Summary

Feature context: #851

Public API

The main consideration for the public API to be exposed for tracking custom events is that the types of attribute values need to be constrained to the following Kotlin types: String, Int, Double, Boolean and Long and the public API should only allow adding these types only.

val attributes = buildAttributes {
  put("sample-key-1", 123)
  put("sample-key-2", 123.45)
  put("sample-key-3", "sample-value")
  put("sample-key-4", true)
  put("sample-key-5", 123L)
}
Measure.trackEvent("custom-event", attributes)

This can be achieved by leveraging inline value classes in Kotlin which can provide type safety and performance benefits without the overhead of creating separate objects for each attribute value. Inline value classes allow us to wrap primitive types with additional type information at compile time, while still using the underlying primitive type at runtime.

For example, to represent an AttributeValue that can only have a string the following sealed interface can be used with the inline value class:

@Serializable(with = AttributeValueSerializer::class)
sealed interface AttributeValue {
    val value: Any
}

@Serializable
@JvmInline
value class StringAttr(override val value: String) : AttributeValue