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helpers.kt

/**
 * Create new class with values from original unless passed in changes map
 */
inline fun <reified T: Any> T.replicateWithChanges(
    changes: Map<String, Any?> = mapOf()
): T {
    val constructor = this.javaClass.kotlin.primaryConstructor
    if(constructor?.parameters == null) throw Exception("Invalid Constructor for Replication")

    val propertyMap = this.mapProperties()
    val paramMap : Map<KParameter, Any?> = constructor.parameters.associateWith { param ->
        val value = if (changes.containsKey(param.name)) {
            changes[param.name]
        } else {
            if (propertyMap.containsKey(param.name)) propertyMap[param.name] else null
        }

        value
    }.toMap()

    return constructor.callBy(paramMap)
}

/**
 * Create key map of class properties
 */
inline fun <reified T: Any> T.mapProperties() : Map<String, Any?> {
    return this.javaClass.kotlin.declaredMemberProperties.associate { field ->
        field.isAccessible = true
        Pair(field.name, field.get(this))
    }
}

/** 
 * Usage
 *
 * data.replicateWithChanges(mapOf("propertyName" to newValue))
 */