chore: establish learning module baseline

OpenMAIC/lib/utils/element-fingerprint.ts

@@ -0,0 +1,76 @@
+import type { PPTElement } from '@openmaic/dsl';
+
+/**
+ * Extract the semantic payload for each element type.
+ * Used by elementFingerprint to detect content-only changes
+ * (same id/position but different text, chart data, media src, etc.).
+ */
+function semanticPart(e: PPTElement): unknown {
+  switch (e.type) {
+    case 'text':
+      return { content: e.content };
+    case 'image':
+      return { src: e.src };
+    case 'shape':
+      return {
+        path: e.path,
+        fill: e.fill,
+        text: e.text?.content ?? '',
+        gradient: e.gradient ?? null,
+        pattern: e.pattern ?? null,
+      };
+    case 'line':
+      return {
+        start: e.start,
+        end: e.end,
+        color: e.color,
+        style: e.style,
+        points: e.points,
+      };
+    case 'chart':
+      return {
+        chartType: e.chartType,
+        data: e.data,
+        themeColors: e.themeColors,
+      };
+    case 'table':
+      return {
+        data: e.data.map((row) => row.map((c) => c.text)),
+        colWidths: e.colWidths,
+        theme: e.theme ?? null,
+      };
+    case 'latex':
+      return { latex: e.latex };
+    case 'video':
+      return { src: e.src, poster: e.poster ?? '' };
+    case 'audio':
+      return { src: e.src };
+    case 'code':
+      return { language: e.language, lines: e.lines, fileName: e.fileName ?? '' };
+    default: {
+      const exhaustiveCheck: never = e;
+      return exhaustiveCheck;
+    }
+  }
+}
+
+/**
+ * Generate a fingerprint string for a list of whiteboard elements.
+ * Used for change detection and deduplication in history snapshots.
+ *
+ * Covers both geometry (id, position, size) AND semantic content
+ * via structured JSON.stringify — avoids delimiter-collision issues
+ * that hand-concatenated strings would have with rich-text HTML content.
+ */
+export function elementFingerprint(els: PPTElement[]): string {
+  return JSON.stringify(
+    els.map((e) => ({
+      id: e.id,
+      left: e.left ?? 0,
+      top: e.top ?? 0,
+      width: 'width' in e ? e.width : 0,
+      height: 'height' in e && e.height != null ? e.height : 0,
+      sem: semanticPart(e),
+    })),
+  );
+}