implement add node mechanism in radar

src/main/kotlin/radar/Radar.kt

+package radar
+
+import kotlin.properties.Delegates
+
+/**
+ * Note: Assume that node values starting from 12 o'clock clockwise
+ */
+class Radar (maxScale: Int, numNodes: Int) {
+    /** Stands for values from each node in Double */
+    private var maxScale = maxScale
+    private var numNodes = numNodes
+        set(value) {
+            field = value
+            nodesValues.subList(numNodes + 1, nodesValues.size - 1).clear()
+        }
+    private var nodesValues: MutableList<Double?> = MutableList(numNodes) {null}
+    private var overwrittenNode by Delegates.notNull<Double>()
+    private var overwrittenNodeIndex by Delegates.notNull<Int>()
+
+    fun addNode(index: Int, value: Double) {
+        if (index < numNodes) {
+            // check if the destination node is null or not
+            // if the destination node is not null, copy to overwritten node then replace with new node
+            nodesValues[index]?.let {
+                overwrittenNode = nodesValues[index]!!
+                overwrittenNodeIndex = index
+                nodesValues[index] = value
+            }
+            // else, just add
+                ?: run {
+                    nodesValues[index] = value
+                }
+        }
+    }
+
+}
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