always sorting arraylist; more wire stuffs

src/net/torvald/util/HistoryArray.kt

@@ -0,0 +1,66 @@
+package net.torvald.util
+
+import java.util.*
+
+/**
+ * Simple ArrayList wrapper that acts as history keeper. You can append any data but cannot delete.
+ *
+ * Created by minjaesong on 2016-07-13.
+ */
+class HistoryArray<T>(val size: Int) {
+
+    val history = ArrayList<T?>(Math.min(size, 256)) // 256: arbitrary set upper bound
+
+    val lastIndex = size - 1
+
+    val elemCount: Int
+        get() = history.size
+
+    fun add(value: T) {
+        if (history.size == 0) {
+            history.add(value)
+            return
+        }
+        // push existing values to an index
+        else {
+            for (i in history.size - 1 downTo 0) {
+                // if history.size is smaller than 'size', make room by appending
+                if (i == history.size - 1 && i < size - 1)
+                    history.add(history[i])
+                // actually move if we have some room
+                else if (i < size - 1)
+                    history[i + 1] = history[i]
+            }
+        }
+        // add new value to the room
+        history[0] = value
+    }
+
+    /**
+     * Get certain index from history. NOTE: index 0 means latest!
+     */
+    operator fun get(index: Int): T? =
+            if (index >= history.size) null
+            else history[index]
+
+    /**
+     * Iterate from latest to oldest
+     */
+    fun iterator() = history.iterator()
+
+    /**
+     * Iterate from latest to oldest
+     */
+    fun forEach(action: (T?) -> Unit) = history.forEach(action)
+
+    val latest: T?
+        get() = this[0]
+
+    val oldest: T?
+        get() = this[history.size - 1]
+
+    fun clear() {
+        history.clear()
+    }
+
+}