Add latest quarter filter (#323)

Resolves #322

Author: dtemkin1

src/components/PEClassTable.tsx

@@ -204,6 +204,7 @@ function ClassInput(props: {
 const filtersNonFlags = {
   fits: (state, cls) => state.fitsSchedule(cls),
   starred: (state, cls) => state.isPEClassStarred(cls),
+  latest: (state, cls) => cls.rawClass.quarter === state.latestQuarter,
 } satisfies Record<string, (state: State, cls: PEClass) => boolean>;
 
 type Filter = keyof PEFlags | keyof typeof filtersNonFlags;
@@ -212,6 +213,7 @@ type FilterGroup = [Filter, string, ReactNode?][];
 /** List of top filter IDs and their displayed names. */
 const CLASS_FLAGS_1: FilterGroup = [
   ["starred", "Starred", <LuStar fill="currentColor" />],
+  ["latest", "Latest quarter"],
   ["nofee", "No fee"],
   ["nopreq", "No prereq"],
   ["fits", "Fits schedule"],

src/lib/state.ts

@@ -405,6 +405,31 @@ export class State {
     this.updateState();
   }
 
+  /** Get latest quarter of PE classes */
+  get latestQuarter(): number {
+    const allQuarters = new Set<number>();
+    this.peClasses.forEach((cls) => {
+      const quarter = cls.rawClass.quarter;
+      allQuarters.add(quarter);
+    });
+
+    // for 1 < 2 < 5 < 3 < 4
+    const quarterOrder: Record<number, number> = {
+      1: 0,
+      2: 1,
+      // 5 is iap for some reason :(
+      5: 2,
+      3: 3,
+      4: 4,
+    };
+
+    const sortedQuarters = Array.from(allQuarters).sort((a, b) => {
+      return quarterOrder[a] - quarterOrder[b];
+    });
+
+    return sortedQuarters[sortedQuarters.length - 1];
+  }
+
   //========================================================================
   // Loading and saving