Hide API key from code by using expect/actual for OpenAPI key

.github/workflows/main.yml

@@ -1,4 +1,4 @@
-name: androidTest
+name: tests
 
 on:
   pull_request:
@@ -9,6 +9,8 @@ on:
 jobs:
   build:
     runs-on: ubuntu-latest
+    env:
+      OPEN_API_KEY: ${{ secrets.OPEN_API_KEY }}
 
     steps:
       - name: Checkout 

composeApp/build.gradle.kts

@@ -1,9 +1,11 @@
+import com.android.build.api.dsl.ApplicationDefaultConfig
 import org.jetbrains.compose.desktop.application.dsl.TargetFormat
 import org.jetbrains.kotlin.gradle.ExperimentalKotlinGradlePluginApi
 import org.jetbrains.kotlin.gradle.ExperimentalWasmDsl
 import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 import org.jetbrains.kotlin.gradle.targets.js.webpack.KotlinWebpackConfig
 import org.jlleitschuh.gradle.ktlint.reporter.ReporterType
+import java.util.Properties
 
 plugins {
     alias(libs.plugins.kotlinMultiplatform)
@@ -118,6 +120,9 @@ android {
         targetSdk = libs.versions.android.targetSdk.get().toInt()
         versionCode = 1
         versionName = "1.0"
+
+        val properties = getLocalProperties()
+        setupBuildConfigFields(properties = properties)
     }
     packaging {
         resources {
@@ -133,6 +138,9 @@ android {
         sourceCompatibility = JavaVersion.VERSION_11
         targetCompatibility = JavaVersion.VERSION_11
     }
+    buildFeatures {
+        buildConfig = true
+    }
 }
 
 dependencies {
@@ -149,4 +157,25 @@ compose.desktop {
             packageVersion = "1.0.0"
         }
     }
+}
+
+fun ApplicationDefaultConfig.setupBuildConfigFields(
+    properties: Properties,
+) {
+    fun secret(key: String): String = System.getenv(key) ?: properties.getProperty(key, "")
+
+    if (secret("OPEN_API_KEY").isEmpty()) {
+        error("OPEN_API_KEY not set in local.properties")
+    }
+
+    buildConfigField(type = "String", name = "OPEN_API_KEY", value = "\"${secret("OPEN_API_KEY")}\"")
+}
+
+fun getLocalProperties(): Properties {
+    return Properties().apply {
+        val file = rootProject.file("local.properties")
+        if (file.exists()) {
+            file.inputStream().use { load(it) }
+        }
+    }
 }

composeApp/src/androidMain/kotlin/com/developersbreach/kotlindictionarymultiplatform/Platform.android.kt

@@ -6,4 +6,6 @@ class AndroidPlatform : Platform {
     override val name: String = "Android ${Build.VERSION.SDK_INT}"
 }
 
-actual fun getPlatform(): Platform = AndroidPlatform()
+actual fun getPlatform(): Platform = AndroidPlatform()
+
+actual fun getOpenApiKey() = BuildConfig.OPEN_API_KEY

composeApp/src/commonMain/kotlin/com/developersbreach/kotlindictionarymultiplatform/Platform.kt

@@ -4,4 +4,6 @@ interface Platform {
     val name: String
 }
 
-expect fun getPlatform(): Platform
+expect fun getPlatform(): Platform
+
+expect fun getOpenApiKey(): String

composeApp/src/commonMain/kotlin/com/developersbreach/kotlindictionarymultiplatform/data/detail/repository/DetailRepository.kt

@@ -1,14 +1,14 @@
 package com.developersbreach.kotlindictionarymultiplatform.data.detail.repository
 
 import arrow.core.Either
-import com.developersbreach.kotlindictionarymultiplatform.core.network.API_KEY
 import com.developersbreach.kotlindictionarymultiplatform.core.network.KtorHttpClient
 import com.developersbreach.kotlindictionarymultiplatform.data.detail.model.KotlinTopicDetails
+import com.developersbreach.kotlindictionarymultiplatform.getOpenApiKey
 
 class DetailRepository {
 
     suspend fun fetchTopic(topicId: String): Either<Throwable, KotlinTopicDetails> =
         Either.catch {
-            KtorHttpClient.generateTopicDetails(topicId, API_KEY)
+            KtorHttpClient.generateTopicDetails(topicId, getOpenApiKey())
         }
 }

composeApp/src/desktopMain/kotlin/com/developersbreach/kotlindictionarymultiplatform/Platform.desktop.kt

@@ -0,0 +1,3 @@
+package com.developersbreach.kotlindictionarymultiplatform
+
+actual fun getOpenApiKey(): String = ""

composeApp/src/nativeMain/kotlin/com/developersbreach/kotlindictionarymultiplatform/Platform.native.kt

@@ -0,0 +1,3 @@
+package com.developersbreach.kotlindictionarymultiplatform
+
+actual fun getOpenApiKey(): String = ""

composeApp/src/wasmJsMain/kotlin/com/developersbreach/kotlindictionarymultiplatform/Platform.wasmJs.kt

@@ -4,4 +4,6 @@ class WasmPlatform : Platform {
     override val name: String = "Web with Kotlin/Wasm"
 }
 
-actual fun getPlatform(): Platform = WasmPlatform()
+actual fun getPlatform(): Platform = WasmPlatform()
+
+actual fun getOpenApiKey(): String = ""