chore: add Gradle convention plugin for injecting build-time secrets

build-logic/src/main/kotlin/gwenedeg.secrets.gradle.kts

@@ -0,0 +1,84 @@
+import java.util.Properties
+
+/**
+ * Injects build-time secrets into `commonMain` so they stay out of version control.
+ *
+ * Each secret is read from the environment first (CI), then from `local.properties`
+ * (local development), and defaults to an empty string when neither provides it —
+ * consumers are expected to degrade gracefully rather than fail.
+ *
+ * The values are emitted as a generated `BuildSecrets` object, available to every
+ * Kotlin target of the module.
+ */
+
+plugins {
+    id("org.jetbrains.kotlin.multiplatform")
+}
+
+val secretsPackage = "bzh.ajaury.chombev"
+
+private val localProperties: Provider<Properties> =
+    providers
+        .fileContents(layout.settingsDirectory.file("local.properties"))
+        .asText
+        .map { text -> Properties().apply { load(text.reader()) } }
+
+/** Resolves a secret from [environmentVariable], falling back to [localPropertyKey], then to an empty string. */
+fun secret(
+    environmentVariable: String,
+    localPropertyKey: String,
+): Provider<String> =
+    providers
+        .environmentVariable(environmentVariable)
+        .orElse(localProperties.map { properties -> properties.getProperty(localPropertyKey).orEmpty() })
+        .orElse("")
+
+// GlitchTip DSN, consumed by initializeSentry() in the shared module.
+val glitchtipDsn: Provider<String> = secret(environmentVariable = "GLITCHTIP_DSN", localPropertyKey = "glitchtip.dsn")
+
+val generateBuildSecrets =
+    tasks.register("generateBuildSecrets") {
+        description = "Generates the BuildSecrets object from local.properties and environment variables."
+
+        // Escaped here so the value can be inlined as-is in a Kotlin string literal.
+        val dsn =
+            glitchtipDsn.map { value ->
+                value
+                    .replace("\\", "\\\\")
+                    .replace("\"", "\\\"")
+                    .replace("$", "\${'$'}")
+            }
+        val outputDir = layout.buildDirectory.dir("generated/secrets/commonMain/kotlin")
+        // Kept in locals so the execution-time action never captures the script instance.
+        val packageName = secretsPackage
+        val packagePath = packageName.replace('.', '/')
+
+        inputs.property("glitchtipDsn", dsn)
+        outputs.dir(outputDir)
+
+        doLast {
+            val file =
+                outputDir
+                    .get()
+                    .asFile
+                    .resolve("$packagePath/BuildSecrets.kt")
+            file.parentFile.mkdirs()
+            file.writeText(
+                """
+                package $packageName
+
+                // Generated by the `gwenedeg.secrets` convention plugin. Do not edit.
+                internal object BuildSecrets {
+                    const val GLITCHTIP_DSN: String = "${dsn.get()}"
+                }
+
+                """.trimIndent(),
+            )
+        }
+    }
+
+kotlin {
+    sourceSets.commonMain {
+        kotlin.srcDir(generateBuildSecrets)
+    }
+}