POC Kotlin provider (#1213)

Signed-off-by: Thomas Poignant <[email protected]>

openfeature/providers/kotlin-provider/.gitignore

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+*.iml
+.gradle
+/local.properties
+/.idea/caches
+/.idea/libraries
+/.idea/modules.xml
+/.idea/workspace.xml
+/.idea/navEditor.xml
+/.idea/assetWizardSettings.xml
+.DS_Store
+/build
+/captures
+.externalNativeBuild
+.cxx
+local.properties

openfeature/providers/kotlin-provider/README.md

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+# GO Feature Flag Kotlin OpenFeature Provider for Android
+
+![Static Badge](https://img.shields.io/badge/status-experimental-red)
+
+This OpenFeature provider is a Kotlin implementation for Android to communicate with the GO Feature
+Flag Server.
+
+The OpenFeature Kotlin is experimental, and the provider is also experimental.  
+We don't recommend using this in production yet.
+
+## About this provider
+
+[GO Feature Flag](https://gofeatureflag.org) provider allows you to connect to your GO Feature Flag
+instance with the OpenFeature Kotlin SDK.
+
+This is a client provider made for Android, we do not recommend using it in a server environment.  
+If you want to use it in a server environment, you should use
+the [`Java` provider](https://gofeatureflag.org/docs/openfeature_sdk/server_providers/openfeature_java).
+
+## What is GO Feature Flag?
+
+GO Feature Flag is a simple, complete and lightweight self-hosted feature flag solution 100% Open
+Source.  
+Our focus is to avoid any complex infrastructure work to use GO Feature Flag.
+
+This is a complete feature flagging solution with the possibility to target only a group of users,
+use any types of flags, store your configuration in various location and advanced rollout
+functionality. You can also collect usage data of your flags and be notified of configuration
+changes.
+
+## Install the provider
+
+TODO
+
+## How to use the provider?
+
+```kotlin
+val evaluationContext = ImmutableContext(
+    targetingKey = "0a23d9a5-0a8f-42c9-9f5f-4de3afd6cf99",
+    attributes = mutableMapOf(
+        "region" to Value.String("us-east-1"),
+        "email" to Value.String("[email protected]")
+    )
+)
+
+OpenFeatureAPI.setProvider(
+    GoFeatureFlagProvider(
+        options = GoFeatureFlagOptions(
+            endpoint = "http://localhost:1031"
+        )
+    ), evaluationContext
+)
+
+val client = OpenFeatureAPI.getClient("my-client")
+if (client.getBooleanValue("my-flag", false)) {
+    println("my-flag is enabled")
+}
+OpenFeatureAPI.shutdown()
+```
+
+### Available options
+
+| Option name        | Type   | Default | Description                                                                                                                                                                                     |
+|--------------------|--------|---------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| endpoint           | String |         | endpoint is the URL where your GO Feature Flag server is located.                                                                                                                               |
+| timeout            | Long   | 10000   | (optional) timeout is the time in millisecond we wait for an answer from the server.                                                                                                            |
+| maxIdleConnections | Int    | 1000    | (optional) maxIdleConnections is the maximum number of connexions in the connexion pool.                                                                                                        |
+| keepAliveDuration  | Long   | 7200000 | (optional) keepAliveDuration is the time in millisecond we keep the connexion open.                                                                                                             |
+| apiKey             | String |         | (optional) If GO Feature Flag is configured to authenticate the requests, you should provide an API Key to the provider. Please ask the administrator of the relay proxy to provide an API Key. |
+| retryDelay         | Long   | 300     | (optional) delay in millisecond to wait before retrying to connect the websocket                                                                                                                |
+
+### Reconnection
+
+If the connection to the GO Feature Flag instance fails, the provider will attempt to reconnect.
+
+### Event streaming
+
+Event streaming is not implemented yet in the GO Feature Flag provider.
+
+## Features status
+
+| Status | Feature            | Description                                                                          |
+|--------|--------------------|--------------------------------------------------------------------------------------|
+| ✅      | Flag evaluation    | It is possible to evaluate all the type of flags                                     |
+| ✅      | Cache invalidation | Websocket mechanism is in place to refresh the cache in case of configuration change |
+| ❌      | Logging            | Not supported by the SDK                                                             |
+| ❌      | Flag Metadata      | Not supported by the SDK                                                             |
+| ❌      | Event Streaming    | Not implemented                                                                      |
+| ❌      | Unit test          | Not implemented                                                                      |
+
+<sub>Implemented: ✅ | In-progress: ⚠️ | Not implemented yet: ❌</sub>
+
+

openfeature/providers/kotlin-provider/build.gradle.kts

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+// Top-level build file where you can add configuration options common to all sub-projects/modules.
+plugins {
+    id("com.android.application") version "8.1.2" apply false
+    id("org.jetbrains.kotlin.android") version "1.9.0" apply false
+    id("com.android.library") version "8.1.2" apply false
+}
+
+allprojects {
+    extra["groupId"] = "org.gofeatureflag.openfeature"
+    ext["version"] = "0.0.1"
+}
+
+group = project.extra["groupId"].toString()
+version = project.extra["version"].toString()

openfeature/providers/kotlin-provider/gofeatureflag-kotlin-provider/.gitignore

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+/build

openfeature/providers/kotlin-provider/gofeatureflag-kotlin-provider/build.gradle.kts

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+plugins {
+    id("com.android.library")
+    id("org.jetbrains.kotlin.android")
+}
+
+val releaseVersion = project.extra["version"].toString()
+
+android {
+    namespace = "org.gofeatureflag.openfeature"
+    compileSdk = 33
+
+    defaultConfig {
+        minSdk = 21
+        version = releaseVersion
+        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
+    }
+
+    buildTypes {
+        release {
+            isMinifyEnabled = false
+            proguardFiles(
+                getDefaultProguardFile("proguard-android-optimize.txt"),
+                "proguard-rules.pro"
+            )
+        }
+    }
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_11
+        targetCompatibility = JavaVersion.VERSION_11
+    }
+    kotlinOptions {
+        jvmTarget = JavaVersion.VERSION_11.toString()
+    }
+}
+
+dependencies {
+    implementation("dev.openfeature:kotlin-sdk:0.0.4")
+    implementation("com.squareup.okhttp3:okhttp:4.12.0")
+    implementation("com.google.code.gson:gson:2.8.9")
+    implementation("dev.gustavoavila:java-android-websocket-client:2.0.2")
+    testImplementation("junit:junit:4.13.2")
+    testImplementation("org.jetbrains.kotlinx:kotlinx-coroutines-test:1.7.3")
+    testImplementation("com.squareup.okhttp3:mockwebserver:4.12.0")
+}

openfeature/providers/kotlin-provider/gofeatureflag-kotlin-provider/proguard-rules.pro

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+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# proguardFiles setting in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Uncomment this to preserve the line number information for
+# debugging stack traces.
+#-keepattributes SourceFile,LineNumberTable
+
+# If you keep the line number information, uncomment this to
+# hide the original source file name.
+#-renamesourcefileattribute SourceFile

openfeature/providers/kotlin-provider/gofeatureflag-kotlin-provider/src/main/AndroidManifest.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+
+</manifest>

openfeature/providers/kotlin-provider/gofeatureflag-kotlin-provider/src/main/java/org/gofeatureflag/openfeature/GoFeatureFlagMetadata.kt

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+package org.gofeatureflag.openfeature
+
+import dev.openfeature.sdk.ProviderMetadata
+import java.security.Provider
+
+class GoFeatureFlagMetadata() : ProviderMetadata {
+    override val name: String
+        get() = "GoFeatureFlagProvider"
+}