActive()) return
-
-        initIntegrationsManagementPlugin()
-
-        integrationsManagementPlugin?.onDestinationReady(plugin, onReady)
-    }
-
-    private fun initIntegrationsManagementPlugin() {
-        synchronized(this) {
-            if (integrationsManagementPlugin == null) {
-                integrationsManagementPlugin = IntegrationsManagementPlugin().also { add(it) }
-            }
-        }
+        integrationsManagementPlugin.removeIntegration(plugin)
     }
 
     private fun setup() {
@@ -276,6 +251,7 @@ class Analytics(
         add(ScreenInfoPlugin())
         add(TimezoneInfoPlugin())
         add(sessionTrackingPlugin)
+        add(integrationsManagementPlugin)
 
         // Add these plugins at last in chain
         add(AndroidLifecyclePlugin())

android/src/main/kotlin/com/rudderstack/sdk/kotlin/android/plugins/devicemode/DestinationResult.kt

@@ -5,4 +5,4 @@ import com.rudderstack.sdk.kotlin.core.internals.utils.Result
 /**
  * The result of a destination initialisation returned in `onDestinationReady` callback.
  */
-typealias DestinationResult = Result<Unit, Exception>
+typealias DestinationResult = Result<Unit, Throwable>

android/src/main/kotlin/com/rudderstack/sdk/kotlin/android/plugins/devicemode/IntegrationPlugin.kt

@@ -1,14 +1,16 @@
 package com.rudderstack.sdk.kotlin.android.plugins.devicemode
 
-import com.rudderstack.sdk.kotlin.android.Configuration
 import com.rudderstack.sdk.kotlin.core.Analytics
 import com.rudderstack.sdk.kotlin.core.internals.logger.LoggerAnalytics
 import com.rudderstack.sdk.kotlin.core.internals.models.Destination
 import com.rudderstack.sdk.kotlin.core.internals.models.Event
 import com.rudderstack.sdk.kotlin.core.internals.models.SourceConfig
+import com.rudderstack.sdk.kotlin.core.internals.models.emptyJsonObject
 import com.rudderstack.sdk.kotlin.core.internals.plugins.EventPlugin
 import com.rudderstack.sdk.kotlin.core.internals.plugins.Plugin
 import com.rudderstack.sdk.kotlin.core.internals.plugins.PluginChain
+import com.rudderstack.sdk.kotlin.core.internals.utils.Result
+import com.rudderstack.sdk.kotlin.core.internals.utils.safelyExecute
 import kotlinx.serialization.json.JsonObject
 import java.util.concurrent.CopyOnWriteArrayList
 
@@ -18,44 +20,51 @@ import java.util.concurrent.CopyOnWriteArrayList
  * An integration plugin is a plugin that is responsible for sending events directly
  * to a 3rd party destination without sending it to Rudder server first.
  */
-@Suppress("TooGenericExceptionCaught")
+@Suppress("TooManyFunctions")
 abstract class IntegrationPlugin : EventPlugin {
 
     final override val pluginType: Plugin.PluginType = Plugin.PluginType.Destination
 
     final override lateinit var analytics: Analytics
 
+    private lateinit var pluginChain: PluginChain
+    private val pluginList = CopyOnWriteArrayList<Plugin>()
+    private val destinationReadyCallbacks = mutableListOf<(Any?, DestinationResult) -> Unit>()
+
+    @Volatile
+    private var isPluginSetup = false
+
+    @Volatile
+    internal var isDestinationReady = false
+        private set
+
     /**
      * The key for the destination present in the source config.
      */
     abstract val key: String
 
+    /**
+     * The configuration for the destination.
+     * This variable always holds the latest configuration for the destination from [SourceConfig].
+     */
     @Volatile
-    internal var destinationState: DestinationState = DestinationState.Uninitialised
+    var destinationConfig: JsonObject = emptyJsonObject
         private set
 
-    private lateinit var pluginChain: PluginChain
-    private val pluginList = CopyOnWriteArrayList<Plugin>()
-
     /**
      * Creates the destination instance. Override this method for the initialisation of destination.
      * This method must return true if the destination was created successfully, false otherwise.
      *
      * @param destinationConfig The configuration for the destination.
-     * @param analytics The analytics instance.
-     * @param config The configuration instance.
-     * @return true if the destination was created successfully, false otherwise.
      */
-    protected abstract fun create(destinationConfig: JsonObject, analytics: Analytics, config: Configuration): Boolean
+    protected abstract fun create(destinationConfig: JsonObject)
 
     /**
      * Returns the instance of the destination which was created.
      *
      * @return The instance of the destination.
      */
-    open fun getUnderlyingInstance(): Any? {
-        return null
-    }
+    abstract fun getDestinationInstance(): Any?
 
     /**
      * Override this method to control the behaviour of [Analytics.flush] for this destination.
@@ -71,50 +80,31 @@ abstract class IntegrationPlugin : EventPlugin {
         super.setup(analytics)
 
         pluginChain = PluginChain().also { it.analytics = analytics }
+        isPluginSetup = true
+        applyDefaultPlugins()
+        applyCustomPlugins()
     }
 
