From 0b6de0840fce8f2a884bb47b1b930276c6d8d7cc Mon Sep 17 00:00:00 2001
From: Colin McMillen <colin@semicolin.games>
Date: Wed, 26 Jul 2023 21:56:27 -0400
Subject: [PATCH] Move photoIndex to wherever the previously active photo was

---
 Program.cs | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/Program.cs b/Program.cs
index 7ce50ac..13e2ba5 100644
--- a/Program.cs
+++ b/Program.cs
@@ -714,9 +714,22 @@ public class Game : GameWindow {
 
   void FilterByRating(int rating) {
     Console.WriteLine("filter to " + rating);
+    Photo previouslyActive = photos[photoIndex];
     photos = allPhotos.Where(p => p.Rating >= rating).ToList();
-    // TODO: put this closest to wherever the previously active photo was.
-    photoIndex = 0;
+    // Move photoIndex to wherever the previously active photo was, or if it
+    // was filtered out, to whichever unfiltered photo comes before it. This
+    // is O(n) in the length of allPhotos, but how bad can it be? :)
+    photoIndex = -1;
+    for (int i = 0; i < allPhotos.Count; i++) {
+      Photo candidate = allPhotos[i];
+      if (candidate.Rating >= rating) {
+        photoIndex++;
+      }
+      if (candidate == previouslyActive) {
+        break;
+      }
+    }
+    photoIndex = Math.Max(0, photoIndex);
   }
 
   protected override void OnLoad() {