From c645ded35da9d99588800dccf7a8a7c797a45b23 Mon Sep 17 00:00:00 2001
From: Aaron Siegel <2014957+aaron-siegel@users.noreply.github.com>
Date: Fri, 22 Dec 2023 23:17:32 -0800
Subject: [PATCH] Add Strip.Decomposition method. (#52)

Adds a method `Strip.Decomposition` analogous to `Grid.Decomposition`.
---
 .../cgsuite/lang/resources/cgsuite/util/Strip.cgs  |  6 ++++++
 .../src/main/scala/org/cgsuite/util/Strip.scala    | 14 ++++++++++++++
 .../scala/org/cgsuite/lang/CgsuiteUtilTest.scala   |  3 +++
 3 files changed, 23 insertions(+)

diff --git a/lib/core/src/main/resources/org/cgsuite/lang/resources/cgsuite/util/Strip.cgs b/lib/core/src/main/resources/org/cgsuite/lang/resources/cgsuite/util/Strip.cgs
index 9a96d92b..484990b7 100644
--- a/lib/core/src/main/resources/org/cgsuite/lang/resources/cgsuite/util/Strip.cgs
+++ b/lib/core/src/main/resources/org/cgsuite/lang/resources/cgsuite/util/Strip.cgs
@@ -41,6 +41,12 @@ system class Strip
     */
   external def op[](index as Integer) as Integer;
 
+  /** The decomposition of this `Strip` into connected components separated by entries with the specified `boundaryValue`.
+    * The result will be a `List` of `Strip`s, each corresponding to a single nonempty connected component of the
+    * original `Strip`.
+    */
+  external def Decomposition(boundaryValue as Integer) as List;
+
   /** A `List` of all indices at which this `Strip` has the specified value. */
   external def FindAll(value as Integer) as List;
 
diff --git a/lib/core/src/main/scala/org/cgsuite/util/Strip.scala b/lib/core/src/main/scala/org/cgsuite/util/Strip.scala
index 03e82e96..2c5f92cb 100644
--- a/lib/core/src/main/scala/org/cgsuite/util/Strip.scala
+++ b/lib/core/src/main/scala/org/cgsuite/util/Strip.scala
@@ -82,6 +82,20 @@ class Strip private[util] (private val values: Array[Byte]) extends Serializable
     new Strip(newValues)
   }
 
+  def decomposition(boundaryValue: Integer): IndexedSeq[Strip] = {
+    val boundaryValueInt = boundaryValue.intValue
+    val boundaryIndices = values.indices filter { values(_) == boundaryValueInt }
+    val tail = boundaryIndices.indices collect {
+      case k if boundaryIndices(k) + 1 < values.length && values(boundaryIndices(k) + 1) != boundaryValueInt =>
+        new Strip(values.slice(boundaryIndices(k) + 1, if (k + 1 < boundaryIndices.length) boundaryIndices(k + 1) else values.length))
+    }
+    if (values.isEmpty || values(0) == boundaryValueInt)
+      tail
+    else
+      new Strip(values.slice(0, if (boundaryIndices.isEmpty) values.length else boundaryIndices(0))) +: tail
+
+  }
+
   def findAll(value: Integer): IndexedSeq[Integer] = {
     val byte = value.intValue.toByte
     var cnt = 0
diff --git a/lib/core/src/test/scala/org/cgsuite/lang/CgsuiteUtilTest.scala b/lib/core/src/test/scala/org/cgsuite/lang/CgsuiteUtilTest.scala
index 0e621b76..502cff7d 100644
--- a/lib/core/src/test/scala/org/cgsuite/lang/CgsuiteUtilTest.scala
+++ b/lib/core/src/test/scala/org/cgsuite/lang/CgsuiteUtilTest.scala
@@ -11,6 +11,9 @@ class CgsuiteUtilTest extends CgscriptSpec {
       ("Empty", "Strip.Empty(8)", "Strip([0,0,0,0,0,0,0,0])"),
       ("Parse", """strip := Strip.Parse(".abbd.", ".abcd")""", "Strip([0,1,2,2,4,0])"),
       ("op []", "strip[3]", "2"),
+      ("Decomposition", """strip.Decomposition(2)""", "[Strip([0,1]),Strip([4,0])]"),
+      ("Decomposition edges", """strip.Decomposition(0)""", "[Strip([1,2,2,4])]"),
+      ("Decomposition empty", """Strip.Empty(0).Decomposition(0)""", "[]"),
       ("FindAll", "strip.FindAll(2)", "[3,4]"),
       ("Length", "strip.Length", "6"),
       ("ToString", """strip.ToString(".abcd")""", "\".abbd.\""),