-    internal fun initialize(sourceConfig: SourceConfig) {
+    internal fun findAndInitDestination(sourceConfig: SourceConfig) {
         findDestination(sourceConfig)?.let { configDestination ->
             if (!configDestination.isDestinationEnabled) {
-                val errorMessage = "Destination $key is disabled in dashboard. No events will be sent to this destination."
-                LoggerAnalytics.warn(errorMessage)
-                destinationState = DestinationState.Failed(SdkNotInitializedException(errorMessage))
+                val errorMessage = "Destination $key is disabled in dashboard. " +
+                    "No events will be sent to this destination."
+                LoggerAnalytics.warn("IntegrationPlugin: $errorMessage")
+                setFailureConfigAndNotifyCallbacks(IllegalStateException(errorMessage))
                 return
             }
-
-            try {
-                when (
-                    create(
-                        configDestination.destinationConfig,
-                        analytics,
-                        analytics.configuration as Configuration
-                    )
-                ) {
-                    true -> {
-                        destinationState = DestinationState.Ready
-                        LoggerAnalytics.debug("IntegrationPlugin: Destination $key is ready.")
-                        applyDefaultPlugins()
-                        applyCustomPlugins()
-                    }
-                    false -> {
-                        val errorMessage = "Destination $key failed to initialise."
-                        destinationState = DestinationState.Failed(SdkNotInitializedException(errorMessage))
-                        LoggerAnalytics.warn("IntegrationPlugin: $errorMessage")
-                    }
-                }
-            } catch (e: Exception) {
-                destinationState = DestinationState.Failed(e)
-                LoggerAnalytics.error("IntegrationPlugin: Error: ${e.message} initializing destination $key.")
-            }
+            createSafelyAndNotifyCallbacks(configDestination.destinationConfig)
         } ?: run {
-            val errorMessage = "Destination $key not found in the source config. No events will be sent to this destination."
-            destinationState = DestinationState.Failed(SdkNotInitializedException(errorMessage))
+            val errorMessage = "Destination $key not found in the source config. " +
+                "No events will be sent to this destination."
             LoggerAnalytics.warn("IntegrationPlugin: $errorMessage")
+            setFailureConfigAndNotifyCallbacks(IllegalStateException(errorMessage))
         }
     }
 
     final override suspend fun intercept(event: Event): Event {
-        if (destinationState.isReady()) {
+        if (isDestinationReady) {
             event.copy<Event>()
                 .let { pluginChain.applyPlugins(Plugin.PluginType.PreProcess, it) }
                 ?.let { pluginChain.applyPlugins(Plugin.PluginType.OnProcess, it) }
@@ -130,10 +120,9 @@ abstract class IntegrationPlugin : EventPlugin {
      * **Note**: Calling of `super.teardown()` is recommended when overriding this method.
      */
     override fun teardown() {
-        if (destinationState.isReady()) {
+        pluginList.clear()
+        if (isPluginSetup) {
             pluginChain.removeAll()
-        } else {
-            pluginList.clear()
         }
     }
 
@@ -143,7 +132,7 @@ abstract class IntegrationPlugin : EventPlugin {
      * @param plugin The plugin to be added.
      */
     fun add(plugin: Plugin) {
-        if (destinationState.isReady()) {
+        if (isPluginSetup) {
             pluginChain.add(plugin)
         } else {
             pluginList.add(plugin)
@@ -156,10 +145,66 @@ abstract class IntegrationPlugin : EventPlugin {
      * @param plugin The plugin to be removed.
      */
     fun remove(plugin: Plugin) {
-        if (destinationState.isReady()) {
+        pluginList.remove(plugin)
+        if (isPluginSetup) {
             pluginChain.remove(plugin)
-        } else {
-            pluginList.remove(plugin)
+        }
+    }
+
+    /**
+     * Registers a callback to be invoked when the destination of this plugin is ready.
+     *
+     * @param callback The callback to be invoked when the destination is ready.
+     */
+    fun onDestinationReady(callback: (Any?, DestinationResult) -> Unit) {
+        getDestinationInstance()?.let { destinationInstance ->
+            if (isDestinationReady) {
+                callback(destinationInstance, Result.Success(Unit))
+            } else {
+                callback(
+                    null,
+                    Result.Failure(null, IllegalStateException("Destination $key is absent or disabled in dashboard."))
+                )
+            }
+        } ?: run {
+            synchronized(this) {
+                destinationReadyCallbacks.add(callback)
+            }
+        }
+    }
+
+    private fun createSafelyAndNotifyCallbacks(destinationConfig: JsonObject) {
+        safelyExecute(
+            block = {
+                if (getDestinationInstance() == null) {
+                    create(destinationConfig)
+                }
+                LoggerAnalytics.debug("IntegrationPlugin: Destination $key created successfully.")
+                setSuccessConfigAndNotifyCallbacks(destinationConfig)
+            },
+            onException = { exception ->
+                LoggerAnalytics.error("IntegrationPlugin: Error: ${exception.message} initializing destination $key.")
+                setFailureConfigAndNotifyCallbacks(exception)
+            }
+        )
+    }
+
+    private fun setFailureConfigAndNotifyCallbacks(throwable: Throwable) {
+        this.destinationConfig = emptyJsonObject
+        this.isDestinationReady = false
+        notifyCallbacks(Result.Failure(null, throwable))
+    }
+
+    private fun setSuccessConfigAndNotifyCallbacks(destinationConfig: JsonObject) {
+        this.destinationConfig = destinationConfig
+        this.isDestinationReady = true
+        notifyCallbacks(Result.Success(Unit))
+    }
+
+    private fun notifyCallbacks(destinationResult: DestinationResult) {
+        synchronized(this) {
+            destinationReadyCallbacks.forEach { callback -> callback(getDestinationInstance(), destinationResult) }
+            destinationReadyCallbacks.clear()
         }
     }
 
@@ -176,13 +221,3 @@ abstract class IntegrationPlugin : EventPlugin {
         return sourceConfig.source.destinations.firstOrNull { it.destinationDefinition.displayName == key }
     }
 }
-
-internal sealed interface DestinationState {
-    data object Ready : DestinationState
-    data object Uninitialised : DestinationState
-    data class Failed(
-        val exception: Exception
-    ) : DestinationState
-
-    fun isReady() = this == Ready
-}