Configuration

FF4K supports loading feature flags and properties from configuration files, making it easy to manage your application's state without changing code.

The Configuration Object

The FF4kConfiguration class represents the complete state of your FF4K instance, including: - Settings: Global behavior like autoCreate. - Features: Initial feature flags. - Properties: Initial configuration properties.

Loading from JSON

FF4K provides a JsonFF4kConfigurationParser to load configurations from JSON files or resources.

Example JSON

{
  "settings": {
    "autoCreate": true
  },
  "features": {
    "dark-mode": {
      "uid": "dark-mode",
      "isEnabled": true,
      "description": "Enable dark mode UI"
    }
  },
  "properties": {
    "api-timeout": {
      "type": "int",
      "name": "api-timeout",
      "value": 5000
    }
  }
}

Loading Resources

You can load a configuration file bundled with your application using parseConfigurationResource.

val parser = JsonFF4kConfigurationParser()
val config = parser.parseConfigurationResource("ff4k_config.json")

Platform Specifics: - JVM/Android: Loads from the classpath (e.g., src/main/resources). - Native: Searches in $FF4K_RESOURCES_PATH/<path>, then the current directory, then resources/<path>.

Loading Files

You can load a configuration file from the filesystem using parseConfigurationFile.

val parser = JsonFF4kConfigurationParser()
val config = parser.parseConfigurationFile("/etc/ff4k/config.json")

This method supports absolute paths and relative paths (resolved against the current working directory). Tilde (~) expansion is supported for user home directories.

Note: - Tilde expansion only supports ~ and ~/... (not ~username). - An IllegalArgumentException is thrown if the home directory cannot be determined. - Paths containing directory traversal sequences (..) are rejected and will cause an IllegalArgumentException.

Initializing FF4K

Once you have an FF4kConfiguration object, you can use it to initialize your stores.

val parser = JsonFF4kConfigurationParser()
val config = parser.parseConfigurationResource("ff4k.json")

val ff4k = ff4k(
    featureStore = InMemoryFeatureStore(config),
    propertyStore = InMemoryPropertyStore(config),
    autoCreate = config.settings.autoCreate
)

Auditing Source

You can optionally specify the source parameter when initializing FF4k to indicate the origin of API calls. This is useful for auditing or logging purposes in your application logic.

val ff4k = ff4k(
    source = FF4k.Source.WebApi // or KotlinApi, EmbeddedServlet, Ssh
) {
    // ...
}

This value is informational and does not affect feature evaluation logic.

Exporting Configuration

You can also export the current configuration state to a JSON string, which is useful for debugging or persisting runtime changes.

suspend fun main() {
    val config = FF4kConfiguration(
        settings = FF4kSettings(autoCreate = ff4k.autoCreate),
        features = ff4k.features(),
        properties = ff4k.properties()
    )

    val json = parser.export(config)
    File("snapshot.json").writeText(json)
}