Added mutable history container

TODO make an imutable observable based history container based on this
one

src/main/scala/nova/monadic_sfx/util/History.scala

@@ -0,0 +1,31 @@
+package nova.monadic_sfx.util
+
+class MutHistory[T](initValue: T) {
+  private var _values = Vector(initValue)
+  def values = _values
+  private var _sp = 0
+  def sp = _sp
+
+  // def current = if (ints.isEmpty) None else Some(ints(sp))
+  def current = _values(_sp)
+
+  def push(v: T) = {
+    if (_sp < _values.length - 1) {
+      _values = _values.splitAt(_sp)._1
+      _values = _values :+ v
+    } else {
+      _values = _values :+ v
+      _sp = _values.length - 1
+    }
+  }
+
+  def forward() = {
+    if (!_values.isEmpty && _sp < _values.length - 1) _sp += 1
+  }
+
+  def backward() = {
+    if (_sp > 0) {
+      _sp -= 1
+    }
+  }
+}

src/test/scala/MutHistoryTest.scala

@@ -0,0 +1,116 @@
+import org.scalatest.funsuite.AnyFunSuite
+import nova.monadic_sfx.util.MutHistory
+import com.typesafe.scalalogging.LazyLogging
+class MutHistoryTest extends AnyFunSuite with LazyLogging {
+  val h = new MutHistory(0)
+
+  test("init") {
+    assert(h.values == Vector(0))
+    assert(h.sp == 0)
+    assert(h.current == 0)
+  }
+  test("push 1") {
+    h.push(1)
+    // logger.debug(mutHistory.ints.toString)
+    assert(h.values == Vector(0, 1))
+    assert(h.values.length - 1 == h.sp)
+    assert(h.current == 1)
+  }
+  test("push 2") {
+    h.push(2)
+    // logger.debug(mutHistory.ints.toString)
+    assert(h.values == Vector(0, 1, 2))
+    assert(h.values.length - 1 == h.sp)
+    assert(h.current == 2)
+  }
+  test("first forward") {
+    // logger.debug(mutHistory.ints.toString)
+    // logger.debug(mutHistory.sp.toString)
+    h.forward()
+    assert(h.values == Vector(0, 1, 2))
+    assert(h.sp == 2)
+    assert(h.current == 2)
+  }
+  test("second forward") {
+    // logger.debug(mutHistory.ints.toString)
+    // logger.debug(mutHistory.sp.toString)
+    h.forward()
+    assert(h.values == Vector(0, 1, 2))
+    assert(h.sp == 2)
+    assert(h.current == 2)
+  }
+
+  test("first backward") {
+    h.backward()
+    assert(h.values == Vector(0, 1, 2))
+    assert(h.sp == 1)
+    assert(h.current == 1)
+  }
+  test("second backward") {
+    h.backward()
+    assert(h.values == Vector(0, 1, 2))
+    assert(h.sp == 0)
+    assert(h.current == 0)
+  }
+  test("third backward") {
+    h.backward()
+    assert(h.values == Vector(0, 1, 2))
+    assert(h.sp == 0)
+    assert(h.current == 0)
+  }
+  test("push 3") {
+    h.push(3)
+    assert(h.sp == 0)
+    assert(h.values == Vector(3))
+    assert(h.current == 3)
+  }
+  test("fourth backward") {
+    h.backward()
+    assert(h.values == Vector(3))
+    assert(h.sp == 0)
+    assert(h.current == 3)
+  }
+  test("lastly") {
+    h.push(4)
+    h.push(5)
+    h.push(6)
+    h.push(7)
+    h.push(8)
+    assert(h.values == Vector(3, 4, 5, 6, 7, 8))
+    assert(h.sp == 5)
+    assert(h.current == 8)
+    h.backward()
+    h.backward()
+    assert(h.current == 6)
+    assert(h.sp == 3)
+    h.push(9)
+    assert(h.values == Vector(3, 4, 5, 9))
+    assert(h.sp == 3)
+    assert(h.current == 9)
+    for (i <- 1 to 4) h.backward()
+    // assert(h.current == None)
+    // assert(h.ints == Vector.empty)
+    assert(h.sp == 0)
+    assert(h.current == 3)
+    h.push(1)
+    assert(h.current == 1)
+    assert(h.sp == 0)
+
+  }
+}
+
+//  test("main") {
+//   assert(mutHistory.ints == Vector.empty)
+//   assert(mutHistory.sp == -1)
+//   mutHistory.push(1)
+//   assert(mutHistory.ints == Vector(1))
+//   assert(mutHistory.sp == 0)
+//   mutHistory.push(2)
+//   assert(mutHistory.ints == Vector(1, 2))
+//   assert(mutHistory.sp == 1)
+//   // mutHistory.forward()
+//   // assert(mutHistory.sp == 1)
+//   // mutHistory.forward()
+//   // assert(mutHistory.sp == 1)
+// }
+//