From 192e25f27e7cc6c710f355cd842bae4f6d657dfd Mon Sep 17 00:00:00 2001
From: Starbeamrainbowlabs <sbrl@starbeamrainbowlabs.com>
Date: Sun, 22 Oct 2017 21:44:30 +0100
Subject: [PATCH] [server] Write initial C# implementation of the JS line
 simplification algorithm I implemented earlier

---
 Nibriboard/Nibriboard.csproj           |  6 +--
 Nibriboard/Utilities/LineSimplifier.cs | 53 ++++++++++++++++++++++++++
 2 files changed, 55 insertions(+), 4 deletions(-)
 create mode 100644 Nibriboard/Utilities/LineSimplifier.cs

diff --git a/Nibriboard/Nibriboard.csproj b/Nibriboard/Nibriboard.csproj
index 9cbfa77..a4b04b4 100644
--- a/Nibriboard/Nibriboard.csproj
+++ b/Nibriboard/Nibriboard.csproj
@@ -119,6 +119,7 @@
     <Compile Include="Utilities\BinaryIO.cs" />
     <Compile Include="Client\Messages\ViewportUpdateMessage.cs" />
     <Compile Include="NibriboardApp.cs" />
+    <Compile Include="Utilities\LineSimplifier.cs" />
   </ItemGroup>
   <ItemGroup>
     <EmbeddedResource Include="ClientFiles\index.html" />
@@ -147,10 +148,7 @@
     <MonoDevelop>
       <Properties>
         <Policies>
-          <DotNetNamingPolicy ResourceNamePolicy="FileFormatDefault" DirectoryNamespaceAssociation="PrefixedHierarchical">
-            <inheritsSet />
-            <inheritsScope />
-          </DotNetNamingPolicy>
+          <DotNetNamingPolicy ResourceNamePolicy="FileFormatDefault" DirectoryNamespaceAssociation="PrefixedHierarchical" />
         </Policies>
       </Properties>
     </MonoDevelop>
diff --git a/Nibriboard/Utilities/LineSimplifier.cs b/Nibriboard/Utilities/LineSimplifier.cs
new file mode 100644
index 0000000..ba9d5d6
--- /dev/null
+++ b/Nibriboard/Utilities/LineSimplifier.cs
@@ -0,0 +1,53 @@
+using System;
+using System.Collections.Generic;
+using Nibriboard.RippleSpace;
+
+namespace Nibriboard.Utilities
+{
+	public static class LineSimplifier
+	{
+		public static List<LocationReference> SimplifyLine(List<LocationReference> points, float minArea)
+		{
+			// This algorithm requires more than 3 points
+			if(points.Count < 3)
+				return points;
+
+			points = new List<LocationReference>(points); // Shallow clone the list
+
+			while(true)
+			{
+				float smallestArea = float.MaxValue;
+				int smallestAreaI = 1;
+
+				for(int i = 1; i < points.Count - 1; i++)
+				{
+					float nextArea = TriangleArea(points[i - 1], points[i], points[i + 1]);
+					if(nextArea < smallestArea) {
+						smallestArea = nextArea;
+						smallestAreaI = i;
+					}
+				}
+
+
+				if(smallestArea >= minArea || points.Count <= 3)
+					break;
+
+				// Remove the central point of the smallest triangle
+				points.RemoveAt(smallestAreaI);
+			}
+
+			return points;
+		}
+
+		public static float TriangleArea(LocationReference a, LocationReference b, LocationReference c)
+		{
+			return Math.Abs(
+				(
+					(float)a.X * (b.Y - c.Y) +
+					(float)b.X * (c.Y - a.Y) +
+					(float)c.X * (a.Y - b.Y)
+				) / 2f
+			);
+		}
+	}
+